FXUS63 KIND 250253
AFDIND
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
950 PM EST THU DEC 24 2009
.SHORT TERM UPDATE...
LATEST SURFACE MAP SHOWS WELL DEVELOPED STORM SYSTEM OVER NORTH
CENTRAL AR THIS EVENING. THIS LOW IS FORECAST TO MOVE NORTHWARD
INTO NERN MO BY 25/12Z AND WILL BE RESPONSIBLE FOR BRINGING RAIN
INTO CENTRAL INDIANA OVERNIGHT. LATEST RADAR SHOWS LIGHT-MODERATE
RAIN OVER EXTREME SOUTHERN ILLINOIS ALSO MOVING NWD. SO...WOULD
EXPECT LIGHT RAIN UNTIL AFTER MIDNIGHT BEFORE SOME OCCASIONAL
MODERATE RAIN OCCURS DURING CHRISTMAS MORNING.
TEMPERATURES ARE RIGHT ON TARGET - THUS WILL LOOK FOR LOW-MIDDLE 40S
MUCH OF THE NIGHT. NOTICED KLAF - KOKK - KMIE ARE IN THE MID TO
UPPER 30S...BUT GIVEN THE WARM ADVECTION OCCURRING WITH SSELY FLOW
OF 45KT AT 1500 FT TO 65 KT AT 4000 FT... THIS SHOULD RESULT IN
TEMPERATURES GRADUALLY REACHING 40 DEGREES BY 25/12Z.
.AVIATION DISCUSSION...FOR THE 00Z TAFS
THE MAIN PROBLEM FOR AVIATION WILL BE INCREASING WINDS THROUGH
FRIDAY AFTERNOON AND CONDITIONS DECREASING TO IFR LEVELS IN RAIN.
AN EXTREMELY STRONG LOW PRESSURE SYSTEM WAS OVER ARKANSAS. THIS LOW
WILL MOVE TO IOWA AROUND 18Z THEN BECOME STATIONARY THERE THROUGH
THE REST OF THE TAF. TAFS WILL START OUT VFR. THERE WILL BE
SCATTERED RAIN SHOWERS BUT THESE SHOULD NOT INITIALLY DECREASE
VISIBILITIES MUCH. AS THE LOW MOVES NORTH MORE MOIST AND UNSTABLE
AIR WILL WRAP AROUND IT INTO INDIANA. THIS WILL DECREASE CONDITIONS
TO MVFR LEVELS IN RAIN FROM 05Z-08Z. THERE WILL BE LOW LEVEL WIND
SHEAR WITH SURFACE WINDS FROM THE SOUTHEAST SHIFTING TO SOUTH AND
INCREASING TO 55-60 KTS AROUND 2 THOUSAND FEET. THE WINDS WILL
CONTINUE TO SHIFT TO THE SOUTH TOWARD MORNING. THERE IS A SHARP CUT
OFF BETWEEN MVFR AND IFR CONDITIONS. THESE IFR CONDITIONS IN
MODERATE RAIN WILL MOVE IN AFTER 08Z AND CONTINUE THROUGH 15Z-18Z.
WITH THE INCREASING PRESSURE GRADIENT WINDS WILL GUST TO 35 KTS FROM
16Z-21Z. MUCH COLDER AIR WILL VERY QUICKLY MOVE INTO INDIANA FRIDAY
AFTERNOON CHANGING THE RAIN TO LIGHT SNOW SHOWERS. AS THE COLDER AIR
MOVES IN THE MOST MOIST AIR WILL BEGIN TO MOVE OUT SO CONDITIONS
WILL INCREASE TO MVFR.
&&
.DISCUSSION...
WILL LET LAST 2 OF OUR FREEZING RAIN ADVISORY COUNTIES EXPIRE WITH
NEW FORECAST ISSUANCE. TEMPERATURES HAVE RISEN ABOVE FREEZING AND
IT ALSO WILL BE SEVERAL HOURS BEFORE MORE PRECIPITATION RETURNS TO
THIS REGION.
