FXUS63 KIND 232309
AFDIND
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
545 PM EST WED DEC 23 2009
.AVIATION DISCUSSION...FOR THE 00Z TAFS
THE MAIN WEATHER PROBLEM FOR AVIATION WILL BE WINDS ON THURSDAY. A
VERY STRONG LOW PRESSURE SYSTEM WILL MOVE INTO IOWA AT 18Z THURSDAY.
THROUGH MOST OF THE TAF PERIOD DRIER AIR IN LOWER LEVELS WILL
CONTINUE TO MOVE INTO THE AREA FROM THE EAST. THIS WILL KEEP
CONDITIONS VFR. THERE WILL BE SOME LIGHT SHOWERS BUT THESE WILL ONLY
HAVE MINOR EFFECTS ON VISIBILITIES. A WARM FRONT WILL MOVE THROUGH
INDIANA ON THURSDAY. AFTER 12Z WIND DIRECTION WILL CHANGE FROM 100
DEGREES AT 15 KTS AT THE SURFACE TO 150 DEGREES AT 35 TO 40 KTS AT 2
THOUSAND FEET. AS THE PRESSURE GRADIENT INCREASES WINDS WILL GUST UP
TO 35 KTS IN THE AFTERNOON. FOR THE EXTENDED PORTION OF THE IND TAF
MOIST AIR WILL BEGIN TO WRAP AROUND THE LOW INTO INDIANA. CONDITIONS
WILL DECREASE TO MVFR LEVELS IN RAIN CHRISTMAS EVE. SURFACE
TEMPERATURES WILL REMAIN ABOVE FREEZING SO ICYING SHOULD NOT BE A
PROBLEM.
&&
.DISCUSSION...
FORECAST FOCUS IS ON POPS/PRECIPITATION TYPE EARLY IN THE FORECAST
THEN ON WINDS.
AT 18Z SURFACE LOW PRESSURE WAS ACROSS EASTERN KANSAS WITH A WARM
FRONT EXTENDING EAST INTO SOUTHERN KENTUCKY. ACROSS THE FORECAST
AREA...FREEZING RAIN WAS EXITING THE NORTHEASTERN PART OF THE AREA
/WHERE TEMPERATURES REMAINED JUST BELOW FREEZING/. RAIN WAS ACROSS
NORTHWESTERN AREAS.
MODELS IN FAIR AGREEMENT THIS RUN. NAM APPEARS TOO COLD WITH SURFACE
TEMPERATURES /COMPARED TO WHAT IS GOING ON NOW/...SO WENT CLOSER TO
GFS THERE. FOR THE MOST PART THOUGH WENT WITH A MODEL BLEND.
CURRENT RAIN ACROSS THE AREA SHOULD MOVE OUT BY TONIGHT...BUT
CONTINUED ISENTROPIC LIFT WILL KEEP THE THREAT AROUND ALL NIGHT
LONG. CURRENT RADAR SHOWS RAIN MOVING NORTHEAST OUT OF SOUTHERN
MISSOURI...AND THIS LOOKS TO REACH THE FAR WESTERN AREA.
MEANWHILE...A DRY EASTERLY SURFACE FLOW WILL TRY TO EAT AWAY AT RAIN
THAT MOVES EAST. PUTTING THIS ALL TOGETHER LEADS TO A POPS GRADIENT
OF LOW CHANCE POPS IN THE EASTERN AREA TO LIKELY OR HIGHER POPS
ACROSS THE FAR WESTERN FORECAST AREA. TEMPERATURES SHOULD COOL
ENOUGH ACROSS THE NORTHEASTERN AREAS TO KEEP CHANCES OF FREEZING
RAIN AROUND THERE. COVERAGE OF PRECIPITATION SHOULD BE LOW ENOUGH TO
NOT CAUSE ANY SIGNIFICANT PROBLEMS. WITH THE NAM LOOKING TOO
COLD...WENT CLOSER TO THE WARMER MAV NUMBERS.
AS THE SYSTEM GETS CLOSER TO THE AREA ON THURSDAY FORCING WILL
INCREASE DURING THE DAY AS CAN BE SEEN IN THE ISENTROPIC AND
Q-VECTOR CONVERGENCE FORECASTS. THIS FORCING COMBINED WITH THE
MOISTURE FLOWING INTO THE AREA FROM THE SOUTH WILL LEAD TO LIKELY OR
HIGHER POPS BY AFTERNOON ALL AREAS. TEMPERATURES WILL BE COLD ENOUGH
AT THE START OF THE DAY FOR A CONTINUED THREAT OF SOME LIGHT
FREEZING RAIN ACROSS NORTHEASTERN SECTIONS OF THE AREA...BUT THIS
ALSO OCCURS AT THE TIME OF THE LOWER CHANCES FOR PRECIPITATION. THUS
NOT EXPECTING ANY SIGNIFICANT PROBLEMS AT THE MOMENT. BY MID TO LATE
MORNING THE SURFACE TEMPERATURES SHOULD BE WARM ENOUGH FOR RAIN.
MET CONTINUES TO LOOK TOO COOL MANY PLACES. AFTER COLLABORATION
ENDED UP WITH TEMPERATURES IN BETWEEN MAV AND MET FOR HIGHS.
THURSDAY NIGHT A 70KT 850 JET MOVES INTO THE AREA. FORCING AND
PLENTIFUL MOISTURE WILL LEAD TO CATEGORICAL POPS ALL AREAS. QPF
AMOUNTS COULD BE AROUND 1 INCH WHICH MAY LEAD TO SOME FLOODING
ISSUES. WILL CONTINUE TO MENTION IN HWO. SHOULD GET BREEZY THURSDAY
NIGHT WITH SURFACE PRESSURE GRADIENT TIGHTENING AND STRONG WINDS NOT
TOO FAR ABOVE THE SURFACE. QUESTION IS HOW WILL THE INVERSION WILL
PROTECT THE SURFACE FROM THE WINDS. AT THE MOMENT BELIEVE THAT THE
INVERSION SHOULD BE STRONG ENOUGH TO KEEP ANY GUSTS BELOW ADVISORY
CRITERIA...AND GRADIENT WINDS SHOULD AVERAGE JUST BELOW. WILL KEEP
AN EYE ON...ESPECIALLY ACROSS SOUTHERN AREAS WHERE MORE MIXING MAY
OCCUR.
DRY SLOT MOVES IN ON CHRISTMAS AND SHOULD CUT OFF BULK OF
PRECIPITATION AS COLDER AIR MOVES IN. WILL KEEP LOW POPS AND RAIN TO
SNOW AS IN PREVIOUS FORECASTS.
&&
.IND WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
PUBLIC...CS
AVIATION...HAINES
