FXUS63 KAPX 080002
AFDAPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
702 PM EST MON DEC 7 2009
.SYNOPSIS.../ISSUED AT 412 PM/
SOME MAINLY MINOR LAKE EFFECT SNOW SHOWERS WILL AFFECT PORTIONS OF
NORTHWEST LOWER MICHIGAN TONIGHT. A POWERFUL WINTER STORM TRACKS
THROUGH THE GREAT LAKES TUE NIGHT INTO WED BRINGING A PERIOD OF
HEAVY SNOW TO MUCH OF THE AREA. THE COLDEST AIR OF THE SEASON
WILL POUR INTO THE REGION BEHIND THIS STORM AND CONTINUE THROUGH
THE WEEKEND. BLUSTERY CONDITIONS AND LAKE EFFECT SNOW WILL FOLLOW
THIS SYSTEM FOR THU AND FRI.
AJS
&&
.SHORT TERM.../ISSUED AT 702 PM/...TONIGHT
REASONABLY VIGOROUS LAKE EFFECT SNOW BEGAN DEVELOPING LATE THIS
AFTERNOON...AND HAS ALREADY PRODUCED LOCAL INCH/HOUR ACCUMS IN
CENTRAL LEELANAU CO. HAVE ISSUED A QUICK LES ADVISORY FOR THEM.
THAT MIGHT NOT BE THE ONLY COUNTY WORTHY OF AN ADVISORY...BUT
WE/LL WAIT AND SEE WHAT DEVELOPS BEHIND THE WELL-DEFINED SURFACE
TROF NOW DROPPING SOUTH ACROSS LTL TRAVERSE BAY. EXPECT MORE OF A
LIGHT NORTHERLY 1000-850MB FLOW BEHIND THAT...WHICH WOULD STILL BE
REASONABLY FAVORABLE FOR LEELANAU...AS WELL AS PERHAPS BENZIE/WRN
CHARLEVOIX/WRN ANTRIM. GIVEN THAT THERE ARE RETURNS ON THE MQT
RADAR MOVING OFF OF ISQ INTO FAR NORTHERN LOWER LAKE MI...AM
REASONABLY CONFIDENT THAT ADDITIONAL SNOW SHOWERS WILL REDEVELOP
BEHIND THE SURFACE TROF (NW OF THE FOX ISLANDS) IN THE NEXT 1-2
HOURS.
JZ
&&
.LONG TERM.../ISSUED AT 412 PM/...TUESDAY AND BEYOND
TUE THRU THU...LET THE FUN BEGIN! MAIN FOCUS OBVIOUSLY CENTERED ON
IMPENDING WINTER STORM TUE NIGHT THRU THU. IMPRESSIVE SHORTWAVE
TROUGH DROPPING INTO SOUTHERN CALIFORNIA THIS AFTN ALREADY INCITING
SFC CYCLOGENESIS OUT THAT WAY...WITH SAID WAVE EXPECTED TO EJECT
INTO THE SOUTHERN PLAINS...WITH ASSOCIATED SFC CYCLONE TRACKING FROM
CENTRAL OKLAHOMA TUE EVENING TO NORTHERN LAKE HURON BY WEDNESDAY
EVENING. A GFS/ECMWF/GGEM COMBO IS THE PREFERRED MODEL SOLUTION
GIVEN AMAZING CONSISTENCY (ESPECIALLY THE GFS/GGEM)...IN LINE WITH
TIGHT CLUSTERING ONCE AGAIN SEEN AMONG ALL 12Z GFS ENSEMBLE MEMBERS.
THE NAM/SREF ON THE OTHER HAND HAVE LITTLE SUPPORT AMONG OTHER
OPERATIONAL GUIDANCE BUT CANNOT COMPLETELY BE DISCOUNTED GIVEN
POTENTIAL FOR UPR WAVE TO KICK NEGATIVE TILT FASTER BENEATH CORE OF
IMPRESSIVE 160 KT JET CUTTING THRU THE MID MISS VALLEY. APPEARS
EVENT WILL COME INTO THREE PARTS...AS SPELLED OUT BELOW.
