SOUTHEAST ALASKA FORECAST DISCUSSION
630 AM AST WED JAN 24 2007
AFDAJK
.SYNOPSIS...
.SHORT RANGE...LANDFALL OF 990 MB LOW TO TAKE PLACE BETWEEN
DRY BAY AND YAKUTAT ABOUT 18Z. ASSOCIATED PRESSURE FALLS
ALREADY UNDERWAY IN YUKON TERRITORY OF AT LEAST A MB PER HOUR.
PRESSURE RISES BEGINNING TO OCCUR IN PNHDL S OF SUMNER STRAIT.
THESE TRENDS ARE CONSISTENT WITH THE MODEL GUIDANCE DISCUSSED
BELOW AND PLEASE NOTE ASSOCAITED WIND ADVISORIES SUMMARIZED
AT THE BOTTOM.
VAPOR CHANNEL IMAGERY AND MDCARS AIRCRAFT DATA ARE CONSISTENT
WITH JETSTREAM MAXIMA OVER A SITKA-JUNEAU LINE AS THIS PRODUCT
IS BEING PREPARED...ALONG WITH LEFT EXIT REGION OF JETSTREAK
OVER DRY BAY. MODELS DO SEEM TO HAVE A LOCK ON THE UPPER LEVEL
STRUCTURE ON EVERYTHING CHECKED...SO SHORT RANGE PACKAGE
WILL FOLLOW SUIT.
MODEL CONSENSUS IS GOOD BETWEEN THE GFS AND NAM AND A HYBRID OF
THE MODELS OR THEIR MOS VALUES WAS USED FOR THE GRIDS.
.LONG RANGE...STRONG UPPER LEVEL HIGH CENTER OVER NORTHEAST
PACIFIC NEARLY STATIONARY THROUGH THE PERIOD. A RIDGE EXTENDING
NORTH FROM THIS HIGH CENTER WILL BLOCK STORM TRACK ACROSS EASTERN
GULF AND KEEP DEEP MOISTURE WEST OF FORECAST AREA. A 1035 MB
SURFACE HIGH BUILDS INTO B.C FRIDAY WITH SOME CLEARING FOR
SOUTHEAST ALASKA. OLD OCCLUSION IN CENTRAL GULF NEARLY STATIONARY
THROUGH FRIDAY THEN WEAKENING AS IT MOVES ACROSS SOUTHEAST ALASKA
SATURDAY NIGHT INTO SUNDAY. USED 00Z GFS40 AND GFSLR FOR GRIDS.
WITH VERY STABLE AND WARM ATMO ALOFT EXPECT INVERSION TO DEVELOP
ACROSS SOUTHEAST ALASKA THURSDAY NIGHT THROUGH SUNDAY. THIS
INVERSION WILL FAVOR MARINE CLOUD DEVELOPMENT IN WEAK ONSHORE
FLOW ACROSS NORTHERN AREAS FOR MOSTLY CLOUDY CONDITIONS WITH
CHANCE OF LIGHT PRECIPITATION. PRECIP TYPE MAY BE TRICKY WITH A
SHALLOW SUB FREEZING BOUNDARY LAYER SUPPORTING FZRA. POPS
GENERALLY A CHANCE OR LESS THURSDAY NIGHT THROUGH SATURDAY THEN
GOING TO LIKELY WITH OLD OCCLUSION MOVING THROUGH. WINDS THROUGH
INNER CHANNELS WILL BE DOMINATED BY A LIGHT EASTERLY WITH SOLID
SMCR TO GALE SE WINDS EXPECTED ACROSS THE EASTERN GULF.
BY MONDAY STRONG UPPER HIGH MOVES OVER NORTHEAST GULF WITH WEAK
DOWN SLOPE AND DRYING. SKIES EXPECTED TO BE PARTLY CLOUDY WITH
POTENTIAL FOR LOCALLY WARM TEMPERATURES IN THE 50S. NIGHTTIME
LOWS STILL EXPECTED TO FALL BELOW FREEZING.
.AJK...WATCHES/WARNINGS/ADVISORIES
PUBLIC...HEAVY SNOW WARNING ZONE 19. WIND ADVISORIES IN ZONES
18...19...22...23...AND 27 THROUGH 29.
NONE
MARINE...GALE OUTSIDE ZONE 43...INSIDE 13...22...AND 36.
NONE
AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
AFDSGX 230 PM PST WED JAN 24 2007
.SYNOPSIS...WEAKENING OFFSHORE FLOW AND HIGH PRESSURE ALOFT WILL
CONTINUE MOSTLY CLEAR SKIES THROUGH THURSDAY. LOCALLY WINDY THROUGH
AND BELOW MOUNTAIN CANYONS AND PASSES INTO THURSDAY. SIGHTLY
COOLER THURSDAY. UPPER LEVEL LOW PRESSURE WILL BRING MORE CLOUDS AND
COOLER DAYS THIS WEEKEND AND EARLY NEXT WEEK.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
.SHORT TERM (TODAY-SAT)...CLEAR SKIES TODAY. ACARS SOUNDINGS SHOWED
WEAK E TO NE WINDS THROUGH MOST OF THE COLUMN. OFFSHORE GRADIENTS
WITH ABOUT -6 MB SAN-TPH AND THERE WERE LOCAL BREEZY CONDITIONS NEAR
MOUNTAIN CANYONS AND PASSES.
THE OFFSHORE FLOW WILL WEAKEN THROUGH THU AND HEIGHTS WILL BEGIN TO
DECREASE FOR A LITTLE COOLING. MORE COOLING FRI AND SAT WITH
VARIABLE HIGH CLOUDINESS AS A WEAK UPPER LOW UNDERCUTS THE HIGH
AMPLITUDE RIDGE NEAR THE W COAST. THERE WILL STILL BE LOCAL OFFSHORE
WINDS...MAINLY IN AND NEAR THE E-W ORIENTED MOUNTAIN CANYONS AND
PASSES LATE THIS AFTERNOON AND EARLY EVENING. ONSHORE FLOW WILL
RETURN FRI AND SAT WITH A LITTLE STRONGER SEA BREEZE EACH AFTERNOON.
A SHALLOW MARINE LAYER COULD DEVELOP AS EARLY AS LATE FRI NIGHT AND
SAT MORNING WITH DENSE FOG POSSIBLE NEAR THE COAST.
.LONG TERM (SUN-WED)...BIG DIFFERENCES BETWEEN THE PROGS FOR THE
EXTENDED PERIOD. IT CURRENTLY LOOKS LIKE THERE WILL BE WEAK UPPER
LEVEL LOW PRESSURE NEAR SRN CA THROUGH EARLY NEXT WEEK. THIS SHOULD
CONTINUE COOLER DAYS WITH OCCASIONAL MARINE LAYER CLOUDS AND
VARIABLE HIGH CLOUDINESS. THE CLOUDS AND HIGHER HUMIDITIES WILL
MODERATE MIN TEMPS W OF THE MOUNTAINS. THERE WILL BE A SMALL CHANCE
OF PRECIP EARLY NEXT WEEK...HOWEVER...STILL TOO MUCH UNCERTAINTY TO
INCLUDE IN THE FORECAST AT THIS TIME.
&&
.AVIATION...
CLEAR SKIES AND UNRESTRICTED VISIBILITIES THROUGH THURSDAY. LOCAL
NORTHEAST TO EAST WINDS 15-25 KT WITH SOME GUSTS TO 30 KT WERE
OCCURRING NEAR AND BELOW THE MOUNTAIN PASSES/CANYONS LATE THIS MORN
AND EARLY THIS AFTN...HOWEVER THESE OFFSHORE WINDS WILL DECREASE
THROUGH THIS EVENING.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
PUBLIC...DVA
AVIATION...LAVIS
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
AFDLOT 530 AM CST WED JAN 24 2007
.DISCUSSION FOR MORNING GRIDS/ZONES...
430 PM CST
CLOSELY SPACED MINOR SHORT WAVES TO CONTINUE TO MOVE QUICKLY ACROSS
THE REGION AS THEY DROP FROM THE WESTERN UPPER RIDGE INTO THE
EASTERN UPPER TROUGH. THE ONE THAT BROUGHT LIGHT SNOW TO CENTRAL IL
LAST NIGHT IS NOW MOVING TOWARD THE UPPER OH VALLEY. ANOTHER IS
CURRENTLY TRAVERSING SOUTHERN WI AND EASTERN IA PRODUCING A FEW
FLURRIES AND IS EXPECTED TO CONTINUE TO DO SO AS IT CROSSES NORTHERN
IL THIS MORNING. STILL ANOTHER MINOR WAVE IS MOVING FROM SD INTO NEB
BUT THIS IMPULSE WILL CONTINUE TO TRACK TO THE SE IN THE
NORTHWESTERLY FLOW AND WILL CROSS INTO SW IL DURING THE AFTERNOON.
A STRONGER SHORT WAVE IS PRESENTLY MOVING FROM MANITOBA INTO WESTERN
ONTARIO AND WILL REACH EASTERN LAKE SUPERIOR AND NORTHERN LAKE
MICHIGAN BY 00Z WED. WITH MORE SIGNIFICANT UVV ASSOCIATED WITH THIS
WAVE MORE THAN FLURRIES EXPECTED BUT THE WAA WILL BE ACROSS THE
NORTHERN INTO CENTRAL LAKES REGION...N OF THE LOCAL FA. THE SHORT
WAVE TROUGH PASSAGE OVERNIGHT WILL REINFORCE THE COLD AIR ACROSS THE
UPPER MIDWEST AND GREAT LAKES FOR THU. THIS COLD AIR IS TEMPORARILY
DISLODGED AS SIGNIFICANT WAA OCCURS AHEAD OF AN UPPER LOW TO MOVE
FROM THE CANADIAN PRARIE TO WESTERN ONTARIO THURSDAY NIGHT AND FRI.
AGAIN THE ASOCIATED PRECIPITATION WILL BE WELL REMOVED FROM THE FA.
AS THE TRAILING COLD FRONT DROPS INTO NORTHERN IL LATE FRI AFTERNOON
AND THROUGH THE FA FRI NIGHT IT WILL LIKELY GENERATE FLURRIES. WITH
THE FROPA COLDER AIR RETURNS AS THE CORE OF THIS COLD AIR WILL BE
MOVING ACROSS THE NORTHERN PLAINS AND UPPER MIDWEST SAT. ANOTHER
SHORT WAVE IS FORECAST TO DROP ACROSS THE UPPER MIDWEST AND WESTERN
GREAT LAKES ON SUN ALLOWING THE COLD AIR TO PENETRATE FURTHER
SE...WHILE YET ANOTHER WAVE MOVES THROUGH THE REGION ON MON
REINFORCING THE COLD AIR. WHILE THE COLD IS NOT OF AN EXTREME
NATURE...CERTAINLY NOTHING UNUSUAL FOR LATE JAN...IT WILL NONE THE
LESS BE COLD PERIOD ESPECIALLY FROM SAT NIGHT THROUGH TUE.
TRS
&&
.AVIATION...
THE MVFR CLOUDS EXTEND WEST AND NORTH TO WISCONSIN...MINNESOTA AND
IOWA THIS MORNING. THE 700 MB PROFILER WIND ARE NORTHWEST. THE
STREAMLINES SHOW A TROUGH OVER NORTHEAST ILLINOIS AT 11 UTC. THE
INVERSION IS STILL PRESENT AT 893 TO 852 MB ON THE ACARS SOUNDING AT
ORD AT 1158 UTC. BY 18 UTC THE LOCAL WRF MODEL SHOWS AN ISOTHERMAL
LAYER FROM 898 TO 825 MB. WILL FORECAST A HIGHER THAN MVFR CEILING
FOR THIS AFTERNOON. THE NEXT SHORT WAVE TROUGH IS FORECAST TO MOVE
THROUGH ABOUT 06 UTC THURSDAY. THERE IS SOME SIGNIFICANT COLD AIR
WITH THIS WAVE AS SEEN ON THE 850 MB TEMPERATURE FORECASTS FROM THE
NAM AND LOCAL WRF MODELS. WE WILL FORECAST A MORE NORTHERLY WIND AND
INCREASE THE SPEED. THE SNOW SHOWERS ARE EXPECTED TO BE WIDELY
SCATTERED AND LIGHT. SO WE WILL LEAVE THEM OUT OF THE TAFS
AT THIS TIME.
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
.IL...NONE.
.IN...NONE.
.LM...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS LOUISVILLE KY
AFDLMK 220 PM EST WED JAN 24 2007
.SHORT TERM (TONIGHT-THURSDAY)...
DUE TO CLIPPER SYSTEM...NE SECTIONS OF THE LMK CWA SAW MEASURABLE
SNOW EARLY THIS MORNING...WITH AMOUNTS RANGING FROM A FEW TENTHS TO
NEARLY 1.5 INCHES. NUMEROUS TRAFFIC ACCIDENTS OCCURRED DURING THE
MORNING COMMUTE. TEMPERATURES HAVE RISEN ABOVE FREEZING...MELTING
NEARLY ALL THE SNOW PER WEBCAMS. POWERFUL JET STREAK OVERHEAD
TODAY...EARLIER 737 AIRCRAFT OBSERVATION AT FL380 NEAR SDF
INDICATED A 183KT WESTERLY WIND (AND MODERATE TURBULENCE).
