Flash Flooding and Flooding in Illinois, August 19, 2002

AREA GRIDDED FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO IL
205 PM CDT SUN AUG 18 2002

VAPOR IMAGERY SUPPORTING A STRONG VORT CROSSING INTO WESTERN DAKOTAS
FORECAST TO TRACK ACROSS WISCONSIN TONIGHT. THUS LATEST AVN/ETA RUNS
HAVE ABOUT AS MUCH LIFT IN NORTHERN PART OF CWFA DURING THE NIGHT AS
TO THE SOUTH. SO MOS BLEND YIELDING LIKELY POPS EVEN FAR NORTH IS
ACCEPTABLE.  MORE OF THIS LIFT WILL PROBABLY NEED TO GO INTO
SATURATION WHICH MAY DELAY ONSET OF PRECIP A BIT.  GOES SOUNDER
DATA, WHERE NOT OBSCURED BY CLOUDS, STILL SHOWING BEST PWS
APPROACHING 2 BOTTLED UP OVER SOUTHERN KANSAS. AS DISCUSSED
EARLIER, HEAVY RAIN THREAT (TREAT?) SUCH AS IT IS, APPEARS CONFINED
TO SOUTHERN COUNTIES. AND IN AMOUNTS EXPECTED TO FALL, IT SHOULD BE
VERY WELCOME. LINGERING MORNING SHOWERS A THREAT OVER ALL BUT FAR
NORTHWEST COUNTIES.  ETA SLOWER TO DRY THINGS OUT BUT WILL GO WITH
FASTER AVN/NGM SOLUTION THAT SHOULD YIELD ABUNDANT SUNSHINE BY
AFTERNOON IN THE NORTHWEST HALF OF THE CWFA.

ETA/AVN/NGM MOS BLEND GENERALLY USED FOR TEMPS.

DELIGHTFUL DAY EXPECTED TUESDAY BEFORE RETURN SOUTHERLY FLOW
BEGINS.  TUESDAY NIGHT INTO WEDNESDAY PRIMARY FOCUS OF 850 JET IS
NORTHWARD THROUGH THE PLAINS AND INTO UPPER MIDWEST.  SUPPOSE SOME
OF THIS DECAYING ACTIVITY COULD BLEED SOUTHEAST ALONG THICKNESS
CONTOURS INTO OUR NORTHERN COUNTIES, BUT FOR NOW WILL STICK WITH
GOING DRY FORECAST.  LATEST AVN RUN IN AGREEMENT WITH EARLIER HPC
GUIDANCE AND GOING FORECAST ON A SMALL THREAT OF PRECIP EARLY ON
THURSDAY NORTHERN CWA. PERHAPS AIDED BY A BOUNDARY LEFTOVER FROM THE
DAY BEFORE.

OTHERWISE FOR DAYS 4-7 MADE SMALL, MOSTLY UPWARD CHANGES TO HPC TEMP
GUIDANCE TO BLEND TOWARD PREVIOUS LOCAL FORECAST.  PRECIP GUIDANCE
ACCEPTED.

.CHI...NONE

KAPLAN