FXUS63 KIND 220936
AFDIND
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
430 AM EST TUE DEC 22 2009
.DISCUSSION...AT 09Z...TEMPS ACROSS THE FORECAST AREA WERE IN THE
UPPER 20S TO MID 30S...WITH LIGHT EAST WINDS AND CLOUDY SKIES. LIGHT
SNOW WAS FALLING OVER NORTHWESTERN PORTIONS OF THE FORECAST AREA.
FORECAST FOCI OF THE DAY WILL BE SNOWFALL TODAY AND PRECIP TYPE
TONIGHT AND INTO THE REMAINDER OF THE WEEK.
.NEAR TERM...TODAY...
NATIONAL RADAR LOOP WAS SHOWING AN AREA OF ACCUMULATING SNOW ACROSS
NORTHEASTERN IOWA AND NORTHERN ILLINOIS AT 06Z EARLY THIS MORNING IN
AN AREA OF POSITIVE VORTICITY ADVECTION AHEAD OF AN UPPER SHORT WAVE
ACROSS EASTERN NEBRASKA AND ALSO WITHIN AN AREA OF 90% MEAN LEVEL
RELATIVE HUMIDITY. THIS AREA WAS ALSO ASSOCIATED WITH AN AREA OF
1000-850 MILLIBAR FRONTOGENESIS. SO...BEST FORCING AND MOISTURE
MENTIONED ABOVE WARRANTS LIKELY POPS NORTH OF INDIANAPOLIS THROUGH
18Z THIS AFTERNOON AFTER WHICH POPS WILL DROP OFF SIGNIFICANTLY.
DON'T SEE WHY AREAS NORTH OF INDIANAPOLIS WON'T GET AN INCH OF TOTAL
SNOWFALL ACCUMULATION BY THIS AFTERNOON. POPS SHOULD TAPER OFF
SIGNIFCANTLY SOUTH AND WEST OF INDIANAPOLIS BASED ON BEST MOISTURE
AND FORCING ALONG WITH RADAR TRENDS. WITH SOUTHEAST LOW LEVEL FLOW
COMMENCING SOUTH OF INDIANAPOLIS...COULD SEE A FEW BREAKS IN THE
CLOUDS AND TEMPERATURES REACH THE LOWER 40S THERE PER MOS.
MEANWHILE...FURTHER NORTH...HIGHS SHOULD ONLY BE IN THE MID 30S PER
MOS DUE TO THICK CLOUD COVER...EVAPORATIVE COOLING AND LOW LEVEL
FLOW MORE FROM THE EAST.
.SHORT TERM...TONIGHT THROUGH FRIDAY NIGHT.
00Z NAM APPEARS TO BE AN OUTLIER WITH A FASTER PROGRESSION OF THE
SYSTEM DEVELOPING ACROSS THE CENTRAL AND SOUTHER PLAINS THIS
WEEK...AS BLOCKING RIDGE UPSTREAM SHOULD LIMIT QUICK EASTWARD
PROGRESSION OF THE UPCOMING STORM. GFS IS CLUSTERED MUCH BETTER IN
SPEED AND STRENGTH WITH UKMET...ECMWF...AND REMAINING MODEL SUITE
AND HAVE LEANED TOWARD GFS FOR THIS FORECAST.
MODELS CONTINUE TRENDING SLIGHTLY SLOWER AND WARMER WITH THIS
STORM...WHICH WILL HAVE A SIGNIFICANT EFFECT ON PRECIP TIMING AND
TYPE. AFTER SNOWFALL TODAY...MODELS INDICATE SOME WEAK FORCING AND
MOISTENING OF THE LOW LEVELS ACROSS OUR WESTERN AREA LATE
TONIGHT...AND HAVE GONE WITH CHANCE POPS THERE. SOUTHWESTERN CORNER
AND WEST CENTRAL SHOULD BE WARM ENOUGH FOR MOSTLY RAIN...OR PERHAPS
A RAIN SNOW MIX...WHILE MODEL SOUNDINGS INDICATE NORTHWESTERN
AREA...NEAR LAF...MAY SEE SNOW OR PERHAPS A PERIOD OF FREEZING
DRIZZLE/RAIN. AS REMAINING FORECAST AREA MOISTENS AND PRECIP CHANCES
INCREASE ACROSS THE AREA ON WEDNESDAY...SOUNDING ANALYSIS INDICATES
FREEZING RAIN OR SNOW POSSIBLE NORTHEAST OF INTERSTATE 74 EARLY
WEDNESDAY...WITH THE POSSIBILITY OF FREEZING PRECIP PUSHING
NORTHEAST SOMEWHAT LATER IN THE DAY AS SURFACE TEMPERATURES WARM.
