Severe Thunderstorm Warning 71, NWS Chicago, IL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
645 AM CDT SUN JUN 8 2008

.DISCUSSION...
343 AM CDT

WHILE SOME SORT OF CONVECTION IS LOOKING LIKE A GOOD BET
TODAY...MORE CONVECTION WILL LIKELY DEVELOP TO OUR WEST ALONG THE
SURFACE BOUNDARY DURING THE DAY TODAY. THIS CONVECTION IS THEN
FORECAST TO PEEL SLOWLY OFF THE FRONT AND PROBABLY INTO OUR CWA
SUNDAY NIGHT...DEPENDING ON HOW MESOSCALE DETAILS PLAY OUT
TODAY...SOME SEVERE POTENTIAL COULD EXIST INTO TONIGHT IF ATMOSPHERE
IS ABLE TO RECOVER SUFFICIENTLY OR ISNT OVERTURNED IN THE FIRST
PLACE.

SHORT RANGE MODELS IN PRETTY GOOD AGREEMENT ON SWINGING SLIGHTLY
HIGHER AMPLITUDE SYNOPTIC SCALE SHORTWAVE AROUND THE BASE OF THE
TROUGH MONDAY...WHICH SHOULD THE SURFACE BOUNDARY A GOOD KICK TO
MOVE EASTWARD. THIS CERTAINLY JUSTIFIES KEEPING POPS HIGH THROUGH
MONDAY...THOUGH CURRENT TIMING WOULD TEND TO FAVOR OUR SOUTHERN
COUNTIES FOR HIGHER SEVERE PROBABILITIES. THE SEVERE THREAT MONDAY
WILL HINGE ON MESOSCALE DETAILS THAT JUST CANT BE RESOLVED THIS FAR
OUT...BUT SYNOPTICALLY THE SET-UP IS CERTAINLY FAVORABLE.

LIKELY OF GREATER CONCERN OVER THE NEXT 48 HOURS IS GOING TO BE THE
HEAVY RAINFALL/FLOODING POTENTIAL. AIRMASS IS VERY JUICED UP WITH
DEWPOINTS WELL INTO THE 70S AND PWATS PROGGED TO APPROACH TWO
INCHES. GIVEN THIS AMOUNT OF MOISTURE...THUNDERSTORMS SHOULD BE VERY
EFFICIENT RAIN PRODUCERS...WITH RAINFALL RATES LOCALLY IN EXCESS OF
2 INCHES PER HOUR QUITE REASONABLE. BELIEVE THAT THERE IS CERTAINLY
A FLASH FLOOD POTENTIAL BETWEEN NOW AND MONDAY...BUT REALLY NOT
COMFORTABLE ENOUGH WITH TIMING/LOCATION OF GREATEST THREAT ATTM TO
HOIST A FFA AND DIDNT FEEL COMFORTABLE WITH A 48 HOUR LONG BLANKET
FFA COVERING THE ENTIRE CWA. FOR NOW...WILL HIT THE FLASH FLOOD
POTENTIAL HARD IN THE HWO AND MENTION +RA IN TEXT FORECAST AND LET
NEXT SHIFT RE-ACCESS POSSIBLE NEED FOR A FLASH FLOOD WATCH.

FOCUS OF THE FORECAST WAS ON THE SHORT TERM AND MADE NO CHANGES TO
GRIDS BEYOND MONDAY. TEMPERATURE FORECAST...PARTICULARLY THE HIGH
TEMPS...WILL ALSO HINGE ON CONVECTIVE EVOLUTION SO TEMP FORECAST
COULD BE A BIT GENEROUS IS CLOUDS/PRECIP DOMINATE EITHER TODAY OR
SUNDAY. ON THE OTHER HAND...IT WOULDNT TAKE TOO MUCH JUNE SUN FOR
TEMPS TO REALLY RESPOND...SO GENERALLY FOLLOWED THE TREND OF
PREVIOUS FORECAST.

IZZI

&&

.AVIATION...

