195
FXUS63 KIWX 090542
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1242 AM EST MON NOV 9 2009
AVIATION
LOW PRES OVER WI WILL MOVE RAPIDLY NE TODAY WITH TRAILING CDFNT
MOVG EAST ACROSS THE AREA THIS AFTN. WINDS INCRSG AHEAD OF THE
FRONT THIS MORNING WITH WOLCOTT PROFILER SHOWING 40KT AROUND 2KFT
IN PAST HR. WITH SOME DECOUPLING OVERNIGHT THERE IS POTENTIAL FOR
LLWS AND HAVE ADDED TO TAFS. CIRRUS STREAMING NEWD INTO THE AREA
ALONG WITH CONTD MIXING DUE TO S-SW GRADIENT...SHOULD LIMIT
RADIATIONAL COOLING OVERNIGHT THUS REMOVED BR FROM FCST.
CONVERGENCE ALONG FRONT MAY SUPPORT SOME LOW CLOUDS BUT SHOULD
REMAIN VFR THROUGH THE PD.
PREV DISCUSSION
/ISSUED 1128 PM EST SUN NOV 8 2009/
UPDATE...
S-SW WINDS PICKING UP LATE THIS EVE...ESPECIALLY NR LM AS LOW
PRESSURE MOVG NE INTO WI WITH WITH TRAILING CDFNT MOVG EAST ACROSS
IA. UPDATED NSH WINDS TO INCREASE TO JUST BLO SCA CRITERIA. LAND
WIND GRIDS IN 5-15MPH RANGE STILL LOOK GOOD AND NO CHANGES MADE,
HWVR, DID REMOVE MENTION OF FOG FROM THE GRIDS AS APPEARS THERE
WILL BE SUFFICIENT MIXING AND INCRSG CIRRUS TO PREVENT SGFNT VSBY
RESTRICTIONS LATE TONIGHT OR EARLY MONDAY.
PREV DISCUSSION... /ISSUED 640 PM EST SUN NOV 8 2009/
AVIATION...
SATELLITE SHOWING SCT CIRRUS TO OUR SOUTHWEST MOVING THIS WAY. THESE
HIGH CLOUDS COUPLED WITH A LIGHT SOUTHERLY WIND OVERNIGHT SHOULD
HELP LIMIT BR FORMATION. CONDITIONS STILL WARRANT CONTINUING WITH
MVFR CONDITIONS. WEAK FRONTAL BOUNDARY APPROACHES ON MONDAY WITH
INCREASING AND LOWERING CLOUDS THROUGH THE DAY. MOISTURE LIMITED SO
JUST BROUGHT CIGS DOWN TO LOW END VFR FOR NOW BY END OF PERIOD. WIND
SHIFT WILL ALSO ACCOMPANY THIS FRONT IN THE AFTERNOON.
SHORT TERM...
SECOND HALF OF A BEAUTIFUL WEEKEND TODAY AS LAST NIGHTS WEAK FRONTAL
BOUNDARY HAS LIFTED BACK NORTH RESUMING WARM SW FLOW ALLOWING TEMPS
TO RISE NEAR 70 ACROSS THE CWA. 12Z MODELS INDICATING SOME VERY DRY
AIR ALOFT WITH DEWPOINT DEPRESSIONS ABOVE H7 AOA 30C WRAPPING
INTO THE REGION WITH THE LAST GASP OF RIDGING OVER THE SOUTHEAST.
THIS SHOULD PRECLUDE ANYTHING BUT HIGH CLOUDS TONIGHT AND WITH XOVER
TEMPS EVEN HIGHER IN THE LOW 50S FEEL THAT SOME PATCHY FOG
DEVELOPMENT IS POSSIBLE ALTHOUGH THE PRESENCE OF GRADIENT WINDS...
SOMEWHAT LESS MOISTURE IN THE NEAR SFC LAYER...AND POSSIBILITY OF
CIRRUS MAKING HEADWAY INTO THE REGION SHOULD MITIGATE THE MORE DENSE
VARIETY WE SAW THIS MORNING. ADDITIONALLY DEEPER MOISTURE WILL
POTENTIALLY ARRIVE JUST BEFORE DAWN IN THE WEST PUTTING A CLAMP ON
TEMPERATURE DROP .
SFC LOW PRESSURE TO OUR NW TODAY WILL RAPIDLY PROGRESS THROUGH
SOUTHERN QUEBEC TO THE CANADIAN ATLANTIC COAST THROUGH MONDAY NIGHT
TRAILING A LONG COLD FRONT THAT BECOMES SLOW MOVING AS UPPER FLOW
LARGELY PARALLELS THE BOUNDARY THROUGH THE PERIOD. RESULTANT LOW
LEVEL CONVERGENCE ASSOC WITH FRONTAL PASSAGE IS UNIMPRESSIVE AND
INSTABILITY AHEAD OF THE FRONT ON MONDAY AFT/EVENING IS SIMILARLY
PALE WITH LI/S OF -1/-2 AND MUCAPES AOB 200J/KG. ADDITIONALLY BUFR
SOUNDINGS SHOW CONSIDERABLE WARM AIR ALOFT TRASHING LAPSE RATES.