FOCUS FOR THIS PERIOD IS ON YET ANOTHER CLIPPER SYSTEM FCST TO ROLL
THOUGH THE DISTRICT THURSDAY. CURRENTLY FEATURE IS POSITIONED OVER
WRN SECTIONS OF ONTARIO...AND IS FCST TO DROP QUICKLY FROM SRN
INDIANA AT 12Z/THU INTO ERN KY BY 18Z/THU. AHEAD OF THIS UPPER WAVE
FCST SOUNDINGS FROM GFS/NAM SHOW STEEPENING LAPSE RATES LATE TONIGHT
AND THURSDAY WITH SATURATION INTO THE CRITICAL ICE CRYSTAL
GENERATION LAYERS OVER NE 1/3 OF THE CWA...THOUGH GFS IS LESS
AGGRESSIVE WITH SATURATION AS COMPARED TO THE NAM. SCT SHSN ARE
EXPECTED OVER THE NRN/ERN ZONES FROM ROUGHLY 8Z TONIGHT THROUGH 15Z
THURSDAY MORNING.
WE WILL GO WITH 30-40% POPS FOR THIS AREA...LESSER VALUES OVER
REMAINDER OF CWA INCLUDING MOST OF SRN KY...WHERE ONLY FLURRIES WILL
BE MENTIONED. BUFKIT DIAGNOSTICS FROM WETTER NAM PRODUCE AROUND 0.5
INCH OF SNOWFALL FROM MADISON INDIANA SE INTO THE FFT/LEX AREAS...
WITH AROUND 0.25 INCH AT SDF. THESE VALUES SEEM REASONABLE...THOUGH
THEY WILL BE LOCALIZED DEPENDING ON EXACTLY WHERE SNOW SHOWERS
DEVELOP. AN SPS WILL BE ISSUED FOR OUR FAR NE COUNTIES HIGHLIGHTING
POTENTIAL FOR MORE SNOW...AND SIMILAR IN NATURE TO THIS MORNINGS
ACTIVITY...IT HAS THE POTENTIAL TO AFFECT THE MORNING DRIVE TOMORROW.
IN THE MEANTIME...CURRENT AREA OF LOW CLOUDS IS EXPECTED TO
DISSIPATE AND/OR SLIDE SE SUCH THAT SKIES WILL GO PARTLY CLOUDY OR
MOSTLY CLEAR OVER MUCH OF THE CWA FROM LATE AFTN INTO EARLY EVENING.
THEN TOWARD 6Z LOW LEVEL RH FIELDS DEPICT CLOUDS RAPIDLY INCREASING
INTO THE OVERNIGHT HOURS. REGARDING TEMPERATURES...HAVE FOLLOWED
LATEST RUC PROJECTIONS FOR TONIGHT AND TOMORROW GIVEN IT`S RECENT
GOOD PERFORMANCE. THIS YIELDS VERY SLOWLY FALLING TEMPS TONIGHT INTO
THE UPPER 20S/LOWER 30S...WITH NEAR STEADY READINGS THURSDAY.
STEEPENING LAPSE RATES WILL PROMOTE GUSTY WINDS THURSDAY...BUFKIT
SUGGESTING GUSTS TO 20KTS OR SO POSSIBLE AND HAVE FOLLOWED THIS.
CS
.LONG TERM (THURSDAY NIGHT-WEDNESDAY)...
THURSDAY NIGHT AND FRIDAY...
COLD AIR ADVECTION WILL IN IN PLACE AT THE BEGINNING OF THIS
FORECAST PERIOD WITH THE 8H ISOTHERM AT 00Z FRIDAY SOUTH OF THE
FORECAST AREA. THIS IS IN THE WAKE OF A CLIPPER MOVING TO OUR
SOUTHEAST. THIS CAA WILL BE SHORT LIVED AS THE NEXT CLIPPER SYSTEM
BEGINS TO DROP SOUTH OUT OF CENTRAL CANADA. LOW LEVEL WINDS WILL
BACK AND INCREASE FROM THE WEST FRIDAY AND A WARM FRONT WILL MOVE
THROUGH THE AREA. BY 00Z SATURDAY H8 TEMPS WILL HAVE WARMED TO THE
FREEZING MARK. SO AFTER A CLEAR AND COLD THURSDAY NIGHT...FRIDAY
WILL BE BREEZY AND WARMER.
TEMPERATURES FRIDAY MORNING WILL START OUT IN THE LOWER 20S BUT WITH
THE WARMING READINGS WILL RISE INTO THE LOWER AND MID 40S BY
AFTERNOON. SOUTHWEST WINDS FRIDAY NIGHT WILL KEEP TEMPERATURES IN
THE 30S WITH INCREASING CLOUDS.
SATURDAY THROUGH WEDNESDAY...
A GREAT LAKES AND OHIO VALLEY UPPER LEVEL TROUGH WILL REMAIN IN
PLACE THROUGH THIS FORECAST PERIOD. EXTENDED MODELS ARE IN AGREEMENT
ON BRINGING SEVERAL DISTURBANCES THROUGH THE FLOW WHICH WILL BRING
SOME ADDITIONAL LIGHT RAIN OR SNOW TO THE AREA AS WELL AS
REINFORCING COLD AIR.
THE FIRST WAVE WILL SHARPEN UP SATURDAY AND SLOWLY MOVE ACROSS THE
REGION SUNDAY. WITH BACKING LOW LEVEL WINDS AHEAD OF THE DEEPENING
TROUGH ENOUGH WARM AIR WILL FILTER INTO THE REGION TO PRODUCE LIGHT
RAIN SATURDAY. COLDER AIR WILL OVERSPREAD THE LOWER OHIO VALLEY
SATURDAY NIGHT SO ANY ADDITIONAL PRECIPITATION WILL BE IN THE FORM
OF SNOW. WE WILL KEEP POPS IN THE LOW CHANCE CATEGORY BUT IF WE SEE
PERSISTENCE IN THIS CLIPPER SYSTEM POPS WILL NEED TO BE RAISED
ESPECIALLY OVER THE NORTHEAST PORTION OF THE FORECAST AREA.
A SECOND WAVE WILL DIG INTO THE REGION TUESDAY WITH SOME VARIATION
IN THE MODELS ON THE LOCATION AND STRENGTH. FOR NOW WE WILL FOLLOW
THE GFS AND KEEP THE FORECAST AREA DRY.
THE INITIAL SHOT OF COLD AIR SATURDAY NIGHT WILL DROP TEMPERATURES
INTO THE 20S AND LOW 30S SUNDAY AND INTO THE TEENS AND 20S MONDAY
WITH A SLIGHT WARM UP TUESDAY. COLDER TEMPERATURES WILL BE NOTED
AGAIN WEDNESDAY AS THE SECOND CLIPPER MOVES TO THE SOUTHEAST.
--JA
&&
.AVIATION (18Z TAFS)...
BASED ON RECENT SATELLITE TRENDS AND GFS/NAM LOW LEVEL RH FIELDS
EXPECTING BKN-OVC LOW STRATUS TO AFFECT THE TAF SITES THIS AFTN.
CIGS ARE CURRENTLY RUNNING AROUND 1KFT AND FEEL THAT THIS WILL
CONTINUE THROUGH AT LEAST 21Z. A FEW FLURRIES ARE POSSIBLE THIS AFTN
BUT NOT ENOUGH TO RESTRICT VSBYS. CONSISTENT WITH UPSTREAM OBS...
FCST SOUNDINGS SHOW THAT CIGS WILL LIKELY RISE INTO THE MVFR
CATEGORY BETWEEN 21Z-3Z...BEFORE DROPPING DOWN INTO THE IFR RANGE
TOWARD MIDNIGHT AHEAD OF ANOTHER CLIPPER SYSTEM MOVING INTO THE
AREA. A FEW -SHSN ARE LIKELY OVERNIGHT INTO THURSDAY MORNING. WILL
INCLUDE LOWERED VSBYS (BUT STILL MVFR) AT SDF/LEX TAF SITES WHERE
BETTER CHANCES FOR -SHSN ARE FORECAST...JUST P6SM -SHSN AT BWG.
WINDS MAY BECOME A LITTLE GUSTY DURING THIS SAME PERIOD AS LOW LEVEL
LAPSE RATES STEEPEN.
CS
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...NONE.
IN...NONE.
&&
$$
AREA FORECAST DISCUSSION...UPDATED
NWS MARQUETTE MI
AFDMQT 1015 PM EST THU JAN 25 2007
.UPDATE...
KMQT RADAR INDICATED INITIAL BAND OF MID/HIGH CLOUDS ALONG WITH A
FEW FLURRIES MOVING THROUGH W UPR MI. UPSTREAM...ADDITIONAL RETURNS
WERE DEVELOPING OVER NW MN. THE 00Z NAM AND 18Z GFS WERE IN GOOD
AGREEMENT IN DEPICTING A TIGHT BAND OF MODERATE TO STRONG 280K-290K
ASCENT FROM W INTO CNTRL UPR MI BY 12Z. THE NAM HAS TRENDED TOWARD
THE GFS WITH GREATER LOW LVL SATURATION WITHOUT AS MUCH LAG BEHIND
THE MID LVL MOISTURE. HOWEVER...GIVEN THE VERY DRY ANTECEDENT
AIRMASS...PER 00 KSAW TAMDAR SNDGS...WILL KEEP ONLY CHANCE POPS
THROUGH THE OVERNIGHT. OVER THE WEST...ENOUGH MOISTURE FCST NEAR THE
-10C ISOTHERM...PER NAM SNDGS...FOR MAINLY SNOW CHANCES RATHER THAN
FREEZING DRIZZLE.
&&
.PREV DISCUSSION...ISSUED 313 PM EST THU JAN 25 2007
SHORT TERMTONIGHT)...
12Z RAOBS/WV IMAGERY AND RUC ANALYSIS SHOW HI AMPLITUDE TROF IN ERN
NAMERICA DOWNSTREAM OF RDG OVER THE ROCKIES. LES OVER THE FA
DOWNWIND OF LK SUP IN COLD NW FLOW BTWN ARCTIC HI PRES OVER ONTARIO
AND LO PRES IN THE LOWER GREAT LKS IS ON THE DIMINISHING TREND AS
VERY DRY/STABLE AIR SHOWN ON UPSTREAM 12Z RAOBS/TAMDAR SDNG FM CYQT
(INVRN BASE H925-95 AND PWAT AS LO AS 0.05 INCH) MOVES OVER THE UPR
LKS UNDER BLDG H5 HGTS/ INCRSG LARGER SCALE ACYC FLOW DESPITE SOME
LINGERING CNVGC ALG LK INDUCED TROFFING EXTENDING FM LO TO THE SE NW
ACRS LK HURON INTO ALGER COUNTY/CNTRL LK SUP. UPSTREAM...A SHRTWV
MOVING INTO NRN ALBERTA/SASKATCHEWAN IS TOPPING THE ROCKIES RDG.
QUITE A BIT OF MID CLD AND EVEN SOME PTCHY -SN NOTED FM SCNTRL CAN
INTO NE ND/NW MN IN THE SW FLOW/WAD PATTERN BTWN LO PRES ASSOCIATED
WITH THIS SHRTWV AND THE HI PRES SYS OVER ONTARIO AND THE UPR MS
RIVER VALLEY. PWAT 0.44 INCH AT YQD...SO THERE IS MORE MSTR AVBL TO
THIS SHRTWV.
MAIN FCST CONCERNS IN THE SHORT TERM ARE LINGERING LES TRENDS AND
-SN CHCS ASSOCIATED WITH SHRTWV NOW TOPPING ROCKIES RDG.
FOR TNGT...GUIDANCE SHOWS RISING HGTS OVER THE UPR GRT LKS IN
ADVANCE OF SHRTWV NOW OVER NRN ALBERTA/SASKATCHEWAN...WHICH IS FCST
TO REACH NR LK WINNIPEG BY 12Z FRI. AS HGTS RISE AND SFC RDG AXIS/
LOWER INVRN BASE/DEEPER DRY AIR PASSES ACRS THE CWA THIS EVNG UNDER
THE RISING HGTS...EXPECT LES TO DIMINISH AND THEN END WITH LTL
ADDITIONAL ACCUMULATION. WL LET ANY GOING HEADLINES EXPIRE AS
SCHEDULED. ALTHOUGH SKIES WL BE PCLDY FOR A TIME WITH ARRIVAL OF RDG
AXIS (EXCEPT OVER THE KEWEENAW WITH BKN-OVC SC LINGERING IN W-SW
FLOW EVEN ON BACK SIDE OF RDG)...NAM/GFS SHOW ISENTROPIC LIFT ON THE
280-290K SFCS OVERSPREADING THE FA QUICKLY AS SW RETURN FLOW DVLPS
IN THE WAKE OF DEPARTING SFC RDG. GFS IS MOST AGGRESSIVE AT PUSHING
HIER MID LVL MSTR TO THE E...AND USED ITS 280K SFC RH AOA 70 PCT TO
TIME ARRIVAL OF MID CLD AS THIS PROG APPEARS TO CORRELATE WELL WITH
OBSVD HI SC/LO AC CLD UPSTREAM. NAM FCSTS LLVLS BLO THE MID CLD DECK
REMAINING SO DRY THAT MODEL QPF IS ZERO...BUT GFS GENERATES SOME LGT
PCPN UNDER THE STRONGER ISENTROPIC LIFT AFT ABOUT 03Z OR SO OVER THE
W AND ACRS THE ENTIRE CWA AFT 06Z WITH ARRIVAL OF UPR DVGC IN RRQ OF
H3 JET MAX FCST TO MOVE OVER SE ONTARIO BY 12Z FRI. GFS FCST SDNGS
ARE QUITE A BIT MORE MOIST THRU MOST OF THE TROP IN LINE WITH OBSVD
12Z YQD SDNG...BUT MODEL FCST SDNGS DO SHOW LINGERING DRY LYR BTWN
H75-55...WHICH WOULD ALSO BE THE PRIME DENDRITIC SN GROWTH LYR.
