FXUS63 KIWX 242359
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
659 PM EST THU DEC 24 2009

.UPDATE/AVIATION...
CONDS IMPROVING EARLY THIS EVENING AS NR SFC COLD LYR ERODES
FURTHER W/CONTD VEERING SFC FLW AND LOSS OF HYDROMETEORS W/LLJ
REFOCUSING BACK WEST IN RESPONSE TO NEGATIVELY TILTING UPPER
TROUGH LIFTING OUT OF NE TX. WILL LEAVE NE CORNER OF PREV FZRA
ADVISORY INTACT BUT DROP ELSEWHERE AS SFC TEMPS AOA 32 IN MOST PLACES.

VFR CONDS EARLY WILL DETERIORATE RAPIDLY TWD DAYBREAK AS DEEPENING
SFC CYCLONE OVR WRN AK LIFTS NWD INTO NE MO AND MID LVL TROUGH
AXIS PASSES. SHLD BE QUITE A FNTL RAIN BAND LATE TONIGHT/XMAS
MORNING W/WIDESPREAD IFR CONDS THEREAFTER.

&&

.PREV DISCUSSION... /ISSUED 330 PM EST THU DEC 24 2009/ 

SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/... 

LOW PRESSURE CENTERED OVER SWRN ARK THIS AFTN WITH A WARM FRONT
EXTENDING NE TO THE UPR OH VALLEY. E-W ORIENTED BANDS OF BANDS OF
ZR CONTG TO DVLP THIS AFTN IN THE STRONG WAA REGIME NORTH OF THE
WARM FRONT AND LIFT NORTH INTO THE DRIER AIR OVER OUR AREA. MODELS
HAVE BEEN UNDER-DOING THIS WAA PRECIP DURING THE PAST 24HRS, THUS
FCST POPS HIGHER AND DUE TO EVAPORATIONAL COOLING... TEMPS A
LITTLE LOWER THAN SUGGESTED BY GUIDANCE THIS EVE. LOW EXPECTED TO
LIFT NORTH INTO EASTERN IA BY 12Z FRI WITH CDFNT ASSOCIATED WITH
THIS SYSTEM PUSHING AHEAD OF IT INTO SWRN INDIANA. WARM SECTOR OF
THE STORM SHOULD REMAIN WELL SOUTH OF OUR CWA, HWVR SFC WINDS
EXPECTED TO VEER TO SE AHEAD OF THE CDFNT ALLOWING FOR SLIGHTLY
WARMER TEMPERATURES TO MOVE INTO THE AREA BEFORE FROPA. BAND OF
STRONG FORCING/DEEP MOISTURE AND LIKELY MOD-HVY RAIN SHOULD SWEEP
NE ACROSS THE CWA AHEAD OF THE CDFNT LATE TONIGHT AND EARLY
FRIDAY. BULK OF MAIN BAND OF HEAVIER PRECIP SHOULD FALL INTO SFC
TEMPS SLIGHTLY ABOVE FREEZING. BUT IT WILL PRBLY BE A CLOSE
CALL...ESPECIALLY ACROSS THE NE WHERE NAM 2M AND BOUNDARY LAYER
TEMPS FCST BLO FREEZING THROUGH THE NIGHT. WILL CONT
WARNINGS/ADVISORIES AS EARLIER ISSUED...ENDING EARLY THIS EVENING
SOUTH AND WEST... MIDDLE OF THE NIGHT CENTRAL...AND 12Z FRI IN THE
NE.

MODELS IN GOOD AGREEMENT ON FRIDAY BRINGING COLDER AIR INTO THE
CWA FROM THE SW ALONG WITH A FAIRLY STRONG UPR LEVEL TROF ROTATING
AROUND LOW TO THE WEST. THIS SHOULD RESULT IN RAIN SHOWERS
CHANGING TO SNOW SHOWERS FROM SW-NE DURING THE AFTN/EVE. DRY SLOT
WILL MOVE ACROSS THE AREA FRIDAY NIGHT BUT WRAP AROUND MOISTURE
MOVES BACK IN BEFORE DAWN SO CHC POPS SOUTH AND LIKELY NORTH
CARRIED THROUGH THE NIGHT.

TEMPS WILL SLOWLY RISE TONIGHT TO THE M-U30S BY FRIDAY MORNING. 
BASED ON UPSTREAM OBS BUMPED HIGHS UP A BIT FOR FRIDAY INTO THE 
U30-L40S. NO CHANGE TO EARLIER FCST MINS FRI NGT...EXPECTED IN THE
L-M20S.

