Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 261901
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
201 PM CDT WED AUG 26 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 200 PM CDT WED AUG 26 2015

LARGE STRATOCUMULUS SHIELD THAT HAS PUSHED SOUTHWARD ACROSS THE
NORTHEAST QUARTER OF THE STATE WAS FINALLY STARTING TO SHOW SOME
CONTRACTION EARLY THIS AFTERNOON. HOWEVER...IT IS FLANKED ON MOST
SIDES BY DIURNAL DEVELOPMENT...SO NET RESULT CONTINUES TO BE QUITE A
BIT OF CLOUDS ESPECIALLY ACROSS THE EAST HALF OF THE CWA. THE 900 MB
PLOT OFF THE RAP MODEL CONTINUES TO DEPICT THE CLOUD SHIELD THE
BEST...AND SHOWS SOME CONTRACTION CONTINUING THIS AFTERNOON. MOST OF
THE DIURNAL CLOUDS SHOULD FADE WITH SUNSET. HOWEVER...SOME RESIDUAL
MOISTURE SHOULD LINGER FROM THE PERSISTENT CLOUDS...AND WILL GO WITH
PARTLY CLOUDY SKIES ACROSS THE NORTHEAST CORNER OF THE FORECAST AREA
NEAR DANVILLE AND CHAMPAIGN.

WITH HIGH PRESSURE OVERHEAD...ENOUGH CLEAR SKIES EXPECTED THAT MOST
AREAS SHOULD FALL INTO THE MID 50S OVERNIGHT. HOWEVER...SOME
ADJUSTMENTS MAY BE NEEDED ACROSS THE NORTHEAST IF THE CLOUDS DO NOT
CLEAR OUT FAST ENOUGH...AS HAS BEEN THE CASE THE LAST COUPLE NIGHTS.

&&

.LONG TERM...(THURSDAY THROUGH WEDNESDAY)
ISSUED AT 200 PM CDT WED AUG 26 2015

ZCZC CHIWRKAFD 260823
TTAA00 KCHI DDHHMM

LATEST MODEL SOLUTIONS IN REASONABLE AGREEMENT FOR ILLINOIS OVER THE
REST OF THE WEEK.  MODELS DIFFER IN STRENGTH AND MOISTURE
AVAILABILITY OF SOUTHERN STREAM WAVE CURRENTLY OVER FOUR CORNERS AREA
AND EXPECTED TO RIDE OVER RIDGE INTO ILLINOIS THIS WEEKEND.

WATER VAPOR IMAGERY SHOWS WAVE OVER NORTHERN ARIZONA THIS MORNING
PUSHING NORTHWARD OVER STRONG ROCKIES RIDGE. MODEL SUITE CONSISTENT
ON BRINGING ENERGY UP OVER THE RIDGE AND INTO MIDWEST FRIDAY AND
SATURDAY. UNTIL THEN...DRY CONDITIONS AND A WARMING TREND IS
EXPECTED AS 850 TEMPS CLIMB 5-10 DEGREES C BETWEEN THIS MORNINGS
RAOB AND FRIDAY EVENING. INCREASING HIGH CLOUDS AHEAD OF THE WAVE
MAY INHIBIT WARMING A BIT FOR FRIDAY...BUT TEMPS SHOULD STILL MAKE
IT INTO THE 80S THROUGHOUT FORECAST AREA BY FRIDAY AFTERNOON.

WAVE APPROACHING FOR THE FIRST PART OF THE WEEKEND IS MOVING INTO A
RELATIVELY DRY BUT MOISTENING AIRMASS. IN ADDITION...DIGGING OF
NORTHERN STREAM ENERGY ALONG THE WEST COAST SHOULD SLOW PROGRESSION
OF SYSTEMS AND THEREFORE SLOW THE INCOMING WAVE. CHANCE OF STORMS
ARE EXPECTED IN THE NORTHWEST BY LATE AFTERNOON FRIDAY AND ACROSS
MUCH OF THE AREA FRIDAY NIGHT AND PARTICULARLY SATURDAY. MAIN MODEL
DIFFERENCES BEGIN TO SHOW UP TOWARD THE END OF THE WEEKEND. LATEST
AVAILABLE ECMWF RUNS HAVE BEEN CONSISTENT ON BEING STRONG ENOUGH
WITH THIS WAVE TO DEVELOP DECENT NVA IN ITS WAKE ON SUNDAY AND
SHUNTING MOISTURE EAST OF THE AREA.  THIS LEADS TO A RELATIVELY DRY
BUT INCREASINGLY HOT FORECAST AS THE LONGWAVE RIDGE AXIS MOVES
ACROSS THE AREA. MEANWHILE...THE 06Z AND 12Z GFS TRENDING WEAKER
WITH THE WAVE AND FORECAST AN EVOLUTION TO JUST A GENERAL WEAKNESS
OVER THE AREA THROUGH EARLY NEXT WEEK. THIS EVOLUTION SUGGESTS AT
LEAST A SLIGHT CHANCE OF THUNDERSTORMS AND LOWER TEMPERATURES
WITH GENERALLY MORE CLOUD COVER. AM LEANING TOWARD A COMPROMISE
WITH A NOD TOWARD THE GFS WHICH SEEMS TO BE SUPPORTED BY THE CMC
AND GEFS MEAN. A QUICK LOOK AT 12Z ECMWF ALSO SUGGESTS IT MAY BE
SWINGING BACK TOWARD A WEAKER SOLUTION.

ANY CONVECTION THAT DEVELOPS THIS WEEKEND INTO NEXT WEEK SHOULD HAVE
LIMITED SEVERE POTENTIAL DUE TO LOW SHEAR IN THE RIDGE AND LIMITED
INSTABILITY GIVEN THE WARM 500 MB TEMPS CLIMBING ABOVE -10C. BIGGEST
THREAT MAY BE LOCALLY HEAVY RAINFALL DUE TO SLOW MOVEMENT.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1220 PM CDT WED AUG 26 2015

LARGE MVFR STRATOCUMULUS DECK CONTINUES TO EDGE SOUTHWARD...
HAVING CLIPPED KBMI AND IS COMING FAIRLY CLOSE TO KCMI AT MIDDAY.
LATEST RAP GUIDANCE DOES NOT SHOW A LOT MORE FURTHER PROGRESS.
HAVE MAINTAINED THE MVFR CONDITIONS AT KBMI AND INCLUDED A TEMPO
MVFR CEILING AT KCMI FOR THE NEXT FEW HOURS. TAF SITES FURTHER
WEST MAINLY BEING AFFECTED BY DIURNAL CUMULUS CLOSER TO 4000
FEET...AND THIS SHOULD FADE WITH SUNSET. VFR CONDITIONS EXPECTED
OVERNIGHT...WITH LIGHT WINDS GRADUALLY TRANSITIONING MORE TOWARD
THE SOUTHEAST AS AN AREA OF HIGH PRESSURE PASSES.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...GEELHART
LONG TERM...BARKER
AVIATION...GEELHART



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