AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
230 PM PST SUN NOV 25 2007
.SYNOPSIS...A DEVELOPING MARINE LAYER WILL CAUSE AREAS OF COASTAL
LOW CLOUDS AND FOG IN THE NIGHTS AND MORNINGS THROUGH TUESDAY. A
COUPLE OF WEAK UPPER LEVEL LOW PRESSURE SYSTEMS WILL BRING VARIABLE
HIGH CLOUDINESS THIS WEEK. THERE COULD BE A FEW SPRINKLES TONIGHT
AND MONDAY MORNING. STRONGER UPPER LEVEL LOW PRESSURE WILL BRING
MORE CLOUDS AND COOLING TOWARD THE END OF THE WEEK.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
.SHORT TERM (REMAINDER OF TODAY-WED)...THERE WAS LOTS OF HIGH
CLOUDINESS TODAY. EARLY AFTERNOON ACARS SOUNDINGS INDICATE A WEAK
INVERSION BASED BELOW 1000 FT WITH SW WINDS ALOFT. WEAK OFFSHORE
GRADIENTS FROM THE N AND ONSHORE TO THE E.
AN UPPER LOW WILL CUT OFF AND MEANDER AROUND SW OF SAN DIEGO THROUGH
THE SHORT TERM. THIS LOW WILL TAP INTO TROPICAL MOISTURE AND BRING
MID TO HIGH CLOUDINESS OVER SRN CA. CANNOT COMPLETELY RULE OUT THE
POSSIBILITY OF A FEW SPRINKLES FROM THE HIGH LEVEL MOISTURE...MAINLY
TONIGHT AND MON NIGHT BUT NO SIGNIFICANT MEASURABLE RAIN IS
EXPECTED. INCREASING ONSHORE FLOW AND A DEVELOPING EDDY WILL CAUSE A
REDEVELOPING MARINE LAYER THROUGH TUE...DECREASING WED AS OFFSHORE
GRADIENTS BECOME A LITTLE STRONGER. THE MID AND HIGH CLOUDS WILL
DISRUPT THE LOW CLOUD COVER SOMEWHAT. WINDS WILL GENERALLY BE LIGHT
EXCEPT LOCAL OFFSHORE BREEZES WILL DEVELOP WEDNESDAY...MAINLY
THROUGH AND BELOW MOUNTAIN CANYONS AND PASSES. RELATIVELY MINOR TEMP
CHANGES EXCEPT A LITTLE COOLER W OF THE MOUNTAINS TUE.
&&
.LONG TERM (THU-SUN)...WEAK OFFSHORE FLOW WILL COME FROM A MORE NE
TO E DIRECTION AS THE UPPER HIGH MOVES SE THU. MODELS REMAIN
INCONSISTENT WITH THE COMPLEX PATTERN TOWARD THE END OF THE WEEK.
THE LOW OFF THE COAST SHOULD MOVE INLAND IN RESPONSE TO A TROUGH
MOVING PAST TO THE N. THIS WOULD RESULT IN MORE CLOUDS AND COOLING
WITH A POSSIBILITY OF PRECIP. IF SHOWERS DEVELOP IT LOOKS LIKE IT
WOULD BE IN THE FRI TO SAT TIME FRAME...ENDING SUN AS THE LOW MOVES
E. WILL CONTINUE LOW POPS BUT KEEP PRECIP WORDING OUT FOR NOW.
&&
.AVIATION...
251930Z...OFFSHORE FLOW CONTINUES TO WEAKEN WITH SOME RECOVERY OF
THE MARINE LAYER TO AROUND 400 FEET EXPECTED TONIGHT. A WEAK COASTAL
EDDY WILL HELP WITH THE MARINE LAYER RECOVERY. THIS COULD BRING SOME
DENSE FOG TO THE VICINITY OF COASTAL AIRPORTS SUCH AS KSAN AND KCRQ
LATE TONIGHT INTO MONDAY MORNING. ANY FOG SHOULD DISSIPATE BY 16Z ON
MONDAY.
ABOVE THE MARINE LAYER...BROKEN TO OVERCAST CLOUDS AT OR ABOVE FL180
TODAY LOWERING TO FL120 ON MONDAY. VISIBILITIES SHOULD REMAIN
UNRESTRICTED THROUGH MONDAY. HORTON
&&
.SGX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
PUBLIC...DA
AVIATION...HORTON
AREA FORECAST DISCUSSION
NWS NORTHERN INDIANA
348 PM EST SUN NOV 25 2007
.SHORT TERM...
DIFFICULT SCENARIO LT THIS AFTN AND EVENING W/VIGOROUS LEAD SW
TROUGH LIFTING ENE OUT OF NE MO. STG WAA OVERTOP SHALLOW POLAR
WEDGE UPSTREAM ACRS IL LEADING TO BAND OF MOD SNOW/SLEET FM NE MO
INTO FAR WRN INDIANA ATTM. 06/12Z MODEL GUIDANCE OF LTL HELP ESP
W/DETAILS AND RELIED HEAVILY ON SHRT TERM RUC ESP IN LIGHT OF COLD
TAMDAR SNDGS ACRS IL. XPC CORE OF HEAVIER PCPN TO SHIFT NEWD
ALG/EITHER SIDE OF A WINAMAC/WARSAW/AUBURN/WAUSEON LINE IN
CONJUNCTION W/STRONGEST SLAB ASCENT ALG 295K ISENTROPIC SFC.
GRIDDED SNOW AMOUNTS A STAB A BEST AND HOPE MIXING/SFC TEMPS JUST
ABV FREEZING KEEP POTENTIAL 2-4 INCH SNOW ACCUMS BLO AN INCH
ALTHOUGH BUST POTENTIAL VRY HIGH THROUGH MID EVENING. OTHERWISE
LIFT BREAKS DOWN BEHIND DEPARTING WAVE ACRS NE CWA BY 05Z.
AFT THAT MESS...SIG SRN STREAM SW OVR W TX THIS AFTN EJECTS
NEWD W/RENEWED MOIST LL ASCENT DVLPG LT TONIGHT. CONTD WK LL WAA SHLD
PRECLUDE ANY MIXED PCPN W/ALL RAIN XPCD ALTHOUGH WILL LIMIT PRIOR
POPS ACRS NRN THIRD W/NOD TWD SLOWER OP GFS EJECTION.
&&
.LONG TERM...
MONDAY THROUGH SUNDAY
MAIN FOCUS REMAINS ON EVOLVING STORM SYSTEM HEADING FOR THE LOWER
GREAT LAKES/UPPER OHIO VALLEY. RAINFALL WILL QUICKLY RAMP UP
ACROSS THE AREA. EXACT TRACK OF THE LOW STILL PROBLEMATIC WITH
MOST OF THE MODELS SHOWING A TIGHT GRADIENT TO THE RAIN/NO RAIN
LINE IN THE NW. HAVE INCREASED TO CAT POPS ALL AREAS WITH ONLY
BRIEFLY THAT HIGH IN THE NW WHERE MAY NOT LINGER VERY LONG. THEN
CHANGEOVER TO SNOW WILL BE THE NEXT CHALLENGE. NEW FACTOR TO
INCLUDE IS LACK OF SIG WARMING TODAY AND SNOW/SLEET HELPING TO
COOL THE GROUND FURTHER INTO TONIGHT...POTENTIALLY ALLOWING FOR
COLDER BOUNDARY LAYER CONDITIONS...ASSISTING IN A FASTER
CHANGEOVER TO SNOW ESPECIALLY NW. FOR NOW WILL HOLD ONTO LIKELY
POPS NW INTO THE LATE AFTERNOON BUT THINK OVERNIGHT SHIFT WILL
LIKELY NEED TO EXPAND TO CAT POPS AS WELL INTO LATE AFTERNOON AS
DEFORMATION ZONE STILL LINGERING ACROSS THE AREA. ACCUMULATIONS
UP TO 1 INCH REMAIN IN THE LATE AFTERNOON GRIDS IN THE NW...BUT
POTENTIAL FOR MORE IF SWITCHOVER IS SOONER. AS NOTED...DEFORMATION
ZONE LOOKS TO BE SLOW TO PULL AWAY DURING THE EVENING SO HOLDING
ONTO HIGHER POPS INTO THE 3 TO 5 Z RANGE AND THEN TAPERING OFF TO
NOTHING TOWARDS 12Z. ADDITIONAL ACCUMUS OF 1 TO 2 INCHES ARE
POSSIBLE...ESPECIALLY EARLY WITH AGAIN THE POTENTIAL FOR LOCALLY
HIGHER AMOUNTS DEPENDING ON EXACT ALIGNMENT AND DURATION OF
MESOBANDING. MAY BE A BAND OF LAKE EFFECT RIGHT AT THE END AS
WELL...BUT AMOUNT OF PRECONDITIONING REMAINS QUESTIONABLE.
AFTER THIS SYSTEM DEPARTS...HIGH PRESSURE BUILDS IN AND CLEAR
THINGS OUT UNTIL LATE WEDS INTO THURS WHEN STRONG TROUGH AND COLD
FRONT PUSH THROUGH THE AREA ACCOMPANIED BY RRQ OF 140 TO 150 KT
JET STREAK. MSTR MAY BE A BIT LIMITED WITH THIS SYSTEM WITH GULF
CUT OF...BUT STILL SHOULD BE SUFFICIENT MSTR WITH SYSTEM TO WARRANT
CONTINUED CHC FOR RAIN/SNOW FOLLOWED BY LAKE EFFECT PRECIP INTO
THURS NGT. MINOR ACCUMULATIONS POSSIBLE AGAIN WITH ANY OF THE
STRONGER SNOWSHOWERS AND PERSISTENT BANDS.
LARGE HIGH PRESSURE WILL PERSIST ACROSS THE DEEP SOUTH AND WILL BE
KEY IN THE EVOLUTION OF THE PATTERN INTO THE REMAINDER OF THE
FORECAST PERIOD. MODELS HINTED AT A DECENT SYSTEM COMING IN FOR
THE WEEKEND BUT SEEM TO HAVE PUSHED THINGS FURTHER SE NOW. WITH
ENTIRE PATTERN STILL IN FLUX...WILL HOLD WITH PREVIOUS GRIDS. DID
KEEP NEW DAY 7 FOR NOW BASED ON SAME REASONING.
.AVIATION...
INITIAL VFR CONDS THIS AFTN WILL DETERIORATE SOME BY MID AFTN AND
ESP THIS EVENING AS STG WAA AHD OF MO WAVE TRANSLATES EWD AND
PRECIP ARRIVES. SOME CONCERN BNDRY LYR TEMPS MAY DROP BLO FREEZING
AT KSBN THIS EVENING W/GREATER DIABATIC COOLING POTENTIAL AND
WHICH COULD LEAD TO SHORT PD OF -FZRA BUT INCLINED AT THIS POINT
GIVEN UPSTREAM OBS TO HOLD OFF ON THAT MENTION YET. OTHERWISE XPC
WIDESPREAD MVFR DVLPMNT THIS EVENING SIMILAR IN SCOPE TO PRIOR
ISSUANCE AND ADDNL REDUCTION TWD DAYBREAK MONDAY W/WIDESPREAD IFR
CIGS/VSBYS XPCD.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&
$$
SHORT TERM/AVIATION...HOLSTEN
LONG TERM...FISHER
AREA FORECAST DISCUSSION
NWS BALTIMORE MD/WASHINGTON DC
305 AM EST SUN NOV 25 2007
.SYNOPSIS...
HIGH PRESSURE WILL MOVE OFFSHORE TODAY. DEVELOPING LOW PRESSURE
OVER THE GULF STATES WILL TRACK ACROSS THE UPPER OHIO VALLEY MONDAY
AFTERNOON. THIS LOW WILL DRAG A COLD FRONT ACROSS THE AREA MONDAY
NIGHT. HIGH PRESSURE WILL RETURN TO THE AREA TUESDAY AND WEDNESDAY.
LOW PRESSURE OVER THE GREAT LAKES WEDNESDAY WILL MOVE TO NORTHERN
NEW ENGLAND THURSDAY...WHICH WILL DRAG A SECOND COLD FRONT ACROSS
THE AREA.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
WATER VAPOR LOOP SHOWS A WEST TO EAST SHEAR AXIS FROM THE MID
ATLANTIC WEST INTO THE UPPER PLAINS...THEN SOUTHWEST TO A VIGOROUS
UPPER LOW OVER NORTHERN MEXICO. THE NEXT WAVE EMBEDDED IN THIS FLOW
IS OVER THE UPPER PLAINS. ACARS 400-250MB WIND OBSERVATIONS REVEAL A
120-160KT WESTERLY JET FROM THE MIDDLE MISSISSIPPI RIVER VALLEY EAST
OVER THE MID ATLANTIC. 04Z SURFACE ANALYSIS PLACED A 1030MB
ANTICYCLONE ALONG THE MID ATLANTIC COASTLINE...AS A COASTAL BOUNDARY
DEVELOPS ALONG THE SOUTHEAST CONUS COAST. A 1020MB CYCLONE HAS
DEVELOPED IN THE WESTERN GULF OF MEXICO OFF THE TEXAS COAST.
AS FIRST SUBTLE SHORT WAVE SHEARS TO THE EAST INTO LOWER NEW
ENGLAND...MID LEVEL DECK WILL CONTINUE CLEARING FROM THE NORTHWEST
EARLY THIS MORNING. VERY TOUGH TO JUDGE HOW FAR SOUTHEAST CLEARING
OCCURS...BUT WITH UPSTREAM RIDGING TAKING PLACE ACROSS THE CENTRAL
MISSISSIPPI RIVER VALLEY...FIND IT PRUDENT TO NOT PUSH CLEARING LINE
TOO FAR SOUTH BEFORE IT LIFTS NORTH DURING THE AFTERNOON.
WITH BEST CLOUD COVER ACROSS CENTRAL VIRGINIA...TEMPERATURES ACROSS
NORTHERN FORECAST AREA EXPECTED TO BE WARMEST ACROSS THE AREA...INTO
THE LOWER 50S. USED 00Z GFS MOS AS A START.
AS RESIDUAL SURFACE RIDGING MOVES OUT OF THE REGION...WINDS WILL BE
RATHER LIGHT DURING THE DAY...AS REPRESENTED BY 00Z LWX WRF-ARW.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH MONDAY NIGHT/...
AS THE NORTHERN MEXICO UPPER LOW BEGINS TO LIFT THROUGH THE PLAINS
TONIGHT...A STRONG LOW LEVEL JET (40-50KT) DEVELOPS FROM THE GULF OF
MEXICO NORTHWARD INTO THE MID ATLANTIC. THE RESULT WILL BE STRONG
WARM ADVECTION JUST OFF THE SURFACE.
