Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 070214
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
914 PM CDT MON JUL 6 2015

.UPDATE...
ISSUED AT 905 PM CDT MON JUL 6 2015

BAND OF SHOWERS AND THUNDERSTORMS CONTINUES TO SLOWLY PUSH EAST
AND SOUTHEAST INTO PORTIONS OF WEST CENTRAL IL THIS EVENING. THE
INTENSITY HAS DROPPED OFF CONSIDERABLY DESPITE THE FACT THE
OBJECTIVE ANALYSIS INDICATES MIXED LAYER CAPES OF 1500-2000 J/KG.
HOWEVER...WITH THE LOSS OF DAYTIME HEATING AND SOME RATHER STOUT
LOW LEVEL LAPSE RATES...THE COMBINATION OF VERY WEAK SHEAR ALOFT
AND POOR MID LEVEL LAPSE RATES HAS LED TO AN OVERALL DECREASE IN
INTENSITY. THESE STORMS ARE STILL VERY CAPABLE OF PRODUCING
TORRENTIAL RAINFALL IN A SHORT PERIOD OF TIME WITH PRECIPITABLE
WATER VALUES OF OVER 2 INCHES ACROSS THE ILLINOIS RIVER VALLEY.
THE STORMS WILL CONTINUE TO MAKE SLOW PROGRESS EAST AND SOUTHEAST
OVERNIGHT AS THE COLD FRONT EDGES INTO OUR NORTHWEST COUNTIES
TOWARDS MORNING. CURRENT FORECAST HAS THE EVENING AND OVERNIGHT
TRENDS WELL IN HAND...AS A RESULT...MAKING ONLY MINOR ADJUSTMENTS
TO THE PRECIPITATION WORDING FOR THE OVERNIGHT HOURS. NO ZFP
UPDATE NEEDED AT THIS TIME.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 307 PM CDT MON JUL 6 2015

ISOLATED SHOWERS AND THUNDERSTORMS WERE DEVELOPING DURING PAST HOUR
ALONG OUTFLOW BOUNDARY EAST OF THE IL RIVER FROM MCS OVER IA FROM
NORTH OF LINCOLN TO EAST OF OTTAWA. HAVE STRONGER CONVECTION WITH
HEAVY RAINS AROUND ST LOUIS METRO WHILE MORE WIDESPREAD
SHOWERS/THUNDERSTORMS OVER IA...WI...NORTHERN IL AND NW MO. THIS
CONVECTION IN A VERY UNSTABLE AIRMASS WITH CAPES 2-4 J/KG OVER
CENTRAL/SE IL (3-4K J/KG WEST OF I-57 AT 19Z). BULK SHEAR IS WEAK 20
KTS OR LESS OVER CWA SO ORGANIZED SEVERE WX . COLD FRONT WAS
EXTENDING FROM 1007 MB SURFACE LOW PRESSURE OVER NW WI WITH COLD
FRONT EXTENDING SW THRU CENTRAL IA/KS. ISOLATED TO SCATTERED SHOWERS
AND THUNDERSTORMS TO CONTINUE TO DEVELOP DURING REST OF THIS
AFTERNOON AND EARLY EVENING ESPECIALLY FROM I-57 WEST. COLD FRONT TO
PUSH SE TOWARD I-55 BY 12Z/TUE WITH INCREASING CHANCES OF SHOWERS
AND THUNDERSTORMS FROM NW TO SE DURING THE EVENING OVER CENTRAL IL
AND INTO SOUTHEAST IL LATER TONIGHT INTO TUE. SPC HAS SLIGHT RISK OF
SEVERE STORMS NW OF I-55 LATE THIS AFTERNOON AND EVENING FOR
DAMAGING WIND GUSTS ALONG WITH HAIL. HEAVY RAINS AND FREQUENT
LIGHTNING MAY ALSO OCCUR WITH SOME OF THESE THUNDERSTORMS. LOWS
TONIGHT RANGE FROM MID 60S NW OF THE IL RIVER TO THE LOWER 70S SE OF
I-55 WHICH STAYS IN WARM SECTOR THROUGH TONIGHT.

