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000
FXUS63 KILX 131947
AFDILX

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

.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
&&

.AVIATION...
ISSUED 1255 PM CDT MON MAY 13 2013

VFR CONDITIONS ARE FORECAST TO CONTINUE ACROSS THE CENTRAL IL
TERMINAL AIRPORTS THROUGH TUE. SCATTERED TO BROKEN MID/HIGH CLOUDS
OVER IA TO SPREAD ACROSS CENTRAL IL LATER THIS AFTERNOON AND EVENING
AND THEN SCATTER OUT TUE MORNING. WNW WINDS 7-11 KTS TO TURN SSW
DURING THE AFTERNOON AND SSE BY SUNSET. EXPECT SW WINDS 10-15 KTS
WITH GUSTS 17-22 KTS AFTER 13Z/TUE. NO FOG EXPECTED OVERNIGHT.
1026 MB HIGH PRESSURE OVER MS AND RIDGING NORTHWARD INTO IL TO SHIFT
EASTWARD ACROSS THE OHIO VALLEY THIS EVENING AND INTO THE SE
STATES AND RIDGING INTO THE ATLANTIC STATES BY 18Z/TUE AS 998 MB LOW
PRESSURE MOVES INTO WEST CENTRAL MN. INCREASING WAA PATTERN OVER
CENTRAL IL TO GIVE SOME PASSING MID/HIGH CLOUDS LATER TODAY INTO
TONIGHT WITH CEILINGS STAYING VFR. INCREASING PRESSURE GRADIENT
SUPPORTS GUSTIER SW WINDS TUE TO AROUND 20 KTS.

07
&&

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

$$