BEST SHOT FOR FREEZING PRECIPITATION ISSUES APPEARS TO BE WEDNESDAY
NIGHT ACROSS PORTIONS OF THE FORECAST AREA NORTHEAST OF A LAFAYETTE
TO INDIANAPOLIS TO GREENSBURG LINE...AS SOUNDINGS IN THIS AREA
INDICATE A SIGNIFICANT WARM LAYER FROM 925 TO ABOUT 800 MILLIBARS
AND SURFACE TEMPERATURES FALLING INTO THE UPPER 20S TO AROUND 30.
FORTUNATELY...ICE ACCUMULATIONS SHOULD BE LIGHT ACROSS THESE
AREAS...AND NO HEADLINES PLANNED FOR THE TIME BEING. HOWEVER...ANY
ICING CAN CAUSE SIGNIFICANT TRAVEL DIFFICULTIES AT TIMES.
TRANSITION TO ALL RAIN ACROSS THE AREA SHOULD TAKE PLACE THURSDAY
MORNING...AND HEAVIEST PRECIPITATION IS EXPECTED LATE THURSDAY
AFTERNOON AND INTO THURSDAY NIGHT AS AN OCCLUDED FRONT PUSHES
NORTHEAST THROUGH THE AREA. ON CHRISTMAS DAY...TEMPERATURES BEGIN TO
COOL ONCE AGAIN AND THIS CONTINUES INTO THE WEEKEND AS THE UPPER LOW
PULLS OFF TO THE EAST-NORTHEAST AND A TRANSITION BACK TO SNOW TAKES
PLACE FOR ANY PRECIPITATION FRIDAY EVENING AND INTO THE WEEKEND.
GFS MOS WAS ACCEPTED FOR MOST TEMPERATURES WITH TWEAKS TO DIURNAL
RANGES FOR CLOUD COVER AND EXPECTED PRECIPITATION.
&&
.AVIATION...DISCUSSION FOR 22/06Z TAFS.
AREA OF SNOW SHOWERS ACROSS NORTHERN ILLINOIS WILL SPREAD ACROSS THE
NORTHERN TWO THIRDS OF CENTRAL INDIANA AFTER 09Z AND CONTINUE TO
ABOUT 15Z. NAM MODEL INDICATE AN INCH OF SNOW MAY FALL AT KLAF WITH
LESSER AMOUNTS FARTHER SOUTH. WILL MENTION PREVAILING VISIBILITY OF
2 MILES AT KLAF...BUT IT COULD DROP TO A MILE AT TIMES.
AFTER SNOW MOVES BY...MVFR CIGS WILL BE THE RULE AS SOME TRAPPING OF
LOW LEVEL MOISTURE OCCURS. MODEL SOUNDINGS INDICATE LOW CLOUDS MAY
BREAK UP SOME ACROSS SOUTHERN INDIANA AND WILL MENTION A PERIOD OF
VFR CONDITIONS AT KBMG. OTHER TAFS MOST LIKELY WILL REMAIN
MVFR...BUT THERE MAY BE SOME IMPROVEMENT TUESDAY AFTERNOON.
FINALLY NAM BRINGS RAIN INTO KHUF BY END OF THE TAF PERIOD AND
FREEZING RAIN AT KIND AND KLAF AFTER 06Z WEDNESDAY. THIS MAY BE A
LITTLE FAST SO WILL NOT MENTION IN THIS SET OF TAFS.
&&
.IND WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
PUBLIC...NIELD
AVIATION...JH