MAIN WEATHER ISSUES INCLUDE TYPE OF PRECIPITATION TONIGHT INTO
CHRISTMAS DAY...TEMPERATURES AND WHETHER OR NOT A WIND ADVISORY WILL
BE NEEDED LATER TONIGHT OR CHRISTMAS DAY.
SURFACE ANALYSIS INDICATED A 994 MB SURFACE LOW OVER WESTERN
ARKANSAS AT 19Z. RADAR LOOPS SHOW AN EXTENSIVE AREA OF RAIN
EXTENDING FROM CENTRAL ILLINOIS SOUTH THROUGH THE LOWER MISSISSIPPI
VALLEY. WATER VAPOR IR SHOWS A VERY STRONG UPPER LOW OVER NORTHEAST
TEXAS AND ANOTHER UPPER LOW OVER EASTERN MONTANA.
IN THE SHORT TERM BOTH NAM AND GFS ARE IN REASONABLE AGREEMENT AS IT
MOVES THE SURFACE LOW NORTHWARD TO IOWA BY CHRISTMAS MORNING...THEN
LOOPS IT AROUND AND THEN MOVING IT EAST NORTHEAST ACROSS THE GREAT
LAKES THIS WEEKEND. MODELS MOVE A STRONG COLD FRONT EAST ACROSS OUR
REGION CHRISTMAS DAY.
FOR TONIGHT RAIN WILL GRADUALLY SPREAD EAST ACROSS OUR REGION PER
MODELS. TRENDED SOMEWHAT TOWARD THE NAM WHICH HOLDS THE BULK OF THE
RAIN ACROSS OUR WEST THIS EVENING AND THEN SHIFTS IT EASTWARD LATER
TONIGHT AS COLD FRONT APPROACHES.
NAM BRINGS AN 80 KNOT 850 MB JET ACROSS OUR REGION BY 06Z. BUT A
LOW LEVEL INVERSION SHOULD KEEP THESE HIGH WINDS FROM MIXING DOWN
OVERNIGHT WHICH WILL PRECLUDE ANY NEED OF A WIND ADVISORY.
TEMPERATURES WILL RISE SOME OVERNIGHT AS STRONG WARM ADVECTION
CONTINUES AND PRECIPITATION WILL BE ALL RAIN TONIGHT.
ON FRIDAY THERE SHOULD BE BETTER MIXING ESPECIALLY AFTER COLD FRONT
MOVES THROUGH. BELIEVE MOS NUMBERS MAY BE A LITTLE ON THE LOW
SIDE. BUFKIT INDICATES WIND GUSTS IN EXCESS OF 30 KNOTS POSSIBLE
FRIDAY. SINCE THE GRADIENT WILL BE DECREASING SOME WILL KEEP WINDS A
LITTLE BELOW ADVISORY CRITERIA ON FRIDAY.
PRECIPITATION FRIDAY WILL START OUT AS RAIN...CHANGING TO LIGHT SNOW
SHOWERS AFTER COLD FRONT FRIDAY AFTERNOON.
THE STRONG UPPER LOW WILL DOMINATE OUR WEATHER OVER THE WEEKEND AS A
COUPLE OF SHORT WAVES ROTATE AROUND IT. BOTH THE GFS AND NAM BRING
THE STRONGEST SHORT WAVE ACROSS OUR REGION AROUND SUNDAY.
IN THE EXTENDED THERE MAY BE LEFT OVER LIGHT SHOWERS MONDAY MAINLY
IN OUR NORTHEAST. THEN DRY MONDAY NIGHT THROUGH WEDNESDAY AS A WEAK
UPPER RIDGE MOVES ACROSS OUR REGION. THE GFS AND EUROPEAN DIG
ANOTHER UPPER TROUGH INTO OUR REGION BY DAY 7 RESULTING IN LOW
CHANCES OF SNOW SHOWERS AGAIN BY DAY 7.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
.IND...NONE
&&
$$
UPDATE...DM
PUBLIC...JH
AVIATION...SH
