Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 210503
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1203 AM CDT TUE APR 21 2015

.UPDATE...
ISSUED AT 857 PM CDT MON APR 20 2015
SOME SCATTERED ECHOES ON RADAR REMAINING FROM DIURNALLY ENHANCED
SHOWERS LATE THIS AFTERNOON. MOSTLY VIRGA STILL...BUT A LITTLE
SLOW TO CLEAR OUT. CLEARING TREND EXPECTED TO CONTINUE AND
TEMPERATURES WILL CONTINUE TO DROP THROUGH THE OVERNIGHT. WEST
WINDS WITH THE SFC LOW TO THE NORTH. NO UPDATES ANTICIPATED TO THE
FORECAST AT THIS TIME.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 306 PM CDT MON APR 20 2015

BROAD CYCLONIC CIRCULATION CONTINUING OVER THE MIDWEST THIS
AFTERNOON...WITH SURFACE LOW PRESSURE CENTERED OVER THE EAST TIP OF
LAKE SUPERIOR AND AN UPPER LOW OVER NORTHWEST MINNESOTA. HAVE BEEN
SEEING SOME FAST MOVING LIGHT SHOWERS/SPRINKLES MOVING THROUGH THE
FORECAST AREA...BUT AS THE SHOWERS AND CLOUDS ARE HIGHLY CELLULAR IN
NATURE...THESE SHOULD FADE WITH LOSS OF DAYTIME HEATING. WEST
PORTION OF THE CWA SHOULD BE MAINLY CLEAR BY SUNSET...BUT IT MAY
TAKE UNTIL MID EVENING FOR THE EAST TO SCATTER OUT. GUSTY WINDS OF
30-40 MPH THIS AFTERNOON WILL BE DIMINISHING WITH SUNSET AS WELL...
BUT WINDS SHOULD STILL AVERAGE AROUND 10 MPH MUCH OF THE NIGHT. MADE
LITTLE CHANGE TO FORECAST LOW TEMPERATURES...WHICH ARE MAINLY A
COUPLE DEGREES EITHER SIDE OF 40.

.LONG TERM...(TUESDAY THROUGH MONDAY)
ISSUED AT 306 PM CDT MON APR 20 2015

WINDY CONDITIONS WILL BE THE HIGHLIGHT FOR TUESDAY AS UPPER AND
LOWER LEVEL JETS INTENSIFY ACROSS IL. UNUSUALLY DEEP MIXING
HEIGHTS FORECAST BY THE NAM/GFS UP TO 9-11K FT APPEAR TO BE A BIT
OVERDONE. HOWEVER, EVEN MIXING HEIGHTS HALF THAT DEEP WILL CAUSE
STRONG WINDS TO MIX DOWN TO THE GROUND DURING THE DAY. IT APPEARS
THAT GUSTS OF 30-40MPH WILL BE COMMON AGAIN TOMORROW. THERE IS A
CHANCE THAT A WIND ADVISORY MAY BE NEEDED ACROSS OUR NORTHERN
COUNTIES, BUT CURRENT INDICATIONS ARE THE SUSTAINED WINDS SHOULD
PREVAIL JUST BELOW THE CRITERIA OF SUSTAINED 30-39 MPH WINDS FOR
AT LEAST AN HOUR.

