FXUS63 KLOT 271142
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO IL
640 AM CDT FRIDAY AUGUST 27 2004

.DISCUSSION FOR MORNING GRIDS/ZONES...

MAIN FORECAST PROBLEM FRIDAY/SATURDAY AND CONVECTIVE TRENDS AND 
HEAVY RAINFALL POTENTIAL. 

MCS ROLLING THROUGH FCST AREA EARLY THIS MORNING BEGINING TO 
WEAKEN...WITH 40-50 MPH GUSTS REPORTED. THREAT APPEARS TO BE TURNING 
TO HEAVY RAINFALL...AS SOUTHERN PORTION OF SYSTEM HAS BECOME 
ORIENTED MORE WEST-EAST FROM IA/MO BORDER INTO WCNTRL IL. WATER 
VAPOR LOOP AND PROFILER PLOTS INDICATE SPD MAX/SHORT WAVE TROUGH 
MOVING ACROSS IA AT THIS HOUR...WITH 50 KTS INDICATED AT H5 AT 
SLATER IA. 30-40 KT H85 JET VEERING FROM SOUTHERN PLAINS INTO NRN 
IL. THIS KEEPING LLVL THETA-E ADVECTION AND MOIST CONVERGENCE INTO 
IA/NRN IL...WITH NEW ELEVATED CONVECTION ACROSS EASTERN IA NORTH OF 
MAIN MCS. EXPECT CONTINUED DVLPMNT/ADVECTION OF TSTMS ACROSS NRN IL 
AND NW IND THIS AM AND WILL KEEP LIKELY POPS THROUGH THIS AM. MCS 
SHOULD LAY OUT OUTFLOW BOUNDARY TO THE SOUTH OF THE FCST AREA 
TODAY...AND AFTER WEAKENING OF LLJ LATER THIS MORNING WILL LIKELY 
SEE A LULL IN ACTIVITY HERE BY EARLY AFTN. SYNOPTIC COLD FRONT STILL 
TO NW OF FCST AREA...AND EXPECT NEW DEVELOPMENT ALONG IT AND MCS 
OUTFLOW LATER THIS AFTERNOON AS NEXT S/WV APPROACHES FROM PLAINS. 
FRONT SAGS INTO FCST AREA WITH 00Z MODEL RUNS ALL BRINING SFC WAVE 
ALONG FRONT TONIGHT. THUS WILL KEEP LIKELY POPS GOING THROUGH 
TONIGHT AND INTO SAT MORNING AS WAVE PROPAGATES ALONG FRONTAL 
BOUNDARY. ETA FCST PWATS AROUND 2 INCHES WITH VERY MOIST AIRMASS IN 
WARM SECTOR...WITH POTENTIAL FOR EXCESSIVE RAINFALL ACROSS/NEAR 
PORTIONS OF FCST AREA TONIGHT/EARLY SAT. FF GUIDANCE CURRENTLY 
RUNNING 2.5-3.5 INCHES ACROSS WESTERN PORTIONS OF CWA WHICH HAVE 
SEEN MOST RAIN OVERNIGHT. MUCH HINGES ON DEVELOPMENT OF MCS TONIGHT 
WITH APPROACHING SFC WAVE...AND WILL HOLD OFF ON 2ND PERIOD FLOOD 
WATCH AND ALLOW DAY SHIFT A BETTER LOOK.

RATZER

&&

.AVIATION FOR 12Z...
A FEW LEFT OVER SHRA IN THE AREA THAT ARE QUICKLY DYING OUT. EXPECT 
VFR CIGS THIS MORNING WITH BKN MVFR CIGS IN AFTN DUE TO SOME HEATING 
OF ALL THE MOISTURE IN THE COLUMN. THERE IS THE CHANCE OF SOME 
SCATTERED TS LATE AFTERNOON DUE TO CLOSENESS OF FRONT, BUT THINK 
SCATTERED SO JUST VCTS IN THE TAFS. BEST CHANCES OF TS AGAIN LATER 
TONIGHT BEGINNING AROUND 06Z AS UPPER TROF APPROACHES WITH WEAK LOW 
RIDING UP THE FRONT. CORE OF MCS PROBABLY JUST S OF TAFS BUT WILL BE 
BIG ENOUGH TO COVER THE AREA. 

AF
&&

.LOT...WATCHES/WARNINGS/ADVISORIES...
.IL...NONE.
.IN...NONE.
.LK MI...NONE.

$$