CONSIDERING THIS DRY LYR AS WELL AS ANTECEDENT DRY AIR...LIMITED
COVG OF OBSVD SN UPSTREAM...AND NAM FCST...HAVE OPTED TO RETAIN POPS
BUT CUT VALUES FM HI CHC TO LWR CHC IN LINE WITH GFS MOS GUIDANCE.
AS FOR TEMPS...EXPECT MIN TEMPS RELATIVELY EARLY BEFORE THICKER MID
CLD/A BIT STRONGER SW FLOW DVLPS W-E AFT EARLY THIS EVNG.
KC
.LONG TERM (FRIDAY THROUGH THURSDAY)...
THE MAIN FORECAST CONCERN FOR THIS PORTION OF THE FORECAST REMAINS
THE LAKE EFFECT SNOW EVENT FOR LATE FRIDAY NIGHT THROUGH MUCH OF THE
WEEKEND.
ONCE AGAIN FOR THIS PERIOD...AM GENERALLY DISCOUNTING THE NAM...AS
IT IS OUT OF BOUNDS WHEN COMPARED TO THE GLOBAL MODELS. AS A
RESULT...HAVE LEANED THIS FORECAST CLOSER TO THE GFS SOLUTION.
GFS OFF OF BUFKIT IS PUTTING OUT OVER HALF AN INCH OF QFP OVER IWD
DURING THE NEXT 5 DAYS. CONTINUE TO MONITOR THE TRACK OF THE
SURFACE LOW...CURRENTLY CENTERED OVER THE SOUTHERN NORTHWEST
TERRITORIES SLIDING INTO NORTHERN SASKATCHEWAN. THIS LOW WILL SLIDE
SOUTHEASTWARD...AND OVER THE WESTERN HALF OF LAKE SUPERIOR BY FRIDAY
AFTERNOON AND THEN SOUTHEASTWARD OVER LAKE HURON BY 12Z SATURDAY.
THIS WILL FIRST ALLOW FOR A LONG SOUTHERLY FETCH ACROSS LAKE
MICHIGAN LATE FRIDAY MORNING THROUGH EARLY AFTERNOON (GENERALLY 2 TO
4 INCHES OF SNOW EXPECTED ACROSS THIS AREA FRIDAY)...AND THEN SWING
THE WINDS OUT OF A GENERALLY NORTH TO NORTHWESTERLY DIRECTION FRIDAY
NIGHT (AND KEEP THEM BETWEEN 300 AND 030 THROUGH TUESDAY). 850MB
TEMPERATURES...AFTER WARMING TO -7C OR SO FRIDAY WILL COOL DOWN TO
-12C ACROSS THE AREA BY 12Z SATURDAY...ALLOWING FOR A BETTER CHANCE
OF LAKE EFFECT OR LAKE ENHANCED SNOW. 850MB TEMPERATURES WILL THEN
SLOWLY COOL TO -20 TO -22C BY 06Z SUNDAY. GIVEN THIS...HAVE HOISTED
LAKE EFFECT SNOW WATCHES FOR GOGEBIC...ONTONAGON...MARQUETTE...AND
ALGER COUNTIES FOR SATURDAY MORNING THROUGH MID DAY SUNDAY.
FOR FRIDAY NIGHT HAVE ADJUSTED TEMPS DOWN A COUPLE OF DEGREES ACROSS
OUR CLIMATOLOGICALLY COOLER SOUTH CENTRAL CWA...WITH THE IDEA THAT
THE DRY SLOT MAY COME IN EARLY AND ALLOW TEMPS TO DROP. FIRST COLD
FRONT IS EXPECTED TO CROSS THE CWA LATE FRIDAY AFTERNOON THROUGH 06Z
SATURDAY. COOLER TEMPS ALOFT WILL TAKE A BIT LONGER TO SLIDE IN.
EXPECT THE SINGLE DIGITS TO LOW TEENS FOR HIGH TEMPERATURES
SUNDAY...AS THE COLDEST AIR SINKS OVERHEAD. WINDS BACK SLIGHTLY
SUNDAY...ADDING TO THE CONVERGENCE OVER THE EASTERN THIRD OF THE
LAKE SUPERIOR SHORELINE FROM MUNISING EAST. AS HAS BEEN THE TREND
OVER THE LAST COUPLE OF SHIFTS...HAVE INCREASED POPS HERE TO
DEFINITE. AS FOR RIGHT NOW...DO NOT HAVE ANY WATCHES/WARNINGS OR
ADVISORIES POSTED FOR THE EASTERN PORTIONS OF THE CWA (EXCEPT ALGER
COUNTY)...BUT AS THE TIME NEARS HEADLINES WILL LIKELY BE NEEDED.
MONDAY THROUGH THURSDAY (DAYS 4-7)...WITH THE RELATIVE CONSISTENCY
IN THE EXTENDED RANGE...WITH LESS MODEL FLIP FLOPPING THAN
USUAL...FEW CHANGES WERE MADE...PARTICULARLY TO TEMPERATURES.
STILL...DID COOL DOWN TEMPERATURES ROUGHLY 4 DEGREES ACROSS THE
BOARD MONDAY AFTERNOON. SO THE OVERALL PATTERN INCLUDES A SERIES OF
SHORTWAVES IN THE POLAR/ARCTIC JET CONTINUALLY RE-ENFORCING OUR
ALREADY COLD AIRMASS.
MONDAY 12Z...LOOKING AT THE MID LEVELS...THE GFS AND ECMWF BEGIN TO
BECOME A LITTLE MORE NOTICEABLE IN THERE DIFFERENCES. THE 500MB
DEPICTED BY THE GFS...ALTHOUGH SIMILAR IN STRENGTH IS ABLE TO SLIDE
FURTHER SOUTHWARD...MAKING IT INTO EASTERN LAKE HURON BY THIS
TIME...WHILE THE ECMWF HAS IT REMAINING OVER EASTERN HUDSON BAY. AS
PREVIOUSLY STATED...GENERALLY DISREGARDED THIS DISCREPANCY...AND
SIDED CLOSER TO THE GFS SOLUTION. UPDATED AND INCREASED CLOUD COVER
FOR MONDAY INTO MONDAY NIGHT...AS SHORTWAVE SLIDES IN FROM THE
NORTHWEST...ACCORDING TO THE 06Z GFS. ALTHOUGH IT SEEMS THAT THE
SHORTWAVE HAS DROPPED FURTHER SOUTH FOR THE 12Z GFS RUN...STILL
BELIEVE THAT WE WILL HAVE MORE THAN 40 PERCENT CLOUD COVER FOR THIS
PERIOD...SO HAVE KEPT THE ADJUSTED MORE PESSIMISTIC CLOUD FOR MONDAY
INTO MONDAY NIGHT.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
LAKE EFFECT SNOW WATCH FROM SATURDAY MORNING THROUGH SUNDAY
AFTERNOON FOR MIZ005-006.
LAKE EFFECT SNOW WATCH FROM LATE FRIDAY NIGHT THROUGH SUNDAY
MORNING FOR MIZ002-009.
&&
$$
.UPDATE...JLB
.SHORT TERM...KC
.LONG TERM...KF
AREA FORECAST DISCUSSION...UPDATE
NWS MARQUETTE MI
AFDMQT 1110 AM EST WED JAN 24 2007
.SECOND UPDATE...
OPTED TO ISSUE LAKE EFFECT SNOW WARNING FOR ALGER COUNTY PER RECENT
SPOTTER REPORT OF 4"/4 HRS NEAR AU TRAIN. WRN LES BAND IN MORE
FOCUSED LLVL CNVGC STREAMING INTO AREAS BTWN MUNISING AND DEERTON IS
PERSISTING...AND REFLECTIVIES HAVE INCRSD IN UPSTREAM PORTIONS OF
THE BAND WITH GREATER COVG OF REFLECTIVITIES AOA 28DBZ. WITH ARRIVAL
OF DPVA/DEEPER MSTR THIS AFTN AND POTENTIAL FOR SGNFT SN TNGT INTO
THU...SEEMS LIKELY SN FALL AOA 10 INCHES/24 HRS WL OCCUR IN WRN
ALGER COUNTY.
KC
.UPDATE...
MQT 88D SHOWS LES BANDS CONTINUING TO DRIFT INTO ALGER COUNTY THIS
MRNG. MOST OF THE BANDS LOOK RATHER DISORGANIZED WITH RELATIVELY DRY
AIR SHOWN BY 12Z TAMDAR SDNG FM SAW IN THE SUB INVRN (ARND H825)
LYR. A FEW REFLECTIVITIES AOA 28DBZ NOTED IN THE FAR WRN BAND OVER
WRN ALGER COUNTY WHERE W LAND BREEZE OFF THE W HALF OF UPR MI
CONVERGING WITH MORE ELY LAND BREEZE OFF ONTARIO. SPOTTER REPORT FM
NEAR AU TRAIN INDICATES 2" FELL THERE IN THE LAST COUPLE OF HRS.
AWAY FM LK EFFECT AREAS E OF MQT...SKIES ARE PCLDY WITH DRY LYR
SHOWN ABV INVRN BASE. NEXT SHRTWV OF CONCERN DROPPING SEWD NR LK
WINNIPEG AT 14Z. ASSOCIATED SFC LO LOCATED OVER NW ONTARIO TO THE
NNW OF INL. SOME LGT -SN NOTED OVER NRN MN/ADJOINING NW ONTARIO...
BUT OVERALL PCPN COVG/INTENSITY ACCOMPANYING THESE FEATURES IS
LIMITED BY DRY AIR SHOWN ON THE 12Z INL/YPL/YQD RAOBS AND MINIMAL
ISENTROPIC LIFT. LEADING EDGE OF THICKER CLD IN ADVANCE OF THIS
SHRTWV NOW APRCHG WRN LK SUP.
MAIN FCST CONCERNS IN THE SHORT TERM ARE LES TRENDS AND SN CHCS
ASSOCIATED WITH SHRTWV NOW MOVING THRU MANITOBA.
LATEST NAM/RUC SHOW SHRTWV NOW OVER MANITOBA DIGGING INTO NRN WI BY
00Z THU...WITH DVPA/H85-5 QVECTOR CNVGC/AREA OF HIER H7 RH
ASSOCIATED WITH OBSVD THICKER CLD AND SOME -SN ON THE CYC SIDE OF
THIS FEATURE IMPACTING THE FA THIS AFTN BEFORE DEPARTING THIS EVNG.
SINCE AIRMASS OVHD IS QUITE DRY AND ISENTROPIC LIFT PROGGED TO
REMAIN NEGLIBLE...THINK SYNOPTIC SN/HIER POPS ASSOCIATED WITH
INCOMING DYNAMICS WL BE RESTRICTED TO AREAS WHERE LKS CAN MOISTEN
THE ATMOSPHERE SIGNIFICANTLY. OTRW...LATEST RUC13/LOCAL HI RES WRF
MODEL INDICATE VORTEX WL DVLP NR MUNISING BAY ALG CONFLUENCE AXIS
STRETCHING FM ECNTRL LK SUP-P53-ISQ. IF THIS VORTEX DVLPS AS FCST...
STRONGER LES BAND NOW IMPACTING WRN ALGER COUNTY SHOULD WEAKEN AND
MOVE OFF TO THE NE. ON THE OTHER HAND...IF THIS FEATURE FAILS TO
DVLP...LES BANDS MAY INTENSIFY ALG CURRENT AXIS IN WRN ALGER COUNTY
ONCE SHARPER DPVA ARRIVES THIS AFTN. WITH EXPECTED HEAVIER SHSN TNGT
IN WRN ALGER COUNTY...MAY NEED TO ISSUE WRNG IF BAND PERSISTS IN THE
SAME AREA FOR A LONGER TIME.
MIXING TO INVRN BASE ON 12Z INL RAOB/TAMDAR SDNG FM SAW WOULD
SUPPORT HI TEMPS IN THE 15-20 RANGE...NOT FAR FM GOING FCST. WL
ADJUST FCST HI TEMPS DOWN A BIT OVER THE W.
KC
&&
.PREVIOUS DISCUSSION (ISSUED AT 436 AM)...
09Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED A POSITIVE
PNA PATTERN...WITH RIDGING ACROSS WESTERN NORTH AMERICA AND
TROUGHING ACROSS EASTERN NORTH AMERICA. THE CENTER OF THIS TROUGH IS
A 500 DAM LOW COVERING MUCH OF HUDSON AND JAMES BAYS. CHILLY 850MB
TEMPS EXIST UNDER AND WEST OF THE UPPER LOW...NOTED BY 00Z SOUNDINGS
OF -23C AT CHURCHILL MB...-22C AT PICKLE LAKE AND -25C AT MOOSONEE.
