FXUS63 KIND 230444
AFDIND

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
1145 PM EST TUE DEC 22 2009

.AVIATION DISCUSSION...FOR THE 06Z TAFS
ACTIVE WEATHER SYSTEMS WITH LITTLE OVERALL CHANGE THROUGH THE TAF 
PERIOD. A STATIONARY FRONT NEAR THE OHIO RIVER EXTENDED TO A LOW IN 
OKLAHOMA. VERY MOIST AIR OVERRUNNING THE FRONT WILL CAUSE MOSTLY 
MVFR CONDITIONS. SOME OF THE TAFS MAY BEGIN WITH IFR BUT IMPROVE TO 
MVFR BY 10Z. AREAS OF MOSTLY RAIN WILL MOVE THROUGH. TEMPERATURES 
SHOULD BE JUST ABOVE FREEZING IN ALL BUT THE LAF AREA SO AT THE MOST 
SOME SNOW MAY BRIEFLY MIX WITH THE RAIN OVERNIGHT. WHILE LAF HAS THE 
SLIGHTLY COLDER AIR THEY HAVE MUCH LESS PRECIPITATION. CONDITIONS 
WILL CHANGE LITTLE ON WEDNESDAY EXCEPT WITH SOME MIXING CONDITIONS 
WILL IMPROVE SOME BUT REMAIN MVFR. THESE CONDITIONS WITH SCATTERED 
SHOWERS WILL CONTINUE THROUGH THE END OF THE TAF.

&&

.DISCUSSION...
HAVE UPDATED OVERNIGHT FORECAST PACKAGE SEVERAL TIMES TO INCLUDE 
PRECIPITATION SPREADING ACROSS ALL OF CENTRAL INDIANA INSTEAD OF 
WEST HALF. FREEZING LINE HAS BEEN HOLDING FAIRLY STEADY IN POSITION.

&&

.SHORT TERM...TONIGHT THROUGH THURSDAY NIGHT...
MODEL DATA SUGGEST LONG WAVE FEATURES WILL REMAIN PROGRESSIVE OVER 
THE NEXT SEVERAL DAYS...WITH DEVELOPING TROUGH CURRENTLY OVER THE 
WEST COAST MOVING INTO THE PLAINS BY FRIDAY MORNING. UPPER LEVEL 
RIDGE CURRENTLY OVER THE MIDWEST IS EXPECTED TO DRIFT EASTWARD TO 
NEAR THE EAST COAST. OPERATIONAL AND ENSEMBLE DATA SUGGEST SURFACE 
SYSTEM TO TRACK FROM ARKANSAS INTO WESTERN ILLINOIS OR IOWA BY 
FRIDAY MORNING. MODELS IN GOOD AGREEMENT ON THE MAJOR FEATURES. 
FORECAST FOCUS CENTERS ON POPS AND PRECIPITATION TYPE THROUGHOUT THE 
SHORT RANGE PERIOD.

MODEL DATA SUGGEST AN AREA OF ENHANCED MID LEVEL LIFT CURRENTLY IN 
THE ARKANSAS/SOUTHERN MISSOURI AREA WILL BE MOVING UP THROUGH 
ILLINOIS LATE TONIGHT AND ON WEDNESDAY...BRUSHING THE WESTERN PARTS 
OF THE FORECAST AREA. REGIONAL RADARS ARE INDICATING SOME SPOTTY 
ECHOES IN THAT AREA WITH A GRADUAL INCREASE IN THE COVERAGE OVER THE 
PAST COUPLE OF HOURS. AS A RESULT...WILL BE PULLING CHANCE POPS FOR 
FOR LIGHT PRECIPITATION LATE TONIGHT A LITTLE FARTHER EAST...UP TO 
ABOUT THE WESTERN HALF OF THE AREA. CRITICAL THICKNESSES SUGGEST 
MAINLY LIQUID...ALTHOUGH THE FAR NORTHERN ZONES MAY GET SOME LIGHT 
SNOW OR SLEET. THE MAJORITY OF THE MODEL DATA SUGGEST THE FREEZING 
LINE TONIGHT WILL SET UP NEAR A VERMILLION-MONROE COUNTY LINE...SO 
FREEZING RAIN POSSIBLE NORTHEAST OF THAT LINE. 

WILL CONTINUE WITH LIKELY POPS BY WEDNESDAY AFTERNOON IN THE WESTERN 
ZONES...AND CHANCE POPS ELSEWHERE AS AREA OF LIFT CONTINUES TO MOVE 
NORTH ACROSS ILLINOIS. AGAIN...FREEZING RAIN APPEARS POSSIBLE OVER 
THE NORTHEAST TWO THIRDS OF THE AREA WEDNESDAY MORNING...BUT THE 
FREEZING LINE SHOULD SHIFT NORTHEAST DURING THE DAY. 

