FXUS63 KIND 090450 AAA
AFDIND
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
1150 PM EST TUE DEC 8 2009
.AVIATION...DISCUSSION FOR 09/06Z TAFS.
MORE WIDESPREAD RAIN HAS SHIFTED EAST OF THE TERMINALS LATE THIS
EVENING...WITH SCATTERED LIGHT SHOWERS REMAINING ACROSS MUCH OF
CENTRAL INDIANA. LOW PRESSURE INTENSIFYING RAPIDLY OVER NORTHEAST
MISSOURI AS OF 05Z...WILL CONTINUE TO MOVE NORTHEAST OVERNIGHT AND
BE LOCATED NEAR CHICAGO BY DAYBREAK WEDNESDAY. COLD FRONT EXTENDING
FROM THE LOW SOUTHEAST INTO WESTERN KENTUCKY/TENNESSEE WILL PROGRESS
ACROSS THE TERMINALS BETWEEN 08Z AND 10Z. AHEAD OF THE FRONT...
WINDS WILL REMAIN FROM THE SOUTH-SOUTHEAST WITH IFR/LIFR CEILINGS.
SOME LOW LEVEL WIND SHEAR IS POSSIBLE AHEAD OF THE FRONT...BUT
HIGHER WINDSPEEDS AT THE SURFACE WOULD SUGGEST THAT CRITERIA WILL
NOT BE MET.
WITH THE PASSAGE OF THE FRONT...WINDS WILL SHIFT TO SOUTHWEST
AND IMMEDIATELY INCREASE. MODEL SOUNDINGS SUGGESTING STRONGER WINDS
ALOFT WILL BEGIN MIXING DOWN TO THE SURFACE FAIRLY QUICKLY WITH
GUSTS EXCEEDING 40KTS DEVELOPING AT ALL TERMINALS BY MID MORNING.
SNOW SHOWERS WILL DEVELOP ACROSS THE REGION BY MID/LATE MORNING AND
CONTINUE THROUGH THE AFTERNOON WITH MVFR CEILINGS. WINDS WILL VEER
TO WESTERLY BY LATE AFTERNOON WITH GUSTS CONTINUING AT OR ABOVE
40KTS. AS THE LOW PULLS AWAY FROM THE REGION WEDNESDAY NIGHT...SNOW
SHOWERS WILL END AND WIND GUSTS WILL BEGIN TO SUBSIDE.
&&
.UPDATE...WILL BE BUMPING UP THE START TIME ON THE WIND ADVISORY TO
090900Z. THINGS SEEM TO BE MOVING A LITTLE FASTER THAN PREVIOUSLY
EXPECTED...WITH OCCLUSION ALREADY INTO SOUTHWEST ILLINOIS. LOOKS
LIKE FRONTAL PASSAGE WILL BE IN THE 090600Z-090900Z TIME FRAME.
GIVEN THE RAPID DEEPENING OF SURFACE LOW EXPECTED AFTER 090600Z AND
THE UNIDIRECTIONAL FLOW THROUGH 850MB AFTER FRONTAL PASSAGE...
CONCERN FOR WIND GUSTS APPROACHING ADVISORY CRITERIA IN THE WAKE OF
FRONT.
WILL ALSO CUT POPS INTO THE CHANCE CATEGORY AFTER 090900Z AS FRONT
SHOULD BE EXITING THE AREA BY THEN. STILL LOOKS LIKE AIR MASS WILL
REMAIN WARM ENOUGH THROUGH MID MORNING WEDNESDAY FOR JUST A RAIN
THREAT.
&&
.DISCUSSION...
NEAR TERM...
