Severe Thunderstorm Warning 2, NWS Chicago, IL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO IL
246 PM CST THU MAR 20 2003

DISCUSSION FOR 330 PM GRIDS/ZFP

MAIN FORECAST CONCERNS INVOLVE CONVECTION/PRECIP TRENDS TONIGHT WITH
UPPER LOW WOBBLING THROUGH MIDWEST...THEN PRECIP TRENDS NEXT SEVERAL
DAYS WITH PROGRESSIVE UPPER PATTERN.

SATELLITE LOOP SHOWS THE LOW AS SWIRL IN CLOUDS OVER SOUTHWEST
MISSOURI THIS AFTERNOON...WITH CONVECTIVE DEVELOPMENT NOTED IN
SAT/RADAR IMAGERY IN MOIST FLOW FEEDING FROM KY-IND-ERN IL. 18Z
SOUNDING OUT OF ILX INDICATES STEEP LAPSE RATES WITH FREEZING LEVEL
AROUND 7500 FT...THOUGH SOMEWHAT DRY LOW LEVELS YIELDING A CAPE OF
930 J/KG. SURFACE DEWPOINTS ARE HIGHER ACROSS MUCH OF WFO CHICAGO FA
HOWEVER...WITH MODIFIED ACARS SOUNDING RESULTING IN ABOUT 1200 J/KG.
SOUNDINGS SHOW SOME BACKING WITH HEIGHT THROUGH LOWEST 3.5 KM...SO
MAIN SEVERE THREAT INTO EARLY EVENING TO BE HAIL WITH RELATIVELY
VERTICAL PULSING UPDRAFTS AND LOW WBZ/FREEZING LEVEL. HIGHEST THREAT
FOR THUNDER OVER EASTERN PORTIONS OF FA...WITH BETTER LOW LEVEL
MOISTURE...HEATING WITH BREAKS IN CLOUD COVER...AND CLOSER PROXIMITY
TO SYNOPTIC SCALE DYNAMICS NORTHEAST OF WEAKENING UPPER SYSTEM. WILL
GO WITH SCATTERED/OCCASIONAL MENTION ESPECIALLY EARLY TONIGHT FOR
SHOWERS/THUNDER WITH HIGHEST POPS EAST. LIGHT WIND FIELD AS SURFACE
TROF MOVES THROUGH TONIGHT...WITH AREAS OF LIGHT FOG LATE.

WILL KEEP CHANCE POPS FOR SHOWERS INTO FRIDAY MORNING AS UPPER LOW
FILLS AND TROF AXIS PASSES TO EAST. SECOND CLOSED UPPER SYSTEM DROPS
INTO PLACE OVER WISCONSIN...WITH DRY AIR WRAPPING INTO IL AROUND
SOUTHERN PERIPHERY...THOUGH COLD POOL ALOFT MAY RESULT IN SOME
AFTERNOON AND EVENING INSTABILITY SHOWERS IN NORTHERN COUNTIES PER
GOING FORECAST. LOW PULLS OFF TO EAST OVER WEEKEND WITH NCEP
ENSEMBLES IN REASONABLE AGREEMENT WITH OPERATIONAL GFS RUNS. NEXT
CHANCE FOR PRECIP TO BE MONDAY...AS LOW PRESSURE MOVES ACROSS
SOUTHERN CANADA AND DRAGS COLD FRONT INTO AREA. CHANCE LINGERS INTO
WED AS FRONT PUSHES SOUTH...THEN WEAK HIGH PRESSURE THURSDAY.

.CHI...NONE

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ILZ003>006-008-010>014-019-020>023-032-033-039-
INZ001-002-010-011-019-211200-

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE CHICAGO IL
1027 AM CST THU MAR 20 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH CENTRAL AND NORTHEAST
ILLINOIS...NORTHWEST INDIANA...AND THE ADJACENT WATERS OF LAKE
MICHIGAN.

.DAY ONE... TODAY AND TONIGHT

SCATTERED SHOWERS AND THUNDERSTORMS WILL AFFECT NORTHERN ILLINOIS
AND NORTHWEST INDIANA TODAY. DEVELOPMENT OF THESE SHOWERS DURING THE
MORNING HOURS HAS HELPED TO MIX OUT DENSE FOG OVER THE AREA EARLIER
THIS MORNING...AND WITH VISIBILITIES IMPROVING TO A MILE OR MORE AT
MOST LOCATIONS...THE DENSE FOG ADVISORY HAS BEEN ALLOWED TO EXPIRE.

SCATTERED THUNDERSTORMS WILL CONTINUE THIS AFTERNOON AND EVENING. A
FEW STORMS MAINLY SOUTH OF I-80 AND EAST OF I-39 COULD PRODUCE
SEVERE HAIL.

.DAYS TWO THROUGH SEVEN... FRIDAY THROUGH WEDNESDAY

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS MAY BE NEEDED THIS AFTERNOON AND EVENING.

           NWS CHICAGO WEBPAGE

    HTTP://WWW.CRH.NOAA.GOV/LOT (LOWER CASE)
OR  HTTP://WEATHER.GOV/CHICAGO (LOWER CASE)

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