925MB WINDS FCST AROUND 50KT LATE TONIGHT AND EARLY FRIDAY...HOWEVER 
SFC BASED INVERSION SHOULD LIMIT MIXING SO WHILE EXPECTING WINDY 
CONDITIONS, WINDS SHOULD STAY BLO ADVISORY CRITERIA.

LONG TERM...

SOME MINOR CHANGES MADE IN THE LONG TERM PERIOD TO REFLECT OVERALL 
SYNOPTIC PATTERN CONCERNS GIVEN A BLOCKED PATTERN INTERACTING WITH A 
POTENT MID/UPPER LEVEL JET. POWERFUL 190 KNOT PLUS UPPER LEVEL JET 
WILL CONTINUE TO SUPPORT STAUNCH HEIGHT RISES INTO WESTERN 
NOAM...SUPPORTING A VERY STALE FLOW REGIME OVER THE CONUS INTO EARLY 
NEXT WEEK AS LONG MERIDONAL NORTHERLY FLOW IS SUPPORTED ON THE 
BACKSIDE OF THE 2 STD H5 NEGATIVE HEIGHT ANOMALY..WITH MASSIVE 
ATLANTIC BLOCKING. MEANWHILE HEIGHT ADJUSTMENT OVER THE EASTERN PAC 
WILL FAVOR A SOUTHWARD BIAS TO MID/UPPER FLOW IN THAT REGION WITH A 
DIGGING SW CONUS TROUGH DEVELOPING BY EARLY NEXT WEEK...SUPPORTING 
SPLIT FLOW AND THE EVENTUAL BREAKDOWN OF THE WESTERN NOAM RIDGE. 
LOCAL SYNOPTIC INFLUENCE WILL BE A LONG PERIOD /2-3 DAYS/ OF DEEP 
CYCLONIC FLOW WITH SEVERAL CHANCES FOR SNOW SHOWERS AT THE BEGINNING 
OF THE PERIOD PER SEVERAL FUJIWARA TYPE ROTATING DISTURBANCES IN THE 
GREAT LAKES/MIDWEST. OCCLUDING SFC CYCLONE...WITH SUFFICIENT 
MOISTURE...WILL SUPPORT A TOTAL OF 1-2 INCHES OF SNOWFALL FROM 
SEVERAL ROUNDS OF SNOW SAT-SUN...WITH A TRANSITION TO NW FLOW SUNDAY 
NIGHT...SETTING THE STAGE FOR LAKE EFFECT SNOW IN THE NW ZONES. 
TEMPS ARE EXPECTED TO REMAIN BELOW SEASONAL NORMS...BUT THERE IS AN 
EXPECTED DELAY IN CAA GIVEN THE OCCLUDED NATURE OF THE SYSTEM 
SUPPORTING WEAK AIRMASS MODERATION AND AN END TO NORTHERLY FLOW 
INFLUENCE ACROSS THE UPPER MIDWEST.

SAT-SUN...HAVE RAISED POPS SOME GIVEN AFOREMENTIONED PATTERN 
SUPPORTING 1-3 ROUNDS OF SNOW SHOWER ACTIVITY WITH PASSING MID LEVEL 
IMPULSES IN CYCLONIC FLOW. ACCUMULATION FROM EACH DISTURBANCE IS 
EXPECTED TO BE LIGHT WITH AN INCH AT MOST...TOTAL ACCUMULATION 
LIKELY 1 TO POSSIBLY 2 INCHES. A FEW PLACES MAY SEE UP TO 3 IF 
DURATION AND INTENSITY IS MAXIMIZED...BUT HAVE OPTED FOR LIGHTER 
AMOUNTS IN THE GRIDS ATTM. EXPECT CLOUDY CONDITIONS WITH SMALL 
DIURNAL TEMP RANGES GIVEN A WELL MIXED BL WITH AMPLE CLOUD COVER. 
FLOW WILL TURN NW LATE SUNDAY AND SUPPORT THE ORGANIZATION OF LAKE 
EFFECT SNOW SHOWERS. PROGGED BUFR INVERSION HEIGHTS AROUND 10 KFT 
FOR AN 8 HOUR WINDOW WOULD LIKELY SUPPORT SOME HEAVIER ACTIVITY IF 
THE PROGGED THERMAL AND MOMENTUM FIELDS COME TO FRUITION. HAVE OPTED 
TO RAISE POPS TO 50 IN THE NW ZONES...AND WILL AWAIT FURTHER 
OBS/GUIDANCE FOR FURTHER ADJUSTMENT. CYCLONIC FLOW COMBINED WITH THE 
ADDITION OF A MID LEVEL VORT LOBE COULD VERY WELL SUPPORT SOME 
DECENT ACCUMS SUNDAY NIGHT AND WILL NEED TO BE WATCHED. INVERSION 
HEIGHTS DO FALL QUICKLY MONDAY MORNING AND THIS MAY BE A LARGE 
LIMITING FACTOR.