WHILE THE 00Z NAM AND 21Z SREF ARE DRY THROUGH TONIGHT...WITH
PRECIPITATION ARRIVING AT THE APPALACHIANS MONDAY MORNING...THE
00Z GFS PRESENTS A DIFFERENT SCENARIO. THE GFS INDICATES
PRECIPITATION OCCURS MAINLY ACROSS THE EASTERN FORECAST AREA LATE
TONIGHT...COINCIDENT WITH THE ARRIVAL OF THE LOW LEVEL JET. DID NOT
DETECT ANY SIGNS OF CONVECTIVE FEEDBACK...INSTEAD IT APPEARS THAT
THE GFS INITIALIZED WELL WITH THE CONVECTION OFF THE FLORIDA PAN
HANDLE. AS THE LOW LEVEL JET INCREASES...ISENTROPIC LIFT SHOULD BE
STRONG ENOUGH FOR THE DEVELOPMENT OF SHOWERS. IF THE COASTAL FRONT
CAN WORK INLAND...CONVECTION ACROSS EASTERN CAROLINAS COULD MIGRATE
NORTHWARD AS SHOWERS AS WELL.
THE 00Z NCEP WRF-NMM SIMULATED REFLECTIVITY IS FAIRLY SIMILAR TO THE
NAM...EXCEPT SHOWS MORE CONVECTION ACROSS THE CAROLINAS AND LIGHT
SHOWERS LATE TONIGHT ACROSS THE SOUTHERN FORECAST AREA. THE NSSL
WRF-ARW SIMULATED REFLECTIVITY WAS UNAVAILABLE AT THE TIME OF
ANALYSIS.
TEMPERATURES TONIGHT WILL BE MUCH WARMER DUE TO THICKNESS OF CLOUD
DECKS AND STRONG WARM ADVECTION. WENT WITH 00Z NGM MOS AS A
BEGINNING POINT. WINDS WILL BE NOTICEABLE OUT OF THE
SOUTH...15-20KTS IN THE HIGHER TERRAIN.
PCPN ASSOC W/ LLJ WL BE SHUNTED INTO WRN ATLC MON AS SFC LOPRES MVS
INTO UPR OHVLY. THAT/S NOT TO SAY THAT WE STILL WONT HV AN ACTIVE
WND FIELD ACRS CWFA. H8 WNDS PROGGED NEAR 50 KT...W/ AREA W/IN THTE
RDG AND PWAT 1.25-1.5 INCHES /MORE THAN 2SD ABV NRML/...MEANING
AMPLE MSTR AVBL LEADING TO HVY RAINERS. WL BUMP IT UP TO CAT POPS...
THO THERE WL BE BREAKS BTWN RAINY PDS. TEMPS WL BE A BALANCE BTWN
WAA AND EFFECTS OF CLDS/RA. GOING FCST NOT FAR FM A MOS BLEND...SO
FEW TWEAKS MADE.
THINGS GET KICKED ANOTHER GEAR HIER MON NGT AHD OF WELL DEFINED
CDFNT. ALTHO NOT QUITE AS DEFINED AS YDA...STILL A LTL BIT OF
INSTBLTY /CPL HND JOULES MUCAPE/ PRESENT IN THE SFC-H8 LYR PER BOTH
GFS AND ECMWF. KINEMATIC PROFILES MOST IMPRESSIVE IN TERMS OF SPD
SHEAR...60-70 KT AVBL AT H8 ALNG/AHD OF FNT. BEST TIME FRAME 00-06Z.
ONLY QSTN BECOMES HOW MUCH OF THAT WL MIX TO SFC. IF EVEN A PORTION
OF THAT W/IN HVIER ELEMENTS...IT/LL BE AN ACTV NGT. WL KEEP SCHC
THUNDER EMBEDDED W/IN CAT POPS.
CDFNT SHUD BE ALNG OR E OF I-95 BY 06Z...AND DRYING SHUD SWEEP ACRS
AREA BY DAYBREAK. ALNG W/ CORE OF CAA XPCT GUSTY WNDS ACRS WRN RDGS
IN THE NW FLOW. THAT WL ALLW FOR COME COOLER TEMPS SHEN VLY W.
LEANED ON HIER SIDE OF MOS IN THE E...AND COOLER W.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
CDFNT WL BE WELL OFFSHORE TUE...AS HIPRES BUILDS. CWFA WL BE W/IN
NW FLOW REGIME. TEMPS WL BE ANOTHR CHALLENGE AS CAA AND DOWNSLOPE
FLOW BALANCE EACH OTHER OUT. WL STAKE OUT MIDDLE GROUND...A CPL
DEG COOLER IN THE E...AND A SHADE COOLER THAN THAT W. MRNG CLDS
SHUD SCOUR OUT AS SUBSIDENCE FM NWLY FLOW TAKES OVR. SOME MTN PCPN
PSBL...BUT TEMPS TOO WARM FOR ANYTHING BUT RAIN.
FLOW PTTN THRU WK WL BE PROGRESSIVE...W/ NRN STREAM JET SINKING ACRS
CONUS. THAT WL DRIVE ANTHR CDFNT ACRS CWFA NEAR THU. HV KEPT POPS
CONSISTENT W/ PRVS FCSTS...IN THE THU DAY TIMEFRAME. DIFFERENCE THIS
TIME IS THAT THERE SHUD BE ENUF COLD AIR ON THE BACKSIDE OF THE
SYSTEM FOR SCT WRN SHSN THU NGT. WL KEEP IT DRY FRI-SAT. NXT
POTENTIAL STORM SYSTEM WL COME SUN. PTYPE WL BE A BIG QSTN...AS ZNL
JET WL KEEP WARMTH ACRS SRN CONUS. BUT... THERE/S A LOT OF WX TO GO
THRU FIRST...AND PLENTY OF TIME FOR DETAILS TO CHG.
&&
.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
AS FIRST SUBTLE SHORT WAVE SHEARS TO THE EAST...MID LEVEL DECK WILL
CONTINUE CLEARING FROM THE NORTHWEST EARLY THIS MORNING. LIGHT
SOUTHERLY FLOW RESIDES WITH THE HIGH MOVING OFF THE COAST.
MID DECK BUILDS BACK IN FROM THE SOUTH BY EVENING...WITH
DETERIORATING CONDITIONS EXPECTED OVERNIGHT WITH WARM ADVECTION
SETTING UP IN THE LOW LEVELS.
12Z TAFS WILL LIKELY START TO INDICATE NEAR IFR CEILINGS AND LOW
LEVEL WIND SHEAR BY THE START OF THE MONDAY MORNING PUSH...ALONG
WITH RAIN SHOWERS DUE TO THE ARRIVAL OF THE LOW LEVEL JET.
LOOK FOR LOW CLDS/VSBYS IN RAIN MON-MON NGT. WIDESPREAD IFR LIKELY.
XPCT SLY WNDS 10-15 KT AT SFC...AND 40-50KT 3000-5000 FT ABV SFC
MON. CDFROPA MON NGT...W/ SHARP WSHFT FM S TO W. WNDS AHD OF CDFNT
MORE THAN 50 KT 2000-3000 FT ABV GRND SHUD LEAD TO GUSTY SFC CONDS.
CUD BE AN ISOL TSRA TOO.
STRONG NW FLOW TUE...BECOME MORE TRANQUIL WED. VFR THRU WED. ADDTL
FLGT RESTRICTIONS PSBL THU AS NXT STORM SYSTM APPROACHES FM W.
&&
.MARINE...
WITH HIGH PRESSURE MOVING OFF THE COAST...LIGHT SOUTHWEST FLOW TODAY
INCREASES OUT OF THE SOUTH TONIGHT. BY DAYBREAK MONDAY...SCATTERED
TO NUMEROUS SHOWERS ARE EXPECTED.
30-40 KT 2000 FT OFF SFC MON...BUT SFC BASED INVSN SHUD KEEP THAT FM
MIXING DOWN. WL NEED TO MONITOR LATER GDNC RUNS TO SEE THE HGT OF
THE INVSN. IF NOT BEFORE...SCA QUITE PSBL MON EVE...AND SEEMS LIKE A
SURE BET MON NGT-TUE MRNG. WND PROFILES SUGGEST THAT EITHER GLW OR
SMW PSBL AHD OF CDFNT MON NGT. WNDS TUE IN RESPONSE TO CAA...WHICH
SHUD SIMMER DOWN LT TUE. SINCE ALL THIS BYD PD 3...WL LV IT IN
SYNOPSIS AND NOT RAISE HEADLINES YET.
NXT CHC FOR SCA COMES LT THU BHD ANTHR CDFNT.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...NONE.
&&
$$
SYNOPSIS...HTS
NEAR TERM...ROGOWSKI
SHORT TERM...ROGOWSKI/HTS
LONG TERM...HTS
AVIATION...ROGOWSKI/HTS
MARINE...ROGOWSKI/HTS
AREA FORECAST DISCUSSION...UPDATED
NWS MARQUETTE MI
636 AM EST SUN NOV 25 2007
...UPDATED FOR AVIATION...
.SYNOPSIS...
08Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED SPLIT FLOW
ACROSS NORTH AMERICA. IN THE CASE OF THIS FORECAST...MUCH OF THE
CONCERN RELIES ON WHAT IS TAKING PLACE IN THE NORTHERN STREAM....
WHICH IS NEARLY ZONAL ALONG THE U.S./CANADIAN BORDER. WITHIN THE
ZONAL FLOW...THE MAIN FEATURE OF INTEREST IN THE SHORT TERM IS A
SHRTWV MOVING ACROSS SOUTHERN ALBERTA...WHICH IS REFLECTED AT THE
SURFACE BY A 1001MB LOW OVER SOUTHERN SASKATCHEWAN. DESPITE DPVA
AHEAD OF THE SHRTWV...NOT MUCH IS TAKING PLACE AHEAD OF THE SYSTEM
ON RADAR...LIKELY DUE TO PLENTY OF DRY AIR SEEN ON THE 00Z GGW AND
BIS SOUNDINGS. HOWEVER...THIS AIRMASS AHEAD OF THE SYSTEM IS
RELATIVELY WARM WITH GGW AT 3C AND BIS AND ABR AT 1C. CLOSER TO
HOME...HIGH CLOUDS COVER SOME OF THE AREA (MOST PROMINENT OVER LAKE
SUPERIOR) DUE TO PACIFIC MOISTURE MOVING THROUGH THE ZONAL FLOW.
THESE CLOUDS HAVE PREVENTED VIEWING ANY LAKE EFFECT BAND WHICH WOULD
LIE ALONG A STALLED OUT SURFACE TROUGH IN NORTHERN LAKE SUPERIOR. IT
APPEARS THIS TROUGH IS A BIT FURTHER NORTH THAN EXPECTED...PERHAPS
BEING KEPT NORTH BY LAND BREEZES THAT ARE ADDING AN EXTRA PUSH TO
THE GENERAL WSW LOW LEVEL FLOW OVER THE AREA. THUS...THE LAKE EFFECT
SNOW ADVISORY WAS CANCELLED LAST EVENING. THE LAST ITEM TO NOTE IS
AN UPPER TROUGH DIVING DOWN THROUGH THE NORTHWEST TERRITORIES. A
COUPLE OF CANADIAN RAOBS NEAR THE TROUGH SHOWED 850MB TEMPS AT OR
BELOW -20C.
&&
.DISCUSSION...
MAIN FORECAST CONCERNS ARE FREEZING DRIZZLE POTENTIAL TONIGHT AND
STORM SYSTEMS AFFECTING THE AREA TUE AND WED.
TODAY...SHRTWV OVER ALBERTA WILL CONTINUE TO MOVE EASTWARD THROUGH
THE ZONAL FLOW...REACHING NORTHERN MN BY 00Z WITH THE SFC LOW MOVING
TO NEAR GRAND MARAIS MN. AGAIN...WITH THE LACK OF ACTIVITY AHEAD OF
THE SHRTWV TROUGH AND ONLY HIGH CLOUDS BEING OBSERVED ON IR
IMAGERY...THERE ARE VERY FEW IF ANY CONCERNS REGARDING PCPN. ANY
LAKE EFFECT BAND OVER NORTHERN LAKE SUPERIOR SHOULD MOVE OUT OF THE
U.S. WATERS THIS MORNING AS WINDS BACK AGAIN TO THE SW. THESE SW
WINDS WILL HELP ADVECT IN WARMER 850MB TEMPS...REACHING 0C BY 18Z.
SINCE SATELLITE IMAGERY DEPICTS VERY FEW LOW CLOUDS AND ONLY HIGH
CLOUDS WILL BE MOVING THROUGH THE AREA...WE SHOULD BE ABLE TO WARM
DECENTLY TODAY...ESPECIALLY WITH A BREEZY SW WIND DEVELOPING. WILL
STAY ON THE WARMER SIDE OF GUIDANCE...ESPECIALLY IN DOWNSLOPING
AREAS.
TONIGHT...MODELS SHOW THE SHRTWV OVER NORTHERN MN AT 00Z MON TO
CONTINUE ITS MARCH EASTWARD...REACHING WESTERN QUEBEC BY
12Z...DRAGGING THE SURFACE LOW WITH IT. THIS WILL ALLOW FOR A COLD
FRONT TO DROP SOUTH INTO THE CWA AFTER 06Z...DROPPING 850MB TEMPS TO
-8 TO -11C OVER WESTERN LAKE SUPERIOR BY 12Z. ALTHOUGH THESE ARE
PLENTY COLD ENOUGH TO DEVELOP LAKE EFFECT GIVEN LAKE SURFACE TEMPS
AROUND 5C...THERE IS SOME CONCERN THAT MOISTURE MAY NOT EXTEND UP TO
THESE COLDER 850MB TEMPS...ESPECIALLY IMMEDIATELY IN THE WAKE OF THE
FRONT. THIS WOULD MEAN THE POSSIBILITY FOR SOME FREEZING DRIZZLE...
ESPECIALLY IN UPSLOPE AREAS FAVORING NORTH OR NW WINDS. THE
NAM...GFS AND LOCAL WRF-ARW RUNS ALL SHOW THIS POSSIBILITY.
EVENTUALLY NEAR 12Z...ENOUGH COLD AIR SHOULD COME IN TO CHANGE THE
FREEZING DRIZZLE OVER TO LAKE EFFECT SNOW SHOWERS...PARTICULARLY
FROM THE KEWEENAW NORTH. DAY SHIFT MAY HAVE TO CONSIDER A FREEZING
RAIN ADVISORY IF THE DRIZZLE LOOKS MORE SIGNIFICANT. GOING LOW
FORECAST SEEMS REASONABLE...WITH TEMPERATURES NOT FALLING MUCH UNTIL
THE COLD FRONTAL PASSAGE.
