091 
FXUS63 KILX 271154
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
654 AM CDT FRI MAY 27 2011

.DISCUSSION...
ISSUED 330 AM CDT FRI MAY 27 2011

00Z MODELS ARE IN FAIR AGREEMENT NEXT FEW DAYS AND WILL USED A
BLEND. FORECAST CONCERN IS CONVECTION CHANCES THIS WEEKEND AND
ALSO DEALING WITH MAJOR WARM UP DURING THIS MEMORIAL DAY WEEKEND.

SHORT TERM...TODAY THROUGH SUNDAY NIGHT.

EARLY MORNING SURFACE MAP SHOWS WEAKENING ELONGATED 1010 MB LOW
PRESSURE FROM THE EASTERN GREAT LAKES THROUGH OH INTO THE SOUTHERN
APPLACHIANS. 1025 MB HIGH PRESSURE NEAR JAMES BAY CANADA WAS
RIDGING SSW THROUGH WESTERN WI INTO MO AND DWON INTO THE LOWER MS
VALLEY. ALOFT A 568 DM 500 MB LOW WAS ALSO WEAKENING NEAR THE
IN/OH/MI BORDER WHILE MUCH STRONGER 546 DM 500 MB LOW WAS
DEEPENING ALONG THE MT AND CANADIAN BORDER. LOW CLOUDS LINGERED SE
OF THE IL RIVER WHILE CIRRUS CLOUDS WERE SPREADING QUICKLY EAST
INTO WESTERN IL FROM IA/MO. COOL TEMPS WERE 45 TO 52F. 

MODELS CONTINUE TO WEAKEN/OPEN UP UPPER LEVEL TROF OVER THE
EASTERN GREAT LAKES TODAY WITH WEAK UPPER LEVLE RIDGING INTO IL AS
WEAK SURFACE HIGH PRESSURE DRIFTS EAST OF IL BY SUNSET. OVERALL A
PARTLY TO MOSTLY CLOUDY DAY AS HIGH CLOUDS INCREASE WITH LOW
CLOUDS TRYING TO DECREASE AND SCATTERED OUT FOR A TIME BUT COULD
REFORM BY AFTERNOON ESPECIALLY IN NE AREAS. HIGHS IN THE MID TO
UPPER 60S AND ABOUT 10 DEGREES COOLER THAN NORMAL FOR LATE MAY
WITH LIGHTER WINDS TODAY.

MODELS HAVE TRENDED SLOWER WITH ARRIVAL OF SCATTERED SHOWERS AND
THUNDERSTORMS TONIGHT WITH MUCH OF AREA ESPECIALLY EASTERN IL
STAYING DRY THIS EVENING. HAVE INCREASING WAA/ISENTROPIC LIFT
PATTERN DEVELOPING BY OVERNIGHT WITH POPS ELEVATING TO 20-40%
OVERNIGHT AND HIGHEST IN WESTERN IL. BUT STRONGEST LOW LEVEL JET
STAYS SW OF IL OVER THE OZARKS WHERE SLIGHT RISK OF SEVERE STORMS
IS. NEAR NORMAL LOWS TONIGHT IN THE MID TO UPPER 50S. 

SPC HAS SLIGHT RISK OF SEVERE STORMS OVER PART OF CENTRAL IL SAT
AFTERNOON AND SAT NIGHT WEST OF I-57 AND AS FAR NORTH AS PEORIA. 
PER SPC DAY 2 OUTLOOK...ELEVATED STORMS WILL BE ONGOING NORTH OF
WARM FRONT OVER MO RESULTING FROM ISENTROPIC LIFT ON NOSE OF A
50 KT AND STRONGER SOUTHERLY LOW LEVEL JET. ACTIVITY WILL LIKELY
DEVELOP EASTWARD INTO IL AND IND AS LOW LEVEL JET MIGRATES EWD IN
ASSOCIATION WITH LEAD IMPULSE MOVING THROUGH THE UPPER MS VALLEY
AND GREAT LAKES. THE ATMOSPHERE WILL BECOME MODERATELY UNSTABLE
SOUTH OF ONGOING ACTIVITY...AND THERE IS A MODEST CHANCE THAT
SURFACE BASED STORMS COULD DEVELOP NEAR WARM FRONT/OUTFLOW
BOUNDARY FROM ERN MO INTO A PORTION OF CNTRL IL WHERE THE
ATMOSPHERE WILL NOT BE AS CAPPED AS FARTHER WEST. IF ENOUGH BOUNDARY
LAYER WARMING OCCURS TO SUPPORT SURFACE BASED STORMS...STRONG
EFFECTIVE SHEAR AND LARGE 0-1 KM HODOGRAPHS WOULD PROMOTE A FEW
SUPERCELLS. THE EXTENT/DEGREE OF SEVERE THREAT IS DEPENDENT ON
EVOLUTION OF MORNING AND ONGOING STORMS. GIVEN THE CONDITIONAL
NATURE OF THIS THREAT ONLY A 15% PROBABILITY AREA WILL BE
INTRODUCED AT THIS TIME.

