Forecast Discussions mentioning "ACARS", "MDCRS", "AIRCRAFT", "TAMDAR", or "AMDAR" received at FSL on 02/10/07

AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
AFDSGX 330 AM PST THU FEB 8 2007

.SYNOPSIS... UPPER LEVEL LOW PRESSURE APPROACHING FROM THE PACIFIC WILL BRING VARIABLE CLOUDINESS. THERE WILL BE AREAS OF FOG WEST OF THE MOUNTAINS...LOCALLY DENSE THIS MORNING. LIGHT RAIN COULD BEGIN AS EARLY AS FRIDAY WITH AN INCREASING CHANCE INTO SUNDAY. SHOWERS COULD LINGER INTO MONDAY THEN ANOTHER SYSTEM WILL BRING A CHANCE OF SHOWERS AGAIN TUESDAY...CLEARING WEDNESDAY.

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES...

.SHORT TERM (TODAY-SAT)... THERE WERE AREAS OF COASTAL LOW CLOUDS AND FOG...EXTENDING INTO THE WRN INLAND VALLEYS EARLY THIS MORNING. FOG WAS LOCALLY DENSE ON THE HIGHER COASTAL TERRAIN AND WRN INLAND VALLEYS. THERE WERE ALSO A FEW HIGH CLOUDS. EARLY MORNING ACARS SOUNDINGS INDICATED A WEAK LOW LEVEL INVERSION WITH INCREASING SW TO NW WINDS ALOFT. ONSHORE GRADIENTS WITH ABOUT 4 MB SAN-IPL.

THERE WILL BE A SOMEWHAT ERRATIC MARINE LAYER THE NEXT COUPLE OF MORNINGS BUT IT SHOULD DEEPEN A LITTLE LATE TONIGHT AND FRI MORNING. THERE WILL BE A BRIEF BREAK IN HIGH CLOUDINESS EARLY TODAY THEN MID TO HIGH CLOUDS WILL INCREASE IN SW FLOW ALOFT AHEAD OF AN APPROACHING PAC TROUGH. A DEEPENING MOIST LAYER COULD BRING LIGHT SHOWERS AS EARLY AS FRIDAY...MAINLY IN THE NRN AREAS. THE CHANCE OF RAIN WILL GRADUALLY INCREASE THROUGH SAT AS A SHORT WAVE MOVES PAST TO THE N. RELATIVELY MINOR TEMP CHANGES TODAY AND FRI WITH MOST AREAS SLIGHTLY BELOW SEASONAL. COOLER SAT. WINDS ALOFT AND STRONGER ONSHORE GRADIENTS WILL CAUSE LOCAL WINDY CONDITIONS IN THE MOUNTAINS AND DESERTS SAT AFTERNOON AND EVENING.

.LONG TERM (SUN-WED)... PROGS INDICATE THE LOW LAT JET WILL MOVE IN TO THE S OF SAN DIEGO AS THE TROUGH MOVES ONSHORE SUN. THIS WILL BRING A BETTER CHANCE OF MORE SUBSTANTIAL PRECIP. THE PRECIP SHOULD TAPER OFF MON IN FLAT MOIST WLY FLOW ALOFT. ANOTHER...COLDER...TROUGH WILL CAUSE AN INCREASED CHANCE OF RAIN AND MOUNTAIN SNOW AROUND TUE. TOTAL RAINFALL COULD REACH NEAR AN INCH WEST OF THE MOUNTAINS FROM THESE TWO SYSTEMS...WITH LOCAL LARGER AMOUNTS ON W FACING MOUNTAINS SLOPES. DRIER NW FLOW ALOFT WED.

&&

.AVIATION... FOG IS MORE WIDESPREAD THAN LOW CLOUDS THIS EARLY MORNING. HOWEVER THE FOG IS MOSTLY CAUSING AOB 3SM AND ONLY ISOLATED DENSE FOG WITH VIS BLW 1SM. FOG EXTENDS ALL THE WAY TO ONT...AND PARTIALLY INTO SAN CO VALLEYS. ONSHORE FLOW IS LESS THAN EXPECTED SO THE MARINE LAYER IS SLUGGISH. THUS DO NOT EXPECT CONDITIONS TO CHANGE MUCH THROUGH 8 AM. NO CHANGE IN THE PRESSURE PATTERN INDICATED IN THE MODELS...SO EXPECTING A SIMILAR MARINE LAYER TONIGHT WITH PATCHY LOW CLOUDS WITH BASE AROUND 1000 FT MSL WITH TOPS 1500 FT...AND AREAS OF AOB 3SM FOG. GOOD VIS WITH HIGH CIRRUS THIS AFTERNOON EXCEPT FOR 5SM HAZE ALONG THE COAST. A LAYER OF 18K FT ALTOCU AND ALTOCIRRUS AROUND 15 TO 20K FT ALSO MOVING IN FROM NW THIS PM. WINDS AT 10 FT WILL BE WSW 15 KT TODAY.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