MONDAY...UPPER TROUGH CURRENTLY OVER THE NORTHWEST TERRITORIES IS
EXPECTED TO BE DIGGING SOUTH THROUGH SOUTH CENTRAL CANADA AND
POSSIBLY REACHING FAR NW MN BY LATE IN THE DAY. MEANWHILE...TO OUR
SOUTH IN THE SOUTHERN STREAM...A SHEARING OUT UPPER LOW IS PROGGED
TO BE MOVING UP THROUGH THE OHIO VALLEY WITH A LOW ASSOCIATED WITH
IT LIFTING INTO WESTERN PA BY 00Z TUE. UPPER MICHIGAN WILL BE IN LOW
LEVEL NORTHERLY FLOW BETWEEN THESE TWO FEATURES...WHICH SHOULD HELP
DRIVE DOWN 850MB TEMPS THROUGH THE DAY...CHANGING ANY FREEZING
DRIZZLE OVER TO SNOW. BY 21Z...THE NAM DEPICTS READINGS OF -10 TO
-13C OVER THE CWA...WHICH FAVORS KEEPING LAKE EFFECT SNOW SHOWERS
GOING. HOWEVER...GIVEN THE TIME OF DAY...LACK OF ANY SIGNIFICANT
CONVERGENCE AREAS...INVERSION HEIGHTS AROUND 5000 FT...AND THE FLOW
BECOMING GRADUALLY ANTICYCLONIC LATE IN THE DAY AS A SURFACE RIDGE
MOVES INTO WESTERN LAKE SUPERIOR...SHOULD HELP TO KEEP THE LAKE
EFFECT SNOW LIGHT. GIVEN THE COLD ADVECTION...TEMPERATURES SHOULD
STRUGGLE TO RISE MUCH EXCEPT IN THE SOUTH CENTRAL WHERE MORE SUN AND
DOWNSLOPING NW FLOW OCCURS. IN FACT...READINGS WILL PROBABLY HOLD
STEADY OR SLOWLY FALL IN THE AFTERNOON.
MON NIGHT INTO TUE...THE GFS CONTINUES TO BE DISCOUNTED WITH THE
UPPER TROUGH DIGGING THROUGH SOUTH CENTRAL CANADA...AND HAVE
FOLLOWED THE MORE CONSISTENT UKMET/ECMWF/CANADIAN IDEA...ALSO PER
HPC PMDHMD DISCUSSION. SURPRISINGLY...THE NAM IS NOT TOO FAR OFF THE
PREFERRED SOLUTION...DESPITE USING THE 18Z GFS FOR ITS BOUNDARY
CONDITIONS. THESE MODELS DEPICT A MORE POTENT BUT STILL QUICK MOVING
NEGATIVELY TILTED TROUGH CENTERED OVER CENTRAL UPPER MICHIGAN AT 12Z
TUE AND HEADING OFF INTO QUEBEC AT 00Z WED. AHEAD OF THE TROUGH...
STRONG Q-VECTOR CONVERGENCE (OWING MOSTLY TO DPVA EFFECTS) IS
PROGGED TO ENTER WESTERN UPPER MICHIGAN BETWEEN 06-09Z...THEN
CONTINUING EASTWARD THROUGH THE REST OF THE MORNING AND EARLY
AFTERNOON WITH THE UPPER TROUGH. HAVE INCLUDED CHANCES FOR SNOW WITH
THE Q-VECTOR CONVERGENCE...WHICH COULD ACCUMULATE A 1/2 INCH TO AN
INCH. HOWEVER...THE MORE SIGNIFICANT IMPACT COULD BE A BRIEF PERIOD
OF MODERATE TO HEAVY LAKE EFFECT SNOW WITH WHATEVER SURFACE
REFLECTION THIS TROUGH WILL HAVE. IT SEEMS MOST LIKELY NW WIND
FAVORED SNOWBELTS COULD PICK UP THE MOST...BUT AGAIN IT WILL HAPPEN
IN A BRIEF WINDOW GIVEN THE QUICK NATURE OF THE UPPER TROUGH. THE
INSTABILITY IS PRETTY IMPRESSIVE...WITH 850MB TEMPS PROGGED TO FALL
TO -15 TO -18C...BUT WOULD NOT BE SURPRISED TO SEE INVERSION HEIGHTS
CRASH WITH THE COLDEST 850MB READINGS...WHICH WOULD LIMIT LES
INTENSITY. FAIRLY STRONG HIGH PRESSURE (1028MB) IS PROGGED TO BUILD
IN ACROSS MUCH OF THE CWA AROUND 00Z WED...WHICH SHOULD REALLY
DIMINISH THE INTENSITY OF THE LAKE EFFECT.
TUE NIGHT THROUGH WED NIGHT...SINCE THE GFS WAS DISCOUNTED WITH
REGARDS TO THE UPPER TROUGH ON MON NIGHT/TUE...IT MAKES IT DIFFICULT
TO USE IT DURING THIS TIME PERIOD. IN FACT...00Z THE
ECMWF/UKMET/CANADIAN ARE ALL IN VERY GOOD AGREEMENT WITH THE NEXT
STORM SYSTEM APPROACHING THE AREA ON WED AND HAVE FOLLOWED THEM FOR
THE FORECAST. BACK ON TUE...AN UPPER LEVEL TROUGH IS SHOWN TO DIG
DOWN THROUGH THE WESTERN U.S...CAUSING CYCLOGENESIS DOWNSTREAM NEAR
DENVER AROUND 00Z WED. AS THE UPPER TROUGH MOVES DOWN INTO THE FOUR
CORNERS REGION ON WED...A SHRTWV EJECTS OUT AND LIFTS THE LOW NEAR
DENVER TOWARDS THE AREA. BY 00Z THU...THE MODELS ALL DEPICT THE LOW
REACHING SOMEWHERE NEAR THUNDER BAY. FRONTOGENESIS/WARM ADVECTION
AHEAD OF THE SYSTEM MAY BRING SOME LIGHT SNOW INTO THE AREA AS EARLY
AS TUESDAY EVENING. HOWEVER...THE STRONGER WARM AND MOIST AIR
ADVECTION WILL LIKELY HOLD OFF UNTIL AFTER MIDNIGHT TUE NIGHT AND
WED. HAVE RAISED POPS AFTER MIDNIGHT TUESDAY NIGHT ALONG THE
WISCONSIN BORDER WHERE WARM ADVECTION BAND OF SNOW MOVES IN...THEN
LEFT THE GOING 60 POPS IN FOR WED. HOWEVER...DID LOWER POPS 10
PERCENT ALONG LAKE MICHIGAN AS DRY AIR ASSOCIATED WITH THE HIGH THAT
MOVED OVER THE AREA LATE TUE MAY HOLD. IN ADDITION...TRIED TO DEPICT
THE SNOW TAPERING OFF IN THE WESTERN U.P. IN THE AFTERNOON WHERE IT
SEEMS MOST LIKELY THE WARM ADVECTION BAND OF SNOW WILL LIFT NORTH.
THE REST OF THE CWA IS A LITTLE MORE UNCERTAIN TO PLACE ANY TIMING
IN AT THIS TIME...BUT FUTURE FORECASTS SHOULD BE ABLE TO PUT IT IN.
COLD ADVECTION COMING IN WEDNESDAY NIGHT SHOULD RESTART LAKE EFFECT
SNOW FOR THE NORTHERN U.P....AND THUS DID NOT MAKE ANY ADJUSTMENTS.
NO CHANGES MADE BEYOND WED NIGHT.
&&
.AVIATION (FOR THE 12Z TAF ISSUANCE)...
VFR CONDITIONS ARE EXPECTED AT KSAW AND KCMX THROUGHOUT TODAY AND
THIS EVENING. A LOW LEVEL JET SWEEPING THROUGH THE BASE OF A LOW
OVER CENTRAL ONTARIO WILL SHIFT ACROSS THE AREA TODAY. SURFACE
HEATING WILL INCREASE THE LOW LEVEL INSTABILITY AND ALLOW SOME OF
THESE WINDS TO MIX TO SURFACE AS GUSTY CONDITIONS THIS AFTERNOON.
THIS ACCOUNTS FOR THE EXPECTED GUSTY CONDITIONS IN THE BOTH TAFS
TODAY. TAMDAR SOUNDINGS OVER KSAW ALREADY SHOWING 38 KNOTS EARLY
THIS MORNING AT 3K FEET. IN THE DISCUSSION ABOVE...WE SEE DELTA-T`S
INCREASING OVER LAKE SUPERIOR ALONG WITH A WEAK SHORTWAVE PASSING
OVER THE AREA COULD PRODUCE SOME SNOW SHOWERS LATE TONIGHT...
ESPECIALLY OVER KCMX AREA.
&&
.MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)...
SOUTHWEST WINDS TO 30 KNOTS WILL CONTINUE THIS MORNING BEFORE
DIMINISHING GRADUALLY THIS AFTERNOON AS A LOW PRESSURE SYSTEM DRAGS
A COLD FRONT ACROSS LAKE SUPERIOR. IN THE WAKE OF THE FRONT A RIDGE
WILL SETTLE OVER THE LAKE...DIMINISHING THE WINDS BELOW 20 KNOTS.
OTHER THAN FOR A BRIEF INCREASE IN WINDS TOWARDS 30 KNOTS ON TUESDAY
WITH A LOW CROSSING LAKE SUPERIOR...THE NEXT CHANCE OF GALES WILL BE
ON THURSDAY WITH A TIGHT PRESSURE GRADIENT DEVELOPING AGAIN.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SYNOPSIS/DISCUSSION...AJ
AVIATION...DLG
MARINE...DLG
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
420 AM EST SUN NOV 25 2007
.SYNOPSIS...
08Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED SPLIT FLOW
ACROSS NORTH AMERICA. IN THE CASE OF THIS FORECAST...MUCH OF THE
CONCERN RELIES ON WHAT IS TAKING PLACE IN THE NORTHERN STREAM....
WHICH IS NEARLY ZONAL ALONG THE U.S./CANADIAN BORDER. WITHIN THE
ZONAL FLOW...THE MAIN FEATURE OF INTEREST IN THE SHORT TERM IS A
SHRTWV MOVING ACROSS SOUTHERN ALBERTA...WHICH IS REFLECTED AT THE
SURFACE BY A 1001MB LOW OVER SOUTHERN SASKATCHEWAN. DESPITE DPVA
AHEAD OF THE SHRTWV...NOT MUCH IS TAKING PLACE AHEAD OF THE SYSTEM
ON RADAR...LIKELY DUE TO PLENTY OF DRY AIR SEEN ON THE 00Z GGW AND
BIS SOUNDINGS. HOWEVER...THIS AIRMASS AHEAD OF THE SYSTEM IS
RELATIVELY WARM WITH GGW AT 3C AND BIS AND ABR AT 1C. CLOSER TO
HOME...HIGH CLOUDS COVER SOME OF THE AREA (MOST PROMINENT OVER LAKE
SUPERIOR) DUE TO PACIFIC MOISTURE MOVING THROUGH THE ZONAL FLOW.
THESE CLOUDS HAVE PREVENTED VIEWING ANY LAKE EFFECT BAND WHICH WOULD
LIE ALONG A STALLED OUT SURFACE TROUGH IN NORTHERN LAKE SUPERIOR. IT
APPEARS THIS TROUGH IS A BIT FURTHER NORTH THAN EXPECTED...PERHAPS
BEING KEPT NORTH BY LAND BREEZES THAT ARE ADDING AN EXTRA PUSH TO
THE GENERAL WSW LOW LEVEL FLOW OVER THE AREA. THUS...THE LAKE EFFECT
SNOW ADVISORY WAS CANCELLED LAST EVENING. THE LAST ITEM TO NOTE IS
AN UPPER TROUGH DIVING DOWN THROUGH THE NORTHWEST TERRITORIES. A
COUPLE OF CANADIAN RAOBS NEAR THE TROUGH SHOWED 850MB TEMPS AT OR
BELOW -20C.
&&
.DISCUSSION...
MAIN FORECAST CONCERNS ARE FREEZING DRIZZLE POTENTIAL TONIGHT AND
STORM SYSTEMS AFFECTING THE AREA TUE AND WED.
TODAY...SHRTWV OVER ALBERTA WILL CONTINUE TO MOVE EASTWARD THROUGH
THE ZONAL FLOW...REACHING NORTHERN MN BY 00Z WITH THE SFC LOW MOVING
TO NEAR GRAND MARAIS MN. AGAIN...WITH THE LACK OF ACTIVITY AHEAD OF
THE SHRTWV TROUGH AND ONLY HIGH CLOUDS BEING OBSERVED ON IR
IMAGERY...THERE ARE VERY FEW IF ANY CONCERNS REGARDING PCPN. ANY
LAKE EFFECT BAND OVER NORTHERN LAKE SUPERIOR SHOULD MOVE OUT OF THE
U.S. WATERS THIS MORNING AS WINDS BACK AGAIN TO THE SW. THESE SW
WINDS WILL HELP ADVECT IN WARMER 850MB TEMPS...REACHING 0C BY 18Z.
SINCE SATELLITE IMAGERY DEPICTS VERY FEW LOW CLOUDS AND ONLY HIGH
CLOUDS WILL BE MOVING THROUGH THE AREA...WE SHOULD BE ABLE TO WARM
DECENTLY TODAY...ESPECIALLY WITH A BREEZY SW WIND DEVELOPING. WILL
STAY ON THE WARMER SIDE OF GUIDANCE...ESPECIALLY IN DOWNSLOPING
AREAS.
TONIGHT...MODELS SHOW THE SHRTWV OVER NORTHERN MN AT 00Z MON TO
CONTINUE ITS MARCH EASTWARD...REACHING WESTERN QUEBEC BY
12Z...DRAGGING THE SURFACE LOW WITH IT. THIS WILL ALLOW FOR A COLD
FRONT TO DROP SOUTH INTO THE CWA AFTER 06Z...DROPPING 850MB TEMPS TO
-8 TO -11C OVER WESTERN LAKE SUPERIOR BY 12Z. ALTHOUGH THESE ARE
PLENTY COLD ENOUGH TO DEVELOP LAKE EFFECT GIVEN LAKE SURFACE TEMPS
AROUND 5C...THERE IS SOME CONCERN THAT MOISTURE MAY NOT EXTEND UP TO
THESE COLDER 850MB TEMPS...ESPECIALLY IMMEDIATELY IN THE WAKE OF THE
FRONT. THIS WOULD MEAN THE POSSIBILITY FOR SOME FREEZING DRIZZLE...
ESPECIALLY IN UPSLOPE AREAS FAVORING NORTH OR NW WINDS. THE
NAM...GFS AND LOCAL WRF-ARW RUNS ALL SHOW THIS POSSIBILITY.
EVENTUALLY NEAR 12Z...ENOUGH COLD AIR SHOULD COME IN TO CHANGE THE
FREEZING DRIZZLE OVER TO LAKE EFFECT SNOW SHOWERS...PARTICULARLY
FROM THE KEWEENAW NORTH. DAY SHIFT MAY HAVE TO CONSIDER A FREEZING
RAIN ADVISORY IF THE DRIZZLE LOOKS MORE SIGNIFICANT. GOING LOW
FORECAST SEEMS REASONABLE...WITH TEMPERATURES NOT FALLING MUCH UNTIL
THE COLD FRONTAL PASSAGE.