STRONG LOW PRESSURE WAS FOUND NEAR THE TEXAS PANHANDLE EARLY THIS
AFTERNOON ALONG WITH A WARM FRONT THAT EXTENDED EAST TO THE
TENNESSEE RIVER VALLEY. ON THE SOUTH SIDE OF THE FRONT TEMPERATURES
AND DEWPOINTS WERE IN THE WARMER 40S AND EVEN 50S ACROSS SOUTHWEST
TENNESSEE. MEANWHILE COLD EASTERLY FLOW WAS IN PLACE ON THE NORTH
SIDE OF THE FRONT...AND INDIANA. ACROSS CENTRAL INDIANA TEMPERATURES
WERE IN THE MIDDLE 30S AND DEWPOINTS WERE IN THE LOWER 30S. RADAR
MOSAICS SHOW FIRST BATCHES OF PRECIPITATION PUSHING ACROSS CENTRAL
INDIANA.
MODELS ARE IN PRETTY GOOD AGREEMENT OVERNIGHT AND HAVE USED A BLEND.
300K GFS ISENTROPIC INDICATES VERY STRONG LIFT THIS EVENING WITH A
VERY MOIST AIR MASS...SPECIFIC HUMIDITIES OVER 5 G/KG. HENCE WILL
USE CATEGORICAL POPS TONIGHT AS TIME SECTIONS AND FORECAST SOUNDINGS
CONFIRM A SATURATED COLUMN. ISENTROPIC LIFT BEGINS TO TAPER OFF
AFTER 06Z AS DRIER AIR WRAPS INTO THE SYSTEM. HAVE TRENDED RAIN
CHANCES LOWER TOWARD 10Z. COLD FRONT SHOULD BE JUST WEST OF INDIANA
NEAR 12Z AND FORECAST SOUNDINGS INDICATE PRECIPITATION SHOULD REMAIN
RAIN UNTIL THEN.
STRONG WARM AIR ADVECTION WILL ALSO BE OCCURRING TONIGHT...AS THE
WARM FRONT SURGES NORTHWARD ON THE NEARLY 70 MPH LOW LEVEL JET. THIS
WILL PLAY HAVOC WITH A TYPICAL DIURNAL TEMPERATURE TREND. AS H8
TEMPS RISE TO NEARLY 6C OVERNIGHT...TEMPERATURES ARE EXPECTED TO
SLOWLY RISE THROUGH THE NIGHT AND LOW TEMPERATURES WILL OCCUR EARLY
THIS EVENING...RIGHT NEAR 00Z. MAVMOS DOES NOT APPEAR TO BE STRONG
ENOUGH WITH THE WARM AIR ADVECTION AND HAVE TRENDED WARMER. WOULD
NOT BE SURPRISED TO SEE A 50 DEGREE TEMPERATURE SOMEWHERE IN CENTRAL
INDIANA OVERNIGHT.
SHORT TERM...
FORECAST FOCUS IN THE SHORT TERM IS ON WINDS AND PRECIPITATION
CHANGEOVER ON WEDNESDAY. MODELS IN DECENT AGREEMENT SO WILL USE A
BLEND UNLESS OTHERWISE NOTED. STRONGEST UPPER FORCING AS
SHOWN BY Q VECTOR CONVERGENCE HAS MOVED OUT THE AREA BY 12Z BUT
FORCING FROM COLD FRONT WILL STILL BE COMING THROUGH. MOISTURE WILL
BE DROPPING OFF AFTER FRONTAL PASSAGE WHICH LOOKS TO BE ARRIVING IN
THE WESTERN COUNTIES RIGHT AROUND 12Z AND THROUGH THE ENTIRE AREA BY
18Z. FOR PRECIPITATION TYPE WITH THE FRONT MOVING THROUGH DURING THE
12-18Z TIME FRAME HAVE TRIED TO ADD A LITTLE TIMING TO CHANGEOVER.
