Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 201731
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1231 PM CDT WED MAY 20 2015

.UPDATE...
ISSUED AT 1006 AM CDT WED MAY 20 2015

LEADING EDGE OF PRECIPITATION SHIELD IS BASICALLY FROM ABOUT
GALESBURG TO JACKSONVILLE...ALTHOUGH SOME VERY LIGHT
SHOWERS/SPRINKLES ARE OCCURRING AS FAR EAST AS PARIS. DEW POINTS
ARE STILL IN THE LOW-MID 30S...SO SOME SATURATION OF THE COLUMN
WILL NEED TO TAKE PLACE BEFORE THE MORE SUBSTANTIAL RAIN OCCURS.
LATEST MODEL GUIDANCE PERSISTS THE SHOWERS INTO MID AFTERNOON...
WITH THE NEW NAM THE MOST PROGRESSIVE WITH DRYING OUT THE WESTERN
CWA BY THEN. AWIPS TIMING TOOL ON THE WEST EDGE OF THE SHIELD
WOULD SUGGEST THIS IS A BIT TOO QUICK...BUT THE RECENT FORECAST
UPDATE DID DROP POP`S INTO THE 50% RANGE IN THE FAR WEST BY 5 PM.
TEMPERATURES WILL LIKELY REMAIN FAIRLY STEADY ONCE THE RAIN
BEGINS...WITH HIGHS WELL BELOW NORMAL IN THE LOW-MID 50S.

&&

.SHORT TERM...(TODAY)
ISSUED AT 330 AM CDT WED MAY 20 2015

A WAVE MOVING EAST-NORTHEAST OUT OF THE PLAINS WILL BRING A PERIOD
OF LIGHT RAIN TO CENTRAL AND SOUTHEAST ILLINOIS TODAY AS IT TRACKS
ACROSS THE AREA. HOWEVER, SIGNIFICANT RAINFALL IS NOT ANTICIPATED AS
THE WAVE WILL BE SHEARING OUT/WEAKENING AS IT PUSHES INTO THE
CONFLUENT UPPER LEVEL FLOW ACROSS MUCH OF THE GREAT LAKES/MIDWEST.
IN ADDITION, THE SYSTEM WILL BE FIGHTING AN INITIALLY DRY AIRMASS IN
PLACE, AS WELL AS CONTINUED DRY LOW-LEVEL FLOW AROUND A SPRAWLING
SURFACE HIGH OVER MUCH OF THE NORTHERN HALF OF THE UNITED STATES.

PLAN TO CONTINUE WITH POPS STEADILY RISING THIS MORNING, WITH
CATEGORICAL POPS OVER MUCH OF THE FORECAST AREA BY MIDDAY OR EARLY
AFTERNOON. HOWEVER, THE FAST MOVING/WEAKENING SYSTEM WILL DEPART AS
QUICKLY AS IT ARRIVES, WITH POPS ALREADY TAPERING OFF FROM WEST TO
EAST BY LATE AFTERNOON. THIS SYSTEM IS LOOKING VERY MUCH LIKE A
TYPICAL HIGH POP/LOW QPF EVENT.

ASIDE FROM THE RAIN, ONE OTHER FORECAST ITEM OF NOTE IS THE
UNSEASONABLY COOL TEMPERATURES. HIGH TEMPERATURES ARE APT TO BE 20
DEGREES OR MORE BELOW NORMAL TODAY, WHICH WILL BE VALUES MORE
SUITABLE FOR MARCH THAN MAY. MOST LOCATIONS SHOULD START THE DAY IN
THE 40S. TEMPERATURES WILL STRUGGLE TO RISE DUE TO THE CLOUDY SKIES
AND RAINFALL. ADDITIONAL COOLING IS LIKELY TO BE PROVIDED BY
EVAPORATIONAL COOLING ONCE THE RAIN BEGINS FALLING INTO THE DRY
ANTECEDENT AIRMASS, AS WELL AS PERSISTENT DRY LOW LEVEL FLOW. SO,
EXPECT MOST LOCATIONS TO ONLY CLIMB INTO THE LOW-MID 50S.