MONDAY...UPPER TROUGH CURRENTLY OVER THE NORTHWEST TERRITORIES IS
EXPECTED TO BE DIGGING SOUTH THROUGH SOUTH CENTRAL CANADA AND
POSSIBLY REACHING FAR NW MN BY LATE IN THE DAY. MEANWHILE...TO OUR
SOUTH IN THE SOUTHERN STREAM...A SHEARING OUT UPPER LOW IS PROGGED
TO BE MOVING UP THROUGH THE OHIO VALLEY WITH A LOW ASSOCIATED WITH
IT LIFTING INTO WESTERN PA BY 00Z TUE. UPPER MICHIGAN WILL BE IN LOW
LEVEL NORTHERLY FLOW BETWEEN THESE TWO FEATURES...WHICH SHOULD HELP
DRIVE DOWN 850MB TEMPS THROUGH THE DAY...CHANGING ANY FREEZING
DRIZZLE OVER TO SNOW. BY 21Z...THE NAM DEPICTS READINGS OF -10 TO
-13C OVER THE CWA...WHICH FAVORS KEEPING LAKE EFFECT SNOW SHOWERS
GOING. HOWEVER...GIVEN THE TIME OF DAY...LACK OF ANY SIGNIFICANT
CONVERGENCE AREAS...INVERSION HEIGHTS AROUND 5000 FT...AND THE FLOW
BECOMING GRADUALLY ANTICYCLONIC LATE IN THE DAY AS A SURFACE RIDGE
MOVES INTO WESTERN LAKE SUPERIOR...SHOULD HELP TO KEEP THE LAKE
EFFECT SNOW LIGHT. GIVEN THE COLD ADVECTION...TEMPERATURES SHOULD
STRUGGLE TO RISE MUCH EXCEPT IN THE SOUTH CENTRAL WHERE MORE SUN AND
DOWNSLOPING NW FLOW OCCURS. IN FACT...READINGS WILL PROBABLY HOLD
STEADY OR SLOWLY FALL IN THE AFTERNOON.
MON NIGHT INTO TUE...THE GFS CONTINUES TO BE DISCOUNTED WITH THE
UPPER TROUGH DIGGING THROUGH SOUTH CENTRAL CANADA...AND HAVE
FOLLOWED THE MORE CONSISTENT UKMET/ECMWF/CANADIAN IDEA...ALSO PER
HPC PMDHMD DISCUSSION. SURPRISINGLY...THE NAM IS NOT TOO FAR OFF THE
PREFERRED SOLUTION...DESPITE USING THE 18Z GFS FOR ITS BOUNDARY
CONDITIONS. THESE MODELS DEPICT A MORE POTENT BUT STILL QUICK MOVING
NEGATIVELY TILTED TROUGH CENTERED OVER CENTRAL UPPER MICHIGAN AT 12Z
TUE AND HEADING OFF INTO QUEBEC AT 00Z WED. AHEAD OF THE TROUGH...
STRONG Q-VECTOR CONVERGENCE (OWING MOSTLY TO DPVA EFFECTS) IS
PROGGED TO ENTER WESTERN UPPER MICHIGAN BETWEEN 06-09Z...THEN
CONTINUING EASTWARD THROUGH THE REST OF THE MORNING AND EARLY
AFTERNOON WITH THE UPPER TROUGH. HAVE INCLUDED CHANCES FOR SNOW WITH
THE Q-VECTOR CONVERGENCE...WHICH COULD ACCUMULATE A 1/2 INCH TO AN
INCH. HOWEVER...THE MORE SIGNIFICANT IMPACT COULD BE A BRIEF PERIOD
OF MODERATE TO HEAVY LAKE EFFECT SNOW WITH WHATEVER SURFACE
REFLECTION THIS TROUGH WILL HAVE. IT SEEMS MOST LIKELY NW WIND
FAVORED SNOWBELTS COULD PICK UP THE MOST...BUT AGAIN IT WILL HAPPEN
IN A BRIEF WINDOW GIVEN THE QUICK NATURE OF THE UPPER TROUGH. THE
INSTABILITY IS PRETTY IMPRESSIVE...WITH 850MB TEMPS PROGGED TO FALL
TO -15 TO -18C...BUT WOULD NOT BE SURPRISED TO SEE INVERSION HEIGHTS
CRASH WITH THE COLDEST 850MB READINGS...WHICH WOULD LIMIT LES
INTENSITY. FAIRLY STRONG HIGH PRESSURE (1028MB) IS PROGGED TO BUILD
IN ACROSS MUCH OF THE CWA AROUND 00Z WED...WHICH SHOULD REALLY
DIMINISH THE INTENSITY OF THE LAKE EFFECT.
TUE NIGHT THROUGH WED NIGHT...SINCE THE GFS WAS DISCOUNTED WITH
REGARDS TO THE UPPER TROUGH ON MON NIGHT/TUE...IT MAKES IT DIFFICULT
TO USE IT DURING THIS TIME PERIOD. IN FACT...00Z THE
ECMWF/UKMET/CANADIAN ARE ALL IN VERY GOOD AGREEMENT WITH THE NEXT
STORM SYSTEM APPROACHING THE AREA ON WED AND HAVE FOLLOWED THEM FOR
THE FORECAST. BACK ON TUE...AN UPPER LEVEL TROUGH IS SHOWN TO DIG
DOWN THROUGH THE WESTERN U.S...CAUSING CYCLOGENESIS DOWNSTREAM NEAR
DENVER AROUND 00Z WED. AS THE UPPER TROUGH MOVES DOWN INTO THE FOUR
CORNERS REGION ON WED...A SHRTWV EJECTS OUT AND LIFTS THE LOW NEAR
DENVER TOWARDS THE AREA. BY 00Z THU...THE MODELS ALL DEPICT THE LOW
REACHING SOMEWHERE NEAR THUNDER BAY. FRONTOGENESIS/WARM ADVECTION
AHEAD OF THE SYSTEM MAY BRING SOME LIGHT SNOW INTO THE AREA AS EARLY
AS TUESDAY EVENING. HOWEVER...THE STRONGER WARM AND MOIST AIR
ADVECTION WILL LIKELY HOLD OFF UNTIL AFTER MIDNIGHT TUE NIGHT AND
WED. HAVE RAISED POPS AFTER MIDNIGHT TUESDAY NIGHT ALONG THE
WISCONSIN BORDER WHERE WARM ADVECTION BAND OF SNOW MOVES IN...THEN
LEFT THE GOING 60 POPS IN FOR WED. HOWEVER...DID LOWER POPS 10
PERCENT ALONG LAKE MICHIGAN AS DRY AIR ASSOCIATED WITH THE HIGH THAT
MOVED OVER THE AREA LATE TUE MAY HOLD. IN ADDITION...TRIED TO DEPICT
THE SNOW TAPERING OFF IN THE WESTERN U.P. IN THE AFTERNOON WHERE IT
SEEMS MOST LIKELY THE WARM ADVECTION BAND OF SNOW WILL LIFT NORTH.
THE REST OF THE CWA IS A LITTLE MORE UNCERTAIN TO PLACE ANY TIMING
IN AT THIS TIME...BUT FUTURE FORECASTS SHOULD BE ABLE TO PUT IT IN.
COLD ADVECTION COMING IN WEDNESDAY NIGHT SHOULD RESTART LAKE EFFECT
SNOW FOR THE NORTHERN U.P....AND THUS DID NOT MAKE ANY ADJUSTMENTS.
NO CHANGES MADE BEYOND WED NIGHT.
&&
.AVIATION (FOR THE 06Z TAF ISSUANCE)...
LAKE EFFECT SNOW BAND REMAINS OUT OVER LAKE SUPERIOR...AND WITH
WINDS EXPECTED TO SHIFT SLIGHTLY MORE SOUTHWEST LATER ON THIS BAND
SHOULD STAY NORTH OF KCMX. SOME LAKE EFFECT SHOWERS STILL POSSIBLE
WITH SOUTHWEST FLOW...SO HAVE CONTINUED IN THE FORECAST FOR KCMX.
VFR CONDITIONS ARE EXPECTED AT KSAW THROUGHOUT THE TAF PERIOD...AND
AT KCMX AFTER 12Z. LLWS EVIDENT AT KSAW...WITH 51 KNOTS REPORTED VIA
0212Z TAMDAR SOUNDING. SIMILAR CONDITIONS AT KCMX EXPECTED OVERNIGHT
AS WINDS WILL BE STRONG OFF THE SURFACE FROM THE WSW.
&&
.MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)...
SOUTHWEST WINDS TO 30 KNOTS WILL CONTINUE THIS MORNING BEFORE
DIMINISHING GRADUALLY THIS AFTERNOON AS A LOW PRESSURE SYSTEM DRAGS
A COLD FRONT ACROSS LAKE SUPERIOR. IN THE WAKE OF THE FRONT A RIDGE
WILL SETTLE OVER THE LAKE...DIMINISHING THE WINDS BELOW 20 KNOTS.
OTHER THAN FOR A BRIEF INCREASE IN WINDS TOWARDS 30 KNOTS ON TUESDAY
WITH A LOW CROSSING LAKE SUPERIOR...THE NEXT CHANCE OF GALES WILL BE
ON THURSDAY WITH A TIGHT PRESSURE GRADIENT DEVELOPING AGAIN.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SYNOPSIS/DISCUSSION...AJ
AVIATION...RJT
MARINE...DLG
AREA FORECAST DISCUSSION...UPDATED
NWS MARQUETTE MI
1220 AM EST SUN NOV 25 2007
...UPDATED FOR AVIATION...
.DISCUSSION...
MAIN FOCUS IS ON ONGOING ADVISORY OVER THE KEWEENAW PENINSULA. WEST
WINDS CONTINUE OVER MUCH OF WESTERN LAKE SUPERIOR PER LATEST SURFACE
ANALYSIS. SPOTTER REPORTS FROM THE KEWEENAW PENINSULA INDICATE GUSTY
WINDS CONTINUE IN EXPOSED AREAS ALONG THE WEST OF THE KEWEENAW...BUT
NO SNOWFALL REPORTED OVER THE PAST SEVERAL HOURS. KP59 DID RECORD
MEASURABLE PRECIPITATION UNTIL 01Z...BUT NOTHING SINCE THEN. LATEST
RADAR DATA SHOWS A FEW WEAK RETURNS...MAINLY NORTH OF COPPER HARBOR.
00Z UPPER AIR SOUNDINGS SHOW WARMER AIR AT 850 MB OFF TO THE WEST...
WITH THIS AIR ADVECTING INTO THE REGION. THIS WILL REDUCE LAKE
SURFACE/850 MB DELTA T/S OVER WESTERN LAKE SUPERIOR TO BETWEEN 8 TO
12 C...AND THUS LESS CONDUCIVE FOR THE GENERATION OF LAKE EFFECT
SNOW. WILL DROP ADVISORY...BUT KEEP MENTION OF SOME LES OVER THE
KEWEENAW.
REMAINDER OF THE FORECAST LOOKS ON TRACK...SO NO OTHER CHANGES
PLANNED FOR THIS UPDATE.
PREVIOUS FORECAST
.SHORT TERM (TONIGHT AND SUN)...
UPPER AIR PATTERN CONSISTS OF A 500 MB TROUGH ACROSS THE UPPER GREAT
LAKES WITH RIDGING ACROSS THE WEST COAST AND A CLOSED 500 MB LOW
WEST OF HUDSON BAY. THE UPPER LEVEL FLOW WILL BECOME MORE ZONAL FROM
WEST TO EAST WITH TIME TONIGHT AND SUN.
THE MAIN WEATHER STORY WILL CONTINUE TO BE A LAKE EFFECT SNOW BAND
ACROSS WESTERN LAKE SUPERIOR AND WHAT EFFECT IT WILL HAVE ON THE
KEWEENAW PENINSULA. EARLIER CALLS THIS MORNING UP TO HOUGHTON AND
KEWEENAW COUNTIES TOLD OF SNOWFALL UP TO 4 INCHES WITH TWO INCHES IN
THE MORNING. KCMX WAS DOWN FOR A WHILE THIS MORNING DUE TO THE SNOW
AND LOOKING AT VISIBLE SATELLITE SHOWED A DOMINANT BAND OR BANDS
ACROSS THE WESTERN LAKE THAT WERE ACROSS KEWEENAW AND HOUGHTON
COUNTIES. THERE WERE ALSO REPORTS EVEN THOUGH WE COULD NOT FIND IT
OF 8 INCHES OF SNOW THIS MORNING UP TOWARDS COPPER HARBOR. BASED ON
THE FACT THAT THE WIND DOES NOT CHANGE DIRECTION MUCH FROM THE WSW
TO W AND GIVEN THAT LAKE-850 MB DELTA T IS ABOUT 14C OR SO WITH -8C
AIR AT 850 MB WITH WATER TEMPERATURES OF 6C...FIGURED AN ADVISORY
SHOULD BE HOISTED AND PUT ONE UP FOR KEWEENAW AND NORTHERN HOUGHTON
COUNTIES BASED ON POTENTIAL OF THE LAKE EFFECT BAND TO CONTINUE TO
AFFECT THOSE COUNTIES TONIGHT WITH A WSW FLOW AND GOOD CONVERGENCE
ORIENTING THE BAND FROM WEST TO EAST ACROSS THE AREA. INVERSION
HEIGHTS OFF THE NAM AND GFS BOTH ARE UP TO 5000 FEET BEFORE THESE
FALL LATE TONIGHT AND THE WIND SWITCHES DIRECTION TO THE SOUTHWEST.
WITH THIS IN MIND...STILL THINK UP TO 7 INCHES OF SNOW MAY FALL IN A
NARROW BAND AND IN A SMALL AREA AND WILL KEEP ADVISORY GOING
TONIGHT. LATE TONIGHT...ENVIRONMENT GETS MORE HOSTILE TO LAKE EFFECT
WITH INVERSION HEIGHTS FALLING...SW FLOW AND WARM AIR ADVECTION...SO
LAKE EFFECT SNOW SHOULD DIMINISH. WINDS WILL ALSO HELP TO BLOW AND
DRIFT THE SNOW AROUND UP THERE WITH THE WEST WINDS FAVORED FOR THEIR
GUSTINESS...SO THIS SHOULD CAUSE SOME VISIBILITY PROBLEMS AS WELL.
MID AND HIGH CLOUDS WILL BE THE RULE FOR THE AREA AND TEMPERATURES
WILL HAVE A HARD TIME FALLING OFF. WENT CLOSE TO ADJMAV FOR LOWS AND
ALSO HIGHS ON SUNDAY.
.LONG TERM (SUN NIGHT THRU SAT)...
A SHORTWAVE TRACKING E THRU THE UPPER GREAT LAKES AND ONTARIO SUN
NIGHT WILL SEND A COLD FRONT S ACROSS LAKE SUPERIOR AND INTO NRN
UPPER MI BY SUNRISE MON. 850MB TEMPS AROUND -7C WILL BE SUFFICIENT
FOR A BAND OF LES ALONG THE COLD FRONT/WIND SHIFT. FORCING
ASSOCIATED WITH THE SHORTWAVE WILL BE WELL E OF THE AREA WHEN THE
COLD FRONT PASSES...SO DO NOT EXPECT A BURST OF HVY LAKE ENHANCED
SNOW WITH THE COLD FROPA. BEHIND THE FRONT...A PURE NW TO N FLOW LES
REGIME WILL TAKE OVER AS 850MB TEMPS FALL TOWARD -12C DURING THE
DAY. NAM/GFS HAVE IMPORTANT DIFFERENCES IN THE INVERSION HEIGHTS
MON. GFS IS AROUND 5KFT WHILE THE NAM IS 7-9KFT FOR AT LEAST A
PORTION OF THE DAY. IN EITHER CASE...BEST DENDRITIC SNOW GROWTH
TEMPS WILL BE ABOVE THE INVERSION WHICH WILL HELP KEEP SNOW
ACCUMULATIONS UNDER CONTROL. OTHERWISE...UNTIL THE INVERSION HEIGHT
BECOMES MORE CERTAIN...CONDITIONS RIGHT NOW APPEAR TO SUPPORT
GENERAL 1-3 INCH ACCUMULATIONS IN THE HIGHER TERRAIN FAVORED BY NNW
WINDS. PRECONDITIONING FROM LAKE NIPIGON WILL BE AN IMPORTANT FACTOR
IN DETERMINING WHERE THE HEAVIEST SNOW FALLS.