PUBLIC...DVA AVIATION...MACKECHNIE

AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
AFDSGX 930 PM PST WED FEB 7 2007

.SYNOPSIS... LOW PRESSURE ALOFT APPROACHING FROM THE PACIFIC WILL BRING OCCASIONAL CLOUDINESS...INCLUDING SOME LOW CLOUDS WEST OF THE MOUNTAINS THROUGH FRIDAY. SOME LIGHT PRECIPITATION COULD BEGIN AS EARLY AS FRIDAY...BUT A MORE VIGOROUS PACIFIC SYSTEM WILL BRING A GOOD CHANCE OF PRECIPITATION BY SUNDAY...WITH LOCAL SNOW AT HIGHER ELEVATIONS. SHOWERS WILL CONTINUE AT TIMES THROUGH AROUND TUESDAY...THEN A CLEARING TREND WILL OCCUR AS THE TROUGH MOVES TO THE EAST. TEMPERATURES WILL AVERAGE SLIGHTLY BELOW NORMAL.

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES...

HIGH CLOUDS HAD DECREASED SOMEWHAT THIS EVENING...BUT LOW CLOUDS WERE FORMING IN COASTAL AREAS. SOME PRECIP HAD MOVED THROUGH CENTRAL CALIFORNIA AS THE TAIL END OF A FRONT WENT THROUGH THAT AREA...BUT NO PRECIP IS EXPECTED FROM THAT FURTHER SOUTH. A SYSTEM NEAR 36N/136W ALSO APPEARS THAT IT WILL STAY TO OUR NORTH...SO A DEEPENING MARINE LAYER AND OCCASIONAL MID-HIGH CLOUDS WILL BE THE FEATURES DOWN HERE THE NEXT 2 DAYS...THOUGH BY FRIDAY...ENOUGH LOW-LEVEL MOISTURE COULD BE IN PLACE FOR LIGHT RAIN...MAINLY NORTH.

A ZONAL JET STREAM AROUND 30 DEG N LATITUDE COVERS A GOOD CHUNK OF THE PACIFIC...ESPECIALLY WEST OF THE DATE LINE. THIS JET STREAM SHOULD EVENTUALLY EXTEND EAST TO SO-CAL AND UNDERCUT ANY RIDGING THAT OCCURS TO THE NORTH OVER THE EAST PAC. THUS...BY THE WEEKEND...WE WILL BE IN A FAVORABLE PATTERN FOR APPRECIABLE RAIN AMOUNTS...WITH CURRENT MODEL GUIDANCE SHOWING SUNDAY BEING THE MOST LIKELY DAY FOR RAIN. AS TYPICAL WITH SYSTEMS ASSOCIATED WITH ZONAL JETS NEAR OUR LATITUDE...THE SNOW LEVELS SHOULD BE FAIRLY HIGH...MOSTLY ABOVE 6000 FEET. ANOTHER SYSTEM COULD FOLLOW TUESDAY AND HAVE A LITTLE BIT MORE COLD AIR AND PRODUCE SLIGHTLY LOWER SNOW LEVELS AND MORE SHOWERY PRECIPITATION. TOTAL RAINFALL COULD POTENTIALLY REACH AN INCH WEST OF THE MTNS WITH THESE 2 SYSTEMS COMBINED...WITH LOCAL HIGHER AMOUNTS IN THE MOUNTAINS. MODELS HAVE BEEN FAIRLY CONSISTENT WITH THE LONG-WAVE TROUGH ASSOCIATED WITH THESE SYSTEMS MOVING EAST INTO THE INTERMOUNTAIN WEST BY WED...SO DRY WEATHER SHOULD BEGIN AROUND THEN.

&&

.AVIATION... EARLY EVENING ACARS SOUNDINGS INDICATE THE MARINE LAYER DEPTH WAS AROUND 1000 FEET OVER THE COASTAL WATERS AND AROUND 700 FEET INLAND FROM THE COAST. EXPECT SOME DEEPENING OF THE MARINE LAYER OVERNIGHT TO AROUND 1200 TO 1500 FEET. AREAS OF STRATUS ALONG THE COAST SHOULD FILL IN THROUGH THE EVENING AND PUSH ONSHORE OVERNIGHT. EXPECT BROKEN TO OVERCAST CEILINGS AT THE COASTAL AND MESA AIRPORTS BY MIDNIGHT. BASES OF THE STRATUS SHOULD BE AROUND 800 TO 1000 FEET MSL WITH TOPS AROUND 1200 FEET. VISIBILITIES BELOW THE STRATUS SHOULD BE 3 MILES OR BETTER EXCEPT SOME INLAND AREAS COULD BE LESS THAN 1 MILE AT TIMES IN FOG. STRATUS SHOULD SCATTER OUT BY LATE MORNING ON THURSDAY.