SOUNDINGS LOOK LIKE COLD AIR ALOFT WILL ARRIVE BEFORE/OR CONCURRENT
WITH COLD AIR AT THE SURFACE AND THUS DO NOT HAVE TO WORRY ABOUT
SLEET OR FREEZING RAIN. HAVE INCLUDED A MIX OF RAIN AND SNOW FOR THE
WESTERN AND CENTRAL COUNTIES IN THE MORNING BEFORE CHANGING OVER TO
ALL SNOW IN THE LATE MORNING. FOR THE WEST WILL START OUT WITH
RAIN...THEN CHANGE TO RAIN AND SNOW IN THE LATE MORNING BEFORE
BECOMING ALL SNOW BY AFTERNOON. THE TIMING OF THE START OF
CHANGEOVER IS A LITTLE VARIABLE IN THE MODELS AND WENT WITH THE
SLOWER TIMING OF COLD AIR ARRIVAL BASED ON THE MODELS UNDERDOING THE
WARMING GOING ON OVERNIGHT TONIGHT. TIMING OF ALL SNOW IS CONSISTENT
BY 18Z OVER THE ENTIRE AREA IN ALL OPERATIONAL MODELS AT THIS POINT
SO AM CONFIDENT ANY PRECIPITATION FALLING AFTER THAT TIME WILL BE
SNOW. WITH THE MOISTURE MOVING OUT WITH THE FRONT AND LITTLE OTHER
FORCING BESIDES THE FRONT ITSELF AND THE LOW DO NOT EXPECT MUCH IN
THE WAY OF SNOW ACCUMULATIONS. NORTHERN COUNTIES CLOSEST TO THE LOW
COULD SEE THE HIGHEST AMOUNTS WHICH SHOULD STILL BE LESS THAN AN
INCH. WHILE TEMPERATURES WILL START OUT WARM /IN THE 40S/ EARLY IN
THE DAY /GOING MUCH HIGHER THAN GUIDANCE BASED ON EARLY DAYTIME
HIGHS FOLLOWING SIGNIFICANT OVERNIGHT WARMING/ TEMPERATURES ARE
EXPECTED TO DROP RAPIDLY BEHIND THE FRONT AND SHOULD CONTINUE
FALLING FOR THE REST OF THE DAY. THE WINDS /DISCUSSED BELOW/ PICKING
UP WITH FRONTAL PASSAGE SHOULD BE SUFFICIENT TO DRY MOST OF THE
MOISTURE UP EXCEPT IN SITUATIONS OF LARGE PUDDLES OR PONDING SO DO
NOT EXPECT A WIDESPREAD ICE SITUATION.
NOW ON TO THE WINDS...SURFACE LOW WILL STRENGTHEN RAPIDLY AS IT
MOVES OUT OF THE PLAINS AND INTO THE GREAT LAKES /MOST MODELS
SHOWING OVER 12 MB DROP IN 12 HOURS/. AFTER FRONTAL PASSAGE WINDS
WILL BE FAIRLY UNIDIRECTIONAL WITH HEIGHT AND THUS ABLE TO MIX DOWN
WINDS FROM 3000 TO 5000 FT. THE NAM SHOWS THIS PRODUCING GUSTS FOR A
FEW HOURS OF OVER 50 KTS. THE GFS KEEPS THE GUSTS IN THE 40S. AFTER
COLLABORATION WITH SURROUNDING OFFICES HAVE DECIDED TO ISSUE WIND
ADVISORY FOR TOMORROW. EXPECTING TO SEE WIDESPREAD SUSTAINED WINDS
OF 30-40 MPH WITH GUSTS OF 45 TO 55 MPH. WOULD NOT RULE OUT A FEW
GUSTS AROUND 60 MPH BUT AT THIS POINT THINK THESE WILL BE ISOLATED
AND NOT WIDESPREAD ENOUGH TO WARRANT A HIGH WIND WARNING. STILL
THESE CONDITIONS WILL BE SUFFICIENT TO SIGNIFICANTLY IMPACT TRAVEL
ESPECIALLY FOR HIGH PROFILE VEHICLES SUCH AS SEMIS AND RVS. THE
EFFECT WILL BE THE WORST ALONG NORTH-SOUTH OR NORTHWEST-SOUTHEAST
ROADS. HOLIDAY DECORATIONS...OUTDOOR FURNITURE...AND TRASH CANS ARE
ALSO LIKELY TO BE BLOWN ABOUT OR AWAY IF NOT VERY SECURELY FASTENED.
ISOLATED POWER OUTAGES WILL BE POSSIBLE FROM DOWNED TREE LIMBS.
