Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 031756
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1256 PM CDT SUN MAY 3 2015

.UPDATE...
ISSUED AT 1045 AM CDT SUN MAY 3 2015

FORECAST WAS UPDATED TWICE THIS MORNING TO ADDRESS THE SMALL
CHANCES OF SHOWERS AND ISOLATED THUNDERSTORMS OVER NORTHERN
COUNTIES TODAY AND HANDLING CLOUD COVER. HAVE 20% CHANCE OF
SHOWERS AND ISOLATED THUNDERSTORMS THIS AFTERNOON MAINLY NW OF
I-55 WITH 30% CHANCE FAR NORTHERN COUNTIES OF KNOX, STARK AND
MARSHALL COUNTIES. SCATTERED SHOWERS OVER SE IA INTO NW IL JUST NW
OF ILX CWA WAS TRACKING ENE AHEAD OF ANOTHER WEAK SHORT WAVE OVER
CENTRAL IA THAT WILL WEAKEN A LIFT INTO NE IL THIS AFTERNOON
KEEPING BETTER CHANCES OF CONVECTION NORTH OF CENTRAL IL REST OF
TODAY. IL RIVER VALLEY WILL BE ON SOUTHERN EDGE OF THIS WEATHER
SYSTEM TO HAVE SMALL CHANCES OF CONVECTION THERE. TEMPS AT 1030 AM
HAVE WARMED INTO THE UPPER 60S TO MID 70S AND WARM HIGHS IN THE
LOWER 80S EXPECTED BY 4 PM TODAY ACROSS MUCH OF THE AREA. BREEZY
SOUTHWEST WINDS OF 15 TO 25 MPH AND PARTLY TO MOSTLY SUNNY SKIES.

&&

.SHORT TERM...(TODAY)
ISSUED AT 338 AM CDT SUN MAY 3 2015

SURFACE TROUGH AND FRONTAL BOUNDARY REMAIN WELL OFF TO THE NORTHWEST
THIS MORNING...DRAPED FROM SD NORTHEAST THROUGH MN. THIS WILL BECOME
THE FOCUS FOR CONVECTIVE ACTIVITY LATER TODAY AS IT MOVES CLOSER TO
CENTRAL IL IN THE LATE AFTERNOON. THIS MORNING A SHORTWAVE EVIDENT
ON WATER VAPOR IMAGERY OVER CENTRAL IL CONTINUES TO PRODUCE A FEW
SHOWERS...EXPECTED TO MOVE EASTWARD AND DISSIPATE LATER THIS MORNING
IN EAST CENTRAL IL ACCORDING TO LATEST HRRR RUN. ANOTHER SHORTWAVE
OVER WEST IA IS EXPECTED TO TRACK ENE AND PASS BY THE CENTRAL IL
FORECAST AREA TO THE NORTH. WITH GENERAL SUBSIDENCE INDICATED ACROSS
THE AREA...HAVE KEPT THE FORECAST DRY LATE MORNING THROUGH LATE
AFTERNOON/EARLY EVENING ONCE THE INITIAL ROUND OF MORNING SHOWERS
PASSES THROUGH. LOW LEVEL SOUTHERLY FLOW WILL KEEP THE WARMING TREND
GOING FOR TODAY WITH HIGHS REACHING AROUND 80 DEGREES. FORECAST
SOUNDINGS INDICATE BOUNDARY LAYER MOMENTUM CAPABLE OF PRODUCING
GUSTS 20-25 MPH FROM I-70 NORTHWARD...WITH SUSTAINED SOUTHERLY WINDS
12-18 MPH.

