Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 290134
AFDILX

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

.UPDATE...
ISSUED AT 825 PM CDT THU MAY 28 2015

LATEST SURFACE ANALYSIS HAS A WARM FRONT BOUNDARY STRETCHING FROM
NEAR PEORIA THRU BLOOMINGTON EAST TO JUST NORTH OF CHAMPAIGN. DEW
POINTS SOUTH OF THE BOUNDARY WERE IN THE LOW TO MID 60S...WHILE TO
THE NORTH OF THE FRONT...SURFACE DEW POINTS WERE IN THE MID 40S TO
LOW 50S. THE WIDELY SCATTERED STORMS THE FIRED EARLIER TODAY ALONG
THE BOUNDARY HAVE SINCE DISSIPATED WITH A COUPLE OF STORMS ABLE TO
PRODUCE WIND GUSTS AROUND 45 MPH AND UP TO PENNY SIZE HAIL IN
SPRINGFIELD...ALONG WITH REPORTS OF TORRENTIAL RAINFALL. LATEST
ILX OBJECTIVE MESO-ANALYSIS HAS BEEN SHOWING A RATHER SHARP CUTOFF
OF INSTABILITY OVER THE FORECAST AREA LATE THIS AFTERNOON INTO
EARLY THIS EVENING...WITH THE BULK OF THE HIGHER MIXED LAYER AND
MOST UNSTABLE CAPES REMAING OVER SOUTHWEST ILLINOIS. THE 00Z ILX
SOUNDING PRETTY WELL SUMS UP WHY THE STORMS DISSIPATED AS QUICKLY
AS THEY DID OVER CENTRAL ILLINOIS WITH THE LACK OF ANY INSTABILITY
NOTED FROM LINCOLN NORTH AND EAST.

A SECOND AREA OF MOSTLY SHOWERS...WITH SOME OCCASIONAL LIGHTNING
STRIKES...WAS LOCATED OVER EXTREME WEST CENTRAL ILLINOIS AND
WAS DRIFTING MORE NORTH THAN EAST OVER THE PAST SEVERAL HOURS.
THIS BAND OF SHOWERS WAS ASSOCIATED WITH A WEAK UPPER LEVEL WAVE
OVER SOUTHWEST MISSOURI EARLY THIS EVENING. MOST OF THE SHORT TERM
FORECAST SOLUTIONS SUGGEST THE BULK OF THE ACTIVITY WILL REMAIN
OVER WEST CENTRAL ILLINOIS WITH A CONTINUED NORTH TO NORTHEAST
MOVEMENT. THIS SHOULD KEEP THE HIGHER CHANCE (ISOLATED TO WIDELY
SCATTERED) POPS OVER THE WESTERN HALF OF THE FORECAST AREA THRU
THE EARLY MORNING HOURS. AFTER 09Z/4AM...IT APPEARS THE SHORTWAVE
OVER MISSOURI WILL PUSH ACROSS THE AREA WITH AN INCREASING CHANCE
FOR SHOWERS OVER THE EAST. CURRENT FORECAST HAS THIS DEPICTED WELL
THIS EVENING SO WILL BE MAKING ONLY MINOR ADJUSTMENTS TO THE POPS
AND HOURLY TEMPERATURE GRIDS (THANKS TO THE COOLING AFFECTS FROM
THE OUTFLOW BOUNDARY THAT PUSHED THRU THE AREA WITH THE SCATTERED
STORMS). THE UPDATED FORECAST SHOULD BE OUT BY 845 PM.

&&

.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 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 550 PM CDT THU MAY 28 2015

MAIN CONCERN WILL BE COVERAGE OF TSRA THIS EVENING AND AGAIN AFTER
MIDNIGHT TONIGHT AND ANY AFFECT ON CIGS ACROSS THE FORECAST AREA.
WDLY SCATTERED TSRA OCCURRING FROM NEAR JACKSONVILLE SOUTHEAST TO
JUST NORTH OF EFFINGHAM WITH THIS AREA EXPECTED TO DIMINISH AFTER
00Z. MAY SEE SOME OF THIS ACTIVITY AFFECT KSPI OVER THE NEXT HOUR
OR TWO SO WE MAY HAVE TO ADD A TEMPO GROUP FOR THIS LOCATION EARLY
THIS EVENING.

ANOTHER WAVE SEEN ON SATELLITE DATA ACROSS SOUTHWEST MISSOURI
WILL SPREAD SHOWERS AND TSRA INTO AT LEAST OUR WESTERN AREAS AFTR
05Z BUT COVERAGE AT THIS POINT STILL UNCERTAIN SO WILL CONTINUE
TO HOLD ON TO VCSH/VCTS FOR THE OVERNIGHT HOURS. UNLESS ONE OF
OUR TAF SITES GETS SOME OF THE SHOWER ACTIVITY MOVE OVER THEIR
AREA THIS EVENING OR LATE TONIGHT/FRI...WE EXPECT VFR CONDITIONS
TO PREVAIL DURING THIS FORECAST PERIOD. LOOK FOR SOUTHEAST TO
SOUTH WINDS OF 7 TO 12 KTS TONIGHT AND SOUTHERLY WINDS AT 10 TO 15
KTS DURING THE DAY FRIDAY.


&&

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

$$

UPDATE...SMITH
SHORT TERM...ONTON
LONG TERM...BARNES
AVIATION...SMITH



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