ABOVE THE STRATUS...VARIABLE AMOUNTS OF CIRRUS ABOVE FL200 ARE EXPECTED THROUGH THURSDAY.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

PUBLIC...MAXWELL AVIATION...HORTON

AREA FORECAST DISCUSSION
NWS DETROIT/PONTIAC MI
AFDDTX 1149 PM EST WED FEB 7 2007

.AVIATION...

AN AREA OF STRATUS OVER SOUTHERN MICHIGAN HAS BEEN STRUGGLING TO MAKE IT INTO THE TAF SITES THIS EVENING DUE TO THE VERY DRY AIRMASS OVER SE MICHIGAN. OVERALL...BASED ON LATEST TRENDS...EXPECT SKIES TO REMAIN SCATTERED OR CLEAR INTO THURS MORNING. A COUPLE OF SHORT WAVE TROUGHS WILL MOVE ACROSS THE REGION FROM THE NORTH DURING THE TAF PERIOD. THE LATEST MODEL GUIDANCE SUGGESTS THE WAVE MOVING ACROSS LOWER MI THURS EVENING WILL HAVE BETTER MOISTURE WITH IT. THIS ALONG WITH SOME DIURNAL ENHANCEMENT SHOULD ALLOW A SCATTERED TO BROKEN STRATO CU FIELD TO DEVELOP IN THE AFTERNOON. GIVEN THE LOW LEVEL DRY AIR...WILL KEEP CEILINGS VFR.