NW WINDS AT 850MB CONTINUE TO BRING THIS COLDER AIR DOWN TOWARDS
LAKE SUPERIOR...WITH RUC ANALYSIS SUGGESTING -15 TO -18C 850MB TEMPS
RIGHT NOW OVER THE LAKE. WITH LAKE TEMPS OF 2-3C...PLENTY OF
INSTABILITY EXISTS FOR LAKE EFFECT. HOWEVER...DRY AIR SEEN ON A 00Z
TAMDAR SOUNDING FROM INL AND THE 00Z RAOB FROM PICKLE LAKE IS HAVING
A CONSIDERABLE IMPACT...ONLY ALLOWING FOR A FEW BANDS ON WESTERN
LAKE SUPERIOR. THANKS TO LONGER FETCH...BANDS CONTINUE ON EASTERN
LAKE SUPERIOR...THOUGH THESE ARE ALSO FEELING THE DRY AIR WITH THE
BANDS SPACED FAIRLY FAR APART AND DISORGANIZED. OUTSIDE OF THE LAKE
EFFECT... CONDITIONS ARE FAIRLY QUIET THANKS TO BOTH THE DRY AIR AND
A 1020MB HIGH BUILDING SOUTHWARD FROM NW ONTARIO BEHIND THE SURFACE
TROUGH THAT WENT THROUGH YESTERDAY. THE WEAKENING PRESSURE GRADIENT
COMBINED WITH MAINLY CLEAR SKIES IN THE INTERIOR HAS ALLOWED TEMPS
TO DROP TO -10F BELOW ZERO AT WATERSMEET. THIS COLD AIR OVER THE
INTERIOR AND WARMER LAKE WATERS HAS RESULTED IN THE DEVELOPMENT OF
SOME LAND BREEZES...WHICH ARE ALSO AFFECTING THE LAKE EFFECT BANDS.
TO THE NW...A SHRTWV CAN BE SEEN DROPPING SE THROUGH CENTRAL
MANITOBA. SOME LIGHT SNOW HAS BEEN GOING ON TO THE S OF THE SHRTWV
ON THE N END OF LAKE WINNIPEG WHERE BETTER LOW LEVEL MOISTURE EXISTS
(SEE THE 00Z THE PAS SOUNDING). LASTLY...A STRONG SHRTWV IS ABOUT
READY TO TOP THE WESTERN NORTH AMERICA RIDGE. THIS SHRTWV IS PROGGED
TO AFFECT THE CWA FRI/SAT.
MAIN FORECAST CONCERNS ARE LES AMOUNTS TONIGHT AND CLIPPER SYSTEM
FOR FRI AND SAT.
TODAY...THE SHRTWV OVER MANITOBA IS PROGGED TO CONTINUE MOVING SE
THROUGH THE NW FLOW ALOFT...REACHING NORTHERN WISCONSIN AROUND 00Z.
THIS SHRTWV WILL HELP BRING THE LOW LEVEL MOISTURE AND LIGHT SNOW
OCCURRING THERE INTO THE CWA THIS AFTERNOON...AS NOTED BY 850MB RH
PROGS. SINCE NAM AND GFS SOUNDINGS DEPICT DECENT OMEGA WITHIN THE
DENDRITIC SNOW GROWTH ZONE...ALONG WITH DEEP MOISTURE UP TO
10000-12000 FT...WOULD NOT BE SURPRISED TO SEE A QUICK INCH OF
SNOWFALL ACROSS THE WEST HALF OF THE CWA. AS FAR AS THE LAKE EFFECT
GOES...THE 00Z 13KM RUC DEPICTS AN INTERESTING SCENARIO...SUGGESTING
THE DEVELOPMENT OF A MESO-LOW THIS MORNING NEAR MUNISING WHICH
BRIEFLY MOVES NE OVER THE LAKE...THEN BACK S THIS AFTERNOON. THE 03Z
RUC IS SIMILAR. THE GFS/NAM AND LOCAL WRF-ARW MODELS HERE SUGGEST
MULTI-PARALLEL BANDS TO CONTINUE. FOR NOW...WILL MAINTAIN NUMEROUS
SNOW SHOWERS EAST OF MARQUETTE WITH AN INCH OR TWO OF ACCUMULATION
TODAY...BUT SNOW AMOUNTS WILL NEED TO BE WATCHED IF THE MESO-LOW
SCENARIO DOES PAN OUT. WILL ALSO PUT NUMEROUS SNOW SHOWERS IN THE
FAR WESTERN U.P. WITH THE IDEA OF A LAKE ENHANCEMENT SCENARIO. GOING
FORECAST TEMPS LOOK REASONABLE.
TONIGHT...MODELS PROG THAT THE SHRTWV OVER NORTHERN WISCONSIN WILL
CONTINUE SE WHILE ANOTHER SHRTWV ON THE WEST SIDE OF THE HUDSON BAY
UPPER LOW DROPS S ACROSS FAR EASTERN LAKE SUPERIOR AFTER MIDNIGHT.
BOTH OF THESE SHRTWVS HELP IN DRAWING ANOTHER SURGE OF COLD AIR
SOUTHWARD FROM ONTARIO (850MB TEMPS FALL TO -20C WEST TO -26C EAST
AT 12Z THU)...STRENGTHENING THE HIGH PRESSURE AREA OVER NW ONTARIO
AND INTENSIFYING THE SURFACE TROUGH THAT HAS BEEN NEARLY STATIONARY
OVER THE CWA. ALTHOUGH THIS TROUGH WILL BE DROPPING S WITH THE
NORTHERN WISCONSIN SHRTWV...A BREEZY NORTH WIND WILL DEVELOP AS A
RESULT OF THE TIGHT PRESSURE GRADIENT. THEREFORE...WITH THE COLD AIR
ADVECTION...NUMEROUS MULTI-PARALLEL BANDS ARE EXPECTED TO OCCUR
ACROSS ALL OF THE NORTHERN U.P. WITH THE BANDS LIKELY CROSSING DELTA
AND SOUTHERN SCHOOLCRAFT COUNTIES. AMOUNTS ARE A BIG QUESTION. FOR
THE WESTERN U.P....CONVERGENCE IS EXPECTED IN THE PORCUPINE
MOUNTAINS AND COPPER PEAK AREA. HOWEVER...INVERSION HEIGHTS ARE
AROUND 850MB AND THERE IS EXPOSURE TO PLENTY OF DRY AIR...WHICH MAY
LIMIT SNOW AMOUNTS. FOR NOW WILL GO SUB-ADVISORY. FOR THE EASTERN
U.P....THERE ARE INDICATIONS FROM THE NAM/REGIONAL CANADIAN AND 13KM
RUC THAT A LAKE INDUCED SURFACE TROUGH MAY FORM EARLY THIS EVENING
AND ALIGN ITSELF FROM THE TIP OF THE KEWEENAW SOUTHEASTWARD TO
TRAVERSE CITY. SOUNDINGS UNDER THE TROUGH SHOW BEFORE 06Z AN
INVERSION HEIGHT AROUND 800MB WITH A SNOW GROWTH LAYER BETWEEN
925-875MB. WITH CONVERGENCE ALONG THE BAND...THIS WOULD BE A GOOD
SETUP FOR HEAVY SNOW...WITH PERHAPS INCH AN HOUR RATES. AFTER
06Z...TOO MUCH COLD AIR IS ADVECTED IN AND THE DENDRITIC GROWTH SNOW
LAYER BASICALLY DISAPPEARS...ALONG WITH THE INVERSION LOWERING TO
850MB. FOR NOW...WILL PUT AN ADVISORY FOR ALGER COUNTY SINCE THIS IS
WHERE THE CONVERGENCE IS MAXIMIZED. IF CURRENT TRENDS CONTINUE
SUGGESTING HEAVY SNOW...A WARNING MAY BE NEEDED. CONFIDENCE IS LOWER
FOR MARQUETTE AND NORTHERN SCHOOLCRAFT COUNTIES AS LAND BREEZES MAY
KEEP THE BAND FROM MOVING INTO EITHER OF THESE AREAS.
THU...MODELS SHOW THAT THE UPPER TROUGH THAT WILL BE OVER THE GREAT
LAKES AT 12Z THU WILL BEGIN TO MOVE EASTWARD DURING THE DAY AS A
RESULT OF THE STRONG SHRTWV CURRENTLY AT THE TOP OF THE WESTERN
NORTH AMERICA RIDGE DIGGING INTO SASKATCHEWAN. THIS MOTION WILL HELP
BRING IN THE HIGH PRESSURE CENTER OVER NW ONTARIO DOWN OVER UPPER
MICHIGAN BY 00Z. THEREFORE...PLANS FOR THE LAKE EFFECT TO DIMINISH
WEST TO EAST STILL LOOK REASONABLE...WITH LOWERING INVERSION HEIGHTS
AND DRIER AIR MOVING IN. THE EASTERN CWA MAY STILL SEE AN ADDITIONAL
INCH OR TWO UNTIL THE DRIER AIR MOVES IN...WHICH PUTS ALGER COUNTY
CLOSE TO 24 HR WARNING CRITERIA. IN ADDITION TO THE DRIER
AIR...THERE WILL BE SOME WARM ADVECTION TOO...WITH 850MB TEMPS
RISING TO -12C WEST TO -20C EAST BY 00Z...THOUGH MUCH OF THIS
ADVECTION WILL NOT BE REALIZED AT THE SURFACE DUE TO CHILLY AIR
MOVING IN ASSOCIATED WITH THE RIDGE. GOING FORECAST TEMPS LOOK GOOD.
THU NIGHT AND FRI...MODEL TRENDS WITH THE GFS/UKMET AND ECMWF NOW
INDICATE THAT THE SHRTWV/CLIPPER SYSTEM OVER SASKATCHEWAN WILL BE
QUICKER TO ARRIVE THAN PREVIOUSLY EXPECTED. THIS HAS RESULTED IN
QUITE A FEW CHANGES TO THE FORECAST. FIRST...WARM AIR
ADVECTION/ISENTROPIC LIFTING AHEAD OF THE TROUGH IS EXPECTED TO
DEVELOP A BAND OF MID AND HIGH CLOUDS ACROSS MINNESOTA THU EVENING.
THESE WILL MOVE INTO THE CWA THU NIGHT AND ALSO GET LOWER AS
ISENTROPIC LIFT INCREASES. IN ADDITION...THERE ARE INDICATIONS OF A
120KT JET STREAK MOVING SOUTHEASTWARD ACROSS LAKE SUPERIOR INTO LAKE
HURON...WHICH WOULD PLACE THE CWA IN THE UPPER DIVERGENCE REGION OF
THE JET. HAVE INCLUDED CHANCE POPS AFTER MIDNIGHT FOR THE WEST HALF
OF THE CWA DUE TO THE ISENTROPIC LIFT/UPPER DIVERGENCE. FOR
FRIDAY...THIS CHANCE IS SPREAD ACROSS THE ENTIRE CWA. THE SNOW MAY
ONLY END UP BEING IN THE MORNING SINCE A DRY SLOT IS PROGGED TO COME
IN ALOFT...BUT SINCE THERE STILL ARE SOME TIMING DIFFERENCES...WITH
THE NAM SUGGESTING A SLOWER SOLUTION THAN THE GFS/UKMET/ECMWF...FEEL
KEEPING A POP IN ALL DAY IS WARRANTED. ANOTHER ITEM TO WATCH WITH
THIS CLIPPER IS A POTENTIAL DOMINANT LES BAND OFF LAKE MICHIGAN DUE
TO SOUTHERLY FLOW AHEAD OF THE CLIPPER...WHICH WOULD AFFECT THE FAR
EASTERN CWA.
HOW QUICK THE CLOUDS COME IN...ALONG WITH THE EXIT SPEED OF THE
SURFACE HIGH...WILL DETERMINE HOW LOW TEMPERATURES FALL THU EVENING.
SINCE TEMPERATURES ARE ONLY EXPECTED IN THE MID TEENS ON
THU...TEMPERATURES SHOULD REALLY DROP AFTER SUNSET. HAVE WENT CLOSER
TO THE MAV COOP GUIDANCE FOR LOWS. READINGS WILL THEN CLIMB AFTER
MIDNIGHT AS RETURN FLOW SETS UP. HAVE WARMED READINGS ON FRI AS
BREEZY SOUTHWESTERLY FLOW ON THE SE SIDE OF THE CLIPPER WILL HELP
DRAW WARMER AIR IN.
FRI NIGHT THROUGH SAT NIGHT...THE SHRTWV ASSOCIATED WITH THE CLIPPER
IS PROGGED TO MOVE INTO UPPER MICHIGAN ON SAT...WHILE THE ASSOCIATED
SURFACE LOW MOVES INTO LAKE HURON. THE FIRST COLD FRONT ASSOCIATED
WITH THE LOW WILL HELP TO BRING IN COLDER 850MB TEMPS ON WESTERLY
WINDS (AROUND -14C). THEREFORE HAVE RAISED POPS TO LIKELY FOR THE
WESTERN U.P.. THE SNOW GETS MORE INTERESTING ON SAT AS A SECONDARY
COLD FRONT MOVES SOUTHWARD ACROSS THE LAKE. THIS COLD FRONT MAY HAVE
AN INTENSE SNOW BAND ALONG IT...GIVEN THAT THERE WILL BE PLENTY OF
MOISTURE PRESENT ASSOCIATED WITH THE SHRTWV AND 850MB TEMPS ARE
BETWEEN -14 AND -16C (DENDRITIC SNOW GROWTH LAYER TEMPS) WHEN THE
FRONT MOVES THROUGH. A GFS SOUNDING FOR 18Z SAT FOR MQT ACTUALLY
SHOWS VERY LITTLE IF ANY INVERSION BELOW THE TROPOPAUSE
INVERSION...WHICH WOULD SUGGEST DEEP SNOW GROWTH. MULTI-PARALLEL
BANDS...PERHAPS WITH A FEW HEAVIER BANDS WHERE CONVERGENCE CAN SET
UP (E.G. IRONWOOD AND MARQUETTE COUNTY) WILL FOLLOW IN THE WAKE OF
THE SHRTWV SAT NIGHT AS 850MB TEMPS FALL TO AROUND -20C. WILL
MENTION THIS EVENT IN THE HWO.
EXTENDED...NO CHANGES MADE FROM SUNDAY ONWARDS. OVERALL
THOUGH...LOOKS LIKE THE OVERALL COOL PATTERN WILL CONTINUE AS LONG
RANGE PROGS SUGGEST THE POSITIVE PNA PATTERN WILL STAY IN PLACE.
