FXUS63 KIND 251657
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
1155 AM EST FRI DEC 25 2009

.AVIATION...DISCUSSION FOR 18Z TAFS
AVIATION CONDITIONS WILL BE MVFR THROUGH THE TAF PERIOD. THROUGH 12Z 
SATURDAY VERY STRONG LOW PRESSURE WILL ROTATE AROUND IOWA. AFTER 12Z 
IT WILL BEGIN TO MOVE THROUGH THE GREAT LAKES. MUCH COLDER AIR WAS 
WRAPPING AROUND THE LOW. THIS AIR WILL MOVE INTO INDIANA DURING THE 
AFTERNOON. LIGHT RAIN SHOWERS WILL QUICKLY CHANGE TO LIGHT SNOW 
SHOWERS. THESE WILL NOT DECREASE CONDITIONS BELOW MVFR WITH ONLY 
MINOR ACCUMULATION. THE STRONGEST WINDS WILL BE WEST OF THE LOW. 
DURING THE AFTERNOON SOME GUSTS IN INDIANA COULD REACH 30 KTS BUT 
WILL DECREASE TO 25 KTS AFTER 00Z. WINDS ALOFT WILL ONLY INCREASE TO 
30 KTS AT 3 THOUSAND FEET OUT OF THE SOUTH SO ANY LOW LEVEL WIND 
SHEAR WILL BE MINOR. WITH THE SYSTEMS MOVING LITTLE THROUGH HE TAF 
PERIOD THERE WILL BE ONLY MINOR CHANGES IN CONDITIONS. 

&&

.DISCUSSION...DEEP LONG WAVE UPPER TROUGH CURRENTLY OVER THE PLAINS 
IS EXPECTED TO DRIFT SLOWLY EAST THROUGH THE GREAT LAKES AND OHIO 
VALLEY OVER THE NEXT FEW DAYS. SEVERAL EMBEDDED DISTURBANCES 
ROTATING THROUGH THE LONG WAVE TROUGH WILL KEEP THE WEATHER 
UNSETTLED INTO THE WEEKEND. MODELS IN GOOD AGREEMENT ON THE MAIN 
FEATURES. FORECAST FOCUS CENTERS ON POPS AND PRECIPITATION TYPE 
THROUGH THE SHORT TERM.

FOR TODAY...MODEL DATA SUGGEST THE SURFACE OCCLUSION SHOULD BE CLOSE 
TO THE SOUTHWEST BORDER ZONES BY 251200Z...AND SHOULD PASS THROUGH 
THE NORTHEAST ZONES BY MID AFTERNOON. WILL KEEP HIGH POPS GOING 
AHEAD OF THE FRONT...AND TAPER DOWN TO CHANCE POPS IN THE POST 
FRONTAL ZONE. GIVEN THE STRONG 70-80KT LOW LEVEL JET IN THE PROFILER 
AND MODEL DATA...WILL HAVE TO KEEP AN EYE ON THE ACTIVITY CLOSE TO 
FRONTAL ZONE FOR THE POSSIBILITY OF SOME HIGH WINDS MIXING DOWN TO 
THE SURFACE...ALTHOUGH LAST EVENING/S UPPER AIR INDICATE A STRONG 
INVERSION BELOW ABOUT 2500FT SO THERE IS SOME QUESTION IF THE WINDS 
ALOFT CAN BREAK THROUGH THAT INVERSION. SO FAR...DOESN/T APPEAR THAT 
IS HAPPENING BASED ON SURFACE REPORTS NEAR THE FRONT. OTHERWISE...
CRITICAL THICKNESS DATA FROM THE MODELS SUGGEST AIR MASS WILL GET 
COLD ENOUGH TO SUPPORT SNOW AFTER ABOUT 251700Z FROM SOUTHWEST TO 
NORTHEAST...SO ANY LINGERING PRECIPITATION THIS AFTERNOON MAY BE IN 
THE FORM OF SNOW SHOWERS.

IN THE LATER PERIODS...WILL KEEP CHANCE POPS FOR SNOW SHOWERS ACROSS 
THE AREA THROUGH SUNDAY...AS SEVERAL DISTURBANCES ROTATE AROUND THE 
LONG WAVE TROUGH. AT THIS POINT...APPEARS THE BEST CHANCES MAY BE ON 
SUNDAY WHEN THE BULK OF THE UPPER ENERGY PASSES THROUGH...BUT WON/T 
GET FANCY WITH THE POPS AT THIS POINT. SOME MINOR ACCUMULATIONS 
POSSIBLE.

APPEARS TEMPERATURES WILL PROBABLY RISE INTO THE UPPER 40S TO LOWER 
50S MOST AREAS LATER THIS MORNING BEFORE FRONTAL PASSAGE...WITH 
TEMPERATURES TAILING OFF BY AFTERNOON TO AROUND 30 BY SUNSET. LOW 
LEVEL THICKNESS PROGS SUGGEST THE GFS MOS HIGHS FOR FRIDAY MAY A FEW 
DEGREES TOO WARM...OTHERWISE THE NUMBERS IN THE BALLPARK.

&&

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

&&

$$

PUBLIC...JAS
AVIATION...HAINES