.LONG TERM...(TONIGHT THROUGH TUESDAY)
ISSUED AT 330 AM CDT WED MAY 20 2015

CONTINUE CHANCE OF LIGHT RAIN SHOWERS OVER EASTERN IL THIS EVENING
MAINLY BEFORE 9 PM AS WEAKENING WEATHER SYSTEM SHIFTS EAST OF IL
INTO INDIANA. CLOUDS WILL DECREASE OVERNIGHT ESPECIALLY OVER THE IL
RIVER VALLEY WHILE SOUTHEAST IL REMAINS MOSTLY CLOUDY THROUGH THE
NIGHT. LOWS TONIGHT IN THE LOWER 40S CENTRAL IL AND MID 40S IN
SOUTHEAST IL.

A NORTHERN STREAM SHORT WAVE TO DROP SE ACROSS THE SOUTHERN GREAT
LAKES THU WHILE CANADIAN HIGH PRESSURE BUILDS INTO MO. EXPECT CLOUDS
TO CONTINUE TO DECREASE FROM NW TO SE DURING THE DAY THU WITH HIGHS
IN THE MID TO UPPER 60S (MILDEST OVER THE IL RIVER VALLEY WHERE MORE
SUNSHINE EXPECTED). LOWS THU NIGHT MOSTLY IN THE UPPER 40S. A WEAK
BACKDOOR COLD FRONT SLIDES OUT OF THE GREAT LAKES AND SOUTH THROUGH
CENTRAL IL FRIDAY AND COMES THROUGH DRY. HIGHS IN THE LOWER 70S
FRIDAY.

AN UNSETTLED WEATHER PATTERN RETURNS TO IL FROM SATURDAY NIGHT
THROUGH THE MIDDLE OF NEXT WEEK AS SW UPPER LEVEL FLOW IS
ESTABLISHED AND SEVERAL SHORT WAVES EJECT NE INTO THE REGION. HIGH
PRESSURE OVER OHIO AND WV SATURDAY ALONG WITH UPPER LEVEL RIDGE OVER
THE MS RIVER VALLEY TO KEEP CENTRAL AND SOUTHEAST IL DRY SATURDAY AS
CLOUDS INCREASE FROM THE WEST. HIGHS MOSTLY IN THE MID 70S SAT WITH
SOME UPPER 70S IN SOUTHEAST IL NEAR THE WABASH RIVER.

EXTENDED FORECAST MODELS TRACK SURFACE LOW PRESSURE INTO WESTERN KS
ON SUNDAY AND INTO THE CENTRAL GREAT LAKES MONDAY NIGHT. EXPECT WARM
FRONT TO APPROACH CENTRAL IL SATURDAY NIGHT AND PULL NORTH OF AREA
DURING THE DAY SUNDAY AND BRING WARMER AND MORE HUMID AIR INTO THE
REGION. CHANCES OF SHOWERS AND THUNDERSTORMS TO SPREAD NE ACROSS
CENTRAL IL DURING SAT NIGHT (LESS OF A CHANCE OVER SOUTHEAST IL) AND
CONTINUE SUNDAY. MODELS SHOW THE HIGHEST CHANCES OF SHOWERS AND
THUNDERSTORMS DURING SUNDAY THROUGH MONDAY WITH APPROACHING COLD
FRONT WHICH TEMPORARILY STALLS TO OUR NW. THAT FRONT DOESN`T REALLY
PUSH ALL THE WAY INTO CENTRAL IL UNTIL WED NIGHT. SO GOOD CHANCES OF
SHOWERS AND THUNDERSTORMS CONTINUES INTO THE MIDDLE OF NEXT WEEK
ALONG WITH WARM AND HUMID CONDITIONS WITH HIGHS IN THE UPPER 70S AND
LOWER 80S.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1231 PM CDT WED MAY 20 2015

AREA OF RAIN CONTINUES TO PUSH EASTWARD...BUT DRY AIR IN LOWER
LEVELS HAS BEEN RESULTING IN LITTLE MORE THAN SPRINKLES AT THE TAF
SITES SO FAR. THE MORE SUBSTANTIAL RAIN HAS BEEN WEST OF KIJX/KMQB
AND THERE WILL GENERALLY BE ABOUT A 2-HOUR WINDOW AT EACH TAF SITE
WHERE IT MAY BE HEAVY ENOUGH TO REDUCE VISIBILITIES TO MVFR RANGE
FOR A TIME. BULK OF THE RAIN SHOULD BE EAST OF THE TAF SITES BY
01Z. NORTHEAST WINDS TO GRADUALLY BECOME NORTHWEST OVERNIGHT AND
INTO THURSDAY MORNING.

&&

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

$$

UPDATE...GEELHART
SHORT TERM...BAK
LONG TERM...07
AVIATION...GEELHART



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