AJ
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
LAKE EFFECT SNOW WARNING FOR MIZ006 REST OF TODAY THRU THURSDAY.
&&
$$
AREA FORECAST DISCUSSION...CORRECTED
NWS MARQUETTE MI
AFDMQT 1030 AM EST WED JAN 24 2007
.UPDATE...
MQT 88D SHOWS LES BANDS CONTINUING TO DRIFT INTO ALGER COUNTY THIS
MRNG. MOST OF THE BANDS LOOK RATHER DISORGANIZED WITH RELATIVELY DRY
AIR SHOWN BY 12Z TAMDAR SDNG FM SAW IN THE SUB INVRN (ARND H825)
LYR. A FEW REFLECTIVITIES AOA 28DBZ NOTED IN THE FAR WRN BAND OVER
WRN ALGER COUNTY WHERE W LAND BREEZE OFF THE W HALF OF UPR MI
CONVERGING WITH MORE ELY LAND BREEZE OFF ONTARIO. SPOTTER REPORT FM
NEAR AU TRAIN INDICATES 2" FELL THERE IN THE LAST COUPLE OF HRS.
AWAY FM LK EFFECT AREAS E OF MQT...SKIES ARE PCLDY WITH DRY LYR
SHOWN ABV INVRN BASE. NEXT SHRTWV OF CONCERN DROPPING SEWD NR LK
WINNIPEG AT 14Z. ASSOCIATED SFC LO LOCATED OVER NW ONTARIO TO THE
NNW OF INL. SOME LGT -SN NOTED OVER NRN MN/ADJOINING NW ONTARIO...
BUT OVERALL PCPN COVG/INTENSITY ACCOMPANYING THESE FEATURES IS
LIMITED BY DRY AIR SHOWN ON THE 12Z INL/YPL/YQD RAOBS AND MINIMAL
ISENTROPIC LIFT. LEADING EDGE OF THICKER CLD IN ADVANCE OF THIS
SHRTWV NOW APRCHG WRN LK SUP.
MAIN FCST CONCERNS IN THE SHORT TERM ARE LES TRENDS AND SN CHCS
ASSOCIATED WITH SHRTWV NOW MOVING THRU MANITOBA.
LATEST NAM/RUC SHOW SHRTWV NOW OVER MANITOBA DIGGING INTO NRN WI BY
00Z THU...WITH DVPA/H85-5 QVECTOR CNVGC/AREA OF HIER H7 RH
ASSOCIATED WITH OBSVD THICKER CLD AND SOME -SN ON THE CYC SIDE OF
THIS FEATURE IMPACTING THE FA THIS AFTN BEFORE DEPARTING THIS EVNG.
SINCE AIRMASS OVHD IS QUITE DRY AND ISENTROPIC LIFT PROGGED TO
REMAIN NEGLIBLE...THINK SYNOPTIC SN/HIER POPS ASSOCIATED WITH
INCOMING DYNAMICS WL BE RESTRICTED TO AREAS WHERE LKS CAN MOISTEN
THE ATMOSPHERE SIGNIFICANTLY. OTRW...LATEST RUC13/LOCAL HI RES WRF
MODEL INDICATE VORTEX WL DVLP NR MUNISING BAY ALG CONFLUENCE AXIS
STRETCHING FM ECNTRL LK SUP-P53-ISQ. IF THIS VORTEX DVLPS AS FCST...
STRONGER LES BAND NOW IMPACTING WRN ALGER COUNTY SHOULD WEAKEN AND
MOVE OFF TO THE NE. ON THE OTHER HAND...IF THIS FEATURE FAILS TO
DVLP...LES BANDS MAY INTENSIFY ALG CURRENT AXIS IN WRN ALGER COUNTY
ONCE SHARPER DPVA ARRIVES THIS AFTN. WITH EXPECTED HEAVIER SHSN TNGT
IN WRN ALGER COUNTY...MAY NEED TO ISSUE WRNG IF BAND PERSISTS IN THE
SAME AREA FOR A LONGER TIME.
MIXING TO INVRN BASE ON 12Z INL RAOB/TAMDAR SDNG FM SAW WOULD
SUPPORT HI TEMPS IN THE 15-20 RANGE...NOT FAR FM GOING FCST. WL
ADJUST FCST HI TEMPS DOWN A BIT OVER THE W.
KC
&&
.PREVIOUS DISCUSSION (ISSUED AT 436 AM)...
09Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED A POSITIVE
PNA PATTERN...WITH RIDGING ACROSS WESTERN NORTH AMERICA AND
TROUGHING ACROSS EASTERN NORTH AMERICA. THE CENTER OF THIS TROUGH IS
A 500 DAM LOW COVERING MUCH OF HUDSON AND JAMES BAYS. CHILLY 850MB
TEMPS EXIST UNDER AND WEST OF THE UPPER LOW...NOTED BY 00Z SOUNDINGS
OF -23C AT CHURCHILL MB...-22C AT PICKLE LAKE AND -25C AT MOOSONEE.
NW WINDS AT 850MB CONTINUE TO BRING THIS COLDER AIR DOWN TOWARDS
LAKE SUPERIOR...WITH RUC ANALYSIS SUGGESTING -15 TO -18C 850MB TEMPS
RIGHT NOW OVER THE LAKE. WITH LAKE TEMPS OF 2-3C...PLENTY OF
INSTABILITY EXISTS FOR LAKE EFFECT. HOWEVER...DRY AIR SEEN ON A 00Z
TAMDAR SOUNDING FROM INL AND THE 00Z RAOB FROM PICKLE LAKE IS HAVING
A CONSIDERABLE IMPACT...ONLY ALLOWING FOR A FEW BANDS ON WESTERN
LAKE SUPERIOR. THANKS TO LONGER FETCH...BANDS CONTINUE ON EASTERN
LAKE SUPERIOR...THOUGH THESE ARE ALSO FEELING THE DRY AIR WITH THE
BANDS SPACED FAIRLY FAR APART AND DISORGANIZED. OUTSIDE OF THE LAKE
EFFECT... CONDITIONS ARE FAIRLY QUIET THANKS TO BOTH THE DRY AIR AND
A 1020MB HIGH BUILDING SOUTHWARD FROM NW ONTARIO BEHIND THE SURFACE
TROUGH THAT WENT THROUGH YESTERDAY. THE WEAKENING PRESSURE GRADIENT
COMBINED WITH MAINLY CLEAR SKIES IN THE INTERIOR HAS ALLOWED TEMPS
TO DROP TO -10F BELOW ZERO AT WATERSMEET. THIS COLD AIR OVER THE
INTERIOR AND WARMER LAKE WATERS HAS RESULTED IN THE DEVELOPMENT OF
SOME LAND BREEZES...WHICH ARE ALSO AFFECTING THE LAKE EFFECT BANDS.
TO THE NW...A SHRTWV CAN BE SEEN DROPPING SE THROUGH CENTRAL
MANITOBA. SOME LIGHT SNOW HAS BEEN GOING ON TO THE S OF THE SHRTWV
ON THE N END OF LAKE WINNIPEG WHERE BETTER LOW LEVEL MOISTURE EXISTS
(SEE THE 00Z THE PAS SOUNDING). LASTLY...A STRONG SHRTWV IS ABOUT
READY TO TOP THE WESTERN NORTH AMERICA RIDGE. THIS SHRTWV IS PROGGED
TO AFFECT THE CWA FRI/SAT.
MAIN FORECAST CONCERNS ARE LES AMOUNTS TONIGHT AND CLIPPER SYSTEM
FOR FRI AND SAT.
TODAY...THE SHRTWV OVER MANITOBA IS PROGGED TO CONTINUE MOVING SE
THROUGH THE NW FLOW ALOFT...REACHING NORTHERN WISCONSIN AROUND 00Z.
THIS SHRTWV WILL HELP BRING THE LOW LEVEL MOISTURE AND LIGHT SNOW
OCCURRING THERE INTO THE CWA THIS AFTERNOON...AS NOTED BY 850MB RH
PROGS. SINCE NAM AND GFS SOUNDINGS DEPICT DECENT OMEGA WITHIN THE
DENDRITIC SNOW GROWTH ZONE...ALONG WITH DEEP MOISTURE UP TO
10000-12000 FT...WOULD NOT BE SURPRISED TO SEE A QUICK INCH OF
SNOWFALL ACROSS THE WEST HALF OF THE CWA. AS FAR AS THE LAKE EFFECT
GOES...THE 00Z 13KM RUC DEPICTS AN INTERESTING SCENARIO...SUGGESTING
THE DEVELOPMENT OF A MESO-LOW THIS MORNING NEAR MUNISING WHICH
BRIEFLY MOVES NE OVER THE LAKE...THEN BACK S THIS AFTERNOON. THE 03Z
RUC IS SIMILAR. THE GFS/NAM AND LOCAL WRF-ARW MODELS HERE SUGGEST
MULTI-PARALLEL BANDS TO CONTINUE. FOR NOW...WILL MAINTAIN NUMEROUS
SNOW SHOWERS EAST OF MARQUETTE WITH AN INCH OR TWO OF ACCUMULATION
TODAY...BUT SNOW AMOUNTS WILL NEED TO BE WATCHED IF THE MESO-LOW
SCENARIO DOES PAN OUT. WILL ALSO PUT NUMEROUS SNOW SHOWERS IN THE
FAR WESTERN U.P. WITH THE IDEA OF A LAKE ENHANCEMENT SCENARIO. GOING
FORECAST TEMPS LOOK REASONABLE.
TONIGHT...MODELS PROG THAT THE SHRTWV OVER NORTHERN WISCONSIN WILL
CONTINUE SE WHILE ANOTHER SHRTWV ON THE WEST SIDE OF THE HUDSON BAY
UPPER LOW DROPS S ACROSS FAR EASTERN LAKE SUPERIOR AFTER MIDNIGHT.
BOTH OF THESE SHRTWVS HELP IN DRAWING ANOTHER SURGE OF COLD AIR
SOUTHWARD FROM ONTARIO (850MB TEMPS FALL TO -20C WEST TO -26C EAST
AT 12Z THU)...STRENGTHENING THE HIGH PRESSURE AREA OVER NW ONTARIO
AND INTENSIFYING THE SURFACE TROUGH THAT HAS BEEN NEARLY STATIONARY
OVER THE CWA. ALTHOUGH THIS TROUGH WILL BE DROPPING S WITH THE
NORTHERN WISCONSIN SHRTWV...A BREEZY NORTH WIND WILL DEVELOP AS A
RESULT OF THE TIGHT PRESSURE GRADIENT. THEREFORE...WITH THE COLD AIR
ADVECTION...NUMEROUS MULTI-PARALLEL BANDS ARE EXPECTED TO OCCUR
ACROSS ALL OF THE NORTHERN U.P. WITH THE BANDS LIKELY CROSSING DELTA
AND SOUTHERN SCHOOLCRAFT COUNTIES. AMOUNTS ARE A BIG QUESTION. FOR
THE WESTERN U.P....CONVERGENCE IS EXPECTED IN THE PORCUPINE
MOUNTAINS AND COPPER PEAK AREA. HOWEVER...INVERSION HEIGHTS ARE
AROUND 850MB AND THERE IS EXPOSURE TO PLENTY OF DRY AIR...WHICH MAY
LIMIT SNOW AMOUNTS. FOR NOW WILL GO SUB-ADVISORY. FOR THE EASTERN
U.P....THERE ARE INDICATIONS FROM THE NAM/REGIONAL CANADIAN AND 13KM
RUC THAT A LAKE INDUCED SURFACE TROUGH MAY FORM EARLY THIS EVENING
AND ALIGN ITSELF FROM THE TIP OF THE KEWEENAW SOUTHEASTWARD TO
TRAVERSE CITY. SOUNDINGS UNDER THE TROUGH SHOW BEFORE 06Z AN
INVERSION HEIGHT AROUND 800MB WITH A SNOW GROWTH LAYER BETWEEN
925-875MB. WITH CONVERGENCE ALONG THE BAND...THIS WOULD BE A GOOD
SETUP FOR HEAVY SNOW...WITH PERHAPS INCH AN HOUR RATES. AFTER
06Z...TOO MUCH COLD AIR IS ADVECTED IN AND THE DENDRITIC GROWTH SNOW
LAYER BASICALLY DISAPPEARS...ALONG WITH THE INVERSION LOWERING TO
850MB. FOR NOW...WILL PUT AN ADVISORY FOR ALGER COUNTY SINCE THIS IS
WHERE THE CONVERGENCE IS MAXIMIZED. IF CURRENT TRENDS CONTINUE
SUGGESTING HEAVY SNOW...A WARNING MAY BE NEEDED. CONFIDENCE IS LOWER
FOR MARQUETTE AND NORTHERN SCHOOLCRAFT COUNTIES AS LAND BREEZES MAY
KEEP THE BAND FROM MOVING INTO EITHER OF THESE AREAS.
