FXUS63 KIWX 060902
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
402 AM EST SUN DEC 6 2009

.SHORT TERM...

TODAY THROUGH MONDAY NIGHT

SFC HIGH PRESSURE CONTINUES TO DOMINATE THE WEATHER...WITH MOSTLY 
CLEAR SKIES/LIGHT WINDS/AND COLD TEMPS ACROSS THE FA. ALTHOUGH 
WINDS HAVE RESPONDED SOME TO INCREASING MOMENTUM JUST OFF THE SFC. 
THIS HAS ALSO ALLOWED TEMP FALLS TO ABATE SOME IN THE WEST WITH MANY 
PLACES HOLDING STRONG IN THE 20S. EASTERN PORTIONS OF THE FA HAVE 
DECOUPLED WELL WITH WIDESPREAD UPPER TEENS BEING REPORTED. SFC HIGH 
WAS CENTERED OVER THE EASTERN OH VALLEY...WITH RETURN SOUTHWEST FLOW 
BEGINNING TO OVERSPREAD THE REGION. DIGGING WESTERN CONUS UPPER 
TROUGH WILL OFFER A LEAD IMPULSE INTO THE FA BY LATE 
TONIGHT...SUPPORTING INCREASING CHANCES FOR LIGHT SNOW ON MONDAY. 
HOWEVER...THIS SYSTEM WILL BE ENTERING A MOISTURE STARVED 
ENVIRONMENT PER THE SCOURED ENVIRONMENT IN PLACE PER THE RECENT 
CP SURGE TO THE GULF. IN ADDITION...FAST PROGRESSIVE NATURE OF THE 
UPPER TROUGH WITH A RELATIVELY WEAK RESPONSE TO LL ADVECTION FIELDS 
WILL NOT OFFER MUCH IN THE WAY OF WAVE DEEPENING. MODEL PROGS 
CONTINUE TO OFFER RELATIVELY DRY QPF PROGS...WITH THE 00Z NAM BEING 
THE DRIEST...KEEPING THE MAJORITY OF THE FA DRY THROUGH THE PERIOD. 
HAVE MAINLY USED A BLEND OF GUIDANCE FOR THE FORECAST WITH A HEAVY 
WEIGHT TOWARD THE NAM/GFS/ECMWF/SREF MEAN.

WEAK HEIGHT RISES AND WAA AHEAD OF THE FAST MOVING ROCKIES 
IMPULSE WILL SUPPORT AN INCREASE IN MID AND CLOUDS WITH INCREASING 
SOUTHERLY FLOW. EXPECT HIGHS TO FINALLY GET ABOVE FREEZING TODAY NOW 
THAT THE PERSISTENT LL CLOUD DECK HAS FINALLY ERODED OUT. RELATIVELY 
GOOD MIXING WITH INSOLATION SHOULD ALLOW TEMPS INTO THE MID 30S MOST 
PLACES. LARGE SCALE ASCENT WILL INCREASE DRAMATICALLY ACROSS THE FA 
TONIGHT AS THE AFOREMENTIONED UPPER IMPULSE NEARS THE REGION. 285K 
ISENTROPIC CHARTS FROM THE GFS AND NAM SOLUTIONS INDICATE MIXING 
RATIO RIDGING AHEAD OF THE IMPULSE...WITH AN EXPECTED WAA WING. 
HOWEVER...GIVEN VERY DRY PROFILES CURRENTLY IN PLACE TO THE 
GOMEX...DECENT MOISTURE RETURN INTO THE FA LOOKS HARD PRESSED AND 
THIS IS CERTAINLY EVIDENT IN MODEL QPF NUMBERS. BEST OVERLAP OF 
THETA-E RIDGING AND LARGE SCALE UVM WILL RESIDE OVER SOUTHERN 
PORTIONS OF THE FA WITH A STRONGER SYSTEM DEFORMATION ZONE WELL NORTH 
OF THE FA. HENCE HAVE LIMITED HIGHER POP MENTION TO THE SOUTHERN 
FA...WITH A DOWNWARD TREND IN CWA AVERAGE VALUES GIVEN ABOVE 
CONCERNS. GIVEN EXPECTED FAST SPEED...HAVE INTRODUCED ENDING POPS IN 
THE WEST BY MONDAY AFTERNOON. DID ADD A RAIN MENTION IN THE SE GIVEN 
WARMING PROFILES...BUT KEPT SNOW MENTION DUE TO EXCESSIVE DRY AIR 
BEING IN PLACE IN THE LOWER COLUMNS...WHICH WOULD TEND TO SUPPORT A 
WETBULB EFFECT. CLOUDS ARE EXPECTED TO HANG THROUGH THE REMAINDER 
OF THE MONDAY AND MONDAY NIGHT...GIVEN LINGER LL MOISTURE PLUME FROM 
THE DEPARTING SYSTEM UNDER A WEAK WIND FIELD. THIS WILL BE 
ESPECIALLY TRUE IN THE NW WHERE WEAK CAA WILL SUPPORT ANOTHER ROUND 
OF INCREASED LAKE CLOUDS AND POSSIBLE FLURRIES.

