Flooding in Illinois, May 12, 2002

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO IL
200 AM CDT SUN MAY 12 2002

MIDNIGHT SURFACE MAP SHOWING ELONGATED LOW PRESSURE TROUGH FROM
SOUTHERN ROCKIES TO ILLINOIS WITH WARM FRONT CONTINUING TO EDGE
NORTHWARD THROUGH OUR CWA.  PROFILERS LATE EVENING HAVE SHOWN STRONG
& BACKING 850/925 WINDS IN SOUTHERN PLAINS REFLECTED IN EXPLOSION
OVER SOUTH CENTRAL KS AND BACKBUILDING IN NORTHERN MO.  THIS MAY
TAKE SOME OF THE STEAM OUT OF ACTIVITY IN OUR AREA BUT RADAR STILL
SHOWS LARGE AREA OF MODERATE/HEAVY RAIN MOVING INTO SOUTHWESTERN
CWFA AND TRAINING ECHOES UPSTREAM.  MESO ETA STILL SHOWS DECENT
850-925 MB SATURATED THETA E-ADVECTION THROUGH 12-15Z ESPECIALLY
SOUTHERN PORTIONS OF CWFA. WHAT RAIN HAS FALLEN, ALTHOUGH LIGHT IN
THE FAR SOUTH, HAS ONLY DECREASED THE ALREADY LOW FLASH FLOOD
THRESHOLDS. MAY A TIER OF COUNTIES FROM FLASH FLOOD WATCH ON THE
NORTH END BUT CONTINUE THROUGH 1800 OTHERWISE.

WILL CONTINUE WITH FORECAST ENDING RAIN/DRIZZLE NORTH TO SOUTH
TODAY.  AMOUNT OF CLEARING OVERNIGHT TONIGHT QUESTIONABLE WITH
CONTINUED CYCLONIC CURVATURE IN 850/925 MB FLOW AND HIGH RH BELOW
850 IN AVN/ETA TIME SECTIONS, SO WILL KEEP SKY COVER 80% OR BETTER
OVERNIGHT.  ON MONDAY A SHORT WAVE DROPS OUT OF CANADA AND THERES
SOME WEAK LOW LEVEL ISENTROPIC LIFT AHEAD OF IT IN THE AFTERNOON AND
EVENING. SOME MODELS SPIT OUT A COUPLE HUNDREDS IN NORTHERN CWA. SEE
THIS AS A POTENTIAL SPRINKLE EVENT FOR NOW, SO WILL MAINTAIN DRY
FORECAST, BUT KEEP MORE CLOUDS NORTH ESPECIALLY INTO THE FIRST PART
OF MONDAY NIGHT THAN PREVIOUS FORECAST.

AVN HAS SPED UP ARRIVAL OF LATE WEEK RAIN BY A DAY OR SO (TO
THURSDAY) AND CANADIAN MODEL SUPPORTS THIS. FOR NOW WILL JUST PUT
CHANCE IN AFTER 00Z FRIDAY. OTHERWISE LONGER TERM LOOKS GOOD.

WILL GENERALLY FOLLOW ETA/AVN/NGM MOS TEMP CONSENSUS SHORT TERM.

.CHI...FLOOD WATCH UNTIL 18Z GENERALLY ALONG AND S OF I-80.

KAPLAN