PART 1: TREMENDOUS WING OF WARM ADVECTION...AS EVIDENCED BY 50+
KNOTS OF DEEP LAYER (280-300K) ISENTROPIC UPGLIDE PERPENDICULAR TO
THE PRESSURE SURFACES...SET TO ROLL INTO NORTHERN MICHIGAN ROUGHLY
06Z-15Z WEDNESDAY. COINCIDENT WITH STRONG 700-300 QG UPWARD FORCING
AND BEST MOISTURE ADVECTION EMANATING FROM PLUME OF HEALTHY 1.75 IN
PWATS OVR THE SOUTHEAST COAST...THIS SHOULD EASILY SUPPORT SOME
DOWNRIGHT INTENSE PRECIP RATES...AUGMENTED BY POTENTIAL FOR
CONVECTIVELY BANDED ELEMENTS WITHIN TRANSIENT BUT BRIEFLY INTENSE
800-600MB FGEN AXIS PUSHING NORTH THRU THE CWA. IN FACT...
INTERESTING TO NOTE GFS/GGEM FCST RAOBS EVEN INDICATING POTENTIAL
FOR A BIT OF NEAR UPRIGHT CONVECTION WITHIN STEEP 600-350MB LAPSE
RATE PLUME (7C/KM OR BETTER) ACRS PORTIONS OF NORTHEAST LOWER...
THOUGH ARGUABLY SUCH AN OCCURRENCE WILL SERVE TO CUT DOWN SNOW
RATIOS. SPEAKING OF WHICH...APPEARS INITIAL ONSET OF SNOW WILL BE
CHARACTERIZED BY SOME FLUFFINESS WITH BEST OMEGA THRU THE
DGZ...HOWEVER CONTINUED LOW/MID LEVEL WARMING WILL EAT AWAY AT
SNOW-WATER RATIOS AS BY 09-12Z...MAJORITY OF LIFT WELL ABOVE THE
-20C LEVEL. THAT SAID...DIFFICULT TO IGNORE MODEL SIGNALS OF 0.4 TO
0.6 INCHES OF LIQUID FALLING IN JUST A 6 HOUR PERIOD CENTERED ON
12Z...WITH A GENERAL 4 TO PERHAPS 8 INCHES OF SNOW (LOCALLY
HIGHER?) LIKELY TO FALL BY MID MORNING WEDNESDAY. WINDS AT THIS
POINT INITIALLY QUITE GUSTY OUT OF THE EAST BUT SLACKENING QUICKLY
AS SFC CYCLONE APPROACHES WITH WEAKENING GRADIENT.
PART 2: PRECIP RATES WILL BE ON THE DECREASE LATER WED MORNING WITH
LOSS OF STRONGEST WARM ADVECTION...HOWEVER PRONOUNCED TROWAL FEATURE
HANGING BACK ACRS THE REGION COUPLED WITH APPROACH OF ELONGATED
850-700MB DEFORMATION AXIS WITHIN RAPIDLY CLOSING 850-500MB CENTERS
SHOULD SUPPORT ADDITIONAL PRECIP ADVANCING THRU THE REGION INTO
EARLY WED EVENING. PER FCST SOUNDINGS...APPEARS THIS PERIOD MAY BE
DOMINATED BY BETTER SNOW-WATER RATIOS GIVEN COOLING THRU THE COLUMN
AND DEEP LAYER OMEGA BULLSEYED THRU THE -13C TO -18C LAYER (BEST
DENDRITIC GROWTH REGION). IN ADDITION...INCREASING LAKE INFLUENCE
SET TO COME INTO PLAY AS FLOW VEERS FROM NORTHEAST TOWARD NORTHWEST
LATE IN THE EVENING. LOOKS LIKE ANOTHER 2 TO 5 INCHES OF SNOW DURING
THRU WED EVENING. WITH INCREASINGLY GUSTY WINDS AS WELL GIVEN
TIGHTENING GRADIENT. BUFKIT DIAGNOSTICS SUGGEST GUSTS MAY WELL
APPROACH 35-40MPH AT TIMES LATE...PARTICULARLY NEAR THE LAKE
MICHIGAN COAST WITH IMPRESSIVE DEVELOPING OVERLAKE INSTABILITY.