TUE...ATTENTION IS ON THE NEXT SHORTWAVE ROTATING SE THRU CANADA
TOWARD LAKE SUPERIOR. GFS IS AN OUTLIER SWINGING THE SHORTWAVE THRU
FAR NRN ONTARIO. UKMET/CANADIAN/ECMWF ARE MUCH MORE AGGRESSIVE
BRINGING THE SHORTWAVE/HEIGHT FALLS FARTHER S...AND THE LATTER
MODELS EVEN HAVE A SFC LOW REFLECTION OVER LAKE SUPERIOR. LEANED IN
THIS DIRECTION FOR THE FCST GIVEN THE CONSISTENCY OF THE ECMWF. IF
THE ECMWF/CANADIAN SOLUTION VERIFIES...THERE WOULD LIKELY BE A
RELATIVELY BRIEF PERIOD OF MDT/HVY LAKE ENHANCED SNOW TUE NEAR LAKE
SUPERIOR. FOR NOW...WILL CARRY LIKELY POPS ALONG MOST OF THE AREA
NEAR LAKE SUPERIOR.
WED THRU SAT...THIS PERIOD OF THE FCST UTILIZED A COMBINATION OF THE
00Z GFS/ECMWF WHICH ARE REASONABLY SIMILAR IN THE PATTERN OVER THE
GREAT LAKES. A LITTLE MORE WEIGHT WAS PLACED ON THE ECMWF GIVEN ITS
GOOD RUN TO RUN CONTINUITY RECENTLY. MOST IMPORTANT FEATURE DURING
THE MID-LATE WEEK TIME FRAME IS THE PROGRESSIVE SHORTWAVE TROF
MOVING ACROSS THE CNTRL/ERN CONUS WED/THU. GFS/ECMWF HAVE SHOWN
DECENT CONTINUITY ON THIS SYSTEM WITH ORGANIZING SFC LOW OVER THE
CNTRL PLAINS WED MORNING LIFTING NE THRU NRN MI WED NIGHT/THU
MORNING. DEPENDING ON THE EXACT TRACK...THIS SYSTEM COULD PROVIDE
THE FIRST WIDESPREAD MODERATE SYNOPTIC SNOWFALL FOR MUCH OF THE FCST
AREA. AT THE MOMENT...MODEL CONSENSUS TRACK WOULD PLACE GREATEST
SNOW ACCUMULATIONS OVER THE NW HALF OF THE FCST AREA. ALSO DEPENDING
ON THE TRACK...THERE IS THE POTENTIAL FOR SIGNIFICANT LAKE
ENHANCEMENT NEAR LAKE SUPERIOR FROM THE WRN FCST AREA INTO THE
NCNTRL. WILL BE INCREASING POPS TO LIKELY WED OVER MUCH OF THE FCST
AREA GIVEN INCREASING CONFIDENCE FOR PCPN. SNYOPTIC PCPN SHOULD EXIT
EARLY THU. IN THE WAKE OF THIS SYSTEM...LES WILL DOMINATE THE PCPN
FCST THRU SAT AS 850MB TEMPS WILL EASILY BE LOW ENOUGH TO SUPPORT
LES (850MB TEMPS PROBABLY NO HIGHER THAN -12C). WHILE IT APPEARS DRY
AIR AND LOW INVERSIONS MAY BE INHIBITING FACTORS...THE COLD AIRMASS
WILL PUT THE IDEAL DENDRITIC SNOW GROWTH TEMPS IN THE CBL FOR MUCH
OF THE TIME...ALLOWING FOR HIGH SNOW-TO-WATER RATIOS. ANY SUBTLE
SHORTWAVES PASSING THRU THE AREA WILL OBVIOUSLY PROVIDE PERIODS OF
HEAVIER LES AS WELL. FOR THE MOST PART...LOW-LEVEL WIND FLOW WILL BE
WNW...SO HIGHER POPS WILL BE PLACED IN THE AREAS FAVORED BY WNW
WINDS. AWAY FROM LES...THE REST OF THE FCST AREA SHOULD SEE LITTLE
OR NO PCPN AFTER THU. TEMPS THRU THE PERIOD WILL AVERAGE AT OR BLO
NORMAL WITH THE COLDEST WEATHER PROBABLY THU/FRI.
&&
.AVIATION (FOR THE 06Z TAF ISSUANCE)...
LAKE EFFECT SNOW BAND REMAINS OUT OVER LAKE SUPERIOR...AND WITH
WINDS EXPECTED TO SHIFT SLIGHTLY MORE SOUTHWEST LATER ON THIS BAND
SHOULD STAY NORTH OF KCMX. SOME LAKE EFFECT SHOWERS STILL POSSIBLE
WITH SOUTHWEST FLOW...SO HAVE CONTINUED IN THE FORECAST FOR KCMX.
VFR CONDITIONS ARE EXPECTED AT KSAW THROUGHOUT THE TAF PERIOD...AND
AT KCMX AFTER 12Z. LLWS EVIDENT AT KSAW...WITH 51 KNOTS REPORTED VIA
0212Z TAMDAR SOUNDING. SIMILAR CONDITIONS AT KCMX EXPECTED OVERNIGHT
AS WINDS WILL BE STRONG OFF THE SURFACE FROM THE WSW.
&&
.MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)...
SW GALES WILL CONTINUE THIS EVENING BEFORE FADING AWAY TONIGHT AS
THE GRADIENT DECREASES WITH SOME GUSTS TO 40 KNOTS IN THE EVENING
ANYWAY. AFTER THIS GALE EPISODE COMES TO AN END...THE NEXT CHANCE
FOR GALES WILL BE WEDNESDAY AFTERNOON WITH A TIGHT PRESSURE GRADIENT
AGAIN.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
LAKE SUPERIOR...
GALE WARNING UNTIL MIDNIGHT EST TONIGHT LSZ263-264.
GALE WARNING UNTIL 1 AM EST SUN LSZ243-244.
GALE WARNING UNTIL 3 AM EST SUN LSZ265>267.
LAKE MICHIGAN...
GALE WARNING UNTIL 1 AM EST SUN LMZ248-250.
&&
$$
SHORT TERM...RJT
LONG TERM...ROLFSON
AVIATION...GJM/TAG
MARINE...GJM
AREA FORECAST DISCUSSION
NWS GAYLORD MI
1201 AM EST SUN NOV 25 2007
.AVIATION...RELATIVELY TRANQUIL CONDITIONS EXPECTED OVER THE NEXT 24
HOURS. LAKE EFFECT CLOUD COVER (VFR) WILL CONTINUE TO ERODE DURING
THE EARLY MORNING HOURS...AND WE WILL BE COMFORTABLY VFR FOR THE
DAYLIGHT HOURS AND INTO SUNDAY NIGHT. BETWEEN AN ARCTIC COLD FRONT
JUST NORTH OF LAKE SUPERIOR...AND HIGH PRESSURE IN THE OHIO
VALLEY...SOUTHWEST WINDS WILL REMAIN ON THE GUSTY SIDE.
JZ
&&
.UPDATE...ISSUED 905 PM SAT NOV 24...
VERY LITTLE GOING ON ACROSS THE NORTH LATE THIS EVENING. LAST OF THE
MID LEVEL MOISTURE STILL PRODUCING A FLURRY OR TWO NEAR OSCODA.
LINGERING SPRINKLES/FLURRIES CONTINUE IN THE TIP OF THE MITT/STRAITS
REGION...INCREASINGLY TRENDING LIQUID AS TEMPS RISE INTO THE UPPER
30S. HOWEVER...THOSE SPRINKLES/FLURRIES ARE ALSO INCREASINGLY
TRENDING TOWARD NOTHING...WITH WARMING SURFACE AND 850MB TEMPS. 00Z
SOUNDINGS FROM GRB AND APX ARE SIMILAR UP TO 825MB...BUT IS WAY
WARMER AND DRIER ALOFT (-4C AT 800MB AT GRB...-9C AT APX). THAT
REFLECTS THE SUBSIDENCE THAT HAS ALREADY OVERSPREAD NORTHERN MI.
THIS WARMING WILL EVENTUALLY WORK DOWN TO 850MB...WHERE TEMPS SHOULD
RISE TO -3C BY DAYBREAK.
WILL LINGER SPRINKLES/FLURRIES FOR A FEW HOURS (AS IN THE PREVIOUS
FORECAST)...THEN END. WITH SIGNIFICANT WARM ADVECTION ALOFT AND A
CONTINUED TIGHT SURFACE PRESSURE GRADIENT...WILL KEEP TEMPS
ESSENTIALLY STEADY THRU THE NIGHT.
JZ
&&
.PREVIOUS DISCUSSION...ISSUED 612 PM SAT NOV 24...
UPDATE...THE MID LEVEL DRYING IS PLAINLY HERE IN FORCE...AS
SIGNIFICANT LAKE EFFECT PRECIP HAS BEEN ALMOST COMPLETELY DEVOURED
IN THE LAST 2 HOURS. WILL CANCEL LAKE EFFECT HEADLINES. THE LIGHTER
PRECIP RATES ARE ALSO LETTING RAIN MIX IN...AND WILL MAKE THAT
ADJUSTMENT AS WELL.
JZ
DISCUSSION...LATEST RUC ANALYSIS AND VIS/IR/WV/RADAR IMAGERY SHOW A
MID-LEVEL WAVE PASSING ACROSS THE CWA ATTM WITH MID-UPPER LEVEL
CLOUDS EXITING TO THE EAST. SOME DRIER LOW LEVEL AIR HAS BEEN
SURGING NE ACROSS SOUTHERN LOWER MICHIGAN THIS AFTERNOON AND
CREATING A FEW HOLES IN THE CLOUD COVER ACROSS THE SOUTHEAST CORNER
OF THE CWA. BUT THE MAIN SHOW HAS BEEN THE SW LAKE EFFECT SNOW
EVENT THAT CONTINUES TO IMPACT THE TIP OF THE MITT AND EASTERN UPPER
MICHIGAN. SNOW REPORTS ACROSS EMMETT...CHEBOYGAN...AND MACKINAC
COUNTIES INDICATED 3-6 INCHES OF SNOW HAVE FALLEN SINCE THIS MORNING
WITH THE HEAVIEST SNOW LOCATED WITHIN A CORRIDOR BETWEEN HARBOR
SPRINGS AND LEVERING. EM IN MACKINAC COUNTY REVEALED NUMEROUS
ACCIDENTS ALONG M-134 NEAR CEDARVILLE WHERE 3 INCHES OF NEW SNOW HAS
FALLEN SINCE THIS MORNING. AS THE MID-UPPER LEVEL MOISTURE
EXITS...PLENTY OF LOW CLOUDS ACROSS WISCONSIN ARE IN THE PROCESS OF
CROSSING NORTHERN LAKE MICHIGAN. ACARS SOUNDINGS REVEAL INVERSION
HEIGHTS REMAIN AROUND 9KFT BUT LOWER FAIRLY QUICKLY OVER NORTH
CENTRAL WISCONSIN TO ABOUT 4KFT. MEANWHILE...VARIOUS SHIP REPORTS
AND BUOYS INDICATE AN OCCASIONAL GALE FORCE GUST IS OCCURRING OVER
THE NORTHERN LAKE MICHIGAN AND LAKE HURON. LAKE EFFECT AND MARINE
HEADLINES ARE THE MAIN FORECAST CONCERNS THROUGH TOMORROW.
TONIGHT...WEAK SHEARED OUT SHORTWAVE WILL MOVE EAST OF THE REGION
AND WILL DRAG ALL THE MID-HIGH LEVEL MOISTURE WITH IT. 850-700MB RH
OVER NORTHERN LAKE MICHIGAN WILL DECREASE FROM 45-65 PCT EARLY THIS
EVENING TO 35-45 PCT BY OVERNIGHT WHILE INVERSION HEIGHTS CRASH FROM
8KFT TO UNDER 3KFT...WITH MOST OF THE CRASHING OCCURRING DURING THE
EVENING. 850MB TEMPS ALSO MODERATE FROM THEIR NEAR -8C LEVELS THIS
AFTERNOON TO ABOUT -4C BY 12Z. THESE PARAMETERS SUGGEST A
DIMINISHING TREND IN LES ACTIVITY THIS EVENING AND COMPLETELY
SHUTTING OFF BY 12Z. WITH THE BACK EDGE OF THE DEEPER MOISTURE NOW
REACHING WESTERN LAKE MICHIGAN...WILL MAKE A LAST MINUTE DECISION
WHETHER TO EXTEND HEADLINES THROUGH THE EVENING. EITHER WAY...WILL
BUMP UP SNOW CHANCES TO NUMEROUS ACROSS EMMET/CHEBOYGAN AND EASTERN
CHIP COUNTIES THROUGH MID-EVENING...BEFORE TRIMMING TO FLURRIES
OVERNIGHT. ADDITIONAL ACCUMULATIONS WILL BE UP TO AN INCH MOSTLY
BETWEEN HARBOR SPRINGS AND LEVERING. ELSEWHERE...SHALLOW LOW LEVEL
MOISTURE OVER WISCONSIN WILL ROTATE ACROSS THE CWA THIS EVENING
BEFORE EXITING BY 12Z SUN. MID-UPPER LEVEL CLOUDS WILL SKIRT BY THE
AREA TO THE NORTH...SO WILL KEEP SKIES MOSTLY CLOUDY NORTH OF THE
STRAITS THE ENTIRE NIGHT. LOWS WILL BE IN THE MIDDLE TO UPPER 20S.
TOMORROW...SHORTWAVE MOVING ACROSS ONTARIO WILL GET SHEARED APART AS
IT MOVES EAST INTO QUEBEC...BUT NOT BEFORE DROPPING A COLD FRONT
ACROSS SOUTHERN ONTARIO JUST NORTH OF LAKE SUPERIOR. TO THE SOUTH
OF THE COLD FRONT...SW WINDS AND WAA WILL CONTINUE TO BRING UP 850MB
TEMPS TO THE -3C TO 0C RANGE DURING THE DAY. MID-UPPER LEVEL CLOUDS
BROUGHT IN BY THE JET STREAM WILL SLOWLY RETREAT TO THE NORTH WHILE
THE 850-700MB RH FALLS BETWEEN 25-35 PCT BY THE END OF THE DAY. LOW
LEVEL INSTABILITY PROBABLY IS STILL SUFFICIENT FOR SOME LAKE CLOUDS
ACROSS SW FLOW REGIMES IN THE MORNING BEFORE THE INFLUX OF DRIER AIR
AND DIURNAL MIXING CAUSE THESE CLOUDS TO DIMINISH. THEREFORE...A
GENERAL DECREASING CLOUDINESS TREND WILL BE OBSERVED AND WILL KEEP
DRY CONDITIONS GOING...WITH HIGHS IN THE MID 30S NORTH TO MID 40S
SW.