MON-WED...DEEP LAYER FLOW STARTS TO BECOME MORE PROGRESSIVE AS THE 
EASTERN CONUS TROUGH PHASES AND LIFTS NE. SFC HIGH PRESSURE WILL 
SUPPORT CLEARING ACROSS THE SOUTH WITH NORTHERN AREAS LIKELY 
REATTAINING A LK MI INFLUENCE. HAVE ADJUSTED LOWS SLIGHTLY BELOW 
NORMAL GIVEN RADIATIONAL COOLING CONCERNS AND COOL DAYTIME HIGHS. 

WED-THU...FORECAST MODELS AND ENSEMBLES CONTINUE TO HIGHLIGHT THE 
EJECTION OF A SW CONUS TROUGH TOWARD THE REGION COINCIDENT WITH 
ANOTHER NORTHERN STREAM SYSTEM. WAS RELUCTANT TO ADD POPS GIVEN THE 
PERIOD AND LARGE UNCERTAINTY STILL PRESENT...BUT WAS LIMITED BY 
COLLABORATION. SEMI-ACTIVE PATTERN DOES SUPPORT A 2-3 DAY WAVE 
PERIOD AND PRECIP CHANCES DO FIT WITH THIS CONCERN. HAVE EXTENDED 
POPS BACK INTO WED NIGHT TO HIGHLIGHT TIMING UNCERTAINTY...WHICH 
WILL ULTIMATELY DEPEND ON THE STRENGTH OF THE ASSOCIATED MID/UPPER 
LEVEL JET AND LL BAROCLINIC SETUP. OTHERWISE...LOOK FOR TEMPS AROUND 
NORMAL IN THIS PERIOD.

AVIATION...
BANDS OF RAIN CONTG TO DVLP IN WAA ZONE NE OF INTENSIFYING LOW
OVER THE ARKLATEX AND MOVE ACROSS NRN INDIANA. LOW LEVELS REMAIN
DRY RESULTING IN RATHER LIGHT PRECIP REACHING THE GROUND...MAINLY
IN THE FORM OF ZR- AND IP- WITH VFR FLYING CONDITIONS. EXPECT THIS
TO REMAIN THE CASE INTO THIS EVE WHEN WAA AND STRENGTHENING
WINDS/MIXING SHOULD RESULT IN TEMPS RISING ABOVE FREEZING. VFR
CONDITIONS SHOULD CONT THROUGH THE EVE. BAND OF HEAVY RAIN
EXPECTED AHEAD OF CDFNT SHOULD MOVE THROUGH LATE TONIGHT CAUSING
FLYING CONDITIONS TO LOWER TO IFR. VERY STRONG WIND FIELD WILL BE
HELD MAINLY ALOFT BY LOW LEVEL INVERSION BUT SHOULD RESULT IN LLWS
IN THE AREA OVERNIGHT AND FRIDAY.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...FREEZING RAIN ADVISORY UNTIL 7 AM EST FRIDAY FOR INZ007-009.
     FREEZING RAIN ADVISORY UNTIL 3 AM EST FRIDAY FOR INZ006-008.
MI...FREEZING RAIN ADVISORY UNTIL 7 AM EST FRIDAY FOR MIZ080-081.
     FREEZING RAIN ADVISORY UNTIL 3 AM EST FRIDAY FOR MIZ079.
OH...FREEZING RAIN ADVISORY UNTIL 7 AM EST FRIDAY FOR OHZ001-002-
     004-005.
LM...GALE WARNING UNTIL 7 PM EST FRIDAY FOR LMZ043-046.
&&

$$

SHORT TERM...JT
LONG TERM...JC
UPDATE/AVIATION...T