Hail and Damaging Winds in Illinois, July 26, 2002

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
155 AM CDT FRI JUL 26 2002

CONFIDENCE IN MODELS REMAINS LOW WITH NO CLEAR CUT TRENDS AND WILL
GO WITH A COMPROMISE PER NCEP. FORECAST CHALLENGE IS TIMING OF
CONVECTION CHANCES THRU TUE...AND HOW HOT IT WILL BE DURING THIS
HEAT WAVE THRU MON.

06Z SURFACE ANALYSIS HAS 1011 MB LOW OVER CENTRAL WI WITH FRONTAL
BOUNDARY EXTENDING SW THRU SOUTH CENTRAL IA...FAR NW MO TO 1008 LOW
OVER CENTRAL KS. CONVECTION FIRED UP OVER SE NE WHERE ENHANCED LOW
LEVEL JET AND SHORT WAVE. ALSO SMALLER AREA OF CONVECTION OVER SE WI
NEAR MILWAUKEE AND MOVING ESE. THETAE RIDGE OVER CENTRAL PLAINS
EXTENDS EAST TOWARD QUINCY AND CONVECTION TO DEVELOP IN THAT
DIRECTION TODAY TOWARD CENTRAL IL. INCREASING POPS TO GOOD CHANCE
TODAY AS SHORT WAVE IN CENTRAL PLAINS MOVES INTO IL. WILL KEEP LOWER
POPS FAR 6 SOUTHERN COUNTIES WHERE PROB30/40. BEST CHANCE THIS
AFTERNOON N OF I-70 AS DAYTIME HEATING INTERACTS WITH TROPICAL LIKE
AIR MASS AND DISTURBANCE MOVES INTO AREA. SPC HAS SLIGHT RISK OF
SEVERE OVER ALL BUT FAR SOUTHERN CWA TODAY. VERY STRONG INSTABILITY
WITH LI DROPPING TO MINUS 6-8C BY AFTERNOON AND ENHANCED SHEAR FROM
DECENT NW MID LEVEL FLOW AND SUFFICIENT LOW LEVEL SRH TO GENERATE A
FEW SUPERCELLS FROM IA/MO BORDER EAST INTO WESTCENTRAL IL. 24 HOUR
SURFACE TO 850 MB TEMP TRAJECTORIES DERIVED FROM SW MO WHERE THU
HIGHS 88 TO 93 AND SHOULD OCCUR HERE TODAY WITH DEWPOINTS IN LOW TO
MID 70S GIVING HEAT INDICES NEAR 100 THIS AFTERNOON.

CONVECTION CHANCES LOOK BEST OVER NE CWA TONIGHT AS WAA/MOISTURE
ADVECTION MOVES NE INTO NE IL SAT. UPPER LEVEL RIDGES NUDGES N
TOWARD CENTRAL IL THIS WEEKEND INCREASING CAP AND THIS TO LESSEN F
CHANCE OF CONVECTION. KEEPING PROB30 BUT MOST OF THIS WEEKEND TO BE
DRY WITH BEST CHANCE OF CONVECTION FOCUSED NORTH. HEAT WAVE ALSO
INTENSIFIES AS 850 MB TEMPS RISE TO BETWEEN 20-22C THIS WEEKEND AND
MORE SUNSHINE. HIGHS IN THE LOW TO MID 90S (WARMEST SW) AND
DEWPOINTS IN LOW TO MID 70S GIVES AFTERNOON HEAT INDICES NEAR 105...
APPROACHING HEAT ADVISORY CRITERIA. THIS IS A COUPLE PERIODS AWAY
AND HAVE TIME TO DETERMINE IF HEAT ADVISORY NEEDS TO BE POSTED THIS
WEEKEND. BETTER CHANCE OF CONVECTION MON AND MON NIGHT AS COLD FRONT
MOVES SE THRU CENTRAL IL MON NIGHT. DRIER AND LESS HUMID WEATHER
RETURNS WITH SEASONABLE TEMPS DURING MID WEEK. TUE LOOKING DRY NORTH
OF I-70 BUT WILL LEAVE CHANCE OF CONVECTION DURING THE DAY TUE AS
FRONT COULD MOVE THRU SLOWER.

...PRELIMINARY CCF FOR COORDINATION PURPOSES...

SPI EB 092/073 094/073 094 07543
PIA EB 090/073 092/073 092 07554
DEC EB 090/073 092/073 092 07543
CMI BB 088/071 091/072 091 07554
MTO BB 090/072 092/073 092 07543
LWV BB 093/073 095/074 095 07443

.ILX...NONE.

KH