&&

.PREV DISCUSSION...ISSUED 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 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 SAN DIEGO CA
847 PM PST FRI FEB 9 2007 .SYNOPSIS... AN APPROACHING PACIFIC STORM SYSTEM WILL BRING AN INCREASING CHANCE OF RAIN FOR SATURDAY AFTERNOON...WITH RAIN BECOMING LIKELY OVER AND WEST OF THE MOUNTAINS LATE SATURDAY INTO SUNDAY. A SLIGHT CHANCE OF SHOWERS WILL LINGER INTO MONDAY AS THE LOW MOVES EAST. ANOTHER... COLDER LOW PRESSURE SYSTEM WILL BRING A CHANCE OF SHOWERS TUESDAY AND TUESDAY NIGHT. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES. MID AND HIGH CLOUDS CONTINUE TO STREAM IN AHEAD OF A FRONTAL SYSTEM THAT IS STILL ABOUT 900 MILES WEST OF SAN DIEGO. TIME CROSS SECTIONS OF GFS MODEL SHOW MAIN DEEP LEVEL MOISTURE TO REACH ORANGE COUNTY AFTER 2 PM SATURDAY AND AFTER 8 PM IN SAN DIEGO COUNTY. EXPECT HEAVIEST RAINFALL AFTER THESE TIMES. THE NAM MODEL IS DISTINCTLY DRIER AND SLOWER BUT STILL SHOWS A DECENT FRONTAL BAND MOVING THROUGH THE AREA BUT NOT UNTIL SUNDAY MORNING. RAINFALL FORECAST AMOUNTS SHOULD RANGE FROM ABOUT 1/4 TO 1/2 INCH W OF THE MOUNTAINS WITH 1/2 TO 1 INCH ON THE W FACING MOUNTAIN SLOPES. THERE SHOULD BE ABOUT 1/3 INCH IN THE HIGH DESERTS AND LESS THAN A 1/4 INCH IN THE LOWER DESERTS. THIS SYSTEM IS QUITE WARM SO EXPECT SNOW ONLY ON THE HIGHER MOUNTAINS OF SAN BERNARDINO AND RIVERSIDE COUNTY. SHOWERS WILL LIKELY LINGER INTO SUNDAY AFTERNOON. STRONGER WINDS ALOFT AND ONSHORE FLOW WILL CAUSE LOCAL GUSTY WINDS...MAINLY IN THE MOUNTAINS AND DESERTS SATURDAY AND SUNDAY BUT WINDS ARE EXPECTED TO REMAIN BELOW ADVISORY STRENGTH. ANOTHER SYSTEM...A LITTLE COLDER WILL BRING ANOTHER THREAT OF PRECIPITATION LATE MONDAY AND TUESDAY. THIS SYSTEM LOOKS TO BRING ABOUT THE SAME PRECIPITATION AMOUNTS. SHOWERS MAY LINGER INTO WEDNESDAY MORNING. DRIER NW FLOW ALOFT WILL DEVELOP DURING THE DAY WEDNESDAY AND CONTINUE THROUGH THURSDAY. && .AVIATION... THE 00Z NKX SOUNDING AND EARLY EVENING ACARS SOUNDINGS INDICATE THE MARINE LAYER REMAINS QUITE SHALLOW...LESS THAN 500 FEET BUT SHOULD DEEPEN UP OVERNIGHT. MID AND HIGH CLOUDS ARE OBSCURING THE LOWER LEVELS SO UNABLE TO DETERMINE THE EXTENT...IF ANY...OF STRATUS OVER THE COASTAL WATERS. HOWEVER...RECENT METAR FROM KAVX AND KNUC SUGGEST THERE IS SOME STRATUS OUT THERE. EXPECT SOME OF THIS STRATUS TO MOVE ONSHORE LATER THIS EVENING BRINGING BROKEN TO OVERCAST CONDITIONS TO THE COASTAL AIRPORTS. BASES SHOULD BE AROUND 1000 FEET MSL WITH TOPS AROUND 1500 FEET. STRATUS IS EXPECTED TO GO SCATTERED FOR A FEW HOURS SATURDAY MORNING BUT BE REPLACED LATER SATURDAY MORNING BY A STRATOCU LAYER AHEAD OF APPROACHING TROUGH OF LOW PRESSURE. ABOVE THE MARINE LAYER...VARIABLE AMOUNTS OF MID AND HIGH CLOUDS THROUGH TONIGHT...MOSTLY ABOVE 12000 FEET. CLOUDS LOWERING ON SATURDAY AS THE TROUGH APPROACHES WITH LAYERS BETWEEN 4 TO 6 THOUSAND FEET EXPECTED TO MOVE IN DURING THE MORNING. THIS WILL BE ABOVE THE LOWER STRATOCU LAYER MENTIONED ABOVE. SOME LIGHT RAIN IS EXPECTED WITH SOME VISIBILITY RESTRICTIONS OVER THE NORTHERN AREAS LATE IN THE MORNING SPREADING SOUTH AND EAST ACROSS THE AREA THROUGH THE AFTERNOON. && .SGX WATCHES/WARNINGS/ADVISORIES... HIGH SURF ADVISORY SUNDAY THROUGH MONDAY FOR THE ORANGE AND SAN DIEGO COUNTY COASTAL AREAS...SEE LAXCFWSGX. SPECIAL WEATHER STATEMENT...SEE LAXSPSSGX. && $$ PUBLIC...ECC AVIATION...HORTON
