Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 190457
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1157 PM CDT MON MAY 18 2015

.UPDATE...
ISSUED AT 856 PM CDT MON MAY 18 2015
DRIER AND COOLER AIR FILTERING IN BEHIND THE FRONT. WITH THE FRONT
MOVING INTO THE OHIO RIVER VALLEY THIS EVENING...WILL SEE THE
PRECIP THREAT PUSH SOUTH OF THE REGION AS WELL. WILL MAKE SOME
MINOR UPDATES TO REMOVE THE POPS IN THE EXTREME SOUTHEAST...BUT NO
MAJOR CHANGES EXPECTED AT THIS TIME.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 300 PM CDT MON MAY 18 2015

HIGH PRESSURE OVER THE PRAIRIE PROVINCES OF CANADA THIS AFTERNOON
WILL BUILD SOUTHEAST INTO THE MIDWEST IN THE WAKE OF THE COLD FRONT
THAT MOVED THROUGH THE FORECAST AREA TODAY. ANY REMNANT CLOUDINESS
SHOULD MOVE EAST OF THE AREA EARLY THIS EVENING. NORTHWEST WINDS
SHOULD REMAIN SUFFICIENT TO REDUCE THE POTENTIAL FOR RADIATIONAL
COOLING SOMEWHAT...BUT GIVEN THE SIGNIFICANT LOWER LEVEL COLD AIR
ADVECTION... TEMPERATURES TONIGHT SHOULD BE 15-25F DEGREES COOLER
THAN LAST NIGHT. GFS FROM 12Z IS MOST AGGRESSIVE WITH THE COLD AIR
INTRUSION AND DROPS 850 TEMPS AS LOW AS 3-5C BY 12Z. FEEL THIS IS A
BIT OVERDONE GIVEN THE ECMWF...NAM...AND CMC BEING SEVERAL DEGREES
WARMER AND WILL KEEPS LOWS IN THE 40S NORTH OF I-70 AND LOW 50S
SOUTH OF I-70.

.LONG TERM...(TUESDAY THROUGH MONDAY)
ISSUED AT 300 PM CDT MON MAY 18 2015

SURFACE HIGH PRESSURE WILL CONTINUE TO BUILD INTO THE REGION
AND BRING DRY AND SLIGHTLY COOLER WEATHER TO THE AREA FOR TUE AND
TUE NIGHT. HOWEVER, IN THE MID LEVELS, A WEAK TROUGH WILL PUSH INTO
THE MIDWEST AND COMBINE WITH AN INVERTED TROUGH TO BRING PCPN TO THE
SOUTHERN TWO THIRDS OF THE STATE FOR WED. THE HIGH PRESSURE WILL
ALSO BE PUSHING THE PCPN SOUTH SO BY WED EVENING MOST OF THE PCPN
WILL BE ACROSS THE SOUTHERN HALF OF THE STATE AND THEN PUSHING
FURTHER SOUTH LATE WED NIGHT. PCPN SHOULD PRIMARILY BE SHOWERS GIVEN
THE LACK OF DEEP MOISTURE WITH THE HIGH COMING DOWN...BUT AN
ISOLATED THUNDERSTORM IS NOT OUT OF THE QUESTION AS LONG AS
CONDITIONS ARE RIGHT. THE HIGH PRESSURE WILL CONTINUE ITS PUSH SOUTH
INTO THE SOUTHERN US/SOUTHERN MISS VALLEY WHICH WILL BRING DRY
WEATHER BACK TO THE CWA FOR THURSDAY AND THURSDAY NIGHT.

THE HIGH PRESSURE WILL USHER IN COOL CANADIAN AIR INTO THE REGION
FOR WED AND THUR. BELIEVE MOS GUIDANCE LOOKS OK FOR TUE BUT IT TOO
HIGH FOR WED AND THUR.

AS THE HIGH PRESSURE EXPANDS ACROSS THE EASTERN HALF OF THE US...DRY
WEATHER WILL CONTINUE ACROSS THE CWA FOR THE REST OF THE WEEK. AS
THE RIDGE MOVES EAST...SOUTHERLY FLOW WILL RETURN AND BRING WARMER
TEMPS TOWARD THE END OF THE WEEK AS WELL AS MOISTURE BACK INTO THE
PLAINS. COMBINED WITH DEVELOPING SOUTHWEST FLOW ACROSS THE MIDDLE US
THE CHANCE OF SHOWERS AND THUNDERSTORMS WILL RETURN. NO MEMORIAL DAY
WEEKEND WOULD NOT BE COMPLETE WITH THE THREAT OF STORMS AT SOME
POINT DURING THE WEEKEND...AND THIS ONE WILL BE NO DIFFERENT. AS THE
RESPECTIVE LOW PRESSURE AREA AND UPPER LEVEL TROUGH PUSH OUT INTO
THE PLAINS AND COMBINE WITH THE WARM MOIST AIR...PCPN WILL RETURN TO
THE REGION BEGINNING AS EARLY AS SATURDAY IN WEST CENTRAL IL. THIS
AREA OF STORMS WILL EXPAND EASTWARD THROUGH SAT NIGHT AND THEN
CONTINUE WITH STORMS BECOMING LIKELY FOR SUN THROUGH MONDAY/MEMORIAL
DAY. SO OVER THE WEEKEND AS THE SURFACE FRONT AND UPPER LEVEL TROUGH
REMAIN WEST OF THE AREA...A NUMBER OF WAVES WILL LIFT OUT OF THE
SOUTHWEST WITH MULTIPLE CHANCES OF SHOWERS AND THUNDERSTORMS.

SURFACE HIGH PRESSURE TO THE EAST AND AN UPPER LEVEL TROUGH TO THE
WEST ALWAYS BRINGS WARM AND MOIST AIR TO THE AREA AND EVEN THROUGH
THE BEGINNING OF THE PERIOD MAY BE A LITTLE ON THE COOL SIDE, WARMER
TEMPS ARE EXPECTED INTO THE WEEKEND. MOS GUIDANCE GOES WARMER BUT
CLOUDS AND PCPN SHOULD TEMPER THAT SOME.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1153 PM CDT MON MAY 18 2015
WINDS STAYING UP AND A LITTLE GUSTY WITH THE PRESSURE GRADIENT
BEHIND THE BOUNDARY. LIKELY TO CONTINUE THROUGH MUCH OF TOMORROW,
THOUGH WEAKENING TOWARDS THE END OF THE DAY WITH THE RIDGE AXIS
DRAWING CLOSER...ALONG WITH A NORTHERLY TURN TO THE WINDS AROUND
SUNSET. MODEL TIME HEIGHTS HINTING AT SOME CIRRUS BY TOMORROW
AFTERNOON. VFR THROUGHOUT.

&&

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

$$

UPDATE...HJS
SHORT TERM...BARKER
LONG TERM...AUTEN
AVIATION...HJS



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