AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
AFDLOT 1030 PM CST WED FEB 7 2007
.UPDATE...
THE WIND IS EXPECTED TO REMAIN AROUND 10 TO 20 KNOTS IN NORTH
CENTRAL ILLINOIS.THE WIND MAY REACH UP TO 15 TO 20 KNOTS NEAR LAKE
MICHIGAN. THIS IS DUE TO THE RELATIVELY WARM WATER IN THE CENTER OF
LAKE MICHIGAN. A LOCAL PRESSURE GRADIENT MAY EXIST DUE TO THE
TEMPERATURE GRADIENT. THE WIND IN THE ACARS SOUNDING OVER ORD AT
0254 UTC SHOWS WIND UP TO 34 KNOTS IN THE LAYER UP TO 5900 FT. WE
EXPECT SOME MIXING TONIGHT BELOW THE INVERSION. THE SNOW WILL KEEP
THE AIR COLD TONIGHT. THE WIND CHILL MAY FALL TO AROUND 25 BELOW
ZERO FAHRENHEIT. WE WILL ISSUE AN ADVISORY FOR WIND CHILL FOR VERY
EARLY MORNING. THIS IS FOR THOSE WAITING FOR TRAINS...BUSES AND
DRIVING TO WORK OR SCHOOL. THE HIGH IS OVER THE NORTHWEST
TERRITORIES AND EXTENDS SOUTH TO IOWA AND ILLINOIS. THIS IS VERY
COLD AIR...MAYBE CONTINENTAL ARTIC. THERE IS SNOW ACROSS MOST OF THE
NORTH CENTRAL UNITED STATES SO THIS AIR MAY HAVE NOT BECOME WARMER
TODAY. SO IT IS VERY COLD TONIGHT.
&&
.DISCUSSION...
400 PM CST
LITTLE DIFFERENCE SEEN IN GENERAL TRENDS SINCE YESTERDAY. POLAR
VORTEX AND THE CORE OF THE COLD AIR TO CONTINUE TO SHIFT E FROM
QUEBEC ACROSS THE CANADIAN MARITIMES TONIGHT THROUGH FRIDAY COMBINED
WITH A DEAMPLIFICATION OF THE WESTERN NOAM UPPER RIDGE. SHORT WAVES
WILL CONTINUE TO ROTATE OUT OF CANADA SOUTHEASTWARD ACROSS THE
NORTHERN AND LOWER GREAT LAKES. THESE WILL SERVE TO HAMPER ANY
SIGNIFICANT RETREAT OF THE COLD FROM THE NORTHERN PLAINS AND GREAT
LAKSES THOUGH A GRADUAL MEGER MODERATON WILL BE UNDERWAY AS THE
DEPTH OF THE COLD AIR DECREASES AND THE UPPER FLOW BACKS TO WEST
NORTHWEST LATE WEEK INTO THE WEEKEND. SURFACE RIDGE AXIS FORECAST TO
REMAIN EXTENDING FROM ALBERTA AND SAKTCHEWAN SOUTHEASTWARD ACROSS
THE NORTHERN PLAINS AND THE MID MS VALLEY INTO THE LOWER OH VALLEY.
AN IMPULSE TRAVELING EAST FROM THE SOUTHERN ROCKIES AND OUT OVER THE
SOUTHERN PLAINS ON THE STREAM STREAM FRIDAY NIGHT AND SATURDAY WILL
SPREAD SOME CLOUDS ACROSS CENTRAL AND MUCH OF NORTHERN IL AND
NORTHWEST IN BUT WITH WNW MID AND UPPER FLOW AND THE RIDGE AXIS
HOLDING FRM IA ACROSS SOUTHERN IL TO WESTERN KY AND TN THE
SIGNIFICANT PRECIP IS EXPECTED TO REMAIN WELL SOUTH OF THE FA. BY
EARLY NEXT WEEK THE SURFACE RIDGE AXIS RETREATS NORTHWARD INTO S
CENTRAL CANADA AND THE GREAT LAKES. ANOTHER WAVE IN THE SOUTHERN
STREAM MAY TRACK A BIT FURTHER NORTH AND MAY SPREAD ENOUGH MOISTURE
ACROSS CENTRAL IL AND IND BY MON NIGHT THUS LOW CHC POPS FOR -SN
INCLUDED ACROSS THE FAR SOUTHERN AND SOUTHEASTERN PARTS OF THE FA
MON NIGHT INTO TUE.
TRS
&&
.AVIATION DISCUSSION FOR 06Z TAFS...
1030 PM CST
LITTLE CHANGE FROM PREVIOUS TAF THINKING. AVIATION WEATHER CONCERNS
WILL REMAIN QUIET OVERNIGHT AND THROUGH THE DAY TOMORROW. PER
LATEST SATELLITE IMAGERY...SKIES HAVE BECOME SKC AND SHOULD REMAIN
SO THROUGH LATE MORNING OR EARLY AFTERNOON. A VERY DRY AIRMASS IS
IN PLACE...AT ALL LEVELS...AND ONLY SOME CI IS EXPECTED TO MOVE OVER
THE REGION AS UPPER RIDGING BUILDS OVER THE WRN HIGH PLAINS AND A
STRONG JET DIVES SEWD OVER THE UPPER MIDWEST. WITH HIGH PRESSURE
BUILDING DOWN FROM THE NRN PLAINS INTO THE LOWER MISSISSIPPI VALLEY
AND LOW PRESSURE OVER ERN CANADA...WINDS WL GRADUALLY TURN MORE WLY
OVERNIGHT AND INTO THE MORNING HRS TOMORROW. THE PRESSURE GRADIENT
IS EXPECTED TO REMAIN STRONG ENOUGH OVERNIGHT FOR WINDS TO REMAIN
ARND 10-15KT. VISIBILITY WILL REMAIN UNRESTRICTED AS THE AREA
REMAINS UNDER THE VERY DRY ARCTIC AIRMASS AND WINDS WILL BE STRONG
ENOUGH TO KEEP THE LOWER LEVELS WELL MIXED.
