Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 282015
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
315 PM CDT THU MAY 28 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 314 PM CDT THU MAY 28 2015

19Z/2PM SURFACE ANALYSIS SHOWS WARM FRONT EXTENDING ALONG A QUINCY
TO PARIS LINE.  NORTH OF THE BOUNDARY ACROSS THE NORTHERN HALF OF
THE KILX CWA...AN EASTERLY FLOW AND AMPLE MIXING HAS RESULTED IN LOW
DEWPOINT READINGS IN THE UPPER 40S AND LOWER 50S.  MEANWHILE SOUTH
OF THE FRONT...SOUTHERLY FLOW HAS BROUGHT A MORE HUMID AIRMASS INTO
SOUTH-CENTRAL ILLINOIS WITH DEWPOINTS RISING INTO THE LOWER TO
MIDDLE 60S.  ISOLATED THUNDERSTORMS ARE BEGINNING TO DEVELOP
ALONG/JUST SOUTH OF THE FRONT AND WILL CONTINUE TO DO SO FOR THE
BALANCE OF THE AFTERNOON.  RAPID REFRESH HAS VERIFIED QUITE NICELY
TODAY...SO WILL FOLLOW ITS SOLUTION CLOSELY FOR THE SHORT-TERM.
EXPECT ISOLATED CELLS TO DRIFT SLOWLY NORTHWARD...REACHING A CANTON
TO PARIS LINE DURING THE EARLY EVENING BEFORE GRADUALLY DISSIPATING
AFTER SUNSET.  AFTER THAT...THERE WILL LIKELY BE A LULL IN THE
CONVECTION FOR SEVERAL HOURS UNTIL A SHORT-WAVE TROUGH NOTED ON
LATEST WATER VAPOR IMAGERY OVER EASTERN KANSAS/OKLAHOMA LIFTS
NORTHEASTWARD INTO ILLINOIS AFTER MIDNIGHT.  WILL CARRY CHANCE POPS
IN CONJUNCTION WITH THIS WAVE OVERNIGHT...PRIMARILY ALONG/WEST OF I-
55.  FURTHER EAST...WILL MAINTAIN DRY CONDITIONS THROUGH DAWN
FRIDAY.

&&

.LONG TERM...(FRIDAY THROUGH THURSDAY)
ISSUED AT 314 PM CDT THU MAY 28 2015

A COLD FRONT CURRENTLY MOVING INTO THE NORTHERN PLAINS WILL BE
APPROACHING THROUGH THE DAY FRIDAY AS WARM MOIST SOUTHERLY FLOW WITH
PRECIPITABLE WATER VALUES AROUND 1.5 INCHES SURGES INTO CENTRAL
IL...PRODUCING MLCAPE VALUES AROUND 1000-1500 JOULES. SFC-6KM BULK
SHEAR VALUES LOOK TO REMAIN AROUND 20 KTS OR LESS THROUGH THE
AFTERNOON AND EARLY EVENING. SEVERE WEATHER THREAT CONTINUES TO BE
IN MARGINAL THREAT CATEGORY ACCORDING TO SPC. TIMING OF
THUNDERSTORMS IN THIS REGIME REMAINS HIGHLY UNCERTAIN AS IT WILL
DEPEND ON SCATTERED THUNDERSTORMS AND SOME POTENTIAL CLUSTERS OF
THUNDERSTORMS. FRONTAL ZONE APPROACHING OVERNIGHT SHOULD BRING A
MORE PRONOUNCED COVERAGE OF THUNDERSTORMS...HOWEVER INSTABILITY WILL
BE WANING WITH NOCTURNAL COOLING AND SEVERE STORMS WILL BECOME LESS
LIKELY OVERNIGHT. THE FRONT LOOKS TO PASS INTO SOUTHEAST IL SOUTH OF
I-70 EARLY IN THE AFTERNOON SATURDAY...WITH MARGINAL SEVERE WEATHER
THREAT SHIFTING INTO THIS AREA.

MUCH COOLER AIR BEHIND THE FRONT WILL PRODUCE HIGHS IN THE 60S
SUNDAY...STEADILY WARMING THROUGH THE WEEK AS A HIGH PRESSURE RIDGE
BUILDS INTO THE AREA. SUNDAY NIGHT THROUGH WED NIGHT SHOULD SEE
LITTLE CHANCE FOR PRECIPITATION ALTHOUGH THE CONVECTION TO THE
SOUTHEAST OF THE AREA WILL RESULT IN KEEPING AT LEAST A SLIGHT
CHANCE OF PRECIPITATION IN SOUTHEAST ILLINOIS FOR MUCH OF THIS TIME.
ANOTHER SURGE OF SOUTHERLY FLOW  BY THURSDAY WILL RESULT IN A CHANCE
FOR PRECIPITATION.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1258 PM CDT THO MAY 28 2015

CU-FIELD HAS DEVELOPED ALONG/SOUTH OF A STATIONARY FRONTAL
BOUNDARY ACROSS SOUTH-CENTRAL ILLINOIS EARLY THIS AFTERNOON AND
WILL CONTINUE TO DEVELOP/SPREAD SLOWLY NORTHWARD OVER THE NEXT FEW
HOURS. MODELS ARE SHOWING ISOLATED SHOWERS/STORMS DEVELOPING IN
THE VICINITY OF THE FRONT...THEN TRACKING NORTHWARD ACROSS MAINLY
WESTERN ILLINOIS LATER THIS AFTERNOON AND EVENING. LATEST RADAR
MOSAIC IS SHOWING A FEW SHOWERS BEGINNING TO POP UP SOUTH AND WEST
OF SAINT LOUIS...SO THIS SOLUTION SEEMS REASONABLE. HAVE THEREFORE
INCLUDED VCSH AT BOTH KSPI AND KPIA THIS EVENING. FURTHER
EAST...WILL REMAIN DRY WITH ONLY HIGH CLOUDINESS EXPECTED. AS A
FRONTAL BOUNDARY BEGINS TO APPROACH FROM THE NORTHWEST...HIGH
DEWPOINT AIR WILL OVERSPREAD ALL OF CENTRAL ILLINOIS BY FRIDAY
MORNING. MAIN FOCUS FOR CONVECTION WILL REMAIN WEST OF THE AREA
UNTIL LATE IN THE DAY...SO HAVE KEPT TAFS DRY THROUGH 18Z.


&&

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

$$

SHORT TERM...ONTON
LONG TERM...BARNES
AVIATION...BARNES



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