Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 290442
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1142 PM CDT FRI AUG 28 2015

.UPDATE...
ISSUED AT 903 PM CDT FRI AUG 28 2015

THE DRY AIR IN PLACE ACROSS CENTRAL IL HAS CAUSED THE LEADING PUSH
OF SHOWERS TO DISSIPATE BEFORE REACHING THE ILLINOIS RIVER. THAT
SHOULD CONTINUE TO BE THE CASE UNTIL AT LEAST 06Z/1AM. WE EXPECT
BETTER POTENTIAL FOR RAIN TOMORROW AS THE LOW AND COLD FRONT
REACH WESTERN IL. THE WEAKENING OF THE ENTIRE LOW PRESSURE SYSTEM
AS IT REACHES ILLINOIS WILL SUPPORT KEEPING THE POPS IN THE LOW
CHANCE CATEGORY. WILL DIMINISH THE SOUTHERN EXTENT OF CHANCE POPS
BETWEEN 06Z AND 12Z, BASED ON TRENDS THIS EVENING. A VEIL OF HIGH
CLOUDS WILL KEEP LOW TEMPS WARMER THAN LAST NIGHT, WITH READINGS
MAINLY IN THE MID 60S. UPDATES THIS EVENING WILL BE MAINLY IN THE
WEATHER/POP AREA, AS THE REMAINDER OF THE FORECAST IS GENERALLY ON
TRACK.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 243 PM CDT FRI AUG 28 2015

AFTERNOON SURFACE MAP SHOWING LOW PRESSURE CENTERED NEAR OMAHA, WITH
A WARM FRONT EXTENDING NORTHEAST ACROSS IOWA AND A COLD FRONT INTO
CENTRAL KANSAS. MAIN ACTIVITY OF SHOWERS AND THUNDERSTORMS HAS BEEN
CLOSER TO THE WARM FRONT AND TRACKING NORTH OF OUR FORECAST AREA. A
GENERAL EASTWARD PROGRESSION OF THE BOUNDARIES IS EXPECTED OVER THE
NEXT SEVERAL HOURS, WITH THE COLD FRONT APPROACHING THE
ILLINOIS/IOWA BORDER TOWARD 3-4 AM. FORECAST SOUNDINGS ARE RATHER
DRY BELOW 12,000 FEET FROM ABOUT PEORIA EAST AND SOUTH, AND AM
STARTING TO GET CONCERNED THAT THERE WILL BE LITTLE MORE THAN
ISOLATED SHOWERS BETWEEN I-55 AND THE ILLINOIS RIVER TONIGHT.
HOWEVER, THE HRRR AND ARW MODELS ARE A BIT MORE AGGRESSIVE WITH
SHOWERS MOVING INTO THIS AREA AFTER 3 AM, SO WILL MAINTAIN CHANCE
POP`S ACROSS THE ILLINOIS RIVER VALLEY MAINLY FROM LATE EVENING
THROUGH OVERNIGHT. INSTABILITY IS A LITTLE MORE SPARSE THOUGH, WITH
THE CURRENT THUNDER ACTIVITY MAINLY NEAR THE UPPER LEVEL DISTURBANCE
TRACKING ACROSS CENTRAL IOWA, AND HAVE TRIMMED BACK THE THUNDER
POTENTIAL TO MAINLY WEST OF THE RIVER. OTHERWISE, HAVE MAINLY GONE
DRY EAST OF I-55. MILDER CONDITIONS EXPECTED OVERNIGHT WITH CLOUD
COVER MUCH MORE EXTENSIVE AND A SOUTHERLY FLOW, WITH MOST AREAS
DIPPING INTO THE MID 60S.