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
335 AM EST SAT FEB 10 2007 .DISCUSSION... 00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW NW ARCTIC BRANCH FLOW ALF OVER THE GRT LKS BTWN PERSISTENT HI AMPLITUDE RDG OVER WRN CAN AND VORTEX CENTERED IN SE CAN. ONE SHRTWV EMBBEDDED WITHIN THIS FLOW HAS TRACKED ACRS NRN WI INTO NRN LWR MI TNGT WHILE ANOTHER HAS DROPPED SE THRU NW ONTARIO TOWARD ANJ. THE TRACK OF THESE SHRTWVS HAS CAUSED LLVL WINDS TO VEER MORE NW THE LAST COUPLE OF HRS...WHICH HAS RESULTED IN LES THAT WAS MAINLY OVER THE KEWEENAW AND OVER THE OPEN WATERS OF ERN LK SUP TO SHIFT INTO ONTONAGON COUNTY AND INTO ALGER/LUCE/NRN SCHOOLCRAFT COUNTIES. MQT 88D SHOWS HIER REFLECTIVITIES IN THE BANDS TO THE E ARE FAIRLY LIMITED...BUT A FEW RETURNS IN THE 24-28DBZ RANGE NOTED WITHIN THE CLOSER BANDS. NW GALE FORCE WINDS OBSVD AT PILM4/STDM4...AND WIND GUSTS ARND 40 MPH NOTED AT P59. LES APPEARS WEAKER OVER THE WRN ZNS WITH SHORTER FETCH (LIMITED BY SOME ICE COVG) AND CLOSER PROXIMITY TO LO INVRNS ARND H9-925 NOTED ON THE 00Z INL/YPL RAOBS AND 03Z TAMDAR SDNG FM CYQT AS WELL AS DRY SUB INVRN LYR (SFC DWPTS UPSTREAM OF WRN LK SUP IN THE -15C TO -20C RANGE). HOWEVER...INL SDNG DOES SHOW SOME MSTR ABV THE INVRN BTWN H925-825. 00Z APX SDNG/TAMDAR SDNG FM CIU HINT THAT INVRN IN AREAS DOWNSTREAM OF LK MODERATION IS H8-85. OVER THE INTERIOR ZNS...SKIES ARE CLR-PCLDY...AND TEMPS HAVE FALLEN AOB 0F AT A NUMBER OF SPOTS. OTRW...SHRTWV RDGING NOTED BLDG INTO SASKATCHEWAN/MANITOBA BEHIND ONTARIO SHRTWV. 00Z YQD SDNG IS QUITE DRY (PWAT 0.06 INCH) AND EXCESSIVELY STABLE (INVRN BASE H95). MAIN FCST CONCERNS THE NEXT COUPLE OF DAYS REVOLVE ARND LES TRENDS/ AMTS/HEADLINES ASSOCIATED WITH SHRTWVS EMBEDDED IN NW ARCTIC BRANCH FLOW AND DROP SE OVER THE GRT LKS. FOR TDAY...SHRTWV RDGING OVER SCNTRL CAN PROGGED TO DRIFT INTO THE UPR GRT LKS. GFS/NAM FCST SDNGS SHOW INVRN BASE AT ERY DROPPING FM H85 THIS MRNG TO H9 BY 00Z SUN WHILE LLVL FLOW BACKS MORE W. INVRN BASE AT CMX FCST TO DROP FM H875 TO H9 (GFS) OR EVEN H925 (NAM) BY THIS EVNG WITH ARPCH OF RDG. ALTHOUGH MOIST H9-85 LYR ON THE INL SDNG MAY SUSTAIN THE LES THRU THE MRNG...SUSPECT ACTIVITY WL REALLY WANE THIS AFTN WITH ARRIVAL OF DRIER AIR W-NW OF INL AND LOWER INVRN BASE. ALTHOUGH RELATIVELY WEAK RADAR RETURNS OVER THE E/SHIFTING NATURE OF LES BANDS SO FAR HAVE PROBABLY LIMITED SN ACCUMULATION THERE...WL EXTEND LES/BLSN ADVY (BLSN PER GALE FORCE WINDS OBSVD OVER LK SUP) THRU THE MRNG FOR ALGER/LUCE ZNS TO ACCOUNT FOR WINDOW OF BETTER MSTR/FVRBL WIND DIRECTION BEFORE INVRN FALLS/FLOW BACKS TOO WSW LATER IN THE AFTN AND DRIER SUB INVRN AIR ARRIVES. DESPITE POTENTIAL FOR FVRBL DENDRITIC SN GROWTH WITH MIXED LYR TEMPS IN THE -12C TO -20C RANGE...STEADILY SHIFTING WINDS/LLVL CNVGC AFT 15Z SHOULD LIMIT THE POTENTIAL FOR WRNG SN AMTS. OVER THE INLAND ZNS...SKIES SHOULD BE PARTLY-MOSUNNY. CONSIDERING THE HI STABILITY OF UPSTREAM AIRMASS/ MAX TEMPS