&&

.LONG TERM...
MID WEEK WINTER STORM REMAINS THE FOCUS OF THIS PD. 

12/00Z GUIDANCE CONTS TO OSCILLATE W/VIGOROUS SW TROUGH OVR 
VANCOUVER DIGGING SWD INTO THE SRN ROCKIES AND THEN EJECTING OUT 
THROUGH THE SRN PLAINS LT TUE W/SUFFICIENT MODEL SPREAD TO INDICATE 
THINGS WILL BE TIGHT HERE W/POSITION OF RAIN/SNOW LINE. AS 
SUCH...GIVEN DECENT GROSS RUN CONTINUITY...WILL MANIPULATE WX/POPS 
GRIDS SLIGHTLY TUE NIGHT/WED AM TO COLLABORATE CLOSER TO SURROUNDING 
OFFICES AND PLAY A WAIT AND SEE APCH IN SUCCESSIVE CYCLES AS GRIDDED 
ALIGNMENT CLOSE ENOUGH ANYWAY AT THIS TIME RANGE. HWVR MORE CONSISTENTLY 
PLACED MID LVL LOW TRACK WOULD POINT TO CRIPPLING SNOW STORM FM SE 
NE E/NE INTO NRN LWR MI...WELL N AND W OF HERE. CAVEAT LIES WITH 
STGR/SHARPER MID LVL REFLECTION EJECTING OUT THE ROCKIES TAKING A 
SLIGHTLY RIGHT OF CONSENSUS SFC LOW TRACK AND REFLECTED IN MAJORITY 
OF 00Z GFS ENSEMBLES. MORE IMPORTANT CONSIDERATION WILL BE HOW SFC 
TEMPS RESPOND SHRT TERM W/EJECTING WK LEAD SW AND BNDRY LYR DIABATIC 
RESPONSE TO SATURATION TUE NIGHT GIVEN DEGREE OF WAA PROGGED. 

OTHERWISE RAPIDLY DEEPENING SFC CYCLONE WILL YIELD UNUSUALLY LARGE 
GRADIENT WIND POTENTIAL WED AFTN-THU IF DEEPEST EC/GEM SOLUTIONS PAN 
OUT TIMED W/INTENSE CAA SURGE AND HIGHEST LL MOMENTUM ALG THE S SIDE 
OF THIS XPCD INTENSE SYS. THIS WILL AGAIN FOSTER TEMPS WELL BLO 
NORMAL THROUGH THE PD AND QUITE WINDY.

&&

.AVIATION.../06Z TAFS/
VFR CONDITIONS THROUGH THE PERIOD. WAA COUPLED WITH AN APPROACHING
WEAK MID LEVEL DISTURBANCE WILL SUPPORT AN INCREASE IN MID AND
HIGH CLOUDINESS THROUGH THE PERIOD WITH INCREASING SSW WINDS. NO
SIG WX EXPECTED.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&

$$

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