KREIN
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
.IL...WIND CHILL ADVISORY 08 UTC TO 14 UTC FOR NORTHERN ILLINOIS.
.IN...NONE.
.LM...SC.Y THRU TONIGHT
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
AFDLOT 930 PM CST WED FEB 7 2007
.UPDATE...
THE WIND IS EXPECTED TO REMAIN AROUND 10 TO 20 KNOTS IN NORTH
CENTRAL ILLINOIS.THE WIND MAY REACH UP TO 15 TO 20 KNOTS NEAR LAKE
MICHIGAN. THIS IS DUE TO THE RELATIVELY WARM WATER IN THE CENTER OF
LAKE MICHIGAN. A LOCAL PRESSURE GRADIENT MAY EXIST DUE TO THE
TEMPERATURE GRADIENT. THE WIND IN THE ACARS SOUNDING OVER ORD AT
0254 UTC SHOWS WIND UP TO 34 KNOTS IN THE LAYER UP TO 5900 FT. WE
EXPECT SOME MIXING TONIGHT BELOW THE INVERSION. THE SNOW WILL KEEP
THE AIR COLD TONIGHT. THE WIND CHILL MAY FALL TO AROUND 25 BELOW
ZERO FAHRENHEIT. WE WILL ISSUE AN ADVISORY FOR WIND CHILL FOR VERY
EARLY MORNING. THIS IS FOR THOSE WAITING FOR TRAINS...BUSES AND
DRIVING TO WORK OR SCHOOL. THE HIGH IS OVER THE NORTHWEST
TERRITORIES AND EXTENDS SOUTH TO IOWA AND ILLINOIS. THIS IS VERY
COLD AIR...MAYBE CONTINENTAL ARTIC. THERE IS SNOW ACROSS MOST OF THE
NORTH CENTRAL UNITED STATES SO THIS AIR MAY HAVE NOT BECOME WARMER
TODAY. SO IT IS VERY COLD TONIGHT.
&&
.DISCUSSION...
400 PM CST
LITTLE DIFFERENCE SEEN IN GENERAL TRENDS SINCE YESTERDAY. POLAR
VORTEX AND THE CORE OF THE COLD AIR TO CONTINUE TO SHIFT E FROM
QUEBEC ACROSS THE CANADIAN MARITIMES TONIGHT THROUGH FRIDAY COMBINED
WITH A DEAMPLIFICATION OF THE WESTERN NOAM UPPER RIDGE. SHORT WAVES
WILL CONTINUE TO ROTATE OUT OF CANADA SOUTHEASTWARD ACROSS THE
NORTHERN AND LOWER GREAT LAKES. THESE WILL SERVE TO HAMPER ANY
SIGNIFICANT RETREAT OF THE COLD FROM THE NORTHERN PLAINS AND GREAT
LAKSES THOUGH A GRADUAL MEGER MODERATON WILL BE UNDERWAY AS THE
DEPTH OF THE COLD AIR DECREASES AND THE UPPER FLOW BACKS TO WEST
NORTHWEST LATE WEEK INTO THE WEEKEND. SURFACE RIDGE AXIS FORECAST TO
REMAIN EXTENDING FROM ALBERTA AND SAKTCHEWAN SOUTHEASTWARD ACROSS
THE NORTHERN PLAINS AND THE MID MS VALLEY INTO THE LOWER OH VALLEY.
AN IMPULSE TRAVELING EAST FROM THE SOUTHERN ROCKIES AND OUT OVER THE
SOUTHERN PLAINS ON THE STREAM STREAM FRIDAY NIGHT AND SATURDAY WILL
SPREAD SOME CLOUDS ACROSS CENTRAL AND MUCH OF NORTHERN IL AND
NORTHWEST IN BUT WITH WNW MID AND UPPER FLOW AND THE RIDGE AXIS
HOLDING FRM IA ACROSS SOUTHERN IL TO WESTERN KY AND TN THE
SIGNIFICANT PRECIP IS EXPECTED TO REMAIN WELL SOUTH OF THE FA. BY
EARLY NEXT WEEK THE SURFACE RIDGE AXIS RETREATS NORTHWARD INTO S
CENTRAL CANADA AND THE GREAT LAKES. ANOTHER WAVE IN THE SOUTHERN
STREAM MAY TRACK A BIT FURTHER NORTH AND MAY SPREAD ENOUGH MOISTURE
ACROSS CENTRAL IL AND IND BY MON NIGHT THUS LOW CHC POPS FOR -SN
INCLUDED ACROSS THE FAR SOUTHERN AND SOUTHEASTERN PARTS OF THE FA
MON NIGHT INTO TUE.
