FXUS63 KIWX 070837
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
337 AM EST MON DEC 7 2009

.SHORT TERM...

TODAY THROUGH TONIGHT

COMPACT WEAKENING UPPER LEVEL DISTURBANCE CONTINUES TO SUPPORT LIGHT 
SNOW OVER PORTION OF IL/WI/AND NOW WEST CENTRAL IN. THIS SYSTEM HAS 
NOW PUSH WELL NE OF A STRONGER LL BAROCLINIC ZONE AND IS BEGINNING 
TO OUTRUN THE ASSOCIATED THETA-E RIDGE INDICATED IN RUC 13 ANALYSIS 
H85 PROFILES. RELATIVELY STRONG MOMENTUM PROFILES ASSOCIATED WITH 
THIS SYSTEM STILL OFFERING SUPPORT FOR DECENT LIFT AS INDICATED BY 
RADAR RETURNS AND PROFILES DATA. HOWEVER...AS THIS SYSTEM PROGRESS 
EAST...A DEFINITE WEAKENING TREND IN ACTIVITY IS EXPECTED. IN 
ADDITION...VERY DRY PROFILES INDICATED IN SURROUNDING RAOBS WILL 
CONTINUE TO OFFER STRONG SUBLIMATION WITH VIRGA BEING THE END 
PRODUCT. SFC OBS OVER NE IL CONTINUE TO OFFER DRY UNOBSTRUCTED OBS 
EVEN WITH RETURNS INDICATED ALOFT ON THE SCOPE. IWX RADAR ANALYSIS 
CONFIRMS /AT THE PRESENT TIME/ SNOWFALL IS CONTAINED TO ABOVE 8KFT. 
HENCE HAVE OPTED TO STAY BELOW LIKELY POPS GIVEN EXPECTED SCT MIX 
DOWN OF SNOWFALL OFFERING VERY LITTLE IN THE WAY OF QPF /AS 
SUPPORTED IN MODEL PROGS/. HAVE ENDED SNOWFALL CHANCES BY AFTERNOON 
OVER THE ENTIRE CWA GIVEN FAST NATURE OF THE SYSTEM AND EXAMINED 
GUIDANCE IN MODEL ISENTROPIC PROGS. CLOUD COVER IS EXPECTED TO HANG 
ON THROUGH MOST OTHER PERIOD WITH SOME BREAKS POSSIBLE ON THE 
BACKSIDE OF THE WAVE LATER THIS AFTERNOON AND INTO TONIGHT. LACK OF 
APPRECIABLE CAA WILL SUPPORT THE STATUS QUO PER THERMAL FIELDS WITH 
LOWS IN THE 20S ONCE AGAIN. WEAK LAKE MI RESPONSE GIVEN 12-14C DELTA 
T/S WILL SUPPORT LAKE EFFECT CLOUD PRODUCTION WITH POSSIBLE FLURRIES 
OVER BERRIEN AND CASS COUNTIES GIVEN RAISED INVERSION HEIGHTS ON THE 
BACKSIDE OF THE DEPARTING SW TROUGH. BUFR PROGGED LAKE INDUCED CAPE 
FIELDS INDICATE UP TO 300 J/KG...BUT ONLY FOR A SHORT WINDOW. NO 
OTHER CONCERNS ATTM. 

&&

.LONG TERM...

DVLPG WINTER STORM REMAINS THE FOCUS FOR THIS PD. 

POTENT SW TROUGH LURKING JUST OFF THE NRN CA COAST THIS MORNING AND 
ABT READY TO TURN INLAND THROUGH THE FOUR CORNERS TUE MORNING. AS 
THIS SYS EJECTS OUT ACRS THE PLAINS...SFC CYCLONE WILL INTENSIFY 
RAPIDLY AND MAKE A BEE LINE FOR THE S END OF LK MI. OVERALL TRACK 
GUIDANCE HAS BEEN VRY CONSISTENT LAST 36HRS AND GIVEN WELL AGREED 
UPON SFC CYCLONE STRENGTH...XPC MORE OF A RAIN EVENT HERE THEN 
ANYTHING ACRS THE IWX CWA AS MONUMENTAL NWD WARM SURGE TAKES PLACE 
TUE NIGHT ON NOSE OF 80KT LLJ. BIGGEST WX IMPACT LOOKS TO BE 
GRADIENT WINDS WED AS TREMENDOUS ISOLLABARIC COUPLET WHICH FOSTERS 
EXTREME GEOSTROPHIC WIND RESPONSE...NR 80 KTS CNTRD NR KBEH AT 12Z 
WED. DEGREE OF LL CAA WOULD SUGGEST FAIRLY DEEP MIXING POTENTIAL MID 
MORNING WED THROUGH MID AFTN ALTHOUGH TEMPERED SOME BY DIRECTIONALLY 
SHEARED WIND FIELD THROUGH THAT TIME FRAME. OTHERWISE CRASHING TEMPS 
W/FROPA BY LT MORNING AND WRAP AROUND SNOW PUSHING IN W/GOOD LK 
ENHANCEMENT XPC BY AFTN ACRS SW MI DOWN TO THE TOLL ROAD AND WHICH 
WILL LIKELY CAUSE CONSIDERABLE TRAFFIC PROBS. ADDNL ROAD RELATED 
PROBS A CONCERN TOO W/FLASH FREEZE XPCD AND MAINLY A QN OF HOW MUCH 
PCPN FALLS WED AM VS DEGREE OF SFC DRYING WHICH TAKES PLACE. 
CERTAINLY COULD SEE SOME POTENTIAL FOR WATCH HEADLINES ACRS SW MI 
FOR WED AFTN/WED NIGHT GIVEN STG WINDS COMBINED W/POTENTIAL 
APPRECIABLE SNOWFALL BUT ON THE OTHER HAND SPEED OF SYS LIFTING OUT 
AND LOSS OF SYNOPTIC ENHANCEMENT TEMPERS THAT CONCERN AND WILL DEFER 
TO DAY SHIFT.

OTHERWISE ARCTIC RIDGING FOLLOWS IN WAKE OF DEPARTING STORM SYS AND 
WILL YIELD VRY COLD TEMPS THROUGH SAT.

&&

.AVIATION...
UPPER LEVEL DISTURBANCE AND ASSOCIATED SFC LOW WILL BRING LOWER
CIGS AND THE CHANCE FOR LIGHT SNOW TO THE FA IN THE PERIOD. LOOK
FOR LIGHT SNOW TO ENTER THE FAR SW FA EARLY THIS MORNING AND
SPREAD EAST QUICKLY. SYSTEM IS EXPECTED TO WEAKEN AS IT PUSHES
INTO THE FA WITH SNOW COVERAGE DIMINISHING. SOUTHERN AREAS CLOSEST
TO LL MOISTURE FLUX WILL SEE THE BEST CHANCE FOR PRECIP AND
POSSIBLE VIS RESTRICTIONS IN SNOW. HAVE INCLUDED A TEMPO MVFR VIS
AT FWA FOR THIS...AROUND DAYBREAK. OTHERWISE...LINGERING MVFR CIGS
ARE EXPECTED THROUGH MUCH OF THE DAY WITH SOME SCATTERING AS
SLIGHTLY DRIER AIR WRAPS IN BEHIND THE DEPARTING WAVE.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...GALE WATCH FROM WEDNESDAY AFTERNOON THROUGH THURSDAY EVENING FOR 
     LMZ043-046.

&&

$$

SHORT TERM...JC
LONG TERM...HOLSTEN
AVIATION...JC