ON FRI/BETTER RECENT VERIFICATION OF THE LO END OF MOS GUIDANCE...WL TEND TOWARD THE LOWER GFS MOS GUIDANCE FOR HI TEMPS TDAY. TNGT...GFS/NAM SHOW ANOTHER SHRTWV DROPPING INTO THE UPR GRT LKS FM SCNTRL CAN. THIS WAVE IS RATHER SHEARED HOWEVER...SO THE FCST IMPACT ON INVRN HGT APPEARS TO BE RATHER MINIMAL. THE GFS SHOWS SOMEWHAT MORE RESPONSE AT CMX WITH INVRN BASE RISING FM H9 TO H875 WITH SOME LO-MID LVL MOISTENING AS WELL. WITH FLOW BACKING TO A MORE 260 DIRECTION...EXPECT LES OVER THE W TO SHIFT TO MAINLY JUST THE KEWEENAW. IN FACT...RECENT RUC13 SHOWS FLOW ENHANCED BY LAND BREEZE BACKING SUFFICIENTLY THAT MODEL QPF IS ALMOST ENTIRELY N OF CMX. IF UPSTREAM AIRMASS WERE MOISTER/SHRTWV STRONGER/INVRN HIER AND ICE OVER THE SRN PORTIONS OF WRN LK SUP WERE ABSENT...POTENTIAL FOR MORE INTENSE DOMINANT BAND IN LAND BREEZE/SYNOPTIC SCALE WNW FLOW CNVGC RUNNING THE LENGTH OF WRN LK SUP TO CAUSE HEAVY SN WOULD BE HI. HOWEVER... NEGATIVES MENTIONED ABV SUG MORE LIKELY SCENARIO WL BE A SUB ADVY EVENT...WITH UP TO 4 INCHES FCST OVER HIER TERRAIN N OF CMX PER RUC13 QPF ARND 0.15 INCH AND FVRBL SN/WATER RATIO. SINCE TEMPS ARND -15C WITHIN MIXED LYR ARE FVRBL FOR DENDRITIC SN GROWTH... REMAIN WARY OF POTENTIAL FOR ADVY SN WITH PERSISTENT LLVL CNVGC. OVER THE E... INCRSG LAND BREEZE WSW FLOW SHOULD PUSH LINGERING LES INTO THE OPEN WATERS OF ERN LK SUP...BUT WL RETAIN CHC POPS NEAR THE SHORE E OF THE PIX ROCKS IN CASE FLOW ABV SHALLOW ARCTIC. SKIES WL BE MARRED BY ONLY SOME HI CLDS ASSOCIATED WITH THE SHRTWV OVER THE INTERIOR...WITH TEMPS NEAR LO END OF MOS GUIDANCE WITH LAND BREEZE/ SHALLOW ARCTIC AIR DESPITE STEADY W WIND/SOME HI CLD. A MORE IMPORTANT SHRTWV/COLD FNT IS FCST TO APRCH ON SUN WITH DPVA/ H85-5 QVECTOR CNVGC IN ADVANCE OF THIS SYS FCST BY GFS/NAM/CNDN MODELS TO RAISE INVRN BASE OVER THE NW AND E TOWARD H8 AND MOISTEN THE LLVLS. CONSIDERING THE POTENTIAL FOR DECENT SN LATER SAT NGT OVER THE KEWEENAW AND APRCH OF THIS SYS/FVRBL TEMPS FOR DENDRITIC SN GROWTH BEFORE ARRIVAL OF COLDER AIR LATE BEHIND THE COLD FROPA... DECIDED TO ISSUE AN LES WATCH FOR THAT AREA SAT NGT INTO SUN BEFORE SHIFTING WINDS TO A MORE UNFVRBL 330 DIRECTION IN THE AFTN DIMINISH THE ACTIVITY THERE. RUC13 SHOWS WSHFT EARLIER IN THE MRNG...BUT NAM/GFS HOLD ON TO FVRBL 270-280 FLOW LONGER UNDER INCRSG DPVA. HAVE TO ADMIT DOUBTS ABOUT ICE COVER/SHORTER FETCH/UPSTREAM DRY AIR MIGHT CUT BACK ON SN AMTS...BUT CONFIDENT ENUF THAT AT LEAST AN ADVY SN WL OCCUR SAT NGT THRU SUN MRNG. SINCE MAIN SN BAND WL BE OFFSHORE OVER THE E WHEN THE SHARPER DYNAMICS ARRIVE...WL HOLD OFF ON ANY ADDITIONAL HEADLINES THERE ATTM. AS LLVL WINDS SHIFT TO MORE NNW SUN NGT...MORE SGNFT LES WL SHIFT MORE TOWARD IWD/MQT. && .MQT WATCHES/WARNINGS/ADVISORIES... HEAVY FREEZING SPRAY WARNING LAKE SUPERIOR. LAKE EFFECT SNOW AND BLOWING SNOW ADVY UNTIL 17Z SAT MIZ006-007. LES WATCH 03Z-22Z SUN MIZ001-003. && $$ KC
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