TRS
&&
.AVIATION DISCUSSION FOR 00Z TAFS...
530 PM CST
A QUIET EVENING EXPECTED FOR AVIATION WEATHER CONCERNS. PER LATEST
SATELLITE IMAGERY...THE CURRENT CLOUD COVER...JUST SOME SCT CI
ASSOCIATED WITH A JET STREAK OVER NRN IL/IN...IS DISSIPATING. FOR
THE REMAINDER OF THE EVENING AND OVERNIGHT...SKIES WL BE CLEAR. THE
ONLY TREAT OF ANY CLOUD COVER IS OVER FAR NORTHWESTERN IL...WHERE A
MID CLOUD DECK IS MOVING SEWD INTO CNTRL IL. BASED ON CURRENT
TRAJECTORIES...DO NOT EXPECT THE MID CLOUD TO MAKE IT INTO THE RFD
AREA. WITH HIGH PRESSURE BUILDING DOWN FROM THE NRN PLAINS INTO THE
LOWER MISSISSIPPI VALLEY AND LOW PRESSURE OVER ERN CANADA...WINDS WL
START OUT NWLY AND GRADUALLY TURN MORE WLY OVERNIGHT AND INTO THE
MORNING HRS TOMORROW. THE PRESSURE GRADIENT IS EXPECTED TO REMAIN
STRONG ENOUGH OVERNIGHT FOR WINDS TO REMAIN ARND 8-10KT. VISIBILITY
SHOULD REMAIN UNRESTRICTED AS THE AREA REMAINS UNDER A VERY DRY
ARCTIC AIRMASS AND WINDS WILL BE STRONG ENOUGH TO KEEP THE LOWER
LEVELS WELL MIXED.
KREIN
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
.IL...WIND CHILL ADVISORY 08 UTC TO 14 UTC FOR NORTHERN ILLINOIS.
.IN...NONE.
.LM...SC.Y THRU TONIGHT
&&
$$
AREA FORECAST DISCUSSION
NWS DETROIT/PONTIAC MI
AFDDTX 939 PM EST WED FEB 7 2007
.UPDATE...
SOME LOW LEVEL CONVERGENCE OVER SW LOWER MI HAS BEEN THE FOCUS FOR
A STRATUS DECK THAT HAS BEEN SLOWLY EXPANDING INTO SE MI OVER THE
LAST COUPLE OF HOURS. DESPITE THE RATHER WEAK INVERSION AND DRY
LOW LEVELS SHOWN ON BOTH 00Z DTX SOUNDING AND LATEST TAMDAR
SOUNDINGS OUT OF METRO...RADIATIONAL COOLING IS ALLOWING AN
EASTWARD EXPANSION OF THE UPSTREAM STRATUS. KAZO HAS EVEN BEEN
REPORTING FLURRIES UNDER THE STRATUS DECK. THE 00Z NAM12 MAINTAINS
WEAK LOW LEVEL CONVERGENCE INTO THE SOUTHERN HALF OF THE FORECAST
AREA THROUGH 09Z. BASED ON LATEST TRENDS...WILL UPDATE THE GRIDS
TO INCREASE CLOUD COVER ACROSS THE SOUTHERN HALF OF THE FORECAST
AREA. WILL ALSO LOWER CLOUD COVER AND REMOVE MENTION OF FLURRIES
ACROSS THE SAGINAW VALLEY AND THUMB. NO OTHER UPDATES TO THE GRIDS
ARE WARRANTED AT THIS TIME.
&&
.PREV DISCUSSION...ISSUED 604 PM EST WED FEB 7 2007
AVIATION...
A SURFACE TROUGH IS FORECAST TO MOVE ACROSS LAKE HURON TONIGHT AND
EARLY THUR MORNING. THIS WILL TIGHTEN THE SURFACE GRADIENT OVER
LOWER MICHIGAN TONIGHT AND MAINTAIN WEST-SOUTHWESTERLY WINDS OF 10 TO
15 KNOTS THROUGH THE TAF PERIOD. THE DRY ARCTIC AIRMASS OVER THE
REGION WILL MAINTAIN VFR CONDITIONS THROUGH THE TAF PERIOD.
PREV DISCUSSION...ISSUED 358 PM EST WED FEB 7 2007
SHORT TERM...TONIGHT AND TOMORROW
FORECAST CONCERN FOR THIS PERIOD IS CLOUDS OVERNIGHT AND INTO THE
MORNING.
WARMER TEMPERATURES WERE OBSERVED TODAY AS SOUTHEASTERN LOWER
MICHIGAN EXPERIENCED AFTERNOON HIGH TEMPERATURES SOME 5 TO 10
DEGREES WARMER THAN TUESDAY. THIS WAS A RESULT OF CLOUD FREE SKIES
AND WARM AIR ADVECTION (APPROXIMATELY 5 DEGREES C WARMER AT
850MB/PREVIOUS 24HRS). THE MSAS/NAM12 ANALYSIS THIS MORNING
DEPICTED A SUBTLE SURFACE RIDGE ACROSS SOUTHERN LOWER MICHIGAN THAT
HAS SINCE ERODED AND GIVEN WAY TO WEAK SURFACE TROUGH ACROSS THE
LOWER PENINSULA.
