Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 251709
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1209 PM CDT TUE AUG 25 2015

.UPDATE...
ISSUED AT 945 AM CDT TUE AUG 25 2015

RATHER COOL START TO THE DAY...WITH SEVERAL LOCATIONS FALLING
BELOW 50 DEGREES. TEMPERATURES REBOUNDING NICELY THIS MORNING WITH
SUNSHINE PREVAILING...MAINLY IN THE LOWER TO MID 60S AT 9 AM. AS
THE UPPER LOW CONTINUES TO SPIN OVER EASTERN ONTARIO...THE LARGE
STRATOCUMULUS SHIELD EXTENDING SOUTH ACROSS THE GREAT LAKES WILL
EDGE INTO THE NORTHERN PARTS OF THE FORECAST AREA LATER THIS
MORNING. THE EXISTING FORECAST HAD THESE ASPECTS UNDER
CONTROL...AND LITTLE CHANGE WAS NEEDED.

&&

.SHORT TERM...(TODAY)
ISSUED AT 312 AM CDT TUE AUG 25 2015

DEEP UPPER TROF FOR LATE AUGUST SITUATED JUST NORTH OF LAKE HURON
EARLY THIS MORNING IS FORECAST TO SLOWLY EDGE EAST OVER THE NEXT FEW
DAYS. MEANWHILE...SEVERAL WEAK SHORTWAVES ROTATING SOUTHEAST INTO
THE LOWER GREAT LAKES WITH ONE SUCH FEATURE NOW PUSHING ACROSS SOUTH
CENTRAL LAKE MICHIGAN. THIS WAVE MAY HAVE BEEN RESPONSIBLE FOR
PUSHING THE STRATOCUMULUS DECK A BIT FURTHER SOUTH THAN ANTICIPATED
LATE YESTERDAY THROUGH EARLY THIS MORNING. AS THE WEAK UPPER LEVEL
DISTURBANCE PUSHES FURTHER OFF TO OUR EAST WE SHOULD SEE THE CLOUD
DECK CONTINUE THIN OUT ACROSS OUR NORTHERN COUNTIES. HOWEVER,
ADDITIONAL PIECES OF ENERGY ARE SEEN ROTATING SOUTHWARD AROUND THE
LARGE UPPER LOW AND THAT COMBINED WITH DAYTIME HEATING MAY LEAD TO A
LEAST SOME SCATTERED CLOUD COVER ACROSS THE NORTH LATER THIS MORNING
INTO THE AFTERNOON HOURS. RAP FORECAST SOUNDINGS ONCE AGAIN
INDICATING SOME STEEP LOW AND MID LEVEL LAPSE RATES ASSOCIATED WITH
THE BROAD CYCLONIC FLOW OVER THE REGION WHICH WILL LEAD TO SOME
GUSTY WEST TO NORTHWEST WINDS LATE THIS MORNING THRU THIS AFTERNOON.
850 MB TEMPS A FEW DEGREES COOLER THAN WHAT WE HAD AROUND OUR AREA
YESTERDAY WHICH SHOULD PRODUCE AFTERNOON HIGHS MOSTLY IN THE MIDDLE
70S.

.LONG TERM...(TONIGHT THROUGH MONDAY)
ISSUED AT 312 AM CDT TUE AUG 25 2015

QUIET FORECAST AT LEAST UNTIL THE END OF THE WORK WEEK WITH HIGH
TEMPS SLIGHTLY BELOW NORMAL, BUT SLOWLY WARMING THROUGH THE END OF
THE WEEK AHEAD OF THE NEXT SYSTEM.  OVERNIGHT LOWS ALSO ON THE COOL
SIDE AT LEAST UNTIL THE CLOUDS INCREASE SOMEWHAT AHEAD OF THE NEXT
SYSTEM THURSDAY NIGHT IN THE NORTHWEST.  PRECIP ASSOCIATED WITH THE
UPPER LEVEL WAVE, HOWEVER, NOT ANTICIPATED TO IMPACT CENTRAL
ILLINOIS UNTIL FRIDAY NIGHT/SATURDAY MORNING.  SOME SLIGHT CHANCES
CREEPING INTO NW OF THE ILLINOIS RIVER VALLEY FOR FRIDAY, WITH
CHANCES INCREASING THROUGH THE OVERNIGHT AND INTO SAT MORNING.
UPPER LEVEL DISTURBANCE IS DIFFUSE AND SLOW MOVING IN BOTH THE GFS
AND THE ECMWF.  THE NAM IS STARTING TO COME IN A LITTLE MORE COMPACT
AND QUICKER, SO NOT OVERLY CONFIDENT WITH ANY PARTICULAR SOLUTION.
THE GFS AND ECMWF HAVE BEEN BACK AND FORTH ENOUGH OVER THE LAST
SEVERAL SYNOPTIC RUNS THAT CONSENSUS IS WEAK. ALSO NOT INCLINED TO
LEAVE CHANCE POPS IN THE FORECAST ALL THE WAY THROUGH THE WEEKEND
WITH THAT SLOW OF A SYSTEM.  FOR NOW, WILL KEEP THE CONCENTRATION TO
SATURDAY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1209 PM CDT TUE AUG 25 2015

LITTLE CHANGE REQUIRED TO EXISTING TAF SET. SOME SCATTERED DIURNAL
CUMULUS STARTING TO FORM AROUND 4000 FEET FROM KPIA-KHUF... BUT
THE MAIN AREA OF CEILINGS STILL IN NORTHERN ILLINOIS AND THE GREAT
LAKES...ASSOCIATED WITH LARGE UPPER LOW OVER EASTERN ONTARIO.
SOME ADDITIONAL DEVELOPMENT ON THE SOUTHERN FLANK IS OCCURRING...
SO SOME BRIEF CEILINGS POSSIBLE KPIA-KCMI CANNOT BE RULED OUT FOR
THE NEXT FEW HOURS. CLOUDS EXPECTED TO FADE AWAY WITH SUNSET.

WINDS HAVE BEEN GUSTING FROM 12-18 KNOTS AT MOST SITES RECENTLY...
AND THIS SHOULD CONTINUE THROUGH LATE MORNING BEFORE SETTLING BACK
DOWN.

&&

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

$$

UPDATE...GEELHART
SHORT TERM...SMITH
LONG TERM...HJS
AVIATION...GEELHART



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