FXUS63 KIND 231041 RRA
AFDIND
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
541 AM EST WED DEC 23 2009
.AVIATION DISCUSSION...FOR THE 12Z TAFS
RADAR WAS SHOWING LARGE AREA OF PRECIPITATION MOVING HAS REACHED HUF
AND WILL REACH THE OTHER SITES BY ISSUANCE TIME. NATIONAL RADAR LOOP
WAS SHOWING THE BACK EDGE MOVING INTO WESTERN ILLINOIS AND SHOULD
REACH HUF AROUND 14Z...BMG AND LAF AROUND 15Z AND IND AROUND 16Z
THIS MORNING. OTHERWISE...WL KEEP VCSH IN AS RADAR WAS ALSO SHOWING
MORE SCATTERED ACTIVITY IN ITS WAKE. WARM AIR ALOFT CONTINUES TO
OVERRUN THE COLDER SURFACE AIRMASS IN PLACE ACROSS CENTRAL INDIANA.
SURFACE OBSERVATION TRENDS FAVOR FREEZING RAIN THIS MORNING AT LAF
AND JUST RAIN ELSEWHERE. MODELS SUGGEST MORE FREEZING RAIN IS
POSSIBLE TONIGHT BUT LIKELY JUST TO THE NORTH AND EAST OF THE
TERMINALS. ALSO...ACTIVITY SHOULD BE SCATTERED...SO WILL JUST LEAVE
VCSH FOR NOW. FINALLY...EAST SOUTHEAST WINDS WILL START TO INCREASE
LATE TODAY TO 15 KNOTS AT TIMES THROUGH TONIGHT AND TOMORROW MORNING
AS A LOW PRESSURE SYSTEM STRENGTHENS ACROSS EASTERN PARTS OF TEXAS
AND OKLAHOMA AND BEGINS LIFTING NORTH.
&&
.PREV DISCUSSION...AT 08Z...TEMPERATURES ACROSS THE FORECAST AREA
WERE IN THE 30S...EXCEPT THE LOWER 40S FAR SOUTHWEST. DEWPOINTS WERE
IN THE UPPER 20S TO THE UPPER 30S...AND WINDS WERE BREEZY OUT OF THE
EAST. 88D SHOWED A SHIELD OF STEADY PRECIP PUSHING ACROSS THE
NORTHEASTERN HALF OF THE AREA...PRODUCING SOME MIXED PRECIPITATION
IN THE NORTHEASTERN CORNER OF THE AREA NEAR MUNCIE. TEMPERATURES
HAVE BEEN HOLDING RATHER STEADY TONIGHT WITH THE FREEZING LINE
STRETCHING FROM NORTHEAST OF LAF TO NEAR FISHERS AND DOWN TO NEAR
RUSHVILLE.
FORECAST CHALLENGE OF THE DAY WILL BE PRECIP TYPE TODAY INTO EARLY
THURSDAY MORNING.
LATEST MODELS WERE IN FAIR AGREEMENT ON OVERALL MASS FIELDS THIS
MORNING...BUT GFS...PER ITS TENDENCY...APPEARS TO BE CAPTURING
BEGINNINGS OF CYCLOGENESIS THE BEST...AND HAVE LEANED ON IT FOR THIS
FORECAST.
AS MAIN UPPER LOW SHIFTS EASTWARD OUT OF THE FOUR CORNERS REGION
THIS MORNING...THE GFS DEVELOPS A COHERENT SURFACE CYCLONE OVER THE
SOUTHERN PLAINS INTO WESTERN ARKANSAS BY TONIGHT...AND THEN PULLS IT
DUE NORTHWARD AS THE UPPER LOW DEEPENS AND CUTS OFF. AHEAD OF THE
CYCLONE...A WIDESPREAD AREA OF ISENTROPIC LIFT IS DEVELOPING AS
EVIDENCED BY LARGE AREAS OF SHOWERS ON NATIONAL 88D MOSAIC TONIGHT.
THIS LIFT IS PRESENT...ALTHOUGH WEAK AT TIMES...ACROSS THE FORECAST
AREA THROUGH AT LEAST LATE THURSDAY NIGHT...AND THUS PERIODS OF
PRECIP ARE TO BE EXPECTED THROUGH AT LEAST THURSDAY NIGHT AND INTO
FRIDAY. HOWEVER...THE BEST MOISTURE AS DEPICTED BY ISENTROPIC MIXING
RATIOS DOES NOT GET INTO THE FORECAST AREA UNTIL THURSDAY INTO
THURSDAY NIGHT...THUS WILL CARRY HIGHEST POPS AND QPF AT THAT TIME.