WILL THEREFORE NOT INTRODUCE THUNDER WORDING...AND CONTINUE THE
GOING TREND OF POPS FROM NW TO SE ALONG AND POST-FRONTAL AS LOW
LEVELS ATTEMPT TO SATURATE WITHIN MODEST MOISTURE INCREASE WITH
PASSAGE OF THE FRONT. MINOR ADJUSTMENTS MADE TO POPS BASED ON 12Z
MODEL TIMING BUT THE GENERAL APPROACH REMAINS INTACT.
LONG TERM /TUESDAY THROUGH SUNDAY/...
CONFIDENCE IS STARTING TO WANE FOR THE EXTENDED FORECAST AS THE
MOVEMENT AND EVENTUAL EXTRATROPICAL TRANSITION OF IDA THIS WEEK WILL
PLAY A STRONG ROLE IN AUGMENTING THE DOWNSTREAM FLOW PATTERN WITH
RAMIFICATIONS IN THIS AREA. THIS LOSS OF CONFIDENCE IS SHOWN WELL
IN THE GEFS RMOP GRAPHICS...WHICH FROM LAST NIGHT/S 00Z SIMULATION
SHOW LESS THAN A 20 PERCENT PROBABILITY OF THE GEFS MEAN FORECAST
VERIFYING BY THE END OF THE PERIOD. BELIEVE THAT THE MAIN IMPACT OF
IDA WILL LIKELY BE TO SLOW DOWN THE UPSTREAM FLOW PATTERN AS BOTH
THE GFS/ECMWF SHOW A PRETTY INTENSE CUT OFF LOW FORMING OFF THE
EASTERN US COAST BY THE WEEKEND.
OUTSIDE OF IDA...THE CORE OF LOW HEIGHT ANOMALIES OVER EASTERN
SIBERIA WILL MOVE EAST...TAKING UP RESIDENCE OVER ALASKA. THIS WILL
PUSH A LOW HEIGHT ANOMALY CURRENTLY OVER THE GULF OF ALASKA INTO THE
WESTERN NOAM...WITH IT/S EASTWARD PROGRESS TOWARDS OUR AREA IMPEDED
BY THE ABOVE MENTIONED IMPACTS OF IDA.
FRONT PASSING TO START THE PERIOD WILL TAKE ON A ANA-FRONT STRUCTURE
WITH CONTINUED LIFT WELL BEHIND THE LLEVEL FRONTAL BOUNDARY. GIVEN
THIS STRUCTURE...AND THE INCREASED AMOUNT OF DOWNSTREAM
BLOCKING...EXPANDED TUESDAY AFTERNOON POPS NORTH AND WEST...AND THIS
TREND MAY HAVE TO BE FURTHERED BY LATER SHIFTS. CLOUDS/PRECIP
CHANCES WILL ALSO KEEP TEMPS DOWN...AND WILL CONTINUE CONSERVATIVE
HIGH TEMP FORECAST...WITH TEMPS IN THE LOWER/MIDDLE 50S...A LITTLE
BELOW FULLY MIXED T92 VALUES.
THE NICE STRETCH OF MID/LATE WEEK WEATHER STILL APPEARS TO BE IN
TACT WITH SURFACE RIDGING BUILDING IN FOR THE WEDNESDAY-FRIDAY TIME
PERIOD. TEMPS WEDNESDAY WILL NOT REBOUND EVEN WITH MORE SUN AS COLD
ADVECTION ON THE WESTERN FLANK OF DEVELOPING EAST COAST CUTOFF WILL
LOWER T92 TO AROUND 3C. BY THURSDAY AND FRIDAY...EXPECT MODERATING
TEMPERATURES AS RIDGING ALOFT SHOULD BEGIN BUILDING IN FROM THE WEST
AND ALLOW TEMPS ALOFT TO REBOUND. HIGHS IN THE MID/UPPER 50S LOOK
GOOD GIVEN T92 7-8C.
BY NEXT WEEKEND...WESTERN CONUS TROUGHING SHOULD CONTINUE TO SLOWLY
TRUDGE EAST...GIVEN PERSISTENT WESTERLY FLOW UPSTREAM SOUTH OF THE
ALASKA LOW HEIGHT ANOMALY. HOWEVER...GIVEN THE DOWNSTREAM BLOCKING
INFLUENCE OF IDA OR IT/S REMNANTS...EXPECT THAT IT WILL TAKE MOST OF
THE WEEKEND FOR ANY FRONTAL SYSTEM TO REACH OUR AREA. THEREFORE...
WILL KEEP SATURDAY DRY...BUT INTRODUCE CHC POPS SATURDAY
NIGHT/SUNDAY. CERTAINLY LOW CONFIDENCE AT THIS RANGE...BUT GIVEN
THE PROXIMITY OF THE TROUGH...BELIEVE POPS AT OR ABOVE CLIMO /ABOUT
30 PERCENT AT SBN-FWA / ARE WARRANTED. WILL CONTINUE TEMPS ABOVE
CLIMO SATURDAY...AND THEN TREND TO JUST ABOVE CLIMO SUNDAY GIVEN
UNCERTAINTY IN THE TIMING OF THE ARRIVING TROUGH. THIS YIELDS MID
50S FOR HIGHS SATURDAY...AND LOWER 50S SUNDAY.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
SHORT TERM...LUDINGTON
LONG TERM...ARNOTT
AVIATION...JT
UPDATE...JT
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