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000
FXUS63 KILX 140435
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1135 PM CDT MON MAY 13 2013

.DISCUSSION...
ISSUED 858 PM CDT MON MAY 13 2013

A WEAK 500 MB SHORTWAVE WILL CONTINUE TO TRIGGER SOME SPRINKLES
ACROSS OUR EASTERN COUNTIES OVER THE NEXT HOUR OR TWO. CLOUD BASES
REMAIN AT 11K FT...WITH PLENTY OF DRY AIR BELOW THAT. THEREFORE...NO
MEASURABLE RAIN WILL OCCUR THIS EVE FROM THIS SHORTWAVE.

SOUTH-SOUTHWEST FLOW IN THE LOW TO MID LAYERS WILL PROVIDE STEADY
WARM AIR ADVECTION OVER THE NEXT COUPLE OF DAYS. THE WARMER AIR
ALONG WITH A LAYER OF HIGH CLOUDS WILL HELP TO KEEP LOWS ON THE
MILD SIDE TONIGHT...AND HIGHS 10 TO 15 DEGREES ABOVE NORMAL
TOMORROW AND WEDNESDAY.

WE UPDATED THE WEATHER GRIDS FOR THIS EVENING TO INCLUDE A MENTION
OF SPRINKLES...OTHERWISE LITTLE CHANGE WAS NEEDED TO THE CURRENT
FORECAST GRIDS. THE LATEST UPDATE WILL BE AVAILABLE SHORTLY.

SHIMON

&&

.AVIATION...
ISSUED 1135 PM CDT MON MAY 13 2013...FOR THE 06Z TAFS

A FEW SPRINKLES ENDED UP BEING REPORTED AT PIA/BMI/CMI OVER THE
LAST COUPLE OF HOURS...BUT NO ADDITIONAL PRECIP IS EXPECTED THE
REST OF THE NIGHT AND THROUGH THIS TAF PERIOD.

THE AREA WILL BE UNDER PERSISTENT LOW-MID LEVEL WARM AIR
ADVECTION...WITH OCCASIONAL MID-HIGH CLOUDS. SOUTHWEST WINDS WILL
INCREASE TOMORROW AS MIXING DEEPENS. HOWEVER...FORECAST SOUNDINGS
ARE INDICATING AN INVERSION AROUND 900 MB MAY LIMIT MIXING HEIGHTS
AND KEEP WIND GUSTS IN THE 20-25KT RANGE.

THE PRESSURE GRADIENT MAY STAY TIGHT ENOUGH FOR SUSTAINED SW WINDS
IN THE 12-15KT RANGE EVEN AFTER SUNSET TOMORROW EVE.

SHIMON
&&

.PREV DISCUSSION...
ISSUED 247 PM CDT MON MAY 13 2013

MAIN CONCERNS THIS FORECAST PACKAGE REMAIN TO BE HOW WARM WILL IT
GET TOMORROW...ONSET OF PCPN WEDNESDAY...AND WHEN AND IF THERE
WILL BE ANY BREAKS IN THE PCPN IN THE EXTENDED.

MODELS ARE IN GOOD AGREEMENT WITH THE FLOW TRANSITIONING FROM
NORTHWEST FLOW TO A ZONAL PATTERN OVER THE NEXT 48HRS. THEN THE
FLOW WILL TRANSITION TO SOUTHWEST FLOW WITH A BUILDING RIDGE
DURING THE WEEKEND...IN THE EXTENDED. ON THE SFC...THE HIGH PRSS
OVER THE EASTERN PART OF THE CWA WILL QUICKLY PUSH EAST TONIGHT
AND ALLOW A SOUTHWEST SFC WIND TO RETURN TO THE AREA. MODELS ARE
ALSO IN BETTER AGREEMENT WITH THE TIMING OF THE FRONT INTO THE CWA
WEDNESDAY. HOWEVER...DIFFERENCES ARE SEEN WITH LOW LEVEL DEWPOINTS
AND TIMING/LOCATION OF THE PCPN. NAM-WRF/GFS/SREF HAVE PCPN OVER
THE AREA BY WED AFTERNOON...BUT ECMWF IS MUCH DRIER. PREVIOUS RUNS
OF THE MODELS HAVE INDICATED SOME AMOUNT OF PCPN OVER THE AREA WED
AFTERNOON...SO WILL CONTINUE WITH THIS FORECAST IN NEW PACKAGE.