LOW TEMPERATURES TONIGHT EXPECTED TO DIP DOWN INTO THE LOWER SINGLE
DIGITS ABOVE ZERO. WINDS AT THIS TIME ARE EXPECTED TO STAY MIXED
ENOUGH TO DISALLOW MINIMUM TEMPERATURES FROM CRASHING.
HOWEVER...WINDS OF 10 TO 15 MPH WILL ALLOW FOR WIND CHILL VALUES
OVERNIGHT TO RANGE FROM 10 TO 15 DEGREES BELOW ZERO.
UPPER LEVEL SHORTWAVE/LOBE FROM HUDSON BAY ARCTIC VORTEX
STILL EXPECTED TO ROTATE THROUGH THE LOWER PENINSULA LATE
TONIGHT/TOMORROW MORNING. NOTHING SIGNIFICANT IS EXPECTED WITH THIS
SYSTEM...BEING VERY DRY. THE PASSING WAVE SHOULD ALLOW A
LOWERING IN CEILINGS AND A CHANCE OF SNOW SHOWERS DIRECTLY ALONG AND
BEHIND THE TROUGH. WINDS WILL GO NORTHWESTERLY FOLLOWING THE TROUGH
AND SHOULD NOT ALLOW CLOUDS TO BE OVERLY PERSISTENT TOMORROW. HIGH
TEMPERATURES TOMORROW SHOULD BE SIMILAR TODAY AS THERE IS SLIGHT
850MB COLD AIR ADVECTION FOLLOWING THE SHORTWAVE.
LONG TERM...THURSDAY NIGHT THROUGH NEXT WEDNESDAY
THE NEXT WAVE MOVING IN FROM CENTRAL CANADA THURSDAY NIGHT WILL
MAINTAIN THE COLD AIR OVER THE REGION BUT WILL BE QUITE MOISTURE
STARVED AS IT WILL BE CUT OFF FROM THE USUAL GULF AND PACIFIC
SUPPLIES. THIS BEING THE CASE, THE 12Z MODELS LOOK GOOD WITH LITTLE
OR NO QPF IN SE MICHIGAN AND IMPLYING NO MORE THAN LOW CHANCE POPS
FOR LIGHT SNOW, AND THAT JUST DURING THE EVENING. THE TRAILING SHORT
WAVE RIDGE AND DEEP NW FLOW WILL THEN HELP BREAK UP THE CLOUDS OVER
SE MICHIGAN AFTER MIDNIGHT. THERE IS SOME SURFACE GRADIENT FLOW
EXPECTED THAT WILL PREVENT IDEAL RADIATIONAL COOLING CONDITIONS BUT
ANTICIPATE LIGHTER WINDS THAN INDICATED IN THE MODELS WITH SOME
DECOUPLING. MOSTLY CLEAR SKY AND LIGHT WINDS WILL THEN ALLOW LOW
TEMPS TO DROP BELOW GUIDANCE AND WELL INTO THE SINGLE DIGITS AROUND
THE AREA BY SUNRISE FRIDAY MORNING.
SUNSHINE STARTING THE DAY ON FRIDAY WILL THEN FADE TO A COMBINATION
OF INCREASED LAKE STRATOCU AND HIGH CLOUDS DURING THE DAY. THIS WILL
OCCUR UNDER CONTINUED DEEP CYCLONIC FLOW BUT GRADUALLY BACKING
TOWARD THE WEST WITH A BIT OF MID LEVEL WARM ADVECTION. THE CLOUD
FORECAST IS ON THE LOW CONFIDENCE SIDE SINCE IT IS DEPENDENT ON A
SUBTLE WAVE IN THE NW FLOW FROM THE 12Z MODEL RUNS. FOR NOW, WE WILL
KEEP A LOW CHANCE OF SNOW SHOWERS IN THE FORECAST AND GIVE THE MID
LEVEL MOISTURE A CHANCE TO SEED SOME LAKE EFFECT FROM LAKE MICHIGAN
BY FRIDAY NIGHT.
THERE IS NOT MUCH CHANGE EXPECTED ON SATURDAY AND SUNDAY. THE CENTER
OF THE POLAR VORTEX WILL BECOME REESTABLISHED IN THE VICINITY OF
JAMES BAY DURING THIS TIME. THE 12Z GFS IS THEN STRONGER THAN THE
OTHER GLOBAL MODELS WITH AN UPPER TROUGH MOVING THROUGH THE GREAT
LAKES ON MONDAY. CORRESPONDINGLY, THE ASSOCIATED COLD FRONT IS SHOWN
TO BRING WITH IT STRONGER SURGE OF ARCTIC AIR BY MONDAY NIGHT. THE
MODEL AGREEMENT IS IN THE SHORT DURATION OF THIS COLD SURGE AS THE
UPPER WAVE MARKS THE BEGINNING OF THE EASTWARD TRANSITION OF THE
LONG-LIVED POLAR VORTEX.
THE BREAKDOWN OF THE BLOCKING PATTERN OVER THE EASTERN PACIFIC WILL
THEN GOVERN THE EVOLUTION OF THE UPPER AIR FLOW HEADING INTO THE
MIDDLE OF NEXT WEEK. THIS WILL FOSTER THE CONTINUED SLOW EASTWARD
PROGRESSION OF THE POLAR VORTEX AND THE FORMATION OF RISING HEIGHTS
AND A MORE ZONAL, CONSOLIDATED, WESTERLY UPPER FLOW OVER THE U.S.
