Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 020205
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
905 PM CDT TUE SEP 1 2015

.UPDATE...
ISSUED AT 904 PM CDT TUE SEP 1 2015

THUNDERSTORMS THAT DEVELOPED FROM NEAR DECATUR TO BLOOMINGTON TO
THE CHAMPAIGN AREA EARLIER THIS EVENING ARE GRADUALLY WEAKENING
AS NIGHTTIME COOLING BEGINS TO STABILIZE THE ATMOSPHERE. HAVE
ALREADY DONE A FEW UPDATES FOR THUNDERSTORM COVERAGE THROUGH THE
EVENING BUT GIVEN CURRENT RADAR TRENDS NOT ANTICIPATING ANY
FURTHER UPDATES. LOCALLY HEAVY RAIN OF UP TO AROUND 1 INCH FELL
WITH SEVERAL OF THESE STORMS DUE TO THEIR SLOW MOVEMENT...AND ONE
STORM OVER CENTRAL PIATT COUNTY ACCUMULATED A RADAR ESTIMATED 4
INCHES JUST NORTH OF I-72 AND SOUTHWEST OF LODGE. FOR
TONIGHT...SKIES EXPECTED TO CLEAR AS UPPER LEVEL HIGH PRESSURE
SETTLES OVER THE AREA. COULD SEE SOME FOG OVERNIGHT ESPECIALLY
TOWARD EASTERN PORTIONS OF THE STATE WHERE THE LIGHTEST WINDS ARE
EXPECTED AND IN AREAS WHERE RAIN FELL THIS EVENING. SOME
ADJUSTMENTS FOR FOG COVERAGE WILL BE SENT SHORTLY.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 223 PM CDT TUE SEP 1 2015

LAST OF THE MORNING THUNDERSTORMS EAST OF I-57 HAS FINALLY FADED
AWAY. LATEST WATER VAPOR IMAGERY SHOWS THE UPPER LOW NEAR
INDIANAPOLIS HAS MOVED ONLY SLIGHTLY NORTHEAST...SO SOME DEEPER
MOISTURE REMAINS IN PLACE ACROSS THE EASTERN CWA. NICE AREA OF
SUBSIDENCE SHOWN ON VISIBLE IMAGERY EXPANDING ACROSS NORTHEAST
ILLINOIS AND NORTHWEST INDIANA...ASSOCIATED WITH THE OUTFLOW FROM
THE MORNING CONVECTION...WITH SOME DIURNAL CUMULUS DEVELOPING TO THE
WEST. RADAR SHOWED A COUPLE CELLS TRYING TO FIRE ALONG THE
BOUNDARY... BUT THESE FADED OFF QUICKLY.

CURRENTLY THINK THAT ANY RESIDUAL SHOWERS THAT DO FORM WILL FADE
WITH SUNSET...SO WILL MAINTAIN THE DRY FORECAST FOR TONIGHT. HAVE
ALSO KEPT MENTION OF PATCHY FOG ALONG AND EAST OF I-57...AS THERE IS
NOW QUITE A BIT OF MOISTURE FROM THE EARLIER HEAVY RAINS AND A WEAK
WIND FLOW AT THE SURFACE. WINDS JUST OFF THE DECK PROGGED TO 15-20
KNOT RANGE...SO ANY FOG SHOULD BE RATHER SHALLOW. TEMPERATURES
EXPECTED TO BE FAIRLY UNIFORM OVERNIGHT...MAINLY 67-70 DEGREES OVER
THE FORECAST AREA.