PART 3: LAKE EFFECT/ENHANCEMENT LOOKS LIKE A BIG PART OF THIS SYSTEM
AS WELL...AND MAY WELL BE THE BIGGEST IMPACT GIVEN INCREASING WIND
ENTERING THE PICTURE. PHENOMENAL OVERLAKE INSTABILITY EXPECTED AS
H85 TEMPS CRASH FROM -12C AT 00Z THU TOWARD -20C AT 00Z FRI...WITH
DEEP LAYER RH PLUME ONLY SLOWLY PULLING EAST THRU THE DAY ON
THURSDAY. STRONG WIND FIELDS LIKELY TO DISRUPT ANY DISCRETE BANDING
BUT ALSO ACT TO SPREAD LAKE INDUCED SNOW SHOWERS ALL THE WAY THRU
THE CWA. APPEARS GREAT SNOW-WATER RATIOS ON TAP WITH VALUES
APPROACHING 25 TO 1 OR SO FOR A TIME...BEFORE INCREASING ARCTIC
CHILL ACTS TO DRAMATICALLY LOWER RATIOS (THE FAMOUS "TALCUM POWDER"
SNOW). MEAN WEST/NORTHWEST TO WESTERLY FLOW REGIME AREAS LOOK TO
CASH IN ON THIS ONE...WITH ADDITIONAL ACCUMULATIONS PUSHING 8 INCHES
OR BETTER IN SPOTS.
SO WHERE CAN THINGS GO WRONG? PLACEMENT OF SFC CYCLONE IN THIS
SITUATION DOES NOT APPEAR TO HAVE AS BIG OF AN INFLUENCE AS IN A
MORE "TYPICAL" WINTER STORM. GIVEN TIGHT LOW LEVEL THERMAL GRADIENT
IN PLACE...AND UPR FEATURES CLOSING OFF ABOUT OVERHEAD...WARM AIR
DOESN'T LOOK LIKE IT HAS MUCH TIME TO GET TOO FAR NORTH. THUS...MAY
WELL SEE SNOW FALL CLOSER TO THE SFC LOW TRACK THAN USUALLY SEEN.
THAT SAID...WILL HAVE TO WATCH THE SOUTHEAST COUNTIES FOR A TIME
AROUND SUNRISE WED GIVEN SUCH IMPRESSIVE WARM ADVECTION. WITH SOME
INDICATION OF CONVECTIVE PRECIP AS WELL AS TYPICAL MODEL BIAS OF
UNDERDOING WARM ADVECTION EFFECTS...WILL CARRY A BRIEF PERIOD OF
RAIN AND SNOW DOWN THAT WAY. OTHERWISE...DIFFICULT TO SEE THIS EVENT
NOT REACHING WARNING CRITERIA IN MOST SPOTS...AND WITH VERY HIGH
CONFIDENCE WILL HOIST A WINTER STORM WARNING CWA-WIDE AT THIS TIME
TO COVER THE SYNOPTIC COMPONENT OF THE STORM (ADDITIONAL HEADLINES
LIKELY TO BE NEEDED LATER INTO THURSDAY/THURSDAY NIGHT).
