Damaging Winds in Illinois, June 25, 2002

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
229 PM CDT TUE JUN 25 2002

CONVECTION WAS OCCURRING ACROSS MAINLY SOUTHEAST HALF CWFA THIS
AFTERNOON AS LOBE OF ENERGY ROTATING AROUND UPPER LOW OVER LA/TEX
APPROACHES FROM SE. HIGH PRECIP WATER AND LITTLE SHEAR OR STEERING
WINDS WILL KEEP THESE OF PULSE VARIETY WITH LOCALLY HEAVY RAINFALL
AND ANTICIPATE THIS ACTIVITY TO CONTINUE THIS EARLY EVENING ACROSS
SOUTH WHERE HIGH INSTABILITY AT SURFACE OVERLAPS MID LEVEL
DEFORMATION ZONE FAVORED FURTHER SOUTH. OTHERWISE...ATTENTION TURNS
TO UPPER TROUGH AND SURFACE LOW MOVING INTO SW ONTARIO THAT WILL
PUSH SURFACE COLD FRONT...FROM NW MN TO NEB PANHANDLE AT
18Z...THROUGH FORECAST AREA ON WEDNESDAY. MAIN FORECAST CHALLENGE IS
ASSOCIATED POPS TONIGHT THROUGH WEDNESDAY.

SHORT TERM MODELS NOT TOO FAR OFF IN HANDLING OF UPPER WAVE THAT
PHASES WITH LOWER MIS VALLEY CIRCULATION ON WED AND THEN SHIFTS TO
EAST WITH N-NW UPPER FLOW AROUND BUILDING H5 RIDGE OVER ROCKIES. AT
SURFACE...AVN HAD BEST MSL DEPICTION AT 18Z BUT ETA WAS HANDLING
AREAS OF PRECIP BEST SO FAR TODAY. BOTH ARE SIMILAR WITH
SURFACE LOW MOVING ACROSS SOUTHERN ONTARIO TONIGHT AND EARLY WED
BEFORE ETA SPEEDS UP EASTWARD PROGRESS OF LOW. BOTH HOWEVER HAVE
SIMILAR DEPICTIONS OF SURFACE FRONT FROM ABOUT RFD TO DSM AT 18Z WED
AND THIS LOOKS REASONABLE. WILL LEAN TOWARD ETA QPF EARLY...THEN
AVN/ETA BLEND LATER TONIGHT...WED AND THRU DAY 3.

QG FORCING AHEAD OF SHORTWAVE AND MID LEVEL SPEED MAX TO NORTH
SHOULD HELP INITIATE CONVECTION THIS EVENING IN SRN MN THAT WILL
WANDER INTO IA ZONES AFTER SUNSET WHERE MID LEVEL LAPSE RATES
STEEPENS AND FORECAST SB CAPES ABOVE 2K J/KG. MET POPS IN LIKELY CAT
FOR THIS AREA AND THIS LOOKS REASONABLE WITH TSRA SHIFTING S INTO
CENTRAL ZONES AFTER MIDNIGHT. IN AREAS TO SOUTH...WILL WAIT UNTIL
LAST MINUTE FOR ON GOING TSRA COVERAGE/POPS TERMS THIS EVENING. ON
WEDNESDAY...FORCING WILL BE MAXIMIZED ALONG AND AHEAD OF FRONT AND
SEVERE POTENTIAL PER SPC DAY 2 LOOKS REASONABLE WITH DIURNAL FRONTAL
TIMING FAVORING AREAS S OF I-80. WITH ABUNDANT MOISTURE AND FOCUS
ALONG ACTIVE FRONT...ETA LIKELY POPS FOR WED FAVORED OVER THE MAINLY
20-30 PERCENT VALUES IN AVN AND NGM MOS. WILL KEEP SCATTERED POPS
GOING FOR SOUTHERN ZONES ALONG FRONT AND WHERE MID LEVEL FORCING
CONTINUES INTO EVENING...THEN A BIT COOLER AND LESS HUMID MAIN STORY
FOR THE REST OF THE WORK WEEK.

WILL KEEP TEMPERATURES CLOSE TO GUIDANCE AND NEAR CLIMO THU AND FRI.
LATEST AVN PRODUCES QUESTIONABLE QPF SAT AND SAT NIGHT...BUT WITH
HIGH FROM H85 THROUGH H85 OVERHEAD AND RIDGING AT SURFACE...WILL
IGNORE. RETURN FLOW AT SURFACE WILL BRING WARMING TREND FOR WEEKEND
WITH HIGHS BACK TO NEAR 90 IN INCREASE IN HUMIDITY. MEDIUM RANGE
GUIDANCE INDICATING SHORTWAVE BREAKING OFF UPPER LOW OFF WESTERN CAN
COAST TO PUSH LONG NORTHERN CONUS SOMEWHERE IN MONDAY AND TUESDAY
TIMEFRAME...WITH LITTLE CONSISTENCY BETWEEN MODELS. WILL INTRODUCE
SHRA/TSRA FOR MONDAY AND TUESDAY AND GO WITH HIGHS TRENDED TOWARD
COOLER MEX GUIDANCE TO ACCOUNT FOR CLOUDS AND RAIN.

IA...NONE.
IL...NONE.
MO...NONE.

DLS