MPC
SUNDAY NIGHT THROUGH TUESDAY...CHANGEABLE WEATHER LOOKS ON TAP FOR
THIS PERIOD. INITIAL FOCUS COMES LATE SUNDAY NIGHT INTO EARLY MONDAY
ACROSS THE NORTH AS WEAK NORTHERN STREAM ENERGY AND LOW LEVEL
RIDGING PUSHING THROUGH THE PLAINS ATTEMPTS TO SHOVE A WEAK FRONTAL
BOUNDARY ACROSS THE UPPER PENINSULA. NOT MUCH IN THE WAY OF MOISTURE
TO WORK WITH...BUT PRONOUNCED AREA OF 900-800MB FRONTOGENESIS GIVEN
VERY TIGHT THERMAL GRADIENT IN PLACE (READINGS LIKELY IN THE LOWER
TEENS ACROSS SOUTHERN ONTARIO) WILL PROBABLY BE SUFFICIENT TO
SQUEEZE OUT A FEW LIGHT SNOW SHOWERS AS WELL AS PROVIDE AN INCREASE
IN CLOUDS. FARTHER SOUTH ACROSS NORTHERN LOWER...NOT A HALF BAD DAY
EXPECTED ON MONDAY AS AREA FALLS IN BETWEEN SYSTEMS - FRONT TO THE
NORTH AND DEVELOPING LOW OVER THE OHIO VALLEY WITH UPPER WAVE OVER
FAR NORTHWESTERN MEXICO THIS AFTERNOON KICKING OUT THROUGH THE
PLAINS. TEMPERATURE-WISE...LOOKS FAIRLY "WARM" WITH H85 TEMPS
MODERATING TO AROUND -1C UNDER BROAD SOUTHWESTERLY FLOW...AND WITH
AT LEAST SOME SUNSHINE EXPECTED...HIGHS IN THE UPPER 30S/LOWER 40S A
PRETTY GOOD BET. THINGS HEAD DOWNHILL ACROSS THE FAR SOUTH BY LATE
AFTERNOON AS AFOREMENTIONED UPPER WAVE LIFTS INTO THE OHIO
VALLEY...WITH INCREASING 700-500MB -DIVQ AXIS AND MID LEVEL BAND OF
FRONTOGENESIS ATTEMPTING TO SPREAD INTO THE REGION. STILL A FEW
QUESTIONS TO BE ANSWERED WITH THIS SYSTEM...NAMELY JUST WHERE WILL
PRECIP END UP AND WHAT TYPE WILL IT BE? GIVEN NATURE OF PRECIP
DRIVEN BY FGEN...WOULD OBVIOUSLY EXPECT A SHARP CUTOFF...AND
NUMERICAL GUIDANCE (INCLUDING 15Z SREF) HAS BEEN ADAMANT ABOUT JUST
BRUSHING THE FAR SOUTHEAST WITH THE SYNOPTICALLY-DRIVE PRECIP.
FORECAST RAOBS AND EXPECTED WARMISH START LEAD TO A CONTINUED
MENTION OF RAIN WITH THE LOWEST 2KFT PROGGED ABOVE FREEZING.
HOWEVER...COLD AIR NOT FAR AWAY (REFERENCE ABOVE) AND WOULD EXPECT
ANYTHING THAT CONTINUES TO CHANGE TO SNOW QUITE QUICKLY. SYSTEM
LOOKS SIMILAR TO WHAT OCCURRED LAST WEEK...ONLY MORE SUPPRESSED BUT
STILL SOMETHING TO BE WATCHED CLOSELY.
BETTER SHOT AT PRECIP FOR MORE OF THE REGION APPEARS TO COME ON
TUESDAY AS SECONDARY PIECE OF NORTHERN STREAM ENERGY PROGGED TO DIVE
DIRECTLY ACROSS THE GREAT LAKES. ECMWF HAS REMAINED CONSISTENT WITH
THIS TREND...AND HAS THE SUPPORT OF THE 00/12Z GEFS MEAN. IN
TYPICALLY CLIPPER FASHION...THIS ONE MAY TURN OUT TO BE A BIT OF A
NUISANCE GIVEN PROGGED DECENT 850-700MB FRONTOGENETICAL AXIS SETTING
UP SOMEWHERE NEAR THE AREA...WHILE LAKE ENHANCEMENT COMES INTO PLAY
PER H85 TEMPS RUNNING ABOUT -13C OR SO. THAT IS...ASSUMING THE ECMWF
IS ONTO THE RIGHT IDEA...AS THE GFS WOULD SUGGEST A MUCH FLATTER
WAVE PASSING HARMLESSLY TO THE NORTH. THE KEY APPEARS TO BE THE
DEGREE OF RIDGING TAKING SHAPE OVER THE PACIFIC/CANADIAN
NORTHWEST...WHICH THE GFS/ECMWF ENSEMBLE MEANS WOULD SUGGEST WILL BE
SUFFICIENT TO ALLOW THE NORTHERN STREAM ENERGY TO PENETRATE FARTHER
SOUTH. GIVEN SOME REMAINING UNCERTAINTIES...PREFER TO HOLD WITH
SMALL POPS AT THIS JUNCTURE.
LATER PERIODS (TUESDAY NIGHT THROUGH SATURDAY)...ANOTHER CHALLENGING
FORECAST IN THE WORKS FOR THE EXTENDED...WITH QUESTIONS ABOUNDING
WITH REGARDS TO PRECIP CHANCES AS WELL AS DAILY TEMPERATURES.
OVERALL PATTERN THROUGH THIS PERIOD LOOKS TO BE DOMINATED BY AN
ACTIVE NORTHERN STREAM...WHILE SOUTHERN STREAM ENERGY LURKS NOT TOO
FAR AWAY. INITIAL CHALLENGE COMES WEDNESDAY NIGHT INTO THURSDAY WITH
PACIFIC ENERGY PROGGED TO DROP THROUGH THE CENTRAL ROCKIES...
INCITING LEE CYCLOGENESIS OVER THE CENTRAL HIGH PLAINS. THIS LOW IS
THEN EXPECTED TO TRACK NORTHEAST ALONG TIGHTENING THERMAL GRADIENT
AS FIRST SURGE OF ARCTIC AIR POURS INTO THE NORTHERN PLAINS PER
DEVELOPING STRONG BLOCKING RIDGE ACROSS INTERIOR ALASKA. MODEL
SOLUTIONS QUITE VARIED WITH REGARDS TO EXACTLY HOW THIS WHOLE THING
WILL PLAY OUT...WITH THE GFS DEPICTING A WEAK SURFACE FEATURES WHILE
THE ECMWF/CANADIAN KEYS IN ON A MUCH MORE PHASED/AMPLIFIED UPPER
SYSTEM...AND A MORE PRONOUNCED ACCOMPANYING SURFACE SYSTEM. LIKELY
STRONG THERMAL GRADIENT WOULD CERTAINLY ARGUE TO A MORE WOUND UP
SYSTEM...AND ALONG THE LINES OF HPC...PREFER TO SIDE WITH THE ECMWF
THIS GO AROUND. EITHER WAY...HOWEVER...THE END RESULT WILL BE
HEIGHTENED CHANCES FOR PRECIP AS ISENTROPIC ASCENT REVVS UP LATE
WEDNESDAY AND UPPER FORCING CATCHES UP ON THURSDAY TO SHOVE WHAT
SHOULD BE A RATHER POTENT COLD FRONT THROUGH THE REGION. PER
FORECAST RAOBS OF EITHER SCENARIO...PTYPE LOOKS TO BE MAINLY
SNOW...THOUGH PENDING EXACT TRACK/STRENGTH OF SYSTEM...COULD FORESEE
SOME RAIN ENTERING THE PICTURE AS WARMER AIR TRIES TO SNEAK IN AHEAD
OF THE COLD FRONT.
HEADING INTO THURSDAY AFTERNOON THROUGH SATURDAY...APPEARS THE LAKE
EFFECT MACHINE WILL BE GOING FULL FORCE AS INITIAL SHOT OF QUITE
COLD AIR (H85 TEMPS PROGGED -16C TO -18C) DROPS INTO THE REGION PER
BRIEF CROSS-POLAR SETUP WITH POLAR VORTEX DROPPING ACROSS HUDSON BAY
WHILE STRONG ALASKA RIDGE HOLDS FIRM. SETUP NOT OVERLY STABLE...
HOWEVER...AS ENERGY PROGGED TO BRIEFLY DISRUPT THE OVERALL MEAN
RIDGE OVER ALASKA...WHILE SECONDARY ENERGY DROPS INTO THE WESTERN
CONUS...EFFECTIVELY SHUNTING THE INTIAL SHOT OF COLD EAST. THAT
SAID...WILL CONTINUE TO CARRY LAKE EFFECT SNOW SHOWER MENTION
THROUGH THE ENTIRE PERIOD FOR WEST/NORTHWEST FLOW LOCATIONS AS
OVERLL CYCLONE FLOW REGIME PERSISTS AND MOISTURE REMAINS
SUFFICIENTLY DEEP (900-700MB RH GREATER THAN 70 PERCENT). AS FOR
TEMPERATURES EACH DAY...WILL SHOW FALLING TEMPS THURSDAY AFTERNOON
AS PLENTIFUL COLD ADVECTION UNDERWAY...WITH READINGS ONLY IN THE 20S
ON FRIDAY UNDER CLOUDS/SNOW SHOWERS. LOOKING AHEAD JUST BIT
MORE...PERHAPS AN EVEN BIGGER STORY LOOMS JUST AFTER THE CURERNT
FORECAST PERIOD ENDS...WITH ALL MODEL GUIDANCE REMAINING IN VERY
GOOD AGREEMENT REGARDING REDEVELOPMENT (AND BETTER SUSTAINMENT) OF
CROSS POLAR FLOW INTO THE NORTHERN TIER OF THE U.S. AS VERY STRONG
RIDGING ONCE AGAIN BUILDS THROUGH ALASKA...WITH ANOTHER SHOT OF VERY
COLD AIR MAKING AN APPEARANCE TOWARD THE END OF THE WEEKEND.
LAWRENCE
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...GALE WARNING UNTIL 11 AM EST SUNDAY FOR LMZ323-341-342-344>346.
LH...GALE WARNING UNTIL 11 AM EST SUNDAY FOR LHZ345>349.
LS...GALE WARNING UNTIL 5 AM EST SUNDAY FOR LSZ321.
&&
$$
AREA FORECAST DISCUSSION
NWS CLEVELAND OH
824 PM EST MON NOV 26 2007
.SYNOPSIS...
LOW PRESSURE WILL MOVE NORTHEAST TO SOUTHWESTERN PENNSYLVANIA BY
THIS EVENING AND INTO NEW ENGLAND BY TUESDAY MORNING. HIGH
PRESSURE WILL BUILD OVER THE REGION FROM THE SOUTH LATE TUESDAY
INTO WEDNESDAY. ANOTHER LOW WILL MOVE ACROSS SOUTHERN ONTARIO
THURSDAY MORNING AND DRAG A STRONG COLD FRONT ACROSS THE LOCAL
AREA.
&&
.NEAR TERM /UNTIL 7 AM TUESDAY MORNING/...
THE PCPN HAS CHANGED TO ALL SNOW IN THE TOLEDO METRO AREA AND
FINDLAY AND LIKELY A RAIN/SNOW MIX AS FAR EAST AS PORT CLINTON AND MARION.
ACARS/TAMDAR SOUNDINGS FROM 23Z OUT OF TOLEDO SUGGEST A NEARLY
ISOTHERMAL PROFILE THROUGH 900MB NEAR 0C. THIS WOULD IMPLY THAT
THE PCPN TYPE WILL BE HIGHLY DEPENDANT ON THE INTENSITY OF
PCPN...THE HEAVIER THE PCPN THE MORE LIKELY SNOW WILL FALL. WITH
GRASSY SURFACES IN TOLEDO ALREADY SEEING A DUSTING TO 1/2 AN INCH
OF SNOW...AND ADDITIONAL SNOW TO COME THIS EVENING...WILL CONTINUE
WITH SNOW ACCUMULATIONS AROUND AN INCH ACROSS THE WEST.
AS FOR THE REMAINDER OF THE FORECAST AREA...TAMDAR/ACARS SOUNDINGS
REMAIN QUITE WARM AT CLE AND CAK...AS WELL AS ERI WITH THE 850MB
WARM FRONT STILL WEST OF A SANDUSKY TO MARION LINE. TEMPS AT 850MB
REALLY DO NOT START COOLING EAST OF I-71 UNTIL AFTER MIDNIGHT SO
IT SEEMS LIKE THE CHANGE OVER TO ALL SNOW IN YNG AND ERI MAY NOT
BE UNTIL LATE TONIGHT. LATEST RUC 1000-850MB THICKNESS VALUES
INDICATE THAT THE RAIN/SNOW LINE GENERALLY ALIGNS WITH THE 1305
METER THICKNESS LINE...AND THIS DOES NOT MOVE EAST OF I-71 UNTIL
JUST AFTER MIDNIGHT AND IT DOES NOT ARRIVE INTO NW PA UNTIL AFTER 09Z.
CURRENT FCST HAS ACCUMULATIONS AROUND AN INCH IN THE SNOWBELT...BUT
THIS MAY BE A LITTLE PESSIMISTIC GIVEN THAT TEMPS ARE STILL IN THE
LOWER 40S IN THESE AREAS. WILL THEREFORE GO WITH RAIN MIXING WITH
OR CHANGING TO SNOW LATE TONIGHT WITH LITTLE OR NO ACCUMULATION IN
NE OH/NW PA.
IN ADDITION...GIVEN THE COOLING ALOFT THAT IS OR WILL
OCCUR...SLEET IS UNLIKELY. THERE COULD BE A BRIEF PERIOD OF SNOW
GRAINS/PELLETS BUT PROBABLY NOT SLEET. WILL REMOVE THIS FROM THE FORECAST.
TEMPS LOOK GOOD AND WILL ONLY MAKE MINOR TWEAKS. UPDATE OUT BY 9 PM.
&&
.SHORT TERM /7 AM TUESDAY MORNING THROUGH WEDNESDAY/...
WRAP AROUND MOISTURE WILL SLIDE SOUTHEAST ACROSS THE AREA ON
TUESDAY AND FLOW BECOMES FAVORABLE FOR SOME RESIDUAL LAKE EFFECT
RAIN AND SNOW SHOWER ACTIVITY DURING THE DAY. AIR MASS IN THE WAKE
OF THE LOW NOT PARTICULARLY COLD SO EXPECTING TEMPERATURES TO WARM
UP ABOVE FREEZING ON TUESDAY.
LAKE EFFECT ACTIVITY WILL CONTINUE INTO TUESDAY AFTERNOON AND THEN
COME TO AN END TUESDAY EVENING IN THE NORTHEAST SNOW BELT AREAS.