12Z TAFS...MAIN CONCERN THIS PERIOD CONTINUES TO BE CHANCE OF
PRECIP AND CONVECTION. ISOLATED SHOWERS CONTINUE TO FORM AND
QUICKLY MOVE NORTHEAST ACROSS NORTHERN IL THIS MORNING. VERY
LITTLE LIGHTNING WITH THESE SHOWERS AND WILL HANDLE THESE WITH A
VCSH GROUP FOR A FEW HRS. ATTENTION THEN TURNS TO COMPLEX OVER IA.
NOT SURE IF THIS WILL HOLD TOGETHER AS IT MOVES ACROSS NORTHERN IL
LATER THIS MORNING INTO THIS AFTERNOON. THINK IT WILL MAKE IT TO
RFD AND HAVE INCLUDED A TEMPO FOR THUNDER THERE BUT WILL LIKELY BE
DISSIPATING AS IT CONTINUES EAST. SO HAVE INCLUDED JUST A VCTS FOR
THE CHICAGO AREA TERMINALS THIS AFTERNOON INTO EARLY THIS EVENING
FOR ONE OF TWO POSSIBLITIES...EITHER CONVECTION ACROSS IOWA DOES
MAKE IT TO NORTHEAST IL OR IT DOESN/T AND ISOLATED CONVECTION
FIRES ALONG VARIOUS OUTFLOW BOUNDARIES THAT EXIST ACROSS THE AREA.
THIS EVENING APPEARS QUIET WITH MORE ACTIVITY DEVELOPING AHEAD OF
THE APPROACHING COLD FRONT LATE TONIGHT.

OTHER CONCERN TODAY ARE THE WINDS. IN THE SHORT TERM...SOUTHEAST
WINDS BEHIND EARLIER BOUNDARY WILL TURN BACK SOUTHWEST OVER THE
NEXT FEW HRS THEN BEGIN TO INCREASE BY LATE MORNING AND EARLY
AFTERNOON. GUSTS TO 25+KTS LIKELY DURING MUCH OF THE AFTERNOON
BUT WIND SPEEDS/GUSTS MAY BE LIMITED BY DEBRIS CLOUDS/CONVECTION
THROUGH THE MORNING HRS. EXPECT MAINLY VFR CIGS THROUGH THIS
EVENING AWAY FROM PRECIP...BRIEF MVFR/IFR CIGS POSSIBLE WITH ANY
HEAVIER SHOWERS/STORMS WITH MVFR CIGS POSSIBLE TOWARD THE END OF
THE PERIOD. CMS

&&

.MARINE...
130 AM...

HIGH PRESSURE WILL REMAIN PARKED OVER THE SOUTHEASTERN STATES FOR
THE NEXT FEW DAYS. A TROUGH OF LOW PRESSURE OVER THE CENTRAL
PLAINS HAS AN ASSOCIATED FRONTAL BOUNDARY WHICH EXTENDS NORTHEAST
INTO INTO MINNESOTA. A SERIES OF WEAK LOWS WILL RIPPLE ALONG THE
FRONT TO THE NORTHEAST INTO THE UPPER MISSISSIPPI VALLEY FORCING
THE NORTHERN PORTION OF THE FRONT EAST TO LAKE SUPERIOR. A
STRONGER LOW WILL DEVELOP OVER THE CENTRAL PLAINS TODAY. THIS LOW
WILL TRACK TO THE NORTHEAST AS THE FRONTAL BOUNDARY MOVES SLOWLY
EASTWARD. THE FRONT WILL FINALLY MOVE EAST ACROSS LAKE MICHIGAN
LAKE TONIGHT OR MONDAY MORNING. DAYTIME HTG ON SUNDAY MIXING
FORCING MIXING OF WINDS TO NEAR 30 KTS ALOFT TO SFC. THIS BLOWING
OFFSHORE TO NEARSHORE WATERS IN LT MRNG THRU AFTN. THUS ISSUING
ANOTHER SCA FOR SUNDAY FOR HIGH WINDS...ALTHO WAVES WORKING FROM
OFFSHORE SHUD BE 4 FEET OR LESS.

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY FROM 11 AM THIS MORNING TO 9 PM CDT THIS
     EVENING FOR LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745.

&&

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