AREA FORECAST DISCUSSION
NWS CHICAGO IL
AFDCHI 1000 PM CST WED MAR 19 2003
DISCUSSION FOR UPDATE ZONES 900 PM
THE ALTIMETER PLOTS AT 03 UTC SHOW THE WARM FRONT FROM
WEST CENTRAL ILLINOIS TO CHICAGO ILLINOIS. A LINE OF
SHOWERS LIES ALONG THE FRONT. ACARS SOUNDINGS FROM ORD
AT 224 UTC SHOW A 32 KNOT WIND FROM THE SOUTH AT 2020 FT.
WARM AIR IS MOVING INTO THE FORECAST AREA TONIGHT. NORTHWEST
OF THE FRONT THERE MAY BE FOG. SO WILL KEEP FOG IN THE
FORECAST FOR THE NORTHERN AND WESTERN PARTS OF THE FORECAST
AREA. WILL RAISE THE LOW TEMPERATURE FORECAST FOR THIS
MORNING AS RESULT OF THE WARM AIR ADVECTION. WILL KEEP A CHANCE
OF SHOWERS OVERNIGHT.
.CHI...NONE
WHW
AVIATION DISCUSSION FOR 18Z TAFS...
FIRST WAVES OF PRECIP CONTINUING TO MOVE NORTH AND OUT OF TAF
AREAS. NEXT BAND SEEN ON RADAR ACROSS CENTRAL ILLINOIS. TIMING IS
FOR ARRIVAL IS MID-AFTERNOON. THOUGH NO LIGHTNING STRIKES WITHIN
LOT 88D RANGE COMPOSITE DATA INDICATED ~40 DBZ RETURNS. AN
ADDITIONAL INSTAB ENOUGH TO INCLUDE CHC TSTMS AS BAND MOVES
THROUGH.
SEQUENCE OF EVENTS FOR REMAINDER OF TAF PERIOD LOOKS OK -- TIMING
IS LESS CERTAIN. AFTER THIS AFTERNOON PRECIP, CHC CONTINUES
THROUGH AROUND MIDNIGHT OR JSUT AFTER. BY THAT TIME TAFS APPEARS
IN SYSTEM DRY SLOT WITH CIGS ICREASING TO VFR AND VSBYS OK. WILL
HAVE TO WAIT UNTIL SUFRFACE LOWS MOVES INTO IL THURSDAY AM FOR
RETURN TO MVFR CIGS.