.LONG TERM...(WEDNESDAY THROUGH TUESDAY)
ISSUED AT 223 PM CDT TUE SEP 1 2015

HIGH PRESSURE RIDGE WILL BUILD INTO THE PLAINS TOMORROW AND CONTINUE
THE HOT AND HUMID CONDITIONS THROUGH THE WEEK AND INTO THE WEEKEND.
WITH ALL MODELS FORECAST 850 TEMPS AROUND +18 TO +20C...AM EXPECTING
HIGHS TO BE AROUND 90S INTO THE LOWER 90S THROUGH THE REST OF THE
WEEK AND THROUGH THE WEEKEND...AND LIKELY INTO MONDAY...LABOR DAY.
CONDITIONS THROUGH THE PERIOD SHOULD BE DRY UNTIL LATE IN THE
WEEKEND AND EARLY NEXT WEEK. HOWEVER...THERE IS ONE PERIOD WHERE A
SHORT WAVE TROUGH IS FORECAST TO COME OVER THE TOP OF THE RIDGE WED
AND WED NIGHT THROUGH THE GREAT LAKES REGION INTO INDIANA. THIS
COULD BRING SOME QPF TO THE NORTHEASTERN PARTS OF THE STATE...WHICH
COULD EFFECT NORTHEASTERN AND EASTERN PARTS OF THE CWA. NAM
CONTINUES TO HAVE PCPN IN THE AREA BUT VARIES WITH THE
AMOUNTS...WHILE GFS BRINGS SOME IN BUT ALSO SEEMS TO OVERDO THE
AMOUNT OF QPF. 12Z ECMWF SEEMS MOST CONSISTENT WITH KEEPING PCPN TO
THE NORTH. FOR NOW WILL KEEP PCPN OUT OF THE CWA WED NIGHT AND THU
AND LET OVERNIGHT SHIFT TAKE A LOOK AFTER ANOTHER MODEL RUN.

THE NEXT CHANCE OF PCPN WILL THEN BE LATE IN THE WEEKEND AND THE
BEGINNING OF NEXT WEEK AND A STRONGER MID LEVEL LOW PRESSURE SYSTEM
FLATTENS THE RIDGE OUT AND TRYS TO DRAG A COLD FRONT INTO THE AREA.
MODELS DIFFER ON THE SFC SOLUTION THROUGH THE PERIOD BUT GFS AND
ECMWF DOES APPEAR TO BE IN BETTER AGREEMENT WITH SOME QPF MOVING
INTO THE AREA MONDAY. HOWEVER...THEY DO NOT AGREE WITH AMOUNTS AS
THE GFS WEAKENS THE SYSTEM AS IT MOVES INTO THE AREA. GIVEN THAT THE
PCPN WILL BE MOVING INTO A STRONG RIDGE...AM INCLINED TO LIMIT QPF
AND HAVE GONE WITH SLIGHT CHANCE FOR MON THROUGH MONDAY NIGHT. THIS
BOUNDARY DOES LOOK TO SAG SOUTH ENOUGH THAT MONDAY NIGHT AND TUE IT
LOOKS TO DEVELOP MORE PCPN THAT MOVES INTO THE AREA FOR TUESDAY.
TEMPS WILL FINALLY COOL AS WELL WITH MOST OF THE CWA BEING NORTH OF
THE BOUNDARY AND EFFECTED BY CLOUDS AND PCPN. HIGHS TUESDAY LOOK TO
HAVE COOLED DOWN INTO THE LOWER TO MIDDLE 80S...WITH UPPER 80S CLOSE
TO THE FRONT.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z Wednesday EVENING)
ISSUED AT 647 PM CDT TUE SEP 1 2015

OUTFLOW BOUNDARY FROM THUNDERSTORMS OVER EAST CENTRAL IL EARLIER
TODAY CONTINUES TO PROVIDE A FOCUS FOR THUNDERSTORM DEVELOPMENT
THIS EVENING FROM AROUND KBMI-KDEC-K1H2 ALTHOUGH THESE STORMS
SHOULD DIMINISH WITHIN A FEW HOURS AFTER SUNSET. TERMINALS LIKELY
TO BE AFFECTED BY EVENING THUNDERSTORMS INCLUDE KBMI-KCMI-KDEC.
TOWARD MORNING...FOG AND HAZE DEVELOPMENT IS POSSIBLE ESPECIALLY
AT TERMINALS RECEIVING RAIN THIS EVENING. MAY NEED UPDATES LATER
FOR HEAVIER FOG AT KCMI-KDEC-KBMI DEPENDING ON EVENING RAINFALL
DISTRIBUTIONS. WINDS GENERALLY SW 5-10 KTS THROUGH THE
PERIOD...EXCEPT VARIABLE/GUSTY NEAR ANY THUNDERSTORMS THIS
EVENING.

&&

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

$$

UPDATE...Onton
SHORT TERM...GEELHART
LONG TERM...AUTEN
AVIATION...Onton


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