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000
FXUS63 KILX 200833 CCA
AFDILX

AREA FORECAST DISCUSSION...CORRECTION
NATIONAL WEATHER SERVICE LINCOLN IL
330 AM CDT MON MAY 20 2013

.DISCUSSION...
ISSUED 330 AM CDT MON MAY 20 2013

SHORT TERM...TODAY THROUGH THURSDAY

UNSETTLED WEATHER PATTERN EXPECTED THROUGH MID WEEK AS LARGE UPPER
LEVEL LOW OVER NE/SD GRADUALLY WEAKENS AS IT MOVES EASTWARD INTO
THE GREAT LAKES. SPC CONTINUES A SLIGHT RISK OF SEVERE STORMS
ACROSS MUCH OF IL FROM THIS AFTERNOON INTO TUE NIGHT. MODELS HAVE
TRENDED A BIT FASTER WITH WX SYSTEM AND SPC RISK OF SEVERE STORMS
ON WED IS EAST OF IL.

LEADING EDGE OF SHOWERS AND A FEW THUNDERSTORMS AS FAR EAST AS
PEORIA AND JACKSONVILLE WHILE STRONG TO SEVERE STORMS HEADING
TOWARD ST LOUIS METRO AREA EARLY THIS MORNING. MORE NUMEROUS
THUNDERSTORMS WERE OVER CENTRAL AND SW MO INTO SE KS WITH MCS
COMPLEX. ANOTHER AREA OF CONVECTION WAS OVER NE WI WITH ANOTHER
WEAKENING MCS. SURFACE MAP SHOWS DEEPENING 998 MB LOW PRESSURE
OVER CENTRAL SD WITH ITS WARM FRONT OVER NORTHERN WI WHILE ITS
COLD FRONT WAS OVER EASTERN NEBRASKA INTO CENTRAL KS/OK. IL WAS IN
WARM SECTOR WITH MOIST DEWPOINTS IN THE 60S AND EVEN 70F AT OLNEY
AND FAIRFIELD IN SE IL. TEMPS AT 3 AM WERE IN THE LOWER TO MIDDLE
70S EXCEPT RAIN COOLED MID 60S OVER WEST CENTRAL IL.

559 DM 500 MB LOW TO SLOWLY MOVE EAST INTO EASTERN SD BY SUNSET
WITH 998 MB SURFACE LOW MOVING INTO WEST CENTRAL MN. ANOTHER ROUND
OF SEVERE STORMS EXPECTED TO FIRE UP DURING MID/LATE AFTERNOON AND
CONTINUE INTO TONIGHT OVER THE CENTRAL PLAINS AND BE FURTHER EAST
INTO IL LATE THIS AFTERNOON AND TONIGHT. VERY UNSTABLE AIR MASS
WITH CAPES OF 2500-3500 J/KG AND GOOD WIND SHEAR TO AID IN THE
DEVELOPMENT OF SEVERE STORMS INCLUDING SOME SUPERCELLS. SPC HAS
15% RISK OF LARGE HAIL AND DAMAGING WIND GUSTS OVER IL WITH 30%
RISK OF LARGE HAIL FROM I-55 WEST AND 30% RISK OF DAMAGING WINDS
GUSTS FROM I-57 WEST. ALSO HAVE AT LEAST A 5% RISK OF TORNADOS
OVER MUCH OF IL EXCEPT FAR SE IL. HIGHS THIS AFTERNOON AGAIN IN
THE UPPER 80S TO NEAR 90F WITH DEWPOINTS IN THE UPPER 60S AND
LOWER 70S SO WILL FEEL LIKE A MID SUMMER DAY IN JULY.

UPPER LEVEL LOW STAYS IN PLACE NEAR SE SD TUE AND THEN WEAKENS A
BIT TO 562 DM AS IT TRACKS EASTWARD INTO EASTERN IA BY SUNSET WED
WHILE SURFACE LOW MOVES INTO SOUTHERN LAKE MI. ANOTHER SLIGHT RISK
OF SEVERE STORMS OVER MUCH OF IL TUE AFTERNOON/EVENING THOUGH NOT
QUITE AS UNSTABLE AS THIS AFTERNOON...AND SYSTEM IS STARTING TO
WEAKEN SO COVERAGE OF SEVERE STORMS APPEARS LESS. SPC HAS AT LEAST
15% RISK OF DAMAGING WINDS AND LARGE HAIL WITH THE 30% RISK SW IL SW
OF CLAY COUNTY. HIGHS TUE IN THE LOW TO MID 80S. SHOWERS STILL
LIKELY WED WITH A FEW THUNDERSTORMS ESPECIALLY OVER EASTERN IL.
RAINFALL AMOUNTS OF 1 TO 2 INCHES POSSIBLE TODAY THROUGH WED.
WEAKENING UPPER LEVEL TROF MOVES INTO IL THU KEEPING A CHANCE OF
SHOWERS AND ISOLATED THUNDERSTORMS ALONG WITH COOLER TEMPS WITH
HIGHS AROUND 70F FROM I-74 NORTH AND MID 70S IN SE IL.

LONG TERM...THURSDAY NIGHT THROUGH SUNDAY NIGHT

DRY WEATHER FINALLY RETURNS TO CENTRAL/SE IL THU NIGHT THROUGH FRI
NIGHT AS HIGHS PRESSURE SETTLES INTO THE GREAT LAKES REGIONS.
CARRIED 20-40% CHANCE OF SHOWERS AND THUNDERSTORMS FROM SAT
AFTERNOON THROUGH SUNDAY NIGHT OVER CENTRAL AND SE IL WITH SOME
MODELS SHOWING SHORT WAVE RIDGING OVER TOP OF UPPER LEVEL RIDGE INTO
PARTS OF IL THIS WEEKEND. THOUGH CONFIDENCE OF THIS HAPPENING IS LOW.
TEMPS SHOULD MODIFY EARLY NEXT WEEK WITH SOME UPPER LEVEL RIDGING
INTO IL.

07

&&

.AVIATION...
ISSUED 1203 AM CDT MON MAY 20 2013
CONTINUING THREAT FOR TS ACTIVITY IN THE OVERNIGHT...MAINLY IN SPI
AND PIA BEFORE DAWN. EXPANSIVE COMPLEX OF THUNDERSTORMS BREAKING
UP ON APPROACH TO THE AREA. REMOVING VCTS MENTION UNTIL JUST
BEFORE DAWN IN DEC AND BMI. NEW TS DEVELOPMENT A CONCERN...BUT FOR
NOW...BIGGER THREAT IN THE NW. TOMORROW SKY CONDITIONS WILL BE
VERY DEPENDENT ON THE REMNANTS OF CONVECTIVE COMPLEX TO THE WEST.
IN SHORT...WILL BE WIDELY VARIABLE AND DIFFICULT TO PINPOINT SINCE
MOST WILL BE BASED ON MESOSCALE BOUNDARIES. BEST CHANCES FOR TS
FOR ILX TERMINALS IS IN THE AFTERNOON...WHICH IS WHEN THE TEMPO IS
IN PLACE. FOR TONIGHT...KEEPING THE GUSTS IN THE OVERNIGHT IN THE
WEST...CLOSEST TO THE LOW CENTER AND STORM ACTIVITY.

HJS

&&

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

&&

$$