AREA FORECAST DISCUSSION
NWS CHICAGO IL
AFDCHI 333 AM CDT THU JUL 29 1999
HEAT WARNING/ADVISORY TO REMAIN IN EFFECT THROUGH FRIDAY AS
OPPRESSIVE HEAT AND HUMIDITY BUILD IN. AIRCRAFT SOUNDINGS INTO ORD
AND RFD SHOWING 850MB TEMPS ALREADY 23-25C WITH 900MB AT 26-27C.
THIS WOULD YIELD MID TO UPPER 90S WITHOUT ANY ADDITIONAL WARMING.
SOURCE REGION AT H8 HAD HIGHS OF 95-101 SO 95 TO 100 RANGE ACROSS FA
REASONABLE. SURFACE DEW POINTS CURRENTLY AROUND 70 WITH TRAJECTORY
FROM NORTHERN MO WHERE MID AND UPPER 70 DEW POINTS WERE OBSERVED.
COMBO OF HOT TEMPS AND HIGH DEW POINTS PUSHES HEAT INDEX VALUES
ABOVE ADVISORY THRESHOLD, AND INTO SIMILAR WARNING TERRITORY FOR
CHICAGO METRO AREA. THUNDERSTORMS IN SOUTHEAST MN AND WEST CENTRAL
WI MOVING EAST SOUTHEAST WITH MOVEMENT OF COLDEST TOPS EASTWARD.
THERE IS A SLIGHT CHANCE THAT FAR NORTHEAST IL WILL BE BRUSHED WITH
A FEW SHOWERS/THUNDERSHOWERS LATER THIS MORNING BUT MOST OR ALL
ACTIVITY TO REMAIN IN WI ON EDGE OF HOT AIR. CHANCES BELOW
THRESHOLD FOR MENTIONING IN FORECAST. HEAT TO REMAIN THROUGH FRIDAY
AND EARLY SATURDAY WITH DRY WX UNTIL APPROACH OF COLD FRONT ON
SATURDAY.
.CHI...HEAT WRNG CHI METRO & HEAT ADVSRY RMNDR OF FA TDY THRU FRI.
TRS