BY WEDNESDAY NIGHT THE SYSTEM WILL BE PULLING OUT OF THE AREA. THE
WIND GUSTS COULD CONTINUE TO REACH ADVISORY CRITERIA THROUGH SOME OF
THE OVERNIGHT HOURS SO WILL KEEP IT GOING THROUGH THEN. WILL HOLD
ONTO A SLIGHT CHANCE OF SNOW SHOWERS IN THE NORTHEAST FOR SOME
WRAPAROUND. TEMPERATURES WILL CONTINUE DROPPING THROUGH THE NIGHT
AND LOWS ARE EXPECTED TO DROP INTO THE LOW TO MIDDLE TEENS. THIS
WILL LEAD TO WIND CHILLS AROUND DAYBREAK THURSDAY THROUGH MID
MORNING TO BE BELOW ZERO IN THE NORTH AND JUST ABOVE ZERO IN THE
SOUTH. WIND CHILLS DURING THE DAY THURSDAY WILL STILL ONLY WARM TO
THE SINGLE DIGITS ACROSS MOST OF THE AREA WITH TEENS IN THE FAR
SOUTH.
LONG TERM.../FRIDAY THROUGH TUESDAY/
IN THE EXTENDED PERIOD...ARCTIC AIR WILL BE ENTRENCHED ACROSS THE
NORTHERN TIER STATES...WHILE A MOIST AND RATHER ACTIVE PATTERN
OCCURS ACROSS THE SOUTHERN U.S.
ON FRIDAY HIGH PRESSURE WILL MOVE FROM THE OHIO VALLEY TO MID
ATLANTIC STATES. THE EUROPEAN...GEM AND GFS MODELS MOVE AN UPPER
LEVEL DISTURBANCE ACROSS THE DEEP SOUTH LATE FRIDAY AND FRIDAY
NIGHT. THE EUROPEAN BRINGS MOISTURE FROM THIS SYSTEM AS FAR NORTH
AS INDIANA LATE FRIDAY NIGHT AND SATURDAY...WHILE THE GEM...GFS
MODELS KEEP PRECIPITATION SUPPRESSED TO THE SOUTH. HPC WENT CLOSE
TO THE EUROPEAN. BUT WITH THE GEM AND GFS COMING IN DRIER WILL
DOWNPLAY PRECIPITATION A LITTLE.
THIS SOUTHERN SYSTEM MOVES ON TO THE EAST BY SUNDAY. THE EUROPEAN
BRINGS AN UPPER LEVEL DISTURBANCE ACROSS OUR AREA BY MONDAY. BOTH
THE GFS AND GEM SHOW VERY LITTLE MOISTURE NORTH OF THE OHIO
RIVER...SO WILL DOWNPLAY PRECIPITATION CHANCES AGAIN TO A SLIGHT
CHANCE LATER SUNDAY NIGHT AND MONDAY.
THE 12Z GFS DEVELOPS A STRONG UPPER TROUGH ACROSS OUR REGION BY
TUESDAY. IT ALSO TAKES A STRONG SURFACE LOW FROM THE NORTHERN GULF
TO THE MID ATLANTIC STATES AND IN TURN SPREADS PRECIPITATION ACROSS
OUR REGION. I HAVE LOW CONFIDENCE ON THIS AND WILL MENTION SLIGHT
CHANCES OF PRECIPITATION MONDAY NIGHT AND THEN KEEP TUESDAY DRY.
AS FAR AS TEMPERATURES ARE CONCERNED...I TRENDED A FEW DEGREES BELOW
HPC NUMBERS...BUT NOT QUITE AS COLD AS MEX. ON MONDAY NIGHT ...I
WENT SLIGHTLY WARMER THAN HPC TEMPERATURES AS THERE COULD BE QUITE A
BIT OF CLOUDINESS ACROSS OUR REGION.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY FROM 4 AM WEDNESDAY TO 1 AM EST THURSDAY FOR
INZ021-028>031-035>049-051>057-060>065-067>072.
&&
$$
UPDATE...JAS
NEAR TERM...JP
SHORT TERM...CP
LONG TERM...JH
AVIATION...RYAN