THU...MODELS SHOW THAT THE UPPER TROUGH THAT WILL BE OVER THE GREAT
LAKES AT 12Z THU WILL BEGIN TO MOVE EASTWARD DURING THE DAY AS A
RESULT OF THE STRONG SHRTWV CURRENTLY AT THE TOP OF THE WESTERN
NORTH AMERICA RIDGE DIGGING INTO SASKATCHEWAN. THIS MOTION WILL HELP
BRING IN THE HIGH PRESSURE CENTER OVER NW ONTARIO DOWN OVER UPPER
MICHIGAN BY 00Z. THEREFORE...PLANS FOR THE LAKE EFFECT TO DIMINISH
WEST TO EAST STILL LOOK REASONABLE...WITH LOWERING INVERSION HEIGHTS
AND DRIER AIR MOVING IN. THE EASTERN CWA MAY STILL SEE AN ADDITIONAL
INCH OR TWO UNTIL THE DRIER AIR MOVES IN...WHICH PUTS ALGER COUNTY
CLOSE TO 24 HR WARNING CRITERIA. IN ADDITION TO THE DRIER
AIR...THERE WILL BE SOME WARM ADVECTION TOO...WITH 850MB TEMPS
RISING TO -12C WEST TO -20C EAST BY 00Z...THOUGH MUCH OF THIS
ADVECTION WILL NOT BE REALIZED AT THE SURFACE DUE TO CHILLY AIR
MOVING IN ASSOCIATED WITH THE RIDGE. GOING FORECAST TEMPS LOOK GOOD.
THU NIGHT AND FRI...MODEL TRENDS WITH THE GFS/UKMET AND ECMWF NOW
INDICATE THAT THE SHRTWV/CLIPPER SYSTEM OVER SASKATCHEWAN WILL BE
QUICKER TO ARRIVE THAN PREVIOUSLY EXPECTED. THIS HAS RESULTED IN
QUITE A FEW CHANGES TO THE FORECAST. FIRST...WARM AIR
ADVECTION/ISENTROPIC LIFTING AHEAD OF THE TROUGH IS EXPECTED TO
DEVELOP A BAND OF MID AND HIGH CLOUDS ACROSS MINNESOTA THU EVENING.
THESE WILL MOVE INTO THE CWA THU NIGHT AND ALSO GET LOWER AS
ISENTROPIC LIFT INCREASES. IN ADDITION...THERE ARE INDICATIONS OF A
120KT JET STREAK MOVING SOUTHEASTWARD ACROSS LAKE SUPERIOR INTO LAKE
HURON...WHICH WOULD PLACE THE CWA IN THE UPPER DIVERGENCE REGION OF
THE JET. HAVE INCLUDED CHANCE POPS AFTER MIDNIGHT FOR THE WEST HALF
OF THE CWA DUE TO THE ISENTROPIC LIFT/UPPER DIVERGENCE. FOR
FRIDAY...THIS CHANCE IS SPREAD ACROSS THE ENTIRE CWA. THE SNOW MAY
ONLY END UP BEING IN THE MORNING SINCE A DRY SLOT IS PROGGED TO COME
IN ALOFT...BUT SINCE THERE STILL ARE SOME TIMING DIFFERENCES...WITH
THE NAM SUGGESTING A SLOWER SOLUTION THAN THE GFS/UKMET/ECMWF...FEEL
KEEPING A POP IN ALL DAY IS WARRANTED. ANOTHER ITEM TO WATCH WITH
THIS CLIPPER IS A POTENTIAL DOMINANT LES BAND OFF LAKE MICHIGAN DUE
TO SOUTHERLY FLOW AHEAD OF THE CLIPPER...WHICH WOULD AFFECT THE FAR
EASTERN CWA.
HOW QUICK THE CLOUDS COME IN...ALONG WITH THE EXIT SPEED OF THE
SURFACE HIGH...WILL DETERMINE HOW LOW TEMPERATURES FALL THU EVENING.
SINCE TEMPERATURES ARE ONLY EXPECTED IN THE MID TEENS ON
THU...TEMPERATURES SHOULD REALLY DROP AFTER SUNSET. HAVE WENT CLOSER
TO THE MAV COOP GUIDANCE FOR LOWS. READINGS WILL THEN CLIMB AFTER
MIDNIGHT AS RETURN FLOW SETS UP. HAVE WARMED READINGS ON FRI AS
BREEZY SOUTHWESTERLY FLOW ON THE SE SIDE OF THE CLIPPER WILL HELP
DRAW WARMER AIR IN.
FRI NIGHT THROUGH SAT NIGHT...THE SHRTWV ASSOCIATED WITH THE CLIPPER
IS PROGGED TO MOVE INTO UPPER MICHIGAN ON SAT...WHILE THE ASSOCIATED
SURFACE LOW MOVES INTO LAKE HURON. THE FIRST COLD FRONT ASSOCIATED
WITH THE LOW WILL HELP TO BRING IN COLDER 850MB TEMPS ON WESTERLY
WINDS (AROUND -14C). THEREFORE HAVE RAISED POPS TO LIKELY FOR THE
WESTERN U.P.. THE SNOW GETS MORE INTERESTING ON SAT AS A SECONDARY
COLD FRONT MOVES SOUTHWARD ACROSS THE LAKE. THIS COLD FRONT MAY HAVE
AN INTENSE SNOW BAND ALONG IT...GIVEN THAT THERE WILL BE PLENTY OF
MOISTURE PRESENT ASSOCIATED WITH THE SHRTWV AND 850MB TEMPS ARE
BETWEEN -14 AND -16C (DENDRITIC SNOW GROWTH LAYER TEMPS) WHEN THE
FRONT MOVES THROUGH. A GFS SOUNDING FOR 18Z SAT FOR MQT ACTUALLY
SHOWS VERY LITTLE IF ANY INVERSION BELOW THE TROPOPAUSE
INVERSION...WHICH WOULD SUGGEST DEEP SNOW GROWTH. MULTI-PARALLEL
BANDS...PERHAPS WITH A FEW HEAVIER BANDS WHERE CONVERGENCE CAN SET
UP (E.G. IRONWOOD AND MARQUETTE COUNTY) WILL FOLLOW IN THE WAKE OF
THE SHRTWV SAT NIGHT AS 850MB TEMPS FALL TO AROUND -20C. WILL
MENTION THIS EVENT IN THE HWO.
EXTENDED...NO CHANGES MADE FROM SUNDAY ONWARDS. OVERALL
THOUGH...LOOKS LIKE THE OVERALL COOL PATTERN WILL CONTINUE AS LONG
RANGE PROGS SUGGEST THE POSITIVE PNA PATTERN WILL STAY IN PLACE.
AJ
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
LAKE EFFECT SNOW ADVISORY FOR MIZ006 FROM 7 PM EST TONIGHT TO 7 AM
EST THURSDAY
&&
$$
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
AFDMQT 1000 AM EST WED JAN 24 2007
.UPDATE...
MQT 88D SHOWS LES BANDS CONTINUING TO DRIFT INTO ALGER COUNTY THIS
MRNG. MOST OF THE BANDS LOOK RATHER DISORGANIZED WITH RELATIVELY DRY
AIR SHOWN BY 12Z TAMDAR SDNG FM SAW IN THE SUB INVRN (ARND H825)
LYR. A FEW REFLECTIVITIES AOA 25DBZ NOTED IN THE FAR WRN BAND WHERE
W LAND BREEZE OFF THE W HALF OF UPR MI CONVERGING WITH MORE ELY LAND
BREEZE OFF ONTARIO. AWAY FM LK EFFECT AREAS E OF MQT...SKIES ARE
PCLDY WITH DRY LYR SHOWN ABV INVRN BASE. NEXT SHRTWV OF CONCERN
DROPPING SEWD NR LK WINNIPEG AT 14Z. ASSOCIATED SFC LO LOCATED OVER
NW ONTARIO TO THE NNW OF INL. SOME LGT -SN NOTED OVER NRN
MN/ADJOINING NW ONTARIO...BUT OVERALL PCPN COVG/INTENSITY
ACCOMPANYING THESE FEATURES IS LIMITED BY DRY AIR SHOWN ON THE 12Z
INL/YPL/YQD RAOBS AND MINIMAL ISENTROPIC LIFT. LEADING EDGE OF
THICKER CLD IN ADVANCE OF THIS SHRTWV NOW APRCHG WRN LK SUP.
MAIN FCST CONCERNS IN THE SHORT TERM ARE LES TRENDS AND SN CHCS
ASSOCIATED WITH SHRTWV NOW MOVING THRU MANITOBA.
LATEST NAM/RUC SHOW SHRTWV NOW OVER MANITOBA DIGGING INTO NRN WI BY
00Z THU...WITH DVPA/H85-5 QVECTOR CNVGC/AREA OF HIER H7 RH
ASSOCIATED WITH OBSVD THICKER CLD AND SOME -SN ON THE CYC SIDE OF
THIS FEATURE IMPACTING THE FA THIS AFTN BEFORE DEPARTING THIS EVNG.
SINCE AIRMASS OVHD IS QUITE DRY AND ISENTROPIC LIFT PROGGED TO
REMAIN NEGLIBLE...THINK SYNOPTIC SN/HIER POPS ASSOCIATED WITH
INCOMING DYNAMICS WL BE RESTRICTED TO AREAS WHERE LKS CAN MOISTEN
THE ATMOSPHERE SIGNIFICANTLY. OTRW...LATEST RUC13/LOCAL HI RES WRF
MODEL INDICATE VORTEX WL DVLP NR MUNISING BAY ALG CONFLUENCE AXIS
STRETCHING FM ECNTRL LK SUP-P53-ISQ. IF THIS VORTEX DVLPS AS FCST...
STRONGER LES BAND NOW IMPACTING WRN ALGER COUNTY SHOULD WEAKEN AND
MOVE OFF TO THE NE. ON THE OTHER HAND...IF THIS FEATURE FAILS TO
DVLP...LES BANDS MAY INTENSIFY ALG CURRENT AXIS IN WRN ALGER COUNTY
ONCE SHARPER DPVA ARRIVES THIS AFTN. WITH EXPECTED HEAVIER SHSN TNGT
IN WRN ALGER COUNTY...MAY NEED TO ISSUE WRNG IF BAND PERSISTS IN THE
SAME AREA FOR A LONGER TIME.
MIXING TO INVRN BASE ON 12Z INL RAOB/TAMDAR SDNG FM SAW WOULD
SUPPORT HI TEMPS IN THE 15-20 RANGE...NOT FAR FM GOING FCST. WL
ADJUST FCST HI TEMPS DOWN A BIT OVER THE W.
KC
&&
.PREVIOUS DISCUSSION (ISSUED AT 436 AM)...
09Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED A POSITIVE
PNA PATTERN...WITH RIDGING ACROSS WESTERN NORTH AMERICA AND
TROUGHING ACROSS EASTERN NORTH AMERICA. THE CENTER OF THIS TROUGH IS
A 500 DAM LOW COVERING MUCH OF HUDSON AND JAMES BAYS. CHILLY 850MB
TEMPS EXIST UNDER AND WEST OF THE UPPER LOW...NOTED BY 00Z SOUNDINGS
OF -23C AT CHURCHILL MB...-22C AT PICKLE LAKE AND -25C AT MOOSONEE.
NW WINDS AT 850MB CONTINUE TO BRING THIS COLDER AIR DOWN TOWARDS
LAKE SUPERIOR...WITH RUC ANALYSIS SUGGESTING -15 TO -18C 850MB TEMPS
RIGHT NOW OVER THE LAKE. WITH LAKE TEMPS OF 2-3C...PLENTY OF
INSTABILITY EXISTS FOR LAKE EFFECT. HOWEVER...DRY AIR SEEN ON A 00Z
TAMDAR SOUNDING FROM INL AND THE 00Z RAOB FROM PICKLE LAKE IS HAVING
A CONSIDERABLE IMPACT...ONLY ALLOWING FOR A FEW BANDS ON WESTERN
LAKE SUPERIOR. THANKS TO LONGER FETCH...BANDS CONTINUE ON EASTERN
LAKE SUPERIOR...THOUGH THESE ARE ALSO FEELING THE DRY AIR WITH THE
BANDS SPACED FAIRLY FAR APART AND DISORGANIZED. OUTSIDE OF THE LAKE
EFFECT... CONDITIONS ARE FAIRLY QUIET THANKS TO BOTH THE DRY AIR AND
A 1020MB HIGH BUILDING SOUTHWARD FROM NW ONTARIO BEHIND THE SURFACE
TROUGH THAT WENT THROUGH YESTERDAY. THE WEAKENING PRESSURE GRADIENT
COMBINED WITH MAINLY CLEAR SKIES IN THE INTERIOR HAS ALLOWED TEMPS
TO DROP TO -10F BELOW ZERO AT WATERSMEET. THIS COLD AIR OVER THE
INTERIOR AND WARMER LAKE WATERS HAS RESULTED IN THE DEVELOPMENT OF
SOME LAND BREEZES...WHICH ARE ALSO AFFECTING THE LAKE EFFECT BANDS.
TO THE NW...A SHRTWV CAN BE SEEN DROPPING SE THROUGH CENTRAL
MANITOBA. SOME LIGHT SNOW HAS BEEN GOING ON TO THE S OF THE SHRTWV
ON THE N END OF LAKE WINNIPEG WHERE BETTER LOW LEVEL MOISTURE EXISTS
(SEE THE 00Z THE PAS SOUNDING). LASTLY...A STRONG SHRTWV IS ABOUT
READY TO TOP THE WESTERN NORTH AMERICA RIDGE. THIS SHRTWV IS PROGGED
TO AFFECT THE CWA FRI/SAT.
MAIN FORECAST CONCERNS ARE LES AMOUNTS TONIGHT AND CLIPPER SYSTEM
FOR FRI AND SAT.
TODAY...THE SHRTWV OVER MANITOBA IS PROGGED TO CONTINUE MOVING SE
THROUGH THE NW FLOW ALOFT...REACHING NORTHERN WISCONSIN AROUND 00Z.