THE RESULTING WARMING TREND IN THE GREAT LAKES WILL BE MODEST AND
SLOW, HOWEVER, AS THE MAIN BAROCLINIC ZONE AND STORM TRACK REMAIN
TO OUR SOUTH. TEMPERATURES, THEN, WILL BE WARMER THAN RECENT DAYS
BUT STILL BELOW NORMAL AND WITH LITTLE OR NO PRECIPITATION.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...GALE WARNING...SOUTH HALF UNTIL 1 AM FRIDAY.
SMALL CRAFT ADVISORY...LHZ441-LHZ442 UNTIL 7 AM FRIDAY.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.
&&
$$
AVIATION/UPDATE...CONSIDINE
SHORT TERM...CB
LONG TERM....BT
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
AREA FORECAST DISCUSSION
NWS DETROIT/PONTIAC MI
AFDDTX 1154 PM EST MON FEB 5 2007
.AVIATION...
LOW LEVEL CONVERGENCE WILL FOCUS A STRATO CU FIELD AND SOME
FLURRIES IN THE DETROIT AREA THROUGH TUES MORNING. A SHORT WAVE
TROUGH CURRENTLY OVER CENTRAL CANADA WILL DROP DOWN INTO THE
NORTHERN OHIO VALLEY LATE TUES AFTERNOON. THIS SYSTEM WILL
INCREASE MOISTURE ACROSS THE REGION AND ENHANCE LAKE EFFECT SNOW
SHOWERS...ESPECIALLY BETWEEN DETROIT AND FLINT. BY TUES
AFTERNOON...MVFR CONDITIONS ARE EXPECTED ACROSS MOST OF SOUTHEAST
MICHIGAN AS THIS MOISTURE MOVES INTO THE REGION.
&&
.PREV DISCUSSION...ISSUED 924 PM EST MON FEB 5 2007
UPDATE...
LOW LEVEL CONVERGENCE CONTINUES TO FOCUS SOME LAKE STRATO CU AND
FLURRIES ALONG THE I-94 AND M 59 CORRIDORS. THE LATEST NAM12
SUGGESTS THIS WILL CONTINUE THROUGH MUCH OF THE NIGHT. THE REST OF
THE FORECAST AREA IS GENERALLY CLEAR. WOULD EXPECT THESE
CONDITIONS TO PERSIST THROUGH THE NIGHT BASED ON LATEST NAM. WILL
THUS UPDATE THE WEATHER GRIDS TO REFLECT THIS.
THE COMBINATION OF MIN TEMPS TONIGHT AND WINDS ARE STILL EXPECTED
TO KEEP WIND CHILL READINGS IN THE -10 TO -15C RANGE...BELOW
ADVISORY CRITERIA. THE ONLY MAJOR UPDATE TO THE TEMPERATURES WAS
TO LOWER MIN TEMPS ACROSS LENAWEE AND MONROE COUNTIES DUE TO THE
SOUTHWEST SURFACE FLOW INHIBITING AIRMASS MODIFICATION FROM LAKE
MICHIGAN. TEMPS IN NORTHERN INDIANA ARE ALREADY SUB ZERO.
PREV DISCUSSION...ISSUED 313 PM EST MON FEB 5 2007
SHORT TERM...
ANOTHER COLD NIGHT IN STORE...AS CLOUDS FROM LAKE MICHIGAN HAVE
STRUGGLED TO ADVANCE EASTWARD...EVEN WITH THE DIURNAL ENHANCEMENT
HELPING TO RAISE INVERSION HEIGHTS UP TOWARD 4000 FEET PER DTW
TAMDAR DATA. THE GOOD NEWS IS THE SUNSHINE HAS HELPED BOOST MAX
TEMPS TO AROUND 10 DEGREES THIS AFTERNOON...A GOOD 3-5 DEGREES
WARMER COMPARED TO YESTERDAY.
PRESSURE GRADIENT OVER SOUTHERN LOWER MICHIGAN TONIGHT LOOKS TO BE
ABOUT 2 MB LESS WHEN COMPARED TO THIS MORNING. THIS SHOULD TRANSLATE
TO LOWS AT OR BELOW ZERO EVERYWHERE...AND HAVE UNDERCUT GFS MOS
GUIDANCE BY A GOOD 5 DEGREES IN MOST SPOTS. A FAR AS WIND CHILLS
GO...WITH THE WEAKER GRADIENT...WINDS LOOK TO BE BORDERLINE...AROUND
10 MPH...WITH WIND CHILLS HOVERING RIGHT AROUND -20 F (ADVISORY
CRITERIA). WILL HOLD OFF ON THE ADVISORY...AS WIND CHILLS OF -20 F
OR COLDER ARE NOT EXPECTED TO BE WIDESPREAD...NOR ARE THEY EXPECTED
FOR AN EXTENDED PERIOD OF TIME.
DRY AIRMASS CONTINUES TO LIMIT LAKE EFFECT ACTIVITY...AND SEE NO
SIGNIFICANT CHANGES INTO TONIGHT. THE WESTERN CLOUD
EDGE/CONDENSATION OVER LAKE MICHIGAN HAS ACTUALLY BEEN PULLING EAST
THIS AFTERNOON.