EXTENDED MODELS SHOW SOME AGREEMENT AS WELL WITH THE SFC FEATURES
AND UPPER LEVEL PATTERN. SO A BLEND OF THE ECMWF AND GFS LOOKS
REASONABLE AGAIN.

SHORT TERM...TONIGHT THROUGH THURSDAY

THE AREA WILL REMAIN DRY FOR ONE MORE DAY AS HIGH PRSS QUICKLY
PUSHES EAST AND SOUTHWESTERLY FLOW RETURNS TO THE AREA AHEAD OF
THE NEXT FRONTAL SYSTEM. THE FRONT WILL THEN SAG INTO THE CWA ON
WEDNESDAY AS THE MAIN LOW PRSS AREA MOVES ACROSS SOUTHERN CANADA.
THE SPEED OF THE FRONT WILL GET SLOWER AS IT BECOMES PARALLEL WITH
THE UPPER LEVEL FLOW. MODELS HAVE BEEN VERY CONSISTENT WITH
HOLDING PCPN OFF TIL WED AFTERNOON...AFTER AN INCREASE IN MOISTURE
AND INSTABILITY. THE FRONT WILL THEN STALL OVER THE AREA FOR WED
NIGHT AND THUR. MODELS REMAIN CONSISTENT HERE TOO WITH HAVING PCPN
IN THE AREA THROUGH THE PERIOD. THEREFORE...WILL HAVE LIKELY POPS
OVER A PORTION OF THE CWA FOR WED NIGHT AND THUR. QPF AMOUNTS WILL
NOT BE THAT HIGH OVERALL...BUT SOME ISOLATED HEAVY RAIN COULD BE
POSSIBLE IF STRONG THUNDERSTORMS DEVELOP AND THEN TRAIN OVER THE
SAME AREA. THIS POSSIBILITY APPEARS TO BE VERY SMALL AT THE MOMENT
BUT WILL KEEP AN EYE ON THIS THROUGH LATER FORECASTS.

TEMPS WILL BE QUITE WARM TOMORROW AND WELL ABOVE NORMAL. 850 TEMPS
WILL REACH TO AROUND 22C BUT FORECAST SOUNDINGS INDICATE AN
INVERSION OVER THE AREA TOMORROW AFTERNOON. HOWEVER...MIXING WILL
BE FROM A LOWER LEVEL WHICH COULD KEEP TEMPS FROM GETTING HOT.
BELIEVE DRIER AIR MASS WILL COUNTER THIS SOME...SO HAVE GONE A
LITTLE ABOVE GUIDANCE TOMORROW ACROSS THE WESTERN HALF OF THE CWA.
FOLLOWED CLOSE TO GUIDANCE FOR WED AS GOOD WAA SHOULD BE TAKING
PLACE AHEAD OF THE FRONTAL SYSTEM. THUR TEMPS SHOULD BE COOLER DUE
TO PCPN AND CLOUDS.

LONG TERM...THURSDAY NIGHT THROUGH MONDAY

THE FRONT WILL REMAIN OVER THE CWA THROUGH FRIDAY NIGHT AND THEN
LIFT BACK NORTH AS A WARM FRONT SAT THROUGH SAT NIGHT. THIS SHOULD
PUSH THE CHANCE OF PCPN NORTH FOR SAT NIGHT. HOWEVER...THE MAIN
SYSTEM WILL BEGIN TO MOVE OUT OF THE PLAINS DURING THE LAST PART
OF THE WEEKEND AND THEN AFFECT THE CWA SUNDAY NIGHT AND MONDAY.
THERE COULD BE OTHER DRY PERIODS THROUGH THE PERIOD BUT STILL TOO
FAR OUT TO TRY TO PINPOINT. TIMING AND LOCATION OF CONVECTIVE PCPN
WILL BE DRIVEN BY MESOSCALE FEATURES THAT CAN NOT BE DEFINED THIS
FAR OUT. SO WILL KEEP CHC POPS IN FORECAST GOING IN EXTENDED WITH
HIGHER CHANCES IN THE SUN TO MON TIME FRAME.

TEMPS WILL REMAIN ABOVE NORMAL THROUGH THE LONG TERM WITH SLIGHTLY
WARMER FOR SUNDAY AHEAD OF THE NEXT MAJOR SYSTEM.

AUTEN


&&

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

$$