436 PM EST SAT FEB 10 2007 .SHORT TERM (TONIGHT AND SUNDAY)... H5 HEIGHTS INDICATE A RIDGE OVR WESTERN NORTH AMERICA WITH TROUGHING OVR EASTERN CANADA INTO THE GREAT LAKES AND NORTHEAST UNITED STATES. POLAR VORTEX HAS SUNK INTO NORTHERN ONTARIO WITH H5 HEIGHTS BLO 500 DAM. COUPLE OF SHORTWAVES WEST OF THE GREAT LAKES TODAY WILL SWING TOWARD THE AREA OR JUST TO THE SOUTH INTO SUNDAY. ISENTROPIC LIFT ON THE 280K SFC WILL PROVIDE A GOOD SWATH OF MID CLOUDS INTO SUN...BUT SYNOPTIC PCPN SHOULD REMAIN FARTHER S OVR WI WHERE LOWER LEVEL MOISTENING IS A BIT MORE PRONOUNCED. AS HAS BEEN THE CASE FOR THE LAST WEEK...ANY PCPN OVR UPR MI WILL BE CAUSED BY LK SUPERIOR. LES RIGHT NOW IS PRETTY MUCH NON EXISTENT. INVERSION LOWERING BLO H9 AS SEEN ON 12Z KINL SOUNDING/EARLY AFTN TAMDAR FM CYQT IS CAUSING THIS TREND. TEMPS AT TOP OF INVERSION CONTINUE TO WARM ALSO... NEARING -15C BY 00Z. LOBES OF LARGE SCALE LIFT FM POLAR VORTEX DROPPING TOWARD LK SUPERIOR LATE TONIGHT/APPROACHING SHORTWAVE FM THE WEST SHOULD BOOST LES AFT MIDNIGHT. LOWER LEVEL WINDS ALSO BECOME LESS SHEARED FM THE WEST AND CONVERGENCE PICKS UP FM SFC-H9 AS WELL. SO...EXPECT LES TO GET SOMEWHAT BETTER ORGANIZED IN THE OVERNIGHT. LOCAL HIGHER RESOLUTION WRF-ARW AND RUC13 INDICATE GREATEST CONVERGENCE OVR KEWEENAW 09Z-18Z SUN AS NW WINDS OVR LK SUPERIOR MEET THE STUBBORN W/SW FLOW OVR LAND. EVEN WITH THESE POSITIVES...INVERSION HEIGHTS STILL ONLY TOP OUT AROUND H85...SO CONVECTIVE DEPTH DOES NOT LOOK TOO IMPRESSIVE. THIS WAS PRIMARY REASON NOT TO GO WITH WARNING. INSTEAD...WILL ISSUE A LES/BLSN ADVY FOR KEWEENAW PENINSULA. ADDED BLSN AS EXPECT BLYR WINDS TO BE BTWN 20-30 MPH LATER TONIGHT THROUGH SUN. WINDS SHIFTING NW IN MIXED LAYER AFT 18Z SHOULD DIMINISH LES ON KEWEENAW SUN AFTN...SO WILL END ADVY AT THAT TIME. OTHER CONCERN IS OVR FAR NE CWA...WHERE AN ADVY MAY BE NEEDED ON SUN. NOT ISSUING THAT NOW SINCE IT IS STILL LATER IN THE SECOND PERIOD. BACK TO WINDS...MODELS HAVE STRUGGLED LATELY WITH WIND SPEEDS OVR LK SUPERIOR. LAST TWO GALE EVENTS...NAM/GFS HAVE UNDERESTIMATED MAX WINDS BY 5-10KT AND IT IS HAPPENING AGAIN TODAY...WITH GALE FORCE GUSTS OBSERVED MOST DAY ON LK SUPERIOR AND 30 KT AT MOST IN MODEL GUIDANCE. SINCE WINDS ARE PROGGED TO INCREASE THROUGH H85 TONIGHT AHEAD OF SHORTWAVES...WENT WITH GALE WARNING ON LK SUPERIOR THROUGH SUN AM. MOS TEMPS FOR TONIGHT/SUNDAY SEEMED REASONABLE. LOWERED TEMPS OVR INLAND WEST HALF (5 TO 10 BLO ZERO) AS CLEAR SKIES THIS EVENING AND FAIRLY LGT WINDS MAY RESULT IN TEMPS DROPPING QUICKLY TOWARD CURRENT DEWPOINTS. .LONG TERM (SUN NIGHT THROUGH SAT)... COLD FRONT REACHING THE KEWEENAW SUN AFTN WILL EXIT THE FCST AREA SUN EVENING. IN ITS WAKE...850MB TEMPS DROP INTO THE -20 TO -24C RANGE OVER LAKE SUPERIOR BY 12Z MON. ALTHOUGH THERE IS PLENTY OF INSTABILITY FOR LES....NAM HAS COME AROUND TO THE GFS WITH RESPECT TO LOWER INVERSIONS OF 4-5KFT AND A LESS SUPPORTIVE MOISTURE PROFILE. SO...AFTER INTIAL BURST OF SNOW WITH FROPA...LES SHOULD SETTLE DOWN TO A RELATIVELY LIGHT INTENSITY THROUGH SUN NIGHT. VEERING WINDS WITH HIGH PRES BUILDING E THRU MANITOBA/ONTARIO WILL ALSO KEEP BANDS SHIFTING...KEEPING ACCUMULATIONS DOWN. IN ADDITION...LARGE SCALE ANTICYCLONIC FLOW WILL BE ANOTHER NEGATIVE. HOWEVER...THERE ARE INDICATIONS THAT LOCAL CONVERGENCE OR EVEN A MESOLOW WILL DEVELOP OVER SCNTRL LAKE SUPERIOR AS VEERING