APPEARS THE BEST CHANCES FOR ORGANIZED PRECIPITATION WILL BE 
WEDNESDAY NIGHT THROUGH THURSDAY NIGHT AS SEVERAL WAVES OF ORGANIZED 
LIFT MOVE INTO THE AREA. WILL CONTINUE WITH LIKELY POPS IN THE WEST 
WEDNESDAY NIGHT AND CHANCE POPS EAST FOR WEDNESDAY NIGHT...AND HIGH 
POPS ALL AREAS BY THURSDAY. AGAIN...PINNING DOWN THE FREEZING LINE 
AT THIS TIME IS DIFFICULT...BUT THE VARIOUS MODEL DATA SUGGEST 
FREEZING RAIN POSSIBLE WEDNESDAY NIGHT INTO THURSDAY MORNING OVER 
ABOUT NORTHEAST ONE HALF OF THE FORECAST AREA. BY THURSDAY AFTERNOON 
AND NIGHT...TEMPERATURES SHOULD WARM ENOUGH TO END THE FREEZING RAIN 
THREAT. ADVISORIES FOR WINTER PRECIPITATION MAY EVENTUALLY BE NEEDED 
OVER SOME OF THE NORTHWEST ZONES BY WEDNESDAY NIGHT INTO THURSDAY AS 
IT APPEARS THESE AREAS MAY GET CLOSE TO ADVISORY CRITERIA.

BASED ON LOW LEVEL THICKNESSES...DON/T HAVE A MAJOR PROBLEM WITH THE 
GFS MOS GUIDANCE...HOWEVER THE NUMBERS MAY BE ABOUT 5 DEGREES TOO 
WARM BY THURSDAY. WILL NUDGE THE NUMBERS DOWN A BIT BY THAT PERIOD.

&&

.LONG TERM...FRIDAY THROUGH TUESDAY...
OCCLUDED FRONT SHOULD BE SOMEWHERE WITHIN THE FORECAST AREA AT 12Z 
FRIDAY MORNING...PROGRESSING EAST OF THE REGION BY MIDDAY FRIDAY AND 
TAKING BULK OF THE HEAVIER RAINFALL WITH IT. MODEL CONSENSUS NOW 
SHOWING A WELL DEVELOPED DRY SLUG OF AIR WRAPPING AROUND THE STACKED 
LOW PRESSURE OVER THE UPPER MIDWEST. HAVE LOWERED TO 30 POPS DURING 
THE AFTERNOON...HOWEVER THERE IS A GROWING LIKELIHOOD AT AN EXTENDED 
PERIOD OF DRY WEATHER OVER CENTRAL INDIANA DURING THE DAY FRIDAY.  
COLDER AIRMASS WILL GRADUALLY ADVECT INTO THE REGION BEHIND THE 
FRONT ON FRIDAY WITH ATMOSPHERE BECOMING SUFFICIENTLY COOLED FOR 
PRECIPITATION TO FALL AS SNOW BY FRIDAY EVENING. WINDS WILL REMAIN 
GUSTY ALL DAY...PERHAPS IN EXCESS OF 30MPH.

SCATTERED SNOW SHOWERS ARE EXPECTED ALL WEEKEND NOW AS THE UPPER LOW 
AND ATTENDANT SURFACE REFLECTION TRUDGE SLOWLY EAST-NORTHEAST ACROSS 
THE GREAT LAKES. STRONG SURFACE HIGH PRESSURE AND A DEEP RIDGE ALOFT 
OVER THE CANADIAN MARITIMES CERTAINLY APPEAR TO BE KEEPING THE 
SYSTEM FROM MOVING WITH ANY SORT OF RAPIDITY. SEVERAL UPPER LEVEL 
DISTURBANCES WILL RIPPLE AROUND THE PARENT UPPER LOW AND THROUGH THE 
REGION OVER THE WEEKEND. THESE DISTURBANCES WILL COMBINE WITH 
PERSISTENT COLD ADVECTION AND SHALLOW WEAK INSTABILITY TO ENABLE 
SCATTERED SNOW SHOWERS THROUGH SUNDAY NIGHT AND POSSIBLY INTO MONDAY 
AS UPPER LOW DEPARTS TO THE NORTHEAST. WITH HIGH TEMPERATURES 
LARGELY REMAINING IN THE 20S AND LOWS IN THE TEENS THROUGH THE 
WEEKEND...LIQUID TO SNOW RATIOS WILL BE ENHANCED OVER THE STANDARD 
10:1 AND IT SEEMS PLAUSIBLE THAT LIGHT ACCUMULATIONS ARE LIKELY OVER 
AN EXTENDED TIME PERIOD FROM FRIDAY NIGHT THROUGH SUNDAY. WITH A 
CONTINUED TIGHT PRESSURE GRADIENT...BREEZY CONDITIONS CAN BE 
EXPECTED ALL WEEKEND. HIGH PRESSURE WILL OVERSPREAD THE OHIO VALLEY 
MONDAY AND TUESDAY PROVIDING POSSIBLY THE FIRST SIGNIFICANT TASTE OF 
SUNSHINE IN QUITE A WHILE. TEMPERATURES WILL REMAIN CHILLY THROUGH 
THE END OF THE EXTENDED. 

UNSETTLED WEATHER LIKELY TO RETURN BY THE MIDDLE OF NEXT WEEK AS 
BOTH ECMWF/OP GFS SUGGESTING LOW PRESSURE DEVELOPS IN THE NORTHERN 
GULF AND MOVES ACROSS THE EASTERN U S. TOO FAR OUT TO DETERMINE 
IMPACTS IF ANY TO CENTRAL INDIANA...BUT THIS WILL BE SOMETHING TO 
KEEP AN EYE ON OVER THE WEEKEND AND INTO EARLY NEXT WEEK.

&&

.IND WATCHES/WARNINGS/ADVISORIES...NONE. 

&&

$$
UPDATE...DRT
SHORT TERM...JAS
LONG TERM...RYAN
AVIATION...SH