HIGH PRESSURE BUILDS IN AND SETS UP FOR A FAIR WEATHER DAY ON WEDNESDAY.
STRONG COLD FRONT APPROACHES THE FORECAST AREA FROM THE WEST
WEDNESDAY NIGHT WITH A TRANSITION FROM RAIN AT ONSET TO SNOW
SHOWERS BY MORNING.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
COLD FRONT PASSING THRU LATE WEDNESDAY NIGHT EARLY THURSDAY AND
EXPECTING MAINLY LAKE EFFECT SNOW SHOWERS TO LINGER INTO THURSDAY
NIGHT. THIS FRONT IS FOLLOWED QUICKLY BY ANOTHER LOW PASSING THROUGH
THE UPPER GREAT LAKES WITH TRAILING COLD FRONT MOVING THRU LATE
FRIDAY/FRIDAY NIGHT AND WILL BRING CHANCE OF SNOW
SHOWERS...PRIMARILY LAKE EFFECT FOR NORTHEAST OHIO/NORTHWEST PA INTO
EARLY SATURDAY. LARGE DIFFERENCE AT THE END OF THE EXTENDED BOTH
BETWEEN GFS AND ECMWF AND RUN TO RUN CONSISTENCY. OPERATIONAL GFS
AND ENSEMBLES GENERALLY TRYING TO TRACK LOW EASTWARD THROUGH THE
OHIO VALLEY WITH EAST COAST DEVELOPMENT SUNDAY NIGHT INTO MONDAY
WHILE ECMWF TRACKS LOW FURTHER N. GFS WOULD LEAD TO POSSIBLE HEAVY
SNOW EVENT WHILE ECMWF WOULD INITIALLY BRING RAIN SHOWERS FOLLOWED
BY SNOW LATE MONDAY AFTER COLD FRONT MOVES THROUGH. FORECAST LEANS
MORE TOWARD THE GFS KEEPING PRECIP ALL SNOW.
&&
.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
SURFACE LOW CENTERED JUST NE OF PIT. CURRENT 3 HOURS PRESSURE
FALLS TRACK INTO CENTRAL NEW YORK STATE. MODELS TRACK LOW ACROSS
ERN NY STATE...AND INTO MAINE BY 12Z TUESDAY. CURRENTLY HEAVIEST
RAIN IS EAST OF A LAKE COUNTY TO STARK COUNTY LINE AND SHOULD BE
NORTHEAST OF THE AREA WITHIN 2 HOURS OR SO. TOLEDO HAS
TRANSISIONED TO SNOW WITHIN THE LAST HOUR...LOCATIONS WILL
GRADUALLY TRANSITION TO SNOW BY AROUND 2AM. SNOW SHOULD ONLY LAST
A FEW HOURS AFTERWARDS...EXPECT A WIDESPREAD DUSTING TO UP TO AN
INCH. ALSO EXPECT WIDESPREAD IFR CIGS TO CONTINUE THROUGH THE
OVERNIGHT HOURS ACROSS THE ENTIRE FORECAST AREA...IMPROVING
QUICKLY FROM THE WEST AFTER SUNRISE.
OUTLOOK...A FEW LAKE EFFECT/LAKE ENHANCED WET SNOW SHOWERS AND
MVFR CONDITIONS WILL LIKELY LINGER NE OH/NW PA TUESDAY AS A
SECONDARY COLD FRONT GRAZES THE AREA OTHERWISE THE AN IMPROVING
TREND SHOULD DEVELOP AS CONDITIONS IMPROVE TO VFR. NICE DAY
(RELATIVELY SPEAKING) WEDNESDAY WITH VFR CONDITIONS. NEXT COLD
FRONT EXPECTED BY THUR MORN WITH MVFR CONDITIONS DEVELOPING WITH
SHOWERS. HIGH PRESSURE AND VFR CONDITIONS EXPECTED AGAIN BY FRIDAY
ALTHOUGH MVFR LAKE EFFECT CLOUDS POSSIBLE EXTREME NE OH/NW PA.
&&
.MARINE...
LOW PRESSURE SOUTH OF OHIO WILL CONTINUE TO MOVE EASTWARD THIS
EVENING...WINDS WILL COME AROUND OUT OF THE NORTHWEST OVERNIGHT AS
THE LOW DEPARTS. WINDS SHOULD STAY BETWEEN 10-20KTS THROUGH DAYBREAK
BUT ANOTHER WAVE WILL APPROACH THE LAKE TOMORROW AFTERNOON. THIS
WAVE CURRENTLY OVER NORTH DAKOTA WILL SWEEP ACROSS THE LAKE TUESDAY
AFTERNOON WITH SOUTHWEST WINDS AROUND 25KTS QUICKLY TURNING AROUND
OUT OF THE NORTHWEST AND INCREASING TO GALES TO 35KTS BY AFTERNOON.
WILL BE ISSUING A GALE WARNING FOR LAKE ERIE WITH THE AFTERNOON
ISSUANCE AND WILL RUN IT FROM LATE TOMORROW MORNING THROUGH TUESDAY
EVENING.
FOLLOWING THIS WAVE...HIGH PRESSURE WILL POSITION ITSELF ACROSS LAKE
ERIE ON WEDNESDAY WITH GENERALLY LIGHT WINDS EXPECTED. ANOTHER AREA
OF LOW PRESSURE WILL APPROACH LAKE ERIE FROM THE CENTRAL PLAINS ON
THURSDAY AND WILL PUSH A STRONG COLD FRONT ACROSS THE LAKE EARLY
THURSDAY MORNING. WAY TOO EARLY TO GO WITH HEADLINES BUT THINK GALES
WILL AGAIN BE POSSIBLE THURSDAY BEHIND THE FRONT ESPECIALLY ON THE
EAST HALF OF THE LAKE. HIGH PRESSURE WILL BUILD ACROSS THE LAKE ON
FRIDAY WITH A TROUGH FORECAST TO CROSS THE LAKE ON SATURDAY.
&&
.CLE WATCHES/WARNINGS/ADVISORIES...
OH...NONE.
PA...NONE.
MARINE...GALE WARNING FROM 10 AM TO 10 PM EST TUESDAY FOR LEZ061-
142>149-162>169.
&&
$$
SYNOPSIS...LOMBARDY
NEAR TERM...MRD
SHORT TERM...LOMBARDY
LONG TERM...RANDEL
AVIATION...DJB
MARINE...LEINS
AREA FORECAST DISCUSSION...UPDATE
NWS FORT WORTH TX
1140 AM CST SUN NOV 25 2007
.AVIATION...
18Z TAF PACKAGE
UPPER LEVEL LOW HAS NOW MOVED INTO WEST CENTRAL TEXAS AND CONTINUES
TO TRACK TO THE NORTHEAST. UPPER LEVEL LOW SHOULD BE MOVING NW OF
THE METROPLEX TONIGHT AND THEN THE RAIN WILL FINALLY COME TO AN END
AS UPPER LEVEL DRY SLOT MOVES INTO THE REGION. BUT FOR THE REMAINDER
OF THE AFTERNOON AND EVENING...LOW CLOUDS /BOUNCING BETWEEN UPPER
END OF IFR AND LOWER END OF MVFR/ AND AREAS OF LIGHT TO MODERATE
RAIN WILL CONTINUE TO AFFECT THE AIRPORTS. THE RAIN WILL BE
ON-AND-OFF THROUGH THE EVENING HOURS AND SHOULD COME TO AN END
AROUND 26/01Z AT KACT AND 26/03Z AT THE METROPLEX AIRPORTS. NO
FROZEN PRECIPITATION IS EXPECTED...BUT IF SOME DOES MIX WITH THE
RAIN...IT WOULD BE IN THE METROPLEX AREA LATER THIS AFTERNOON OR
EVENING...SHORT-LIVED...AND WILL NOT CREATE ANY HAZARDS AT THE
SURFACE.
CLOUD HEIGHTS WILL BEGIN TO RISE TONIGHT AS THE UPPER LEVEL LOW
MOVES NW OF THE AIRPORTS BUT MAY RETURN TO IFR CONDITIONS AT THE
METROPLEX AIRPORTS FOR A FEW HOURS AS THE LOW MOVES ACROSS. CEILINGS
WILL RAPIDLY RISE INTO VFR TOMORROW MORNING AS THE SYSTEM MOVES OUT
AND MAY EVEN RISE EARLIER THAN REFLECTED IN THIS TAF ISSUANCE.
82/JLD
&&
.UPDATE...
1140 AM
THE CURRENT FORECAST LOOKS GOOD OVERALL. RAINFALL AHEAD OF EJECTING
UPPER LOW CONTINUES TO INCREASE IN COVERAGE AND INTENSITY JUST EAST
OF THE INTERSTATE 35 CORRIDOR. EXPECT PERIODS OF LIGHT TO
OCCASIONAL MODERATE RAIN THROUGH THE AFTERNOON. WE HAVE OBSERVED
PERIODS OF SNOW IN WEST TEXAS ASSOCIATED WITH THE CORE OF THE UPPER
LOW. THEREFORE...WE STILL EXPECT THE WESTERN COUNTIES TO PICKUP A
LITTLE SNOW BEFORE THE SYSTEM EXITS THE REGION OVERNIGHT.
WILL UP THE POPS TO LIKELY ACROSS THE CENTRAL ZONES THIS AFTERNOON
TO ACCOUNT FOR INCREASING LIGHT RAIN MOVING NORTHWARD FROM SOUTHWEST
TEXAS. WILL ALSO BUMP HIGH TEMPS UP A DEGREE OR TWO IN A FEW PLACES
AS SOME BRIEF RAIN FREE PERIODS THIS MORNING HAVE ALLOWED TEMPS TO
CREEP UP...ESPECIALLY ACROSS THE METROPLEX AND AREAS EAST OF
INTERSTATE 35.
&&
.AVIATION...
518 AM
UPPER LEVEL STORM SOUTHWEST OF KMRF AT 11Z WILL MOVE NORTHEAST
TOWARD KADM BY 06Z AND KMKO BY 12Z. WIDESPREAD LIGHT TO MODERATE
RAIN IS EXPECTED TODAY THROUGH 00Z TO THE SOUTHEAST OF THIS PATH
WHILE SNOW...MIXED WITH RAIN AT TIMES...PREVAILS TO THE NORTHWEST OF
THIS PATH THROUGH TONIGHT. THE RAIN SHOULD DIMINISH TO VERY LIGHT
RAIN BY THIS EVENING AND END BEFORE OR AROUND MIDNIGHT. LOCAL TAFS
SITES WILL EXPERIENCE PERIODS OF IFR WITH SOME BRIEF EPISODES OF
MVFR TODAY...THEN TRENDING TO JUST MVFR BY THIS EVENING AND
OVERNIGHT. FORECAST SOUNDINGS INDICATE COOLING TO NEAR OR SLIGHTLY
BELOW FREEZING OF A SATURATED ENVIRONMENT BY 00Z...THUS ICING IS A
CONCERN AOA 1000 FEET AFTER 21Z AND OVERNIGHT. 75
&&
.DISCUSSION...
502 AM CST.
POWERFUL UPPER LEVEL LOW CURRENTLY MOVING TOWARD THE BIG BEND
REGION OF TEXAS AND WILL BEGIN TO PIVOT TOWARD THE NORTHEAST LATER
TODAY. THE MODELS FORECAST THE UPPER LEVEL LOW TO CROSS RIGHT OVER
THE NW CWA...WHICH IS JUST A LITTLE FURTHER SOUTH THAN PREVIOUS
RUNS. CURRENT ACARS SOUNDINGS DO SHOW AN ABOVE FREEZING LAYER
HOLDING STRONG NEAR 800 MB OVER THE CENTRAL CWA. RADAR LOOP OF
THE PAST SEVERAL HOURS CONFIRMS THE PRESENCE OF BRIGHT BANDING
CAUSED BY MELTING SNOW AT 5000 TO 7000 FT. ACROSS THE EASTERN
ZONES...GREATER LOW LEVEL INSTABILITY IS ALLOWING FOR SCATTERED
THUNDERSTORMS. NEEDLESS TO SAY...WILL CONTINUE THE FORECAST OF
CATEGORICAL POPS ACROSS ALL OF NORTH TEXAS FOR THIS MORNING. THE
PRECIPITATION WILL BEGIN TO WANE BY AFTERNOON AS A DRY SLOT WORKS
INTO THE CENTRAL AND EASTERN ZONES.
SNOW HAS YET TO MAKE IT TO THE GROUND IN ANY SIGNIFICANT QUANTITY
ACROSS MUCH OF TEXAS...BUT MODEL FORECASTS CONTINUE TO DEPICT
COOLING OF THE LOW LEVELS WITH THE WARM NOSE ACROSS THE WESTERN
ZONES DROPPING BELOW FREEZING DURING THE DAY WITH THE APPROACH OF
THE UPPER LOW. DYNAMIC FORCING ASSOCIATED WITH THE CORE OF AN
UPPER LOW OFTEN COMPENSATES FOR LACK OF COLD AIR...AS IT LIFTS
AND COOLS THE ENTIRE COLUMN ADIABATICALLY. THE LAST EXAMPLE OF
THIS WAS LATE MARCH OF 2005 WHEN A SURPRISE BAND OF SNOW OCCURRED
FROM WEATHERFORD TO BENBROOK ON EASTER SUNDAY MORNING. WITH THE
UPPER LEVEL LOW TRACKING OVER THE NW CWA AROUND SUNSET TONIGHT...
WE WILL CONTINUE TO MENTION SNOW MIXING WITH RAIN WITH FAIRLY HIGH
CONFIDENCE TO THE NW OF A COMANCHE TO WEATHERFORD TO SHERMAN LINE.
WE WILL MENTION SNOW FLURRIES JUST TO THE EAST OF THIS LINE
WHERE CONFIDENCE IN SNOW FLAKES SURVIVING THE TRIP THROUGH THE
ABOVE FREEZING WARM NOSE IS LOWER. THE WINTER WEATHER ADVISORY HAS
BEEN EXTENDED THROUGH MIDNIGHT FOR 6 OF OUR NW COUNTIES WHERE
BRIEF BURSTS OF HEAVY/WET SNOW ARE POSSIBLE TODAY AND THIS
EVENING. WITHIN HEAVY BANDS OF SNOW ACROSS THE NW A BRIEF
ACCUMULATION OF AN INCH OR SO IS POSSIBLE BEFORE GRADUAL MELTING
OCCURS. OTHERWISE...TEMPS ACROSS THE REMAINDER OF NORTH TEXAS WILL
BE SAFELY ABOVE FREEZING. WRAP AROUND PRECIPITATION WILL QUICKLY
EXIT NORTH TEXAS BY MIDNIGHT WITH SOME CLEARING OCCURRING ACROSS
THE SW COUNTIES WHERE FREEZING TEMPS ARE POSSIBLE.