TOMORROW LOOKS TO BE A DIFFERENT STORY...AS UPPER WAVE CURRENTLY
OVER NORTHERN ALBERTA QUICKLY DIVES SOUTHEAST...TRACKING ALONG THE
SOUTHERN MICHIGAN BORDER...PER NAM/GFS TROPOPAUSE PRESSURE FIELDS.
THIS SHOULD AT LEAST ALLOW FOR AN ENHANCEMENT TO THE I-94/M-59
CONVERGENT BAND. HOWEVER...MODELS IMPLYING MOST/ALL OF THE SYNOPTIC
SNOW WILL STAY SOUTH OF THE BORDER AS MAIN 850-700 MB THETA
GRADIENT REMAINS CONFINED TO THE SOUTHERN OHIO VALLEY...WITH LITTLE
IN THE WAY OF MOISTURE TRANSPORT INTO SOUTHERN LOWER MICHIGAN. STILL
A LITTLE LEARY THE UPPER WAVE MAY BE DRAWN A LITTLE FARTHER NORTH
THAN INDICATED...AND WILL CARRY A 50 POP FOR M-59 AND POINTS SOUTH.
NO CHANGES TO MAXES TOMORROW...LOWER TEENS EXPECTED.
LONG TERM...TUESDAY NIGHT THROUGH MONDAY
VERY LITTLE CHANGE IN THE ONGOING PATTERN THROUGH THE WEEKEND AS
SEVERAL STRONG SHORTWAVES DIG INTO THE EASTERN NORTH AMERICAN UPPER
TROUGH AND KEEP THE EASTERN CANADIAN POLAR VORTEX WELL-ESTABLISHED.
THIS WILL MAINTAIN A COLD AIRMASS ACROSS THE REGION WITH HIGHS ONLY
IN THE TEENS/LOWER 20S AND LOWS IN THE SINGLE DIGITS TO OCCASIONALLY
BELOW ZERO.
THE FIRST OF THESE SHORTWAVES WILL BE PASSING SOUTH OF THE REGION
TUESDAY EVENING. THERE MAY BE SOME LEFTOVER LIGHT SNOW OVER THE FAR
SOUTHERN CWA FROM THIS SYSTEM (OR AT LEAST AN ENHANCEMENT TO LAKE
EFFECT SNOW SHOWERS FROM THE MOISTURE IT WILL BRING)...BUT OVERALL
IT WILL JUST ENSURE THAT THE STATUS QUO HOLDS...AND WE REMAIN IN THE
SAME TEMPERATURE REGIME. THE NEXT SHORTWAVE WILL DROP DOWN FROM THE
ARCTIC CIRCLE AND SPIN AROUND THE POLAR VORTEX. SO...EXPECT THIS
FEATURE TO BRING A RESURGENCE OF COLDER AIR BY LATE FRIDAY INTO
SATURDAY. ATTM...IT APPEARS THIS AIRMASS IS SOME 5-7 DEGREES C
MILDER THAN THE ARCTIC AIRMASS OF THIS PAST WEEKEND...SO DO NOT
EXPECT TEMPERATURES TO STRUGGLE QUITE AS MUCH.
THE FORECAST FOR SNOW SHOWERS REMAINS TRICKY...AT LEAST IN TRYING TO
PICK OUT THE DAY(S) THAT HAVE THE BEST CHANCE OF LIGHT ACCUMULATION.
NO LARGE STORM SYSTEMS ARE ON THE WAY...AND ANY ACCUMULATING SNOWS
WILL MAINLY BE LAKE EFFECT/ENHANCED SNOW SHOWERS. AFTER A PERIOD OF
ENHANCED SNOW SHOWER ACTIVITY TO START THE LONG TERM FORECAST...THE
GENERAL FORECAST WILL BE FOR PERIODIC FLURRIES IN THE WEDNESDAY AND
THURSDAY TIMEFRAME...WITH MORE WIDESPREAD SNOW SHOWERS BY FRIDAY AND
SATURDAY AS THE AFOREMENTIONED ARCTIC SHORTWAVE DIVES THROUGH THE
GREAT LAKES.
AT THE VERY END OF THE FORECAST...THE AMPLIFIED PATTERN CONTINUES TO
SHOW SOME SIGNS OF RELAXING...WHICH WOULD ALLOW MORE INTRUSION OF
PACIFIC AIR INTO THE REGION...AND LESS INTRUSION OF THE COLDEST AIR
FROM THE ARCTIC. WILL MAINTAIN THE SLIGHT MODERATION IN THE SUNDAY
TO MONDAY TIMEFRAME GIVEN SOME CONSISTENCY IN GFS RUNS DURING THE
PAST FEW DAYS FOR THIS BASIC SCENARIO. STILL...TEMPERATURES SHOULD
REMAIN LARGELY BELOW NORMAL.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...GALE WARNING...SOUTH HALF UNTIL 7 AM TUESDAY.
SMALL CRAFT ADVISORY...LHZ441-LHZ442 UNTIL 7 PM WEDNESDAY.
SMALL CRAFT ADVISORY...LHZ421 UNTIL 7 AM TUESDAY.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...SMALL CRAFT ADVISORY FOR WINDS...UNTIL 7 AM TUESDAY.
