Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 041545
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1045 AM CDT MON MAY 4 2015

.UPDATE...
ISSUED AT 1045 AM CDT MON MAY 4 2015

15Z/10AM SURFACE ANALYSIS SHOWS STATIONARY FRONTAL BOUNDARY
EXTENDING FROM SOUTHERN LAKE MICHIGAN TO KANSAS. WIDELY SCATTERED
SHOWERS ARE CURRENTLY ONGOING NEAR AND JUST SOUTH OF THE FRONT
ACROSS MUCH CENTRAL ILLINOIS...ALTHOUGH AREAL COVERAGE OF PRECIP
HAS BEEN DIMINISHING OVER THE PAST COUPLE OF HOURS. 12Z NAM
SUGGESTS THE GREATEST INSTABILITY AND STRONGEST LOW-LEVEL WIND
SHEAR WILL OVERLAP NEAR AN AREA OF LOW PRESSURE ALONG THE BOUNDARY
FROM SOUTHERN IOWA SOUTHWESTWARD INTO KANSAS LATER THIS AFTERNOON.
THINK THIS WILL BE THE PRIMARY AREA WHERE WIDESPREAD CONVECTION
WILL DEVELOP...WITH ONLY SCATTERED SHOWERS/STORMS FURTHER EAST
ACROSS ILLINOIS WHERE INSTABILITY/SHEAR WILL BE WEAKER. HRRR SHOWS
THIS TREND AS WELL...WITH CONVECTION DEVELOPING/SPREADING EASTWARD
ACROSS THE NORTHERN HALF OF THE KILX CWA AFTER SUNSET. HAVE MADE
SOME MINOR ADJUSTMENTS TO THE FORECAST...MAINLY TO FEATURE
SCATTERED POPS ALONG/NORTH OF I-72 TODAY AND ONLY ISOLATED FURTHER
SOUTH. BETTER RAIN CHANCES WILL ARRIVE TONIGHT. WITH SOME PARTIAL
SUNSHINE...AFTERNOON HIGH TEMPERATURES WILL RISE INTO THE UPPER
70S AND LOWER 80S.

&&

.SHORT TERM...(TODAY)
ISSUED AT 342 AM CDT MON MAY 4 2015

OUTFLOW BOUNDARY FROM CONVECTION THAT DEVELOPED AHEAD OF A FRONTAL
BOUNDARY EXTENDING THROUGH THE GREAT LAKES AND INTO THE CENTRAL
PLAINS HAS MOVED INTO PORTIONS OF THE CENTRAL IL FORECAST
AREA...EXTENDING FROM NEAR PEORIA TO PONTIAC. BOUNDARY CONTINUES TO
TRIGGER SCATTERED THUNDERSTORMS BEHIND IT...WHILE AHEAD LIGHT
SHOWERS ARE WIDELY SCATTERED ACROSS CENTRAL IL. MID-LEVEL
INSTABILITY ACROSS THE REGION WILL CAUSE SHOWERS AND THUNDERSTORMS
TO CONTINUE TO DEVELOP ACROSS MUCH OF CENTRAL IL MAINLY FROM I-70
NORTHWARD THROUGH MORNING. A POSSIBLE LULL IN PRECIPITATION
INDICATED BY MODEL FORECASTS LATE MORNING AS CURRENT AREA OF
CONVECTION SHIFTS NORTHEASTWARD AND RE-DEVELOPMENT OF CONVECTION
TAKES PLACE ALONG THE APPROACHING FRONTAL BOUNDARY FOR THE
AFTERNOON. SPC CONTINUES TO ADVERTISE A MARGINAL RISK FOR SEVERE
STORMS CONTAINING HAIL/STRONG WIND GUSTS THIS AFTERNOON/EVENING
THROUGH MUCH OF CENTRAL AND NORTHERN IL NEAR THE FRONTAL BOUNDARY
WHERE AT LEAST SOME OVERLAP OF MODERATE BULK SHEAR MAY COMBINE WITH
1000-2000 J CAPE. HIGH TEMPERATURES QUITE WARM AGAIN TODAY...UPPER
70S TO LOW 80S...WITH BREEZY SW WINDS 10-15 MPH.