HAVE GOOD CHANCE OF SHOWERS AND THUNDERSTORMS NORTHERN AREAS SAT
AND SAT NIGHT CLOSER TO WARM FRONT WHILE SE IL WILL ONLY HAVE
20-30% POPS. HIGHS BACK TO NORMAL SAT FROM MID 70S NORTH TO AROUND
80F SOUTH. HAVE JUST SLIGHT CHANCE OF CONVECTION SUNDAY NW OF THE
IL RIVER AS STRONG UPPER LEVEL RIDGE BUILDS NORTHWARD ACROSS THE
EASTERN STATES. VERY WARM HIGHS SUNDAY FROM 85 TO 90F WITH BREEZY
SOUTH WINDS AND MORE HUMID DEWPOINTS IN THE UPPER 60S.

LONG TERM...MONDAY THROUGH THURSDAY.

EXTENDED MODELS/ENSEMBLES CONTINUE TO SHOW STRONG UPPER LEVEL
RIDGE OVER THE OH/TN VALLEYS DURING EARLY AND MIDDLE OF NEXT WEEK.
THIS TO BRING A SUMMERLIKE WEATHER PATTERN TO CENTRAL AND SE IL
WITH HOT AND HUMID WEATHER WITH HIGHS IN THE UPPER 80S AND LOWER
90S AND LOWS IN THE UPPER 60S AND LOWER 70S WHICH IS MORE TYPICAL
OF JULY. A WEAKENING FRONTAL BOUNDARY TO DROP DOWN TOWARD
CENTRAL/NORTHERN IL TUE AFTERNOON AND TUE NIGHT BRINGING JUST
SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS TO CENTRAL IL...WITH
BEST CHANCES STAYING NORTH OF OUR AREA. GFS APPEARS TOO AGGRESSIVE
WITH QPF MOVING INTO CENTRAL IL WITH STRONG UPPER LEVEL RIDGE JUST
TO OUR SE. 

HUETTL


&&

.AVIATION...
ISSUED 644 AM CDT FRI MAY 27 2011

LOW CLOUDS WILL PERSIST EAST OF I-55 FOR A FEW MORE HOURS...BEFORE
SLOWLY ERODING LATER THIS MORNING. WILL HANG ON TO 2500 TO 3500FT
CEILINGS AT KDEC THROUGH 15Z AND AT KCMI THROUGH 17Z. ONCE THE LOW
CLOUDS SCATTER OUT...PLENTY OF HIGH CLOUDS WILL STREAM ACROSS THE
SKY FOR THE BALANCE OF THE DAY. A DEVELOPING WARM FRONT WILL
SPREAD A DECK OF MID-LEVEL CLOUDS INTO CENTRAL ILLINOIS THIS
EVENING...FOLLOWED BY SCATTERED SHOWERS/STORMS OVERNIGHT. GIVEN
SCATTERED NATURE OF CONVECTION AND FORECAST SOUNDINGS INDICATING
SUB-SATURATED PROFILES...HAVE OPTED TO ONLY MENTION VCTS AT THE
TERMINALS BETWEEN 06Z AND 12Z. WINDS WILL INITIALLY BE FROM THE
NORTHEAST THIS MORNING...BUT WILL THEN VEER TO SOUTHEAST BY EVENING.


BARNES
&&

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

$$