&&
$$
AVIATION...CONSIDINE
SHORT TERM...SF
LONG TERM....DG
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
AREA FORECAST DISCUSSION
NWS SEATTLE WA
AFDSEW 900 PM PST MON FEB 5 2007
.SYNOPSIS...LIGHT FLOW WITH PLENTY OF MOISTURE AT THE LOWER LEVELS
COMBINING TO CREATE FOGGY CONDITIONS OVER THE AREA THROUGH TUESDAY
MORNING. AN APPROACHING LOW PRESSURE SYSTEM WILL BRING A CHANCE OF
RAIN TO SOUTHWEST WASHINGTON TUESDAY AFTERNOON AND THE REST OF THE
AREA TUESDAY NIGHT. A SERIES OF WEATHER SYSTEMS WILL MOVE THROUGH
WESTERN WASHINGTON THROUGH THE WEEKEND KEEPING A CHANCE OF RAIN IN
THE FORECAST THROUGH THE REMAINDER OF THE WEEK.
&&
.SHORT TERM...LATEST ACARS SOUNDINGS STILL SHOW THE TOP OF THE
STRATUS DECK AROUND 2500K FT THIS EVENING. THE INVERSION WILL REMAIN
IN PLACE THROUGH TONIGHT WITH AREAS OF DENSE FOG PERSISTING. THE
MAIN FORECAST CHALLENGE IS DETERMINING IF THIS WILL LIFT ON TUE AND
AT WHAT TIME. THE NAM-12 SOUNDINGS IMPLY STRATUS AND FOG WILL
REMAIN OVER THE AREA THROUGH AROUND 21Z...THEN PERHAPS LIFTS INTO A
HIGHER DECK AS SHORT WAVES MOVES ACROSS THE AREA. LOOKS LIKE ANOTHER
CLOUDY DAY IN STORE BUT PERHAPS SOME IMPROVEMENTS IN CIGS AND
VISIBILITY LATE IN THE DAY. RAIN SHOULD MOVE IN AFTER 00Z AND
CONTINUING AT TIMES THROUGH MID WEEK. SEVERAL SHORT WAVES MOVING
ACROSS SHOULD HELP KEEP THE LOW LEVELS RELATIVELY MIXED. NO CHANGES
MADE THIS EVENING. MERCER
.LONG TERM...NO CHANGES TO PREVIOUS DISCUSSION...EXTENDED MODELS
SHOWING GOOD RUN TO RUN CONSISTENCY WITH THE TROUGH REMAINING OFF
THE COAST AND A SERIES OF NEGATIVELY TILTED SYSTEMS MOVING THROUGH
THE AREA APPROXIMATELY EVERY 24 HOURS. AS IS THE CASE WITH THE FIRST
COUPLE OF SYSTEMS...BY THE TIME THE FRONTS GET TO WESTERN WASHINGTON
THEY WILL BE FAIRLY WEAK BUT WILL HAVE TO KEEP AT LEAST CHANCE POPS
IN THE FORECAST FOR NOW THROUGH THE LONG TERM. FELTON
&&
.AVIATION...WIDESPREAD LOW STRATUS AND FOG WILL HANG TOUGH THRU
ABOUT 20Z AS LIGHT OFFSHORE FLOW IN A STRONG SUBSIDENCE INVERSION
CONTINUES. A DISTURBANCE MOVING INTO THE OFFSHORE WATERS LATE TUE
AND TUE NIGHT SHOULD START TO MIX THINGS OUT AROUND 20Z.
LIGHT NELY WIND AT KSEA WILL VEER TO SE AND S EARLY TUE. ALBRECHT
&&
.SEW WATCHES/WARNINGS/ADVISORIES...SMALL CRAFT ADVISORY WEST
ENTRANCE TO THE STRAIT AND NEARSHORE NORTHERN COASTAL WATERS.
$$
WEATHER.GOV/SEATTLE
AREA FORECAST DISCUSSION...UPDATED
NWS GREEN BAY WI
AFDGRB 930 PM CST WED FEB 7 2007
UPDATE...NO CHANGES PLANNED TONIGHT. WILL LET ADVISORY RUN. TEMPS
RUNNING 2 TO 5 DEGREES WARMER THAN PREVIOUS NIGHT...THOUGH WINDS ARE
STAYING UP AHEAD OF WAVE PUSHING THROUGH SOUTHERN ONTARIO.
PROFILERS/TAMDAR SHOWING LOW LEVEL WINDS HAVE INCREASED INTO THE 30 TO
35 KT RANGE. REMAINING WELL MIXED IN LOWER LAYERS...SO WINDS NOT THE
ISSUE TONIGHT. TEMPERATURES ON THE OTHER HAND ARE THE ISSUE REGARDING
THE ADVISORY. AT THIS POINT BELIEVE WILL SEE ADVISORY CRITERIA MET FOR
A BRIEF TIME NORTH CENTRAL...ALSO LIKELY TO BE MET IN PARTS OF CENTRAL
FOR A FEW HOURS. BUT SINCE WILL BE CLOSE TO 25 BELOW WILL NOT EXPAND
ADVISORY AT THIS TIME.
REMAINING DISCUSSION FROM PREVIOUS SHIFT.