THIS SHRTWV WILL HELP BRING THE LOW LEVEL MOISTURE AND LIGHT SNOW
OCCURRING THERE INTO THE CWA THIS AFTERNOON...AS NOTED BY 850MB RH
PROGS. SINCE NAM AND GFS SOUNDINGS DEPICT DECENT OMEGA WITHIN THE
DENDRITIC SNOW GROWTH ZONE...ALONG WITH DEEP MOISTURE UP TO
10000-12000 FT...WOULD NOT BE SURPRISED TO SEE A QUICK INCH OF
SNOWFALL ACROSS THE WEST HALF OF THE CWA. AS FAR AS THE LAKE EFFECT
GOES...THE 00Z 13KM RUC DEPICTS AN INTERESTING SCENARIO...SUGGESTING
THE DEVELOPMENT OF A MESO-LOW THIS MORNING NEAR MUNISING WHICH
BRIEFLY MOVES NE OVER THE LAKE...THEN BACK S THIS AFTERNOON. THE 03Z
RUC IS SIMILAR. THE GFS/NAM AND LOCAL WRF-ARW MODELS HERE SUGGEST
MULTI-PARALLEL BANDS TO CONTINUE. FOR NOW...WILL MAINTAIN NUMEROUS
SNOW SHOWERS EAST OF MARQUETTE WITH AN INCH OR TWO OF ACCUMULATION
TODAY...BUT SNOW AMOUNTS WILL NEED TO BE WATCHED IF THE MESO-LOW
SCENARIO DOES PAN OUT. WILL ALSO PUT NUMEROUS SNOW SHOWERS IN THE
FAR WESTERN U.P. WITH THE IDEA OF A LAKE ENHANCEMENT SCENARIO. GOING
FORECAST TEMPS LOOK REASONABLE.
TONIGHT...MODELS PROG THAT THE SHRTWV OVER NORTHERN WISCONSIN WILL
CONTINUE SE WHILE ANOTHER SHRTWV ON THE WEST SIDE OF THE HUDSON BAY
UPPER LOW DROPS S ACROSS FAR EASTERN LAKE SUPERIOR AFTER MIDNIGHT.
BOTH OF THESE SHRTWVS HELP IN DRAWING ANOTHER SURGE OF COLD AIR
SOUTHWARD FROM ONTARIO (850MB TEMPS FALL TO -20C WEST TO -26C EAST
AT 12Z THU)...STRENGTHENING THE HIGH PRESSURE AREA OVER NW ONTARIO
AND INTENSIFYING THE SURFACE TROUGH THAT HAS BEEN NEARLY STATIONARY
OVER THE CWA. ALTHOUGH THIS TROUGH WILL BE DROPPING S WITH THE
NORTHERN WISCONSIN SHRTWV...A BREEZY NORTH WIND WILL DEVELOP AS A
RESULT OF THE TIGHT PRESSURE GRADIENT. THEREFORE...WITH THE COLD AIR
ADVECTION...NUMEROUS MULTI-PARALLEL BANDS ARE EXPECTED TO OCCUR
ACROSS ALL OF THE NORTHERN U.P. WITH THE BANDS LIKELY CROSSING DELTA
AND SOUTHERN SCHOOLCRAFT COUNTIES. AMOUNTS ARE A BIG QUESTION. FOR
THE WESTERN U.P....CONVERGENCE IS EXPECTED IN THE PORCUPINE
MOUNTAINS AND COPPER PEAK AREA. HOWEVER...INVERSION HEIGHTS ARE
AROUND 850MB AND THERE IS EXPOSURE TO PLENTY OF DRY AIR...WHICH MAY
LIMIT SNOW AMOUNTS. FOR NOW WILL GO SUB-ADVISORY. FOR THE EASTERN
U.P....THERE ARE INDICATIONS FROM THE NAM/REGIONAL CANADIAN AND 13KM
RUC THAT A LAKE INDUCED SURFACE TROUGH MAY FORM EARLY THIS EVENING
AND ALIGN ITSELF FROM THE TIP OF THE KEWEENAW SOUTHEASTWARD TO
TRAVERSE CITY. SOUNDINGS UNDER THE TROUGH SHOW BEFORE 06Z AN
INVERSION HEIGHT AROUND 800MB WITH A SNOW GROWTH LAYER BETWEEN
925-875MB. WITH CONVERGENCE ALONG THE BAND...THIS WOULD BE A GOOD
SETUP FOR HEAVY SNOW...WITH PERHAPS INCH AN HOUR RATES. AFTER
06Z...TOO MUCH COLD AIR IS ADVECTED IN AND THE DENDRITIC GROWTH SNOW
LAYER BASICALLY DISAPPEARS...ALONG WITH THE INVERSION LOWERING TO
850MB. FOR NOW...WILL PUT AN ADVISORY FOR ALGER COUNTY SINCE THIS IS
WHERE THE CONVERGENCE IS MAXIMIZED. IF CURRENT TRENDS CONTINUE
SUGGESTING HEAVY SNOW...A WARNING MAY BE NEEDED. CONFIDENCE IS LOWER
FOR MARQUETTE AND NORTHERN SCHOOLCRAFT COUNTIES AS LAND BREEZES MAY
KEEP THE BAND FROM MOVING INTO EITHER OF THESE AREAS.
THU...MODELS SHOW THAT THE UPPER TROUGH THAT WILL BE OVER THE GREAT
LAKES AT 12Z THU WILL BEGIN TO MOVE EASTWARD DURING THE DAY AS A
RESULT OF THE STRONG SHRTWV CURRENTLY AT THE TOP OF THE WESTERN
NORTH AMERICA RIDGE DIGGING INTO SASKATCHEWAN. THIS MOTION WILL HELP
BRING IN THE HIGH PRESSURE CENTER OVER NW ONTARIO DOWN OVER UPPER
MICHIGAN BY 00Z. THEREFORE...PLANS FOR THE LAKE EFFECT TO DIMINISH
WEST TO EAST STILL LOOK REASONABLE...WITH LOWERING INVERSION HEIGHTS
AND DRIER AIR MOVING IN. THE EASTERN CWA MAY STILL SEE AN ADDITIONAL
INCH OR TWO UNTIL THE DRIER AIR MOVES IN...WHICH PUTS ALGER COUNTY
CLOSE TO 24 HR WARNING CRITERIA. IN ADDITION TO THE DRIER
AIR...THERE WILL BE SOME WARM ADVECTION TOO...WITH 850MB TEMPS
RISING TO -12C WEST TO -20C EAST BY 00Z...THOUGH MUCH OF THIS
ADVECTION WILL NOT BE REALIZED AT THE SURFACE DUE TO CHILLY AIR
MOVING IN ASSOCIATED WITH THE RIDGE. GOING FORECAST TEMPS LOOK GOOD.
THU NIGHT AND FRI...MODEL TRENDS WITH THE GFS/UKMET AND ECMWF NOW
INDICATE THAT THE SHRTWV/CLIPPER SYSTEM OVER SASKATCHEWAN WILL BE
QUICKER TO ARRIVE THAN PREVIOUSLY EXPECTED. THIS HAS RESULTED IN
QUITE A FEW CHANGES TO THE FORECAST. FIRST...WARM AIR
ADVECTION/ISENTROPIC LIFTING AHEAD OF THE TROUGH IS EXPECTED TO
DEVELOP A BAND OF MID AND HIGH CLOUDS ACROSS MINNESOTA THU EVENING.
THESE WILL MOVE INTO THE CWA THU NIGHT AND ALSO GET LOWER AS
ISENTROPIC LIFT INCREASES. IN ADDITION...THERE ARE INDICATIONS OF A
120KT JET STREAK MOVING SOUTHEASTWARD ACROSS LAKE SUPERIOR INTO LAKE
HURON...WHICH WOULD PLACE THE CWA IN THE UPPER DIVERGENCE REGION OF
THE JET. HAVE INCLUDED CHANCE POPS AFTER MIDNIGHT FOR THE WEST HALF
OF THE CWA DUE TO THE ISENTROPIC LIFT/UPPER DIVERGENCE. FOR
FRIDAY...THIS CHANCE IS SPREAD ACROSS THE ENTIRE CWA. THE SNOW MAY
ONLY END UP BEING IN THE MORNING SINCE A DRY SLOT IS PROGGED TO COME
IN ALOFT...BUT SINCE THERE STILL ARE SOME TIMING DIFFERENCES...WITH
THE NAM SUGGESTING A SLOWER SOLUTION THAN THE GFS/UKMET/ECMWF...FEEL
KEEPING A POP IN ALL DAY IS WARRANTED. ANOTHER ITEM TO WATCH WITH
THIS CLIPPER IS A POTENTIAL DOMINANT LES BAND OFF LAKE MICHIGAN DUE
TO SOUTHERLY FLOW AHEAD OF THE CLIPPER...WHICH WOULD AFFECT THE FAR
EASTERN CWA.
HOW QUICK THE CLOUDS COME IN...ALONG WITH THE EXIT SPEED OF THE
SURFACE HIGH...WILL DETERMINE HOW LOW TEMPERATURES FALL THU EVENING.
SINCE TEMPERATURES ARE ONLY EXPECTED IN THE MID TEENS ON
THU...TEMPERATURES SHOULD REALLY DROP AFTER SUNSET. HAVE WENT CLOSER
TO THE MAV COOP GUIDANCE FOR LOWS. READINGS WILL THEN CLIMB AFTER
MIDNIGHT AS RETURN FLOW SETS UP. HAVE WARMED READINGS ON FRI AS
BREEZY SOUTHWESTERLY FLOW ON THE SE SIDE OF THE CLIPPER WILL HELP
DRAW WARMER AIR IN.
FRI NIGHT THROUGH SAT NIGHT...THE SHRTWV ASSOCIATED WITH THE CLIPPER
IS PROGGED TO MOVE INTO UPPER MICHIGAN ON SAT...WHILE THE ASSOCIATED
SURFACE LOW MOVES INTO LAKE HURON. THE FIRST COLD FRONT ASSOCIATED
WITH THE LOW WILL HELP TO BRING IN COLDER 850MB TEMPS ON WESTERLY
WINDS (AROUND -14C). THEREFORE HAVE RAISED POPS TO LIKELY FOR THE
WESTERN U.P.. THE SNOW GETS MORE INTERESTING ON SAT AS A SECONDARY
COLD FRONT MOVES SOUTHWARD ACROSS THE LAKE. THIS COLD FRONT MAY HAVE
AN INTENSE SNOW BAND ALONG IT...GIVEN THAT THERE WILL BE PLENTY OF
MOISTURE PRESENT ASSOCIATED WITH THE SHRTWV AND 850MB TEMPS ARE
BETWEEN -14 AND -16C (DENDRITIC SNOW GROWTH LAYER TEMPS) WHEN THE
FRONT MOVES THROUGH. A GFS SOUNDING FOR 18Z SAT FOR MQT ACTUALLY
SHOWS VERY LITTLE IF ANY INVERSION BELOW THE TROPOPAUSE
INVERSION...WHICH WOULD SUGGEST DEEP SNOW GROWTH. MULTI-PARALLEL
BANDS...PERHAPS WITH A FEW HEAVIER BANDS WHERE CONVERGENCE CAN SET
UP (E.G. IRONWOOD AND MARQUETTE COUNTY) WILL FOLLOW IN THE WAKE OF
THE SHRTWV SAT NIGHT AS 850MB TEMPS FALL TO AROUND -20C. WILL
MENTION THIS EVENT IN THE HWO.
EXTENDED...NO CHANGES MADE FROM SUNDAY ONWARDS. OVERALL
THOUGH...LOOKS LIKE THE OVERALL COOL PATTERN WILL CONTINUE AS LONG
RANGE PROGS SUGGEST THE POSITIVE PNA PATTERN WILL STAY IN PLACE.
AJ
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
LAKE EFFECT SNOW ADVISORY FOR MIZ006 FROM 7 PM EST TONIGHT TO 7 AM
EST THURSDAY
&&
$$
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
AFDMQT 436 AM EST WED JAN 24 2007
.SYNOPSIS...
09Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED A POSITIVE
PNA PATTERN...WITH RIDGING ACROSS WESTERN NORTH AMERICA AND
TROUGHING ACROSS EASTERN NORTH AMERICA. THE CENTER OF THIS TROUGH IS
A 500 DAM LOW COVERING MUCH OF HUDSON AND JAMES BAYS. CHILLY 850MB
TEMPS EXIST UNDER AND WEST OF THE UPPER LOW...NOTED BY 00Z SOUNDINGS
OF -23C AT CHURCHILL MB...-22C AT PICKLE LAKE AND -25C AT MOOSONEE.
NW WINDS AT 850MB CONTINUE TO BRING THIS COLDER AIR DOWN TOWARDS
LAKE SUPERIOR...WITH RUC ANALYSIS SUGGESTING -15 TO -18C 850MB TEMPS
RIGHT NOW OVER THE LAKE. WITH LAKE TEMPS OF 2-3C...PLENTY OF
INSTABILITY EXISTS FOR LAKE EFFECT. HOWEVER...DRY AIR SEEN ON A 00Z
TAMDAR SOUNDING FROM INL AND THE 00Z RAOB FROM PICKLE LAKE IS HAVING
A CONSIDERABLE IMPACT...ONLY ALLOWING FOR A FEW BANDS ON WESTERN
LAKE SUPERIOR. THANKS TO LONGER FETCH...BANDS CONTINUE ON EASTERN
LAKE SUPERIOR...THOUGH THESE ARE ALSO FEELING THE DRY AIR WITH THE
BANDS SPACED FAIRLY FAR APART AND DISORGANIZED. OUTSIDE OF THE LAKE
EFFECT... CONDITIONS ARE FAIRLY QUIET THANKS TO BOTH THE DRY AIR AND
A 1020MB HIGH BUILDING SOUTHWARD FROM NW ONTARIO BEHIND THE SURFACE
TROUGH THAT WENT THROUGH YESTERDAY. THE WEAKENING PRESSURE GRADIENT
COMBINED WITH MAINLY CLEAR SKIES IN THE INTERIOR HAS ALLOWED TEMPS
TO DROP TO -10F BELOW ZERO AT WATERSMEET. THIS COLD AIR OVER THE
INTERIOR AND WARMER LAKE WATERS HAS RESULTED IN THE DEVELOPMENT OF
SOME LAND BREEZES...WHICH ARE ALSO AFFECTING THE LAKE EFFECT BANDS.