A WARM-UP WILL OCCUR MONDAY AND TUESDAY AS SW FLOW AND SUBSIDENCE
BEHIND THE STORM SYSTEM RESULTS IN WARMING LOW LEVEL TEMPS. THE
MODELS ARE IN A BIT OF DISAGREEMENT IN THE EXTENDED WITH THE
TIMING OF A FRONT/POPS. WILL CONTINUE TO FOLLOW THE GFS...WITH
RESPECT TO THE ECMWF SOLUTION. WILL BACK OFF ON THE SOUTHWARD PUSH
OF THE FRONT EXPECTED LATE WEDNESDAY AND HANG ON TO WARMER
TEMPS/MOISTURE ACROSS THE SOUTHERN ZONES. ECMWF FORECASTS AN
ACTIVE SUBTROPICAL BRANCH AND HAS RAIN ON THURSDAY WHILE GFS IS
DRY. WILL SHOW TEMPERATURES NEAR CLIMO AND WAIT UNTIL FRIDAY TO
BRING RAIN CHANCES IN THE FORECAST. ANOTHER MODEL RUN OR TWO
SHOULD CLEAR UP THIS UNCERTAINTY AND WILL LET LATER SHIFTS DECIDE
IF POPS ON THURSDAY NEED TO BE ADDED.
TR.92
&&
.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX 43 37 57 34 64 / 100 30 0 0 0
WACO, TX 45 37 59 35 64 / 100 10 0 0 0
PARIS, TX 44 38 54 33 62 / 100 30 0 0 0
DENTON, TX 42 36 57 31 63 / 100 40 0 0 0
MCKINNEY, TX 43 36 55 30 62 / 100 30 0 0 0
DALLAS, TX 44 39 57 36 64 / 100 30 0 0 0
TERRELL, TX 44 39 56 35 63 / 100 20 0 0 0
CORSICANA, TX 46 38 58 36 64 / 100 10 0 0 0
TEMPLE, TX 45 36 61 36 65 / 90 10 0 0 0
&&
.FWD WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL MIDNIGHT CST TONIGHT FOR THE
FOLLOWING ZONES: TXZ091-100-101-115-116-129.
&&
$$
92/75
AREA FORECAST DISCUSSION...UPDATE
NWS FORT WORTH TX
518 AM CST SUN NOV 25 2007
.AVIATION...
UPPER LEVEL STORM SOUTHWEST OF KMRF AT 11Z WILL MOVE NORTHEAST
TOWARD KADM BY 06Z AND KMKO BY 12Z. WIDESPREAD LIGHT TO MODERATE
RAIN IS EXPECTED TODAY THROUGH 00Z TO THE SOUTHEAST OF THIS PATH
WHILE SNOW...MIXED WITH RAIN AT TIMES...PREVAILS TO THE NORTHWEST OF
THIS PATH THROUGH TONIGHT. THE RAIN SHOULD DIMINISH TO VERY LIGHT
RAIN BY THIS EVENING AND END BEFORE OR AROUND MIDNIGHT. LOCAL TAFS
SITES WILL EXPERIENCE PERIODS OF IFR WITH SOME BRIEF EPISODES OF
MVFR TODAY...THEN TRENDING TO JUST MVFR BY THIS EVENING AND
OVERNIGHT. FORECAST SOUNDINGS INDICATE COOLING TO NEAR OR SLIGHTLY
BELOW FREEZING OF A SATURATED ENVIRONMENT BY 00Z...THUS ICING IS A
CONCERN AOA 1000 FEET AFTER 21Z AND OVERNIGHT. 75
&&
.DISCUSSION...
502 AM CST.
POWERFUL UPPER LEVEL LOW CURRENTLY MOVING TOWARD THE BIG BEND
REGION OF TEXAS AND WILL BEGIN TO PIVOT TOWARD THE NORTHEAST LATER
TODAY. THE MODELS FORECAST THE UPPER LEVEL LOW TO CROSS RIGHT OVER
THE NW CWA...WHICH IS JUST A LITTLE FURTHER SOUTH THAN PREVIOUS
RUNS. CURRENT ACARS SOUNDINGS DO SHOW AN ABOVE FREEZING LAYER
HOLDING STRONG NEAR 800 MB OVER THE CENTRAL CWA. RADAR LOOP OF
THE PAST SEVERAL HOURS CONFIRMS THE PRESENCE OF BRIGHT BANDING
CAUSED BY MELTING SNOW AT 5000 TO 7000 FT. ACROSS THE EASTERN
ZONES...GREATER LOW LEVEL INSTABILITY IS ALLOWING FOR SCATTERED
THUNDERSTORMS. NEEDLESS TO SAY...WILL CONTINUE THE FORECAST OF
CATEGORICAL POPS ACROSS ALL OF NORTH TEXAS FOR THIS MORNING. THE
PRECIPITATION WILL BEGIN TO WANE BY AFTERNOON AS A DRY SLOT WORKS
INTO THE CENTRAL AND EASTERN ZONES.
SNOW HAS YET TO MAKE IT TO THE GROUND IN ANY SIGNIFICANT QUANTITY
ACROSS MUCH OF TEXAS...BUT MODEL FORECASTS CONTINUE TO DEPICT
COOLING OF THE LOW LEVELS WITH THE WARM NOSE ACROSS THE WESTERN
ZONES DROPPING BELOW FREEZING DURING THE DAY WITH THE APPROACH OF
THE UPPER LOW. DYNAMIC FORCING ASSOCIATED WITH THE CORE OF AN
UPPER LOW OFTEN COMPENSATES FOR LACK OF COLD AIR...AS IT LIFTS
AND COOLS THE ENTIRE COLUMN ADIABATICALLY. THE LAST EXAMPLE OF
THIS WAS LATE MARCH OF 2005 WHEN A SURPRISE BAND OF SNOW OCCURRED
FROM WEATHERFORD TO BENBROOK ON EASTER SUNDAY MORNING. WITH THE
UPPER LEVEL LOW TRACKING OVER THE NW CWA AROUND SUNSET TONIGHT...
WE WILL CONTINUE TO MENTION SNOW MIXING WITH RAIN WITH FAIRLY HIGH
CONFIDENCE TO THE NW OF A COMANCHE TO WEATHERFORD TO SHERMAN LINE.
WE WILL MENTION SNOW FLURRIES JUST TO THE EAST OF THIS LINE
WHERE CONFIDENCE IN SNOW FLAKES SURVIVING THE TRIP THROUGH THE
ABOVE FREEZING WARM NOSE IS LOWER. THE WINTER WEATHER ADVISORY HAS
BEEN EXTENDED THROUGH MIDNIGHT FOR 6 OF OUR NW COUNTIES WHERE
BRIEF BURSTS OF HEAVY/WET SNOW ARE POSSIBLE TODAY AND THIS
EVENING. WITHIN HEAVY BANDS OF SNOW ACROSS THE NW A BRIEF
ACCUMULATION OF AN INCH OR SO IS POSSIBLE BEFORE GRADUAL MELTING
OCCURS. OTHERWISE...TEMPS ACROSS THE REMAINDER OF NORTH TEXAS WILL
BE SAFELY ABOVE FREEZING. WRAP AROUND PRECIPITATION WILL QUICKLY
EXIT NORTH TEXAS BY MIDNIGHT WITH SOME CLEARING OCCURRING ACROSS
THE SW COUNTIES WHERE FREEZING TEMPS ARE POSSIBLE.
A WARM-UP WILL OCCUR MONDAY AND TUESDAY AS SW FLOW AND SUBSIDENCE
BEHIND THE STORM SYSTEM RESULTS IN WARMING LOW LEVEL TEMPS. THE
MODELS ARE IN A BIT OF DISAGREEMENT IN THE EXTENDED WITH THE
TIMING OF A FRONT/POPS. WILL CONTINUE TO FOLLOW THE GFS...WITH
RESPECT TO THE ECMWF SOLUTION. WILL BACK OFF ON THE SOUTHWARD PUSH
OF THE FRONT EXPECTED LATE WEDNESDAY AND HANG ON TO WARMER
TEMPS/MOISTURE ACROSS THE SOUTHERN ZONES. ECMWF FORECASTS AN
ACTIVE SUBTROPICAL BRANCH AND HAS RAIN ON THURSDAY WHILE GFS IS
DRY. WILL SHOW TEMPERATURES NEAR CLIMO AND WAIT UNTIL FRIDAY TO
BRING RAIN CHANCES IN THE FORECAST. ANOTHER MODEL RUN OR TWO
SHOULD CLEAR UP THIS UNCERTAINTY AND WILL LET LATER SHIFTS DECIDE
IF POPS ON THURSDAY NEED TO BE ADDED.
TR.92
&&
.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX 43 37 57 34 64 / 100 30 0 0 0
WACO, TX 45 37 59 35 64 / 100 10 0 0 0
PARIS, TX 44 38 54 33 62 / 100 30 0 0 0
DENTON, TX 42 36 57 31 63 / 100 40 0 0 0
MCKINNEY, TX 43 36 55 30 62 / 100 30 0 0 0
DALLAS, TX 44 39 57 36 64 / 100 30 0 0 0
TERRELL, TX 44 39 56 35 63 / 100 20 0 0 0
CORSICANA, TX 46 38 58 36 64 / 100 10 0 0 0
TEMPLE, TX 45 36 61 36 65 / 90 10 0 0 0
&&
.FWD WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL MIDNIGHT CST TONIGHT FOR THE
FOLLOWING ZONES: TXZ091-100-101-115-116-129.
&&
$$
92/75
AREA FORECAST DISCUSSION
NWS FORT WORTH TX
502 AM CST SUN NOV 25 2007
.DISCUSSION...
POWERFUL UPPER LEVEL LOW CURRENTLY MOVING TOWARD THE BIG BEND
REGION OF TEXAS AND WILL BEGIN TO PIVOT TOWARD THE NORTHEAST LATER
TODAY. THE MODELS FORECAST THE UPPER LEVEL LOW TO CROSS RIGHT OVER
THE NW CWA...WHICH IS JUST A LITTLE FURTHER SOUTH THAN PREVIOUS
RUNS. CURRENT ACARS SOUNDINGS DO SHOW AN ABOVE FREEZING LAYER
HOLDING STRONG NEAR 800 MB OVER THE CENTRAL CWA. RADAR LOOP OF
THE PAST SEVERAL HOURS CONFIRMS THE PRESENCE OF BRIGHT BANDING
CAUSED BY MELTING SNOW AT 5000 TO 7000 FT. ACROSS THE EASTERN
ZONES...GREATER LOW LEVEL INSTABILITY IS ALLOWING FOR SCATTERED
THUNDERSTORMS. NEEDLESS TO SAY...WILL CONTINUE THE FORECAST OF
CATEGORICAL POPS ACROSS ALL OF NORTH TEXAS FOR THIS MORNING. THE
PRECIPITATION WILL BEGIN TO WANE BY AFTERNOON AS A DRY SLOT WORKS
INTO THE CENTRAL AND EASTERN ZONES.
SNOW HAS YET TO MAKE IT TO THE GROUND IN ANY SIGNIFICANT QUANTITY
ACROSS MUCH OF TEXAS...BUT MODEL FORECASTS CONTINUE TO DEPICT
COOLING OF THE LOW LEVELS WITH THE WARM NOSE ACROSS THE WESTERN
ZONES DROPPING BELOW FREEZING DURING THE DAY WITH THE APPROACH OF
THE UPPER LOW. DYNAMIC FORCING ASSOCIATED WITH THE CORE OF AN
UPPER LOW OFTEN COMPENSATES FOR LACK OF COLD AIR...AS IT LIFTS
AND COOLS THE ENTIRE COLUMN ADIABATICALLY. THE LAST EXAMPLE OF
THIS WAS LATE MARCH OF 2005 WHEN A SURPRISE BAND OF SNOW OCCURRED
FROM WEATHERFORD TO BENBROOK ON EASTER SUNDAY MORNING. WITH THE
UPPER LEVEL LOW TRACKING OVER THE NW CWA AROUND SUNSET TONIGHT...
WE WILL CONTINUE TO MENTION SNOW MIXING WITH RAIN WITH FAIRLY HIGH
CONFIDENCE TO THE NW OF A COMANCHE TO WEATHERFORD TO SHERMAN LINE.
WE WILL MENTION SNOW FLURRIES JUST TO THE EAST OF THIS LINE
WHERE CONFIDENCE IN SNOW FLAKES SURVIVING THE TRIP THROUGH THE
ABOVE FREEZING WARM NOSE IS LOWER. THE WINTER WEATHER ADVISORY HAS
BEEN EXTENDED THROUGH MIDNIGHT FOR 6 OF OUR NW COUNTIES WHERE
BRIEF BURSTS OF HEAVY/WET SNOW ARE POSSIBLE TODAY AND THIS
EVENING. WITHIN HEAVY BANDS OF SNOW ACROSS THE NW A BRIEF
ACCUMULATION OF AN INCH OR SO IS POSSIBLE BEFORE GRADUAL MELTING
OCCURS. OTHERWISE...TEMPS ACROSS THE REMAINDER OF NORTH TEXAS WILL
BE SAFELY ABOVE FREEZING. WRAP AROUND PRECIPITATION WILL QUICKLY
EXIT NORTH TEXAS BY MIDNIGHT WITH SOME CLEARING OCCURRING ACROSS
THE SW COUNTIES WHERE FREEZING TEMPS ARE POSSIBLE.
A WARM-UP WILL OCCUR MONDAY AND TUESDAY AS SW FLOW AND SUBSIDENCE
BEHIND THE STORM SYSTEM RESULTS IN WARMING LOW LEVEL TEMPS. THE
MODELS ARE IN A BIT OF DISAGREEMENT IN THE EXTENDED WITH THE
TIMING OF A FRONT/POPS. WILL CONTINUE TO FOLLOW THE GFS...WITH
RESPECT TO THE ECMWF SOLUTION. WILL BACK OFF ON THE SOUTHWARD PUSH
OF THE FRONT EXPECTED LATE WEDNESDAY AND HANG ON TO WARMER
TEMPS/MOISTURE ACROSS THE SOUTHERN ZONES. ECMWF FORECASTS AN
ACTIVE SUBTROPICAL BRANCH AND HAS RAIN ON THURSDAY WHILE GFS IS
DRY. WILL SHOW TEMPERATURES NEAR CLIMO AND WAIT UNTIL FRIDAY TO
BRING RAIN CHANCES IN THE FORECAST. ANOTHER MODEL RUN OR TWO
SHOULD CLEAR UP THIS UNCERTAINTY AND WILL LET LATER SHIFTS DECIDE
IF POPS ON THURSDAY NEED TO BE ADDED.
TR.92
&&
.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX 43 37 57 34 64 / 100 30 0 0 0
WACO, TX 45 37 59 35 64 / 100 10 0 0 0
PARIS, TX 44 38 54 33 62 / 100 30 0 0 0
DENTON, TX 42 36 57 31 63 / 100 40 0 0 0
MCKINNEY, TX 43 36 55 30 62 / 100 30 0 0 0
DALLAS, TX 44 39 57 36 64 / 100 30 0 0 0
TERRELL, TX 44 39 56 35 63 / 100 20 0 0 0
CORSICANA, TX 46 38 58 36 64 / 100 10 0 0 0
TEMPLE, TX 45 36 61 36 65 / 90 10 0 0 0
&&
.FWD WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL MIDNIGHT CST TONIGHT FOR THE
FOLLOWING ZONES: TXZ091-100-101-115-116-129.
&&
$$
92/75
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