LATER PERIODS (THU NIGHT THRU MON)...WX REGIME TO QUIET DOWN A GOOD
BIT HEADING THRU THE WEEKEND/EARLY NEXT WEEK AS UPR TROUGHING EASES
A BIT ACRS THE GREAT LAKES IN RESPONSE TO RETROGRESSION OF DEEP
MERIDIONAL RIDGING ACRS INTERIOR ALASKA. APPEARS A PERIOD OF MORE
TYPICAL LAKE EFFECT SNOW SHOWERS IN THE WORKS HEADING THRU THE
PERIOD...INITIALLY ON NORTHWEST FLOW REGIME BUT TRANSITIONING TOWARD
SOUTHWEST REGIME INTO SAT AS LOW LEVEL RIDGING SLIPS INTO THE OHIO
VALLEY. 00Z GUIDANCE AGREES ON NEXT FRONTAL PASSAGE SOMETIME ON
SAT/SAT NIGHT...SHIFTING WINDS BACK NORTHWEST AS NEXT DUMP OF ARCTIC
AIR ATTEMPTS TO APPROACH THE GREAT LAKES. ALL OF THIS RATHER
NEBULOUS IN TERMS OF PRECIP POSITIONING/AMOUNTS...BUT WHAT IS MUCH
MORE CLEAR IS THAT TEMPS WILL REMAIN QUITE COLD FOR MID DECEMBER...
WITH READINGS STRUGGLING THRU THE TEENS AND 20S FOR HIGHS...BRRRRR!
LAWRENCE
&&
.MARINE.../ISSUED AT 412 PM/
THE CALM BEFORE THE STORM ON AREA NEARSHORE WATERS TONIGHT INTO THE
DAY ON TUESDAY AS WEAK HIGH PRESSURE NOSES INTO NORTHERN MICHIGAN.
THEREAFTER...EASTERLY GALES WILL RAPIDLY DEVELOP LATER TUESDAY NIGHT
INTO WEDNESDAY...GRADUALLY SHIFTING NORTH THEN NORTHWEST BY
WEDNESDAY NIGHT AS DEEP LOW PRESSURE PUSHES THROUGH THE REGION. ALL
OF THIS WILL BE ACCOMPANIED BY A PERIOD OF HEAVY SNOW LATE TUESDAY
NIGHT INTO WEDNESDAY...WITH SNOW SQUALLS MAKING AN APPEARANCE
WEDNESDAY NIGHT INTO THURSDAY AS MUCH COLDER AIR PUSHES INTO THE
AREA. GIVEN HIGH CONFIDENCE IN THIS EVENT...WILL GO AHEAD AND HOIST
A GALE WARNING FOR ALL NEARSHORE WATERS THROUGH THE DAY ON THURSDAY.
LAWRENCE
&&
.AVIATION.../ISSUED AT 628 PM/...VALID FOR 00Z TAFS
LAKE EFFECT SNOW SHOWERS WILL BRING OCCASIONAL MVFR TO PERHAPS IFR
VSBYS TO PLN/TVC THIS EVENING INTO EARLY OVERNIGHT. OTHERWISE...A
RELATIVELY QUIET PERIOD IS IN STORE FOR THE DAY ON TUESDAY. EAST
WINDS WILL DEVELOP AND HIGH CLOUDS WILL THICKEN IN THE
AFTERNOON...WELL IN ADVANCE OF A MAJOR WINTER STORM THAT WILL GET
UNDERWAY TUESDAY NIGHT.
JZ
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...WINTER STORM WARNING FROM 10 PM TUESDAY TO 7 AM EST THURSDAY FOR
MIZ008-015>036-041-042.
LAKE EFFECT SNOW ADVISORY UNTIL 8 AM EST TUESDAY FOR MIZ020.
LM...GALE WARNING FROM 11 PM TUESDAY TO 11 PM EST THURSDAY FOR LMZ323-
341-342-344>346.
LH...GALE WARNING FROM 11 PM TUESDAY TO 11 PM EST THURSDAY FOR
LHZ345>349.
LS...GALE WARNING FROM 11 PM TUESDAY TO 11 PM EST THURSDAY FOR LSZ321-
322.
&&
$$