TO THE NW...A SHRTWV CAN BE SEEN DROPPING SE THROUGH CENTRAL
MANITOBA. SOME LIGHT SNOW HAS BEEN GOING ON TO THE S OF THE SHRTWV
ON THE N END OF LAKE WINNIPEG WHERE BETTER LOW LEVEL MOISTURE EXISTS
(SEE THE 00Z THE PAS SOUNDING). LASTLY...A STRONG SHRTWV IS ABOUT
READY TO TOP THE WESTERN NORTH AMERICA RIDGE. THIS SHRTWV IS PROGGED
TO AFFECT THE CWA FRI/SAT.
&&
.DISCUSSION...
MAIN FORECAST CONCERNS ARE LES AMOUNTS TONIGHT AND CLIPPER SYSTEM
FOR FRI AND SAT.
TODAY...THE SHRTWV OVER MANITOBA IS PROGGED TO CONTINUE MOVING SE
THROUGH THE NW FLOW ALOFT...REACHING NORTHERN WISCONSIN AROUND 00Z.
THIS SHRTWV WILL HELP BRING THE LOW LEVEL MOISTURE AND LIGHT SNOW
OCCURRING THERE INTO THE CWA THIS AFTERNOON...AS NOTED BY 850MB RH
PROGS. SINCE NAM AND GFS SOUNDINGS DEPICT DECENT OMEGA WITHIN THE
DENDRITIC SNOW GROWTH ZONE...ALONG WITH DEEP MOISTURE UP TO
10000-12000 FT...WOULD NOT BE SURPRISED TO SEE A QUICK INCH OF
SNOWFALL ACROSS THE WEST HALF OF THE CWA. AS FAR AS THE LAKE EFFECT
GOES...THE 00Z 13KM RUC DEPICTS AN INTERESTING SCENARIO...SUGGESTING
THE DEVELOPMENT OF A MESO-LOW THIS MORNING NEAR MUNISING WHICH
BRIEFLY MOVES NE OVER THE LAKE...THEN BACK S THIS AFTERNOON. THE 03Z
RUC IS SIMILAR. THE GFS/NAM AND LOCAL WRF-ARW MODELS HERE SUGGEST
MULTI-PARALLEL BANDS TO CONTINUE. FOR NOW...WILL MAINTAIN NUMEROUS
SNOW SHOWERS EAST OF MARQUETTE WITH AN INCH OR TWO OF ACCUMULATION
TODAY...BUT SNOW AMOUNTS WILL NEED TO BE WATCHED IF THE MESO-LOW
SCENARIO DOES PAN OUT. WILL ALSO PUT NUMEROUS SNOW SHOWERS IN THE
FAR WESTERN U.P. WITH THE IDEA OF A LAKE ENHANCEMENT SCENARIO. GOING
FORECAST TEMPS LOOK REASONABLE.
TONIGHT...MODELS PROG THAT THE SHRTWV OVER NORTHERN WISCONSIN WILL
CONTINUE SE WHILE ANOTHER SHRTWV ON THE WEST SIDE OF THE HUDSON BAY
UPPER LOW DROPS S ACROSS FAR EASTERN LAKE SUPERIOR AFTER MIDNIGHT.
BOTH OF THESE SHRTWVS HELP IN DRAWING ANOTHER SURGE OF COLD AIR
SOUTHWARD FROM ONTARIO (850MB TEMPS FALL TO -20C WEST TO -26C EAST
AT 12Z THU)...STRENGTHENING THE HIGH PRESSURE AREA OVER NW ONTARIO
AND INTENSIFYING THE SURFACE TROUGH THAT HAS BEEN NEARLY STATIONARY
OVER THE CWA. ALTHOUGH THIS TROUGH WILL BE DROPPING S WITH THE
NORTHERN WISCONSIN SHRTWV...A BREEZY NORTH WIND WILL DEVELOP AS A
RESULT OF THE TIGHT PRESSURE GRADIENT. THEREFORE...WITH THE COLD AIR
ADVECTION...NUMEROUS MULTI-PARALLEL BANDS ARE EXPECTED TO OCCUR
ACROSS ALL OF THE NORTHERN U.P. WITH THE BANDS LIKELY CROSSING DELTA
AND SOUTHERN SCHOOLCRAFT COUNTIES. AMOUNTS ARE A BIG QUESTION. FOR
THE WESTERN U.P....CONVERGENCE IS EXPECTED IN THE PORCUPINE
MOUNTAINS AND COPPER PEAK AREA. HOWEVER...INVERSION HEIGHTS ARE
AROUND 850MB AND THERE IS EXPOSURE TO PLENTY OF DRY AIR...WHICH MAY
LIMIT SNOW AMOUNTS. FOR NOW WILL GO SUB-ADVISORY. FOR THE EASTERN
U.P....THERE ARE INDICATIONS FROM THE NAM/REGIONAL CANADIAN AND 13KM
RUC THAT A LAKE INDUCED SURFACE TROUGH MAY FORM EARLY THIS EVENING
AND ALIGN ITSELF FROM THE TIP OF THE KEWEENAW SOUTHEASTWARD TO
TRAVERSE CITY. SOUNDINGS UNDER THE TROUGH SHOW BEFORE 06Z AN
INVERSION HEIGHT AROUND 800MB WITH A SNOW GROWTH LAYER BETWEEN
925-875MB. WITH CONVERGENCE ALONG THE BAND...THIS WOULD BE A GOOD
SETUP FOR HEAVY SNOW...WITH PERHAPS INCH AN HOUR RATES. AFTER
06Z...TOO MUCH COLD AIR IS ADVECTED IN AND THE DENDRITIC GROWTH SNOW
LAYER BASICALLY DISAPPEARS...ALONG WITH THE INVERSION LOWERING TO
850MB. FOR NOW...WILL PUT AN ADVISORY FOR ALGER COUNTY SINCE THIS IS
WHERE THE CONVERGENCE IS MAXIMIZED. IF CURRENT TRENDS CONTINUE
SUGGESTING HEAVY SNOW...A WARNING MAY BE NEEDED. CONFIDENCE IS LOWER
FOR MARQUETTE AND NORTHERN SCHOOLCRAFT COUNTIES AS LAND BREEZES MAY
KEEP THE BAND FROM MOVING INTO EITHER OF THESE AREAS.
THU...MODELS SHOW THAT THE UPPER TROUGH THAT WILL BE OVER THE GREAT
LAKES AT 12Z THU WILL BEGIN TO MOVE EASTWARD DURING THE DAY AS A
RESULT OF THE STRONG SHRTWV CURRENTLY AT THE TOP OF THE WESTERN
NORTH AMERICA RIDGE DIGGING INTO SASKATCHEWAN. THIS MOTION WILL HELP
BRING IN THE HIGH PRESSURE CENTER OVER NW ONTARIO DOWN OVER UPPER
MICHIGAN BY 00Z. THEREFORE...PLANS FOR THE LAKE EFFECT TO DIMINISH
WEST TO EAST STILL LOOK REASONABLE...WITH LOWERING INVERSION HEIGHTS
AND DRIER AIR MOVING IN. THE EASTERN CWA MAY STILL SEE AN ADDITIONAL
INCH OR TWO UNTIL THE DRIER AIR MOVES IN...WHICH PUTS ALGER COUNTY
CLOSE TO 24 HR WARNING CRITERIA. IN ADDITION TO THE DRIER
AIR...THERE WILL BE SOME WARM ADVECTION TOO...WITH 850MB TEMPS
RISING TO -12C WEST TO -20C EAST BY 00Z...THOUGH MUCH OF THIS
ADVECTION WILL NOT BE REALIZED AT THE SURFACE DUE TO CHILLY AIR
MOVING IN ASSOCIATED WITH THE RIDGE. GOING FORECAST TEMPS LOOK GOOD.
THU NIGHT AND FRI...MODEL TRENDS WITH THE GFS/UKMET AND ECMWF NOW
INDICATE THAT THE SHRTWV/CLIPPER SYSTEM OVER SASKATCHEWAN WILL BE
QUICKER TO ARRIVE THAN PREVIOUSLY EXPECTED. THIS HAS RESULTED IN
QUITE A FEW CHANGES TO THE FORECAST. FIRST...WARM AIR
ADVECTION/ISENTROPIC LIFTING AHEAD OF THE TROUGH IS EXPECTED TO
DEVELOP A BAND OF MID AND HIGH CLOUDS ACROSS MINNESOTA THU EVENING.
THESE WILL MOVE INTO THE CWA THU NIGHT AND ALSO GET LOWER AS
ISENTROPIC LIFT INCREASES. IN ADDITION...THERE ARE INDICATIONS OF A
120KT JET STREAK MOVING SOUTHEASTWARD ACROSS LAKE SUPERIOR INTO LAKE
HURON...WHICH WOULD PLACE THE CWA IN THE UPPER DIVERGENCE REGION OF
THE JET. HAVE INCLUDED CHANCE POPS AFTER MIDNIGHT FOR THE WEST HALF
OF THE CWA DUE TO THE ISENTROPIC LIFT/UPPER DIVERGENCE. FOR
FRIDAY...THIS CHANCE IS SPREAD ACROSS THE ENTIRE CWA. THE SNOW MAY
ONLY END UP BEING IN THE MORNING SINCE A DRY SLOT IS PROGGED TO COME
IN ALOFT...BUT SINCE THERE STILL ARE SOME TIMING DIFFERENCES...WITH
THE NAM SUGGESTING A SLOWER SOLUTION THAN THE GFS/UKMET/ECMWF...FEEL
KEEPING A POP IN ALL DAY IS WARRANTED. ANOTHER ITEM TO WATCH WITH
THIS CLIPPER IS A POTENTIAL DOMINANT LES BAND OFF LAKE MICHIGAN DUE
TO SOUTHERLY FLOW AHEAD OF THE CLIPPER...WHICH WOULD AFFECT THE FAR
EASTERN CWA.
HOW QUICK THE CLOUDS COME IN...ALONG WITH THE EXIT SPEED OF THE
SURFACE HIGH...WILL DETERMINE HOW LOW TEMPERATURES FALL THU EVENING.
SINCE TEMPERATURES ARE ONLY EXPECTED IN THE MID TEENS ON
THU...TEMPERATURES SHOULD REALLY DROP AFTER SUNSET. HAVE WENT CLOSER
TO THE MAV COOP GUIDANCE FOR LOWS. READINGS WILL THEN CLIMB AFTER
MIDNIGHT AS RETURN FLOW SETS UP. HAVE WARMED READINGS ON FRI AS
BREEZY SOUTHWESTERLY FLOW ON THE SE SIDE OF THE CLIPPER WILL HELP
DRAW WARMER AIR IN.
FRI NIGHT THROUGH SAT NIGHT...THE SHRTWV ASSOCIATED WITH THE CLIPPER
IS PROGGED TO MOVE INTO UPPER MICHIGAN ON SAT...WHILE THE ASSOCIATED
SURFACE LOW MOVES INTO LAKE HURON. THE FIRST COLD FRONT ASSOCIATED
WITH THE LOW WILL HELP TO BRING IN COLDER 850MB TEMPS ON WESTERLY
WINDS (AROUND -14C). THEREFORE HAVE RAISED POPS TO LIKELY FOR THE
WESTERN U.P.. THE SNOW GETS MORE INTERESTING ON SAT AS A SECONDARY
COLD FRONT MOVES SOUTHWARD ACROSS THE LAKE. THIS COLD FRONT MAY HAVE
AN INTENSE SNOW BAND ALONG IT...GIVEN THAT THERE WILL BE PLENTY OF
MOISTURE PRESENT ASSOCIATED WITH THE SHRTWV AND 850MB TEMPS ARE
BETWEEN -14 AND -16C (DENDRITIC SNOW GROWTH LAYER TEMPS) WHEN THE
FRONT MOVES THROUGH. A GFS SOUNDING FOR 18Z SAT FOR MQT ACTUALLY
SHOWS VERY LITTLE IF ANY INVERSION BELOW THE TROPOPAUSE
INVERSION...WHICH WOULD SUGGEST DEEP SNOW GROWTH. MULTI-PARALLEL
BANDS...PERHAPS WITH A FEW HEAVIER BANDS WHERE CONVERGENCE CAN SET
UP (E.G. IRONWOOD AND MARQUETTE COUNTY) WILL FOLLOW IN THE WAKE OF
THE SHRTWV SAT NIGHT AS 850MB TEMPS FALL TO AROUND -20C. WILL
MENTION THIS EVENT IN THE HWO.
EXTENDED...NO CHANGES MADE FROM SUNDAY ONWARDS. OVERALL
THOUGH...LOOKS LIKE THE OVERALL COOL PATTERN WILL CONTINUE AS LONG
RANGE PROGS SUGGEST THE POSITIVE PNA PATTERN WILL STAY IN PLACE.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
LAKE EFFECT SNOW ADVISORY FOR MIZ006 FROM 7 PM EST TONIGHT TO 7 AM
EST THURSDAY
&&
$$
AJ