.LONG TERM...(TONIGHT THROUGH SUNDAY)
ISSUED AT 342 AM CDT MON MAY 4 2015

SOME CONVECTION SETTLING INTO THE MIDWEST THIS MORNING ALONG AND
AHEAD OF THE BOUNDARY JUST TO THE NORTHWEST. SAME BOUNDARY PROVIDING
THE FOCUS FOR SHOWERS TODAY WILL KEEP THE THREAT FOR SOME SHOWERS
AND THUNDERSTORMS THROUGH THE OVERNIGHT IN THE NORTHERN HALF OF THE
STATE.  EXACT LOCATION OF THE STALLED BOUNDARY VARIES A BIT FROM
MODEL TO MODEL.  SMALL WAVES MOVING ALONG THE BOUNDARY WILL KEEP
PRECIP CHANCES IN THE NORTHERN TIER OF THE STATE THROUGH TUESDAY.
HIGH PRESSURE SLOWLY BUILDING IN WITH SOME SOUTHERLY WINDS PUSHING
THE FRONT BACK TO THE NORTH AND OUT OF THE FORECAST AREA FOR TUESDAY
NIGHT THROUGH WED NIGHT. PRECIP CHANCES SLOWLY EDGING BACK INTO
CENTRAL ILLINOIS AS AN UPPER LEVEL WAVE PUSHES OUT OF THE SW.  THE
ENERGY IS PART OF A GENERAL PATTERN SHIFT TO MORE SOUTHWESTERLY FLOW
WITH THE UPPER LEVEL TROF DIGGING BACK IN OVER THE SWRN CONUS.  THE
SFC LOW WITH THAT STORM MOVES OUT INTO THE UPPER MIDWEST AND INTO
CANADA BY THE END OF THE WEEK, BUT IN SHIFTING TO MORE SOUTHWESTERLY
FLOW ALOFT, OPENS THE DOOR TO A SERIES OF SHORTWAVES THAT KEEP THE
FORECAST WET FOR THE END OF THE WORK WEEK AND INTO THE WEEKEND.
TEMPS RATHER WARM THROUGH THE FORECAST WITH OVERCAST AND RAINY SKIES
KEEPING THE OVERNIGHT LOWS UP A BIT, BUT LIKELY NOT NEARLY AS WARM
AS THE TREND IN THE GUIDANCE.  HAVE KNOCKED THEM DOWN A COUPLE
DEGREES. SOUTHERLY FLOW AND A RELATIVELY WARM AIRMASS KEEPING THE
HIGHS A BIT ABOVE NORMS.  HOWEVER, WITH THE LIFTING OF THE DEEP TROF
OVER THE SW INTO THE GREAT LAKES, THE WARMER AIRMASS IS SHUNTED OFF
TO THE EAST AND COOLER AIR MOVES INTO THE MIDWEST AT LEAST BRIEFLY
AT THE END OF THE FORECAST PD.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 0657 AM CDT MON MAY 4 2015

SCATTERED SHRA/TSRA FROM KSPI-KDEC-KCMI NORTHWARD WITH ISOLD-SCT
SHRA TO THE SOUTH AS A COLD FRONTAL BOUNDARY APPROACHES FROM THE
NORTHWEST. GENERALLY VFR CONDITIONS WITH CIGS BKN050-070 BUT ISOLD
IFR/MVFR VSBYS AND MVFR CIGS IN HEAVIER TSRA AND BR. EXPECT THIS
ACTIVITY TO SHIFT SOUTHWARD THROUGH THE DAY AND EVENING BEFORE
BEGINNING TO SHIFT BACK NORTHWARD AFTER 06Z. POTENTIAL IMPROVEMENT
IN CONDITIONS BRIEFLY FROM AROUND 15-18Z HOWEVER
TIMING/OCCURRENCE TOO UNCERTAIN FOR MENTION IN 12Z TAFS. WINDS
GENERALLY SSW 8-12 KTS UNTIL 00Z...SHIFTING TO SE04-08 KTS.
BRIEFELY GUSTY AND VARIABLE IN VICINITY OF THUNDERSTORMS.


&&

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

$$

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



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