.SHORT TERM...TONIGHT AND THURSDAY...MAIN ISSUE WITH SHORT TERM IS TEMPS
AND WINDS FOR WIND CHILL VALUES TONIGHT.
STRONG POLAR VORTEX JUST EAST OF HUDSON BAY AND A RIDGE LOCATED OVER THE
WRN US...WILL KEEP NE WI IN NW FLOW FOR THE PERIOD. STRONG SHORT WAVE
ROTATING AROUND VORTEX WAS SEEN OVER WRN ONTARIO ON WV IMAGERY...WHICH
WILL QUICKLY DROP SE ACROSS LAKE SUPERIOR AFTER MIDNIGHT TONIGHT. MODELS
IN PRETTY GOOD AGREEMENT WITH LOCATION OF SHORT WAVE...WITH THE BEST
ENERGY TRACKING ACROSS UPPER MICHIGAN AND JUST SLIGHTLY BRUSHING FAR NRN
WI. MOISTURE IS VERY LIMITED OVER THE REGION AS SEEN ON FORECAST
SOUNDINGS AND TIME HEIGHTS. THEREFORE EXPECT AREA TO REMAIN MOSTLY CLEAR
TONIGHT...OTHER THAN A FEW MID CLOUDS ACROSS THE FAR N...AS THE SHORT
WAVE PUSHES THROUGH. GFS SLIGHTLY FASTER THAN NAM...BUT WITH SPEED OF
SYSTEM AND LACK OF MOISTURE...IT IS NOT TOO MUCH OF AN ISSUE.
WITH STRONG HIGH PRESSURE DEVELOPING TO THE W OVER THE NRN PLAINS AND
STRONG LOW OVER HUDSON BAY...PRESSURE GRADIENT SHOULD REMAIN UP TONIGHT.
WITH THE CLEAR SKIES...TEMPS EXPECTED TO FALL TO AROUND GFS GUIDENCE
VALUES. THIS WILL CREATE WIND CHILLS OF -25 TO -30 ACROSS NC WI AND HAVE
PUT UP A WIND CHILL ADVISORY FOR THAT AREA. WIND SPEED WILL LARGELY
DEPEND ON THE STRENGTH OF THE INVERSION...AS A H925 40KT WIND MAX WILL
BE SEEN ACROSS MOST OF AREA TONIGHT.
MODELS SHOWING NEXT SHORT WAVE DROPPING SOUTH AROUND POLAR VORTEX LATE
ON THURSDAY AFTERNOON...REACHING UPPER MICHIGAN AROUND 00Z ON FRIDAY.
DRY AIR REMAINS IN PLACE AGAIN ON THURSDAY...WITH ONLY A FEW CLOUDS
AGAIN OVER THE FAR N...AS THE SHORT WAVE APPROACHES WITH A SLIGHT
INCREASE IN MOISTURE. SO HAVE ONLY MADE A FEW TWEAKS TO THE FORECAST AND
WENT WITH SIMILAR VALUES TO TODAY WITH TEMPS...WITH ONLY A DEGREE OR SO
COOLER DUE TO SOME WEAK CAA BEHIND THE SHORTWAVE.
.LONG TERM...THURSDAY NITE THRU NEXT WEDNESDAY. FORECAST FOCUS ON
TEMPERATURES THRU THE PERIOD AND SNOW CHANCES FROM SUNDAY NITE TO
WEDNESDAY.
HIGH PRESSURE CONTINUES TO INFLUENCE THE AREA DURING THE WEEKEND AS
TEMPERATURES REMAIN BELOW NORMAL. WILL CONTINUE TO KEEP TEMPERATURES
BELOW GUIDANCE AS THE COLD AIRMASS REMAINS IN PLACE. THE MODELS THEN
BRING A SYSTEM THRU THE AREA LATE SUNDAY AND INTO SUNDAY NITE. THE GFS
IS THE FURTHEST NORTH WITH THE QPF BRINGING IT THRU THE SOUTHERN CWA.
GIVEN THIS IS THE FURTHEST NORTH SOLUTION AND THE LIGHT AMOUNT OF QPF
INVOLVED WILL LEAVE DRY FOR NOW.
WINDS THEN TURN FAVORABLE FOR LES FROM MONDAY TO WEDNESDAY ACROSS NORTH
CENTRAL WISCONSIN AND SEMI FAVORABLE FOR EXTREME EAST CENTRAL WISCONSIN
TUESDAY AND WEDNESDAY. HOWEVER THE LAKES ARE FREEZING UP RATHER QUICKLY
AND GIVEN THE COLD TEMPERATURES ARE EXPECTED TO CONTINUE WILL LEAVE
THESE PERIODS DRY AS THE AVAILABLE FETCH WILL BE REDUCED.
&&
.AVIATION...AVAIATION...VFR CONDITIONS WILL BE IN PLACE ACROSS THE
REGION TONIGHT AND THURSDAY. THE MAIN CONCERN WILL BE LLWS TONIGHT...AS
A 40KT JET AT 2KFT PASSES OVER THE REGION BETWEEN 00Z AND 12Z.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
WIND CHILL ADVISORY MIDNIGHT TONIGHT UNTIL 9 AM THURSDAY
WIZ005-010>012-018-019-
&&
$$
WEATHER.GOV/GREENBAY