FXUS63 KIWX 232107
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
407 PM EST WED DEC 23 2009

.SHORT TERM...
INITIAL BAND OF WAA PRECIP ASSOCIATED WITH DEEPENING SFC LOW OVER 
THE SRN PLAINS WAS MOVG ACROSS THE CWA THIS AFTN. ZR BEING REPORTED 
A LITTLE FARTHER NE THAN PREVIOUS ADVISORY AREA, SO HAVE EXPANDED 
ADVISORY NE A COUPLE OF COUNTIES IN NORTH CENTRAL INDIANA AND 
SOUTHWEST MICHIGAN FOR THIS EVENING. SHOULD BE A LULL IN THE PRECIP 
AS STRONGER WAA SHIFTS TO THE NW OF OUR CWA AS LOW CONTS TO 
INTENSIFY...HOWEVER...SOME LIGHT FREEZING RAIN MAY PERSIST ALONG OUR 
WRN BORDER LATE TONIGHT AND INTO THU MORNING. FOR NOW CONTD WITH 
ENDING TIME OF ADVISORY AT 1AM BUT THIS MAY NEED TO BE EXTENDED OVER 
NW INDIANA. 

COLD FRONT ASSOCIATED WITH VERY STRONG PLAINS LOW WILL APPROACH THE 
CWA FROM THE SW ON THURSDAY. CONTINUED EASTERLY SFC WINDS WILL LIMIT 
WARMUP AHEAD OF THE CDFNT AS SGFNT BAND OF RAIN MOVES TOWARD THE 
AREA. STILL APPEARS THAT INITIAL RAINFALL WITH THIS HEAVIER BAND OF 
PRECIP MAY OCCUR INTO FREEZING SFC TEMPS OVER NRN PORTIONS OF THE 
CWA LATE THU/THU EVE, BEFORE WAA RAISES TEMPS ABOVE FREEZING. THUS, 
HAVE CONTINUED WITH A WINTER STORM WATCH FOR THU AFTN/NGT WHERE 
PREVIOUSLY ISSUED ACROSS SRN MI AND FAR NRN INDIANA, THOUGH AT THIS 
POINT SEEMS MORE LIKELY THAT EVENTUAL HEADLINE WILL BE FOR AN 
ADVISORY RATHER THAN WARNING DUE TO SHORT DURATION OF SUB-FREEZING 
TEMPS DURING THE WATCH PERIOD. ADDED MENTION OF HEAVY RAIN THU NGT 
AS STRONG FORCING COMBINED WITH GULF MOISTURE ADVECTING INTO THE 
AREA AHEAD OF THIS SYSTEM'S COLD FRONT SHOULD RESULT IN A PERIOD OF 
HEAVY RAIN. APPEARS THIS WILL MOVE THROUGH THE AREA QUICKLY ENOUGH 
THAT FLOODING WILL NOT BE A CONCERN.&&

.LONG TERM...
FRIDAY THROUGH WEDNESDAY...FOR THIS PACKAGE...FAVOR A BLEND OF THE 
SLOWER CANADIAN GEM AND THE OPERATIONAL ECMWF. THESE MODELS ARE 
SLOWER THEN THE GFS ENSEMBLE MEAN. THE GFS APPEARS TO BE SHOWING THE 
TYPICAL BIAS OF TRYING TO EJECT THIS TYPE OF SYSTEM EAST TOO FAST. 
THERE WILL BE A RATHER COMPLEX FUJIWHARA INTERACTION OF 2 UPPER 
LEVEL SYSTEMS FRIDAY. THE MOIST CONVEYOR BELT OF WARM AIR WILL BE 
COMPLETELY CUT OFF AS THE SYSTEM BECOMES OCCLUDED. THE DRY SLOT 
SHOULD BE MOVING INTO THE AREA FRIDAY MORNING WITH THE HEAVIEST 
PRECIPITATION NORTHEAST OF THE AREA. TEMPERATURES SHOULD WARM TO 
AROUND 40F OVER MOST OF THE AREA BEFORE THE COLD FRONT MOVES IN FROM 
THE SOUTHWEST. SOME CONCERN EXISTS FOR FLOODING FROM OVERNIGHT 
RAINFALL AMOUNTS THURSDAY NIGHT PLUS SNOWMELT FRIDAY. THE RAINFALL 
COMBINED WITH SNOW MELT WILL LIKELY BRING RISES TO AREA RIVERS 
FRIDAY. AT THIS TIME...FEEL POTENTIAL FLOOD ISSUES WILL BE MAINLY 
AREA RIVER RISES...BUT ISOLATED FLOODING OF LOW AREAS ARE 
POSSIBLE...ESPECIALLY IF STORM DRAINS BECOME PLUGGED BY DEBRIS OR 
MELTING SNOW AND ICE. MUCH COLDER CONDITIONS WILL OCCUR EARLY FRIDAY 
NIGHT WITH FLASH FREEZING LIKELY. THE UPPER LOW SHOULD THEN EJECT 
OUT OVER THE FORECAST AREA OVER THE WEEKEND. HAVE RAISED SNOW 
CHANCES TO HIGH CHANCE. GIVEN THIS PATTERN...BELIEVE THERE WILL 
PROBABLY BE ANOTHER 1-4 INCHES OF SNOW OVER THE WEEKEND BASED ON THE 
DURATION OF LIGHT SNOW. THE POTENTIAL FOR LAKE EFFECT SNOW LOOKS 
MARGINAL EARLY...BUT SHOULD INCREASE LATE IN THE PERIOD AS WINDS 
BECOME NORTHWEST. HAVE INDICATED THIS POTENTIAL WITH A CHANCE FOR 
LAKE EFFECT SNOW SUNDAY NIGHT THROUGH MONDAY NIGHT.

&&

.AVIATION /18Z TAFS/... 
BAND OF LIGHT SNOW/SLEET WITH MVFR CONDITIONS WAS LIFTING NORTH
ACROSS NRN INDIANA THIS AFTN. PRECIP MAY END AS A BRIEF PD OF ZR-
AS WAA ALOFT CONTS. AFTER THIS INITIAL BAND OF PRECIP MOVES
THROUGH, CONDITIONS SHOULD IMPROVE TO VFR THROUGH 18Z THU. OCNL
LIGHT PRECIP MAY CONT AT SBN OVERNIGHT AND EARLY THU, BUT ATTM
EXPECT IT WOULD BE VERY LIGHT IF IT OCCURS AT ALL SO LEFT MENTION
OUT OF TAFS.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...WINTER STORM WATCH FROM THURSDAY AFTERNOON THROUGH FRIDAY 
     MORNING FOR INZ003>007.

     WINTER WEATHER ADVISORY UNTIL 1 AM EST /MIDNIGHT CST/ THURSDAY 
     FOR INZ003>005-012>016-020-022.

     WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR 
     INZ023>027-032>034.

MI...WINTER STORM WATCH FROM THURSDAY AFTERNOON THROUGH FRIDAY 
     MORNING FOR MIZ077>081.

     WINTER WEATHER ADVISORY UNTIL 1 AM EST THURSDAY FOR MIZ077-078.

OH...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 7 AM EST THURSDAY FOR LMZ043-046.

     GALE WARNING FROM 7 AM THURSDAY TO 1 PM EST FRIDAY FOR LMZ043-
     046.

&&

$$

SHORT TERM...JT
LONG TERM...SKIPPER
AVIATION...JT