FXUS63 KIND 221601
AFDIND
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
1101 AM EST TUE DEC 22 2009
.UPDATE...
AREA OF LIGHT SNOW IS QUICKLY MOVING EAST AND AS OF 16Z...WAS MAINLY
IMPACTING NORTHEAST PORTIONS OF THE FORECAST AREA. MANY LOCATIONS
ALONG AND TO THE NORTHEAST OF INTERSTATE 74 RECEIVED A HALF INCH TO
AROUND ONE INCH. THERE HAVE BEEN SOME REPORTS OF HIGHER AMOUNTS
BETWEEN ONE AND TWO INCHES JUST NORTH OF THE INDY METRO EAST INTO
MADISON COUNTY.
FOCUS OF THE UPDATE IS ON ADJUSTING TIMING OF SNOW DEPARTURE OVER
THE NEXT FEW HOURS. APPEARS ENTIRE FORECAST AREA WILL BE DRY WITHIN
THE NEXT HOUR OR TWO AND THUS ADJUSTED POPS ACCORDINGLY. DRY YET
CHILLY AFTERNOON ON TAP FOR CENTRAL INDIANA AS WEAK MID LEVEL
RIDGING AND WARM ADVECTION ATTEMPT TO TAKE ROOT. HAVE SEEN A FEW
BREAKS IN THE STRATUS DECK THIS MORNING...MOST NOTABLY OVER FAR
SOUTHERN COUNTIES. JUST BASED ON SATELLITE IMAGES THOUGH...GENERAL
STATE OF THE SKY WILL BE MAINLY CLOUDY ONCE AGAIN THIS AFTERNOON. AS
HAS BEEN THE CASE THE LAST FEW DAYS...CLOUDS WILL MAKE TEMPERATURE
RISES STRUGGLE TO SOME EXTENT THIS AFTERNOON ESPECIALLY ACROSS THE
NORTH. HAVE TEMPERED HIGHS TO ABOUT A 2-4 DEGREE RISE FROM 16Z
READINGS. AS 12Z MODEL DATA TRICKLES IN...STILL APPEARS A POTENTIAL
FOR FREEZING DRIZZLE/RAIN WILL EXIST OVER WEST CENTRAL INDIANA
TONIGHT...POSSIBLY AS EARLY AS THIS EVENING. WILL CONTINUE TO
MONITOR TRENDS THROUGH THE AFTERNOON.
ZONE AND GRID UPDATES OUT. REST OF THE FORECAST LOOKS GREAT.
&&
.AVIATION...DISCUSSION FOR 22/12Z TAFS.
THE SNOW SHOULD BY DONE BY ISSUANCE TIME AT IND AND BY 13Z AT LAF.
UNTIL THEN...WILL SEE IFR CONDITIONS AT LAF. THEN...MODELS FAVOR
KEEPING MVFR CEILINGS IN ACROSS THE TAF SITES THROUGH THE
PERIOD...ALTHOUGH WOULD NOT BE SURPRISED TO SEE SOME BREAKS AND
CEILINGS LIFTING TO VFR MAINLY AT HUF AND BMG AS DRY AIR ALOFT MOVES
IN...STILL WILL STICK WITH MVFR FOR NOW. ALSO...COULD SEE SOME IFR
CEILINGS AND VISIBILITIES OVERNIGHT TONIGHT AS MODELS ARE TRYING TO
BRING SOME PRECIPITATION IN TOWARD MORNING. BUFKIT SUGGESTS FREEZING
RAIN OR SNOW AT LAF AND IND AND RAIN AT HUF. BUT...WITH ONLY SMALL
CHANCES IN THE FORECAST...WILL LEAVE IT OUT FOR NOW. EAST SOUTHEAST
WINDS LESS THAN 10 KNOTS TODAY SHOULD INCREASE TO AROUND 10 KNOTS
OVERNIGHT.
&&
.PREV 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.
&&
.IND WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
PUBLIC...NIELD
AVIATION...MK