.LONG TERM...(TONIGHT THROUGH SATURDAY)
ISSUED AT 338 AM CDT SUN MAY 3 2015

NOT A LOT OF CHANGES IN THE FORECAST. MAJORITY OF FORECAST REVOLVES
AROUND A SLOWING/STALLED FRONTAL BOUNDARY ACROSS THE REGION FOR
TONIGHT AND THROUGH TOMORROW BEFORE BEING EDGED TO THE NORTH BEFORE
ANOTHER SYSTEM SPINS UP OVER THE PLAINS AND MOVES INTO THE REGION.
FOR TONIGHT, THE FRONTAL BOUNDARY SETTLING IN JUST TO THE NORTHWEST
WILL PROVIDE AN INCREASING CHANCE FOR SHOWERS AND THUNDERSTORMS FOR
THE AREA...SETTLING INTO THE NORTHERN HALF OF THE STATE AND BECOMING
HUNG UP IN QUASI ZONAL FLOW ALOFT.  BEST CHANCES FOR PRECIP REMAIN
IN THE NORTHERN HALF OF THE STATE PROVIDING SOME FOCUS FOR STORM
DEVELOPMENT.  MODELS HAVE TRENDED A LITTLE MORE SCATTERED IN THE QPF
FIELDS, ALTHOUGH THE NORTHERN HALF OF THE STATE STILL SEEMS PRIMED
FOR THE BEST CHANCES OF PRECIP THROUGH MONDAY NIGHT, SPECIFICALLY
THE AREAS WHERE THE BOUNDARY STALLS. SPC HAS KEPT THE NORTHERN HALF
OF THE CWA IN A MARGINAL RISK FOR STORMS INVOF THE BOUNDARY ON
MONDAY. CLUSTERS OF STORMS NEAR A WEAK BOUNDARY LOOKING BORDERLINE
AT THIS POINT, BUT IN AN AREA OF CONTINUING WARM AIR ADVECTION
PROVIDING POTENTIAL INSTABILITY JUST SOUTH OF THE BOUNDARY THAT WILL
SLOWLY BE SETTLING SOUTH INTO THE WARMER AND MORE BUOYANT AIR.

A RIDGE BEGINS TO BUILD INTO THE MIDWEST FROM THE SOUTHEAST...WITH
ENOUGH SUBSIDENCE IN THE REGION OF THE RIDGE AXIS TO ERODE SHOWER
CHANCES AT LEAST TUES NIGHT THROUGH WED NIGHT. ANOTHER PATTERN SHIFT
TAKES HOLD FOR THE LATER HALF OF THE WEEK, SETTING UP MORE OF A
SOUTHWESTERLY FLOW AND AN ACTIVE WEATHER PATTERN AGAIN AS WAVES
CONTINUE TO RIPPLE AROUND THE SWRN LOW AND INTO THE MIDWEST.  A
RATHER WET FORECAST OVERALL, WITH SEVERAL DIFFERENT PATTERNS
ESTABLISHING THEMSELVES...AND KEEPING SHOWERS AND THUNDERSTORMS IN
THE OUTLOOK.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1255 PM CDT SUN MAY 3 2015

VFR CONDITIONS GENERALLY EXPECTED TO CONTINUE ACROSS THE CENTRAL
IL AIRPORTS NEXT 24 HOURS THROUGH 18Z/1 PM MONDAY DUE TO UPPER
LEVEL RIDGE INTO THE MID MS RIVER VALLEY. SCATTERED TO BROKEN
MID/HIGH CLOUDS TO OCCUR AT TIMES THROUGH MONDAY MORNING. FEW TO
SCATTERED CUMULUS CLOUDS 5-8 KFT APPEARING THIS AFTERNOON AND
COULD GO BROKEN AT TIMES TONIGHT INTO MID MONDAY MORNING. VCSH AT
PIA THIS AFTERNOON WHILE BRUNT OF SHOWERS AND ISOLATED
THUNDERSTORMS THIS AFTERNOON STAY NORTH OF I-80 AS WEAKENING SHORT
WAVE IN EASTERN IA LIFT ACROSS NORTHERN IL AND SE WI THROUGH
SUNSET. CARRIED VCSH SHOWERS AT PIA AND BMI THIS EVENING THOUGH
BEST CHANCES AGAIN TO THE NW PER HIGH RES MODELS LIKE HRRR AND RAP.
A LITTLE BETTER CHANCE OF SHOWERS AND ISOLATED THUNDERSTORMS FROM
09Z-15Z ESPECIALLY AT NORTHERN AIRPORTS OF BMI AND PIA AS ANOTHER
SHORT WAVE TRACKS EASTWARD FROM IA INTO THE IL RIVER VALLEY BY
15Z/MON. BREEZY SSW WINDS 13-18 KTS WITH GUSTS OF 20-27 KTS THIS
AFTERNOON TO DIMINISH SOUTH CLOSER TO 10 KTS AFTER SUNSET AND
BECOME SW 10-13 KTS WITH GUSTS 15-20 KTS AFTER 15Z/MONDAY.

&&

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

&&

$$

UPDATE...07
SHORT TERM...ONTON
LONG TERM...HJS
AVIATION...07



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