.LONG TERM...(TUESDAY THROUGH MONDAY)
ISSUED AT 307 PM CDT MON JUL 6 2015

FRONT THAT IS MOVING INTO THE AREA TONIGHT WILL BE SITTING OVER
SOUTHEASTERN PART OF THE STATE TUESDAY. THIS WILL BE THE FOCUS FOR
MORE THUNDERSTORMS FOR TUESDAY AND TUESDAY NIGHT...THAT SHOULD
EFFECT MOSTLY THE SOUTHERN HALF OF THE STATE...OR THE SOUTHERN PART
OF THE CWA. THEN MODELS ARE SIMILAR IN FORECASTING ANOTHER WAVE
LIFTING OUT OF THE SOUTHERN PLAINS ALONG THE FRONT AND ACROSS
CENTRAL ILLINOIS WED THROUGH WED NIGHT...AND THEN MOVING EAST OF THE
AREA EARLY THURSDAY. THUNDERSTORMS WITH MODERATE RAIN CAN BE
EXPECTED TOMORROW AND TOMORROW NIGHT...BUT THEN HEAVY RAINFALL WILL
BE POSSIBLE WHEN THE SFC LOW PRESSURE AREA MOVES ACROSS THE AREA FOR
WED AND WED NIGHT. FLASH FLOOD WATCH MAY BE NECESSARY FOR THIS TIME
PERIOD BUT THINK ANOTHER LOOK TONIGHT AND/OR TOMORROW IS
WARRANTED...AFTER SEEING WHAT THE CONVECTION DOES WITH THE
FRONT/OUFLOW BOUNDARY TOMORROW AND TOMORROW NIGHT.

UNFORTUNATELY THE BOUNDARY REMAINS AROUND OR NEAR THE AREA THE
REST OF THE WEEK...WHICH WILL KEEP A CHANCE OR LIKELY PCPN IN THE
AREA THROUGH FRI NIGHT. THE FRONT SHOULD BE LIFTING FRI NIGHT AS
WELL...WHICH WILL PUSH THE CHANCE OF PCPN NORTH OF THE I-74 FRIDAY
NIGHT THROUGH SUNDAY. THEN MODELS BRING ANOTHER WEATHER SYSTEM
ACROSS ILLINOIS WITH MORE PCPN FOR SUNDAY NIGHT AND MONDAY.

AFTER THIS FRONT MOVES THROUGH THE AREA...TEMPS WILL COOL A LITTLE.
BUT THEN THEY WILL WARM AGAIN FOR THE WEEKEND AND INTO NEXT WEEK.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)
ISSUED AT 545 PM CDT MON JUL 6 2015

MAIN CONCERN THIS FORECAST PERIOD WILL BE COVERAGE OF TSRA ACROSS
THE FORECAST AREA AND AFFECT ON CIGS/VSBYS. COLD FRONT WELL OUT TO
OUR WEST EARLY THIS EVENING WILL TAKE UNTIL TOMORROW MORNING
BEFORE IT MAKES IT ACROSS THE AREA. MOST MODELS SUGGEST A BAND OF
SHOWERS AND STORMS WILL ACCOMPANY THE FRONT SLOWLY EAST AND
SOUTHEAST TONIGHT INTO TUESDAY MORNING. INITIALLY...WE SHOULD SEE
VFR CONDITIONS BUT AS THE PRECIP TRACKS ACROSS THE AREA...LOW VFR
TO BRIEF MVFR CIGS CAN BE EXPECTED. POST FRONTAL MVFR CIGS ARE
EXPECTED GENERALLY IN THE TIME RANGE BETWEEN 08Z AND 12Z FROM
WEST TO EAST. THEN AS WINDS SHIFT FROM A SOUTH TO SOUTHWEST
DIRECTION INTO THE NORTHEAST BY MORNING...MOST OF THE FORECAST
MODELS INDICATE AT LEAST MVFR CIGS WILL HANG AROUND INTO THE
AFTERNOON HOURS WITH A FEW MODELS SUGGESTING SOME PERIODIC
IFR CIGS AS WELL AS THE NORTHEAST TO EAST FLOW BUILDS IN DURING
THE DAY. WIND SPEEDS TONIGHT WILL BE AT 8 TO 13 KTS FROM THE
SOUTH TO SOUTHWEST AND THEN NORTHEAST AT 10 TO 15 KTS DURING
THE DAY ON TUESDAY.


&&

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

$$

UPDATE...SMITH
SHORT TERM...07
LONG TERM...AUTEN
AVIATION...SMITH


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