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 243 PM CDT FRI AUG 28 2015

LOW PRESSURE AREA AND ASSOCIATED FRONT WEST OF THE AREA WILL
CONTINUE TO SLOWLY MOVE EAST AND INTO THE CWA DURING THE WEEKEND.
HOWEVER...VERY LITTLE SUPPORT FOR THIS SYSTEM AS IT MOVES EAST SO
ALL MODELS HAVE THIS SYSTEM WEAKENING AS IT MOVES INTO THE AREA.
THEREFORE...WILL ONLY HAVE CHANCE POPS FOR SAT MORNING WEST OF I-55
AND THEN MOVE POPS EAST DURING THE AFTERNOON BUT REMAINING MAINLY
NORTH OF I-70 AS FRONT CONTINUES TO WEAKEN AND BECOME SOMEWHAT
PARALLEL TO THE FLOW AND VERY LACKING ON CONVERGENCE/SUPPORT. CHANCE
POPS FOR SAT NIGHT WILL CONTINUE AS THE UPPER LEVEL WAVE SHIFTS EAST
ACROSS THE AREA. PCPN WILL BE MAINLY SHOWERS AND ISOLATED
THUNDERSTORMS...DUE TO LACK OF FORCING AND INSTABILITY. BY
SUNDAY...THE WAVE SHOULD BE VERY WEAK AND EAST OF THE CWA...SO WILL
ONLY HAVE SLIGHT CHANCE POPS. FOR REMAINDER OF THE WEEKEND AND INTO
THE BEGINNING OF NEXT WEEK...DRY CONDITIONS CAN BE EXPECTED AS HIGH
PRESSURE BEGINS TO BUILD IN THE WEST AND PUSH INTO THE NORTHERN PART
OF THE AREA.

BEGINNING TUE AND THROUGH MOST OF THE WEEK...A COUPLE OF MODELS
BRING REMNANTS OF TS ERIKA INTO THE AREA. HOWEVER...THIS IS
DEPENDENT ON WHERE THE TS GOES. AND IT IS FAR ENOUGH AWAY IN TIME
THAT WILL JUST KEEP CLOSE TO WHAT THE CRINT HAS...AND THAT IS JUST
SLIGHT CHANCE POPS IN SOME AREAS FOR WED THROUGH THUR. SLIGHT CHANCE
POPS WILL BE IN THE GRIDS BUT NOT MENTIONED IN THE WORDED FORECAST.

TEMPS THROUGH THE WEEKEND WILL BE TEMPERED DUE TO CLOUD COVER AND
SCATTERED PCPN...BUT STILL EXPECTING THEM TO RISE INTO THE 80S FOR
THE WEEKEND. BY NEXT WEEK...WITH UPPER LEVEL RIDGING BUILDING INTO
THE AREA AND DEWPOINTS BEING DRIER...EXPECTING TEMPS TO RISE INTO
THE UPPER 80S TO AROUND 90 FOR THE ENTIRE WEEK. THIS WILL BE MUCH
ABOVE NORMAL FOR THE BEGINNING OF SEPT.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1142 PM CDT FRI AUG 28 2015

LOW PRESSURE CENTERED IN WESTERN IOWA WILL CONTINUE TO DRIFT EAST
TONIGHT. IT WILL GRADUALLY DISSIPATE NEAR WESTERN ILLINOIS
SATURDAY AFTERNOON/EVE. SHOWERS HAVE EXPANDED IN COVERAGE BETWEEN
04Z-05Z, AND RAIN IS STARTING TO REACH THE GROUND FROM CLOUD
BASES AT 8K FT OR HIGHER. SCATTERED RAIN SHOWERS WILL PERIODICALLY
AFFECT THE TERMINAL SITES OVER THE NEXT 18 HOURS, BEFORE
DISSIPATING SATURDAY EVENING. THE CHANCES ONLY WARRANTED A VCSH
AND VFR CLOUD COVER, BASED ON FORECAST SOUNDINGS FROM HRRR AND
RAP/NAM OUTPUT. USED ONLY VCSH IN ALL TAFS TO ACCOUNT FOR PRECIP,
AS TIMING WILL BE HIGHLY VARIABLE IN TERMS OF TIMING AND LOCATION.
ENDED ALL MENTION OF PRECIP BEFORE 00Z/30. WINDS ARE EXPECTED TO
REMAIN SOUTH THROUGH AT LEAST 18Z, THEN BEGIN TO SHIFT TO THE
SOUTHWEST AS THE LOW AND COLD FRONT APPROACH WESTERN ILLINOIS.
PREVAILING WIND SPEEDS SHOULD REMAIN 10KT OR LESS THROUGH TOMORROW
AFTERNOON.

&&

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

$$

UPDATE...SHIMON
SHORT TERM...GEELHART
LONG TERM...AUTEN
AVIATION...SHIMON


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