LARGE SCALE WINDS ARE ENHANCED BY LAND BREEZE OFF ONTARIO TO TAKE ON A MORE ERLY COMPONENT OVER ERN SUPERIOR. WILL NEED TO KEEP AN EYE ON THIS POTENTIAL WHICH COULD LEAD TO LOCAL HVY LES IN MARQUETTE OR ALGER COUNTIES LATE SUN NIGHT. ON MON...WINDS CONTINUING VEERING TO A NE DIRECTION...BUT THERE IS LITTLE CHANGE WITH RESPECT TO INVERSION HEIGHTS/MOISTURE PROFILES. SO...LES WILL REMAIN ON THE LIGHT SIDE (SUB ADVY ACCUMULATIONS). IF A MESOLOW DOES DEVELOP OVER SCNTRL LAKE SUPERIOR LATE SUN NIGHT... SNOW COULD BE LOCALLY HVY THRU MON MORNING OVER A SMALL PART OF NCNTL UPPER MI. ALTHOUGH CORE OF COLDEST AIR PASSES JUST NE OF FCST AREA...TEMPS WILL PROBABLY STRUGGLE TO REACH 10F OVER THE HIGHER TERRAIN OF THE W AND NCNTL FCST AREA WITH 850MB TEMPS HOVERING AROUND -22C. TUE THRU SAT...OTHER THAN LES...THERE WON`T BE MUCH PCPN DURING THIS PERIOD UNDER A GENERAL DRY NW FLOW PATTERN. MAIN FCST ISSUE IS POTENTIAL OF A MIDLEVEL LOW TO DROP INTO THE UPPER GREAT LAKES MIDWEEK. 00Z/12Z FEB9 ECWMF/GFS/GLOBAL CANADIAN RUNS WERE IN GOOD AGREEMENT ON SUCH A SCENARIO. THE 00Z/12Z FEB10 ECMWF RUNS STILL SHOW THIS SOLUTION (JUST SLIGHTLY W AND SLIGHTLY DEEPER THAN FEB9 RUNS). THE 00Z/06Z/12Z GFS RUNS HAVE BACKED AWAY FROM THE MIDLEVEL LOW OVER THE UPPER LAKES AND NOW ONLY SHOW AN OPEN WAVE SWINGING THRU THE UPPER LAKES WED OR KEEP MIDLEVEL LOW N OF LAKE SUPERIOR. THE 00Z GLOBAL CANADIAN SUPPORTS THE ECWMF...BUT WITH HEIGHTS NOT NEARLY AS LOW AS THE ECMWF (500MB HEIGHT WITH MIDLEVEL LOW OVER NE LWR MI 00Z THU IN THE CANADIAN SOLUTION IS 180M HIGHER THAN THE ECWMF). THE 00Z UKMET WHICH HAS SHOWN VERY POOR RUN-TO-RUN CONSISTENCY DOES SUPPORT AN ECMWF/CANADIAN SOLUTION BUT IS ABOUT 24HR SLOWER WITH THE WHOLE PROGRESSION OF MIDLEVEL LOW. 12Z UKMET NOW LOOKS JUST LIKE THE ECWMF WITH TIMING AND DEPTH OF MIDLEVEL SYSTEM. 12Z CANADIAN HAS TRENDED DEEPER AND FARTHER W WITH MIDLEVEL LOW AND JUST DRIFTS IT ACROSS THE WRN GREAT LAKES WED AND THU. AT THIS POINT...DIFFERENCES IN THE DETAILS FOR A SYSTEM 3-5DAYS OUT YET WON`T MAKE TOO MUCH DIFFERENCE IN THE BASIC WEATHER HERE AS ALL SUGGEST A GENERAL NRLY FLOW LES PATTERN TUE/WED WITH LIKELY POPS NEAR LAKE SUPERIOR. IF THE ECMWF SOLUTION WORKS OUT...THERE WOULD BE A SIGNIFICANT LAKE EFFECT/LAKE ENHANCED SNOW EVENT FOR AREAS FAVORED BY NRLY LOW-LEVEL WINDS LATE TUE THRU WED NIGHT. ALTHOUGH NON GFS SOLUTIONS SUPPORT POTENTIAL FOR SIGNIFICANT SNOW... CONFIDENCE IS NOT HIGH ENOUGH RIGHT NOW TO START HIGHLIGHTING POSSIBILITY IN HAZARDOUS WX OUTLOOK. LES WILL WIND DOWN WITH MODERATING AIRMASS AND BACKING WINDS THU AND SHOULD ACTUALLY END FRI AS 850MB TEMPS CONTINUE TO RISE. DESPITE REASONABLE GFS/ECMWF AGREEMENT LATE IN THE WEEK...HAVE LOW CONFIDENCE ON TIMING NEXT SHORTWAVE APPROACHING UPPER LAKES LATE FRI. HAVE INCLUDED LOW CHC POPS FOR -SN FRI NIGHT INTO SAT FOR THIS SYSTEM. TEMPS WILL BE BELOW NORMAL EARLY IN THE PERIOD AND WILL RISE TO AROUND NORMAL BY THE END OF THE PERIOD. && .MQT WATCHES/WARNINGS/ADVISORIES... LAKE EFFECT SNOW AND BLSN ADVY 06Z UNTIL 18Z SUN MIZ001-003. GALE WARNING LAKE SUPERIOR. HEAVY FREEZING SPRAY WARNING LAKE SUPERIOR. && $$ JLA (SHORT TERM) ROLFSON (LONG TERM)