THE UPPER TROUGH WILL REMAIN ENTRENCHED ACROSS THE GREAT LAKES FOR
THE REST OF THE WEEK, PROVIDING SUSTAINED NW FLOW AND COOLER THAN
NORMAL CONDITIONS. A SHORTWAVE AND COLD FRONT WILL BE PUSHED ACROSS
IL ON TUESDAY NIGHT...TRIGGERING SCATTERED SHOWERS. THE
NAM/GFS/ECMWF ARE INDICATING A MESO-SCALE BAND OF ENHANCED LIFT
ACROSS OUR NORTHERN COUNTIES OVERNIGHT, SO WE INCREASED POPS INTO
THE CHANCE CATEGORY THERE, WITH SLIGHT CHANCES ACROSS THE SOUTH.
FORCING FOR PRECIP WANES QUICKLY WEDNESDAY MORNING, SO WE WENT WITH
DRY CONDITIONS WED. REINFORCING COLD AIR BEHIND THE COLD FRONT WILL
KEEP HIGHS FOR THE REMAINDER OF THE WEEK IN THE UPPER 50S TO NEAR
60, WITH OVERNIGHT LOWS IN THE 30S. FROST CONDITIONS STILL LOOK
POSSIBLE MAINLY NORTH OF I-74 WED NIGHT AND THUR NIGHT, AS WINDS
BECOME LIGHT AND SKIES CLEAR OUT. LOWS MAY DIP TO 34-35 IN SPOTS. A
FROST ADVISORY MAY BE NEEDED FOR ONE OR BOTH OF THOSE NIGHTS FOR OUR
NORTHERN COUNTIES.

THE EXTENDED MODELS HAVE COME INTO A LITTLE BETTER AGREEMENT ON HOW
FAST THE NEXT SYSTEM MAY TRIGGER RAIN SHOWERS AHEAD OF THE
APPROACHING SOUTHERN STREAM LOW. THE ECMWF HAS JOINED THE GFS IN
ADVANCING SHOWERS INTO CENTRAL IL ON FRIDAY, WHILE THE CANADIAN IS
NOT FAR OFF, SHOWING RAIN IN OUR FAR WESTERN COUNTIES FRIDAY
AFTERNOON. WE INTRODUCED SLIGHT CHANCE POPS SW OF A LINE FROM
RUSHVILLE TO LAWRENCEVILLE TO TREND PRECIP INTO THE FORECAST.

DESPITE DIFFERENCES IN THE TRACK OF THE SURFACE LOW FROM THE PLAINS
INTO ILLINOIS FRIDAY NIGHT INTO SATURDAY, THERE REMAINS SOME
AGREEMENT ON THE FORCING FOR PRECIP ACROSS IL AHEAD OF THE LOW. RAIN
NOW APPEARS LIKELY ACROSS OUR S-SW COUNTIES, WITH CHANCE POPS
INCLUDED IN THE REMAINDER OF THE AREA FRIDAY NIGHT. CHANCE POPS WERE
INCLUDED ACROSS THE BOARD ON SATURDAY, WITH DRY CONDITIONS
RETURNING SAT NIGHT AS THE LOW DEPARTS TO THE EAST.

AS THE UPPER TROUGH FINALLY MOVES TOWARD THE EAST COAST NEXT
WEEKEND, A ZONAL WESTERLY FLOW WILL PUSH ADDITIONAL SHORTWAVES
TOWARD ILLINOIS. WE COULD SEE A FEW SHOWERS DEVELOP SUNDAY NIGHT AND
MONDAY IN OUR WESTERN COUNTIES AS THE NEXT WAVE ARRIVES.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1158 PM CDT MON APR 20 2015
WINDS UP OVERNIGHT, DRIVEN PARTIALLY BY A PRESSURE GRADIENT STILL
IN PLACE IN THE WAKE OF THE EXITING LOW PRESSURE SYSTEM TO THE
NORTH/NORTHEAST. WINDS REMAIN GUSTY TOMORROW, GUSTING IN EXCESS OF
30-35KTS THROUGH THE AFTERNOON WITH DAYTIME HEATING/MIXING.
DIFFERING MOISTURE PROFILES PUT CU POTENTIAL AT 5KFT IN THE EAST
AND HIGHER IN THE WEST...ALTHOUGH THE CU RULE IS ACTUALLY
MINIMIZED IN A RIDGE THROUGH CENTRAL ILLINOIS. QUICK WAVE THROUGH
THE REGION WILL BRING THREAT OF PRECIP BUT COVERAGE IS LIKELY TO
BE SCATTERED AT THIS POINT AND MOSTLY NORTH AND SOUTH OF THE
AREA...SO VCSH FOR BMI AND PIA IS ALL THAT IS MENTIONED IN THE
TAFS FOR NOW.

&&

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

$$

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


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