OCCLUDED FRONT PASSES THROUGH THE AREA EARLY FRIDAY...AND COLD
ADVECTION BEGINS BEHIND IT...WHICH WILL CHANGE ANY PRECIP OVER TO
LIGHT SNOW THROUGH THE END OF THE SHORT TERM.
FREEZING PRECIP IS AN ISSUE THROUGH EARLY THURSDAY MORNING FOR AT
LEAST PORTIONS OF THE FORECAST AREA. BASED ON WHERE LOW LEVEL
TEMPERATURES HAVE BEEN HOLDING THIS EVENING...FEEL THAT GFS FORECAST
SOUNDINGS ARE RUNNING JUST SLIGHTLY TOO COOL NEAR THE
SURFACE...WHICH OF COURSE HAS MAJOR IMPLICATIONS FOR PRECIP TYPE.
FREEZING LINE HAS BEEN HOLDING FAIRLY STEADY FROM CARROLL COUNTY TO
NEAR RUSH COUNTY...AND THIS SHOULD REMAIN STEADY EARLY THIS MORNING
AS SURFACE TEMPERATURES STRUGGLE TO RISE UNDER SCATTERED PRECIP AND
CLOUDY SKIES. SOUNDINGS REMAIN BARELY FAVORABLE FOR FREEZING RAIN
NEAR MUNCIE THIS AFTERNOON...AND WILL PUSH FREEZING LINE NORTHEAST
TO A KOKOMO TO NEW CASTLE LINE THIS AFTERNOON...BEFORE DROPPING IT
BACK TO A NEAR LAFAYETTE TO NORTHEAST INDY METRO TO NEAR GREENSBURG
LINE AS WARM ADVECTION CONTINUES ALOFT TONIGHT OVER COOL NEAR
SURFACE LAYER. STRONGEST WARM ADVECTION KICKS IN LATE TONIGHT INTO
EARLY THURSDAY MORNING ACROSS THE AREA...AND ANY PRECIP AFTER EARLY
THURSDAY MORNING SHOULD BE ALL RAIN...WITH A WIDESPREAD
INCH...PERHAPS UP TO TWO INCHES...APPEARING LIKELY THURSDAY AND
THURSDAY NIGHT. FLASH FLOOD GUIDANCE ACROSS THE AREA IS GENERALLY
RUNNING AROUND 2-3 INCHES IN SIX HOURS...WHICH APPEARS UNLIKELY AT
THE MOMENT...BUT WITH SOME WATERSHEDS IN THE SOUTHEASTERN FORECAST
AREA COMING OFF OF A RECENT MINOR FLOOD...THE HYDRO SITUATION WILL
BEAR WATCHING LATER IN THE WEEK.
ADDITIONAL ISSUE TO MONITOR WILL BE WINDS AS THE PRESSURE GRADIENT
STRENGTHENS THURSDAY INTO THURSDAY NIGHT. WHILE INVERSION WILL LIMIT
THE ABILITY OF 70+ KNOT 850 JET TO MIX DOWN...GUIDANCE INDICATES
SUSTAINED WINDS AT OR ABOVE 20 KNOTS...WITH 40 KNOTS JUST OFF THE
SURFACE ON FORECAST SOUNDINGS. WILL GO WITH GUSTS TO NEAR 30 KNOTS
FOR NOW...AND MONITOR AS TIME GOES ON.
FOR TEMPS...WITH WEAK LOW LEVEL WARM ADVECTION TODAY THROUGH
THURSDAY...WENT JUST A FEW DEGREES ABOVE PERSISTENCE EACH
PERIOD...WHICH AGREES WELL WITH MAV MOS. SPLIT THE DIFFERENCE
BETWEEN MAV/MET ON FRIDAY...AS IT APPEARS WE COULD BE DRY
SLOTTED...BUT ALSO COLD ADVECTING. COLD POOL SETTLES OVER US FOR THE
WEEKEND...AND SKIES SHOULD REMAIN CLOUDY...SO TEMPS WILL BE AT LEAST
SEVERAL DEGREES BELOW NORMAL.
NO CHANGES TO THE EXTENDED THIS MORNING.
&&
.IND WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
PUBLIC...NIELD
AVIATION...KOCH
