Severe Thunderstorm Warning 83, NWS Quad Cities, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
225 AM CDT TUE JUL 3 2001

NW FLOW CONTINUES AT UPPER LEVELS ACROSS CWFA WITH LONG WAVE RIDGE
OVER WESTERN CONUS AND . AT LOWER LEVELS...H85 WARM FRONT STRETCHED
FROM NEB PANHANDLE EAST INTO S CENTRAL IA ON 00Z UPPER AIR ANALYSIS.
H5 SHORT WAVE EVIDENT ON WATER VAPOR MOVING INTO S CENTRAL SOUTH
DAKOTA HELPING TO PUSH ALONG LARGE MCS OCCURRING ALONG LOW LEVEL
BAROCLINIC AXIS. MAIN FORECAST CHALLENGE IS HANDLING OF POPS...SKY
COVER...AND TEMPERATURES IN FIRST PERIOD AS ON-GOING CONVECTION
MOVING INTO WESTERN IA AND CURRENTLY DEVELOPING IN PORTIONS OF CWA
AFFECT AREA THIS MORNING.

ALL MODELS INITIALIZED THE SHORTWAVE AND VORT MAX OVER WRN SD AT 00Z
AND PREDICTED MCS ACTIVITY. AVN WAS SUPERIOR IN QPF LOCATION...WITH
ETA AND NGM TOO FAR EAST INTO SE IA BY 06Z. BASED ON THIS...AND
RECENT PERFORMANCE...AVN IS MODEL OF CHOICE.

06Z SURFACE ANALYSIS SHOWS SURFACE FRONT EXTENDING EAST FROM LOW
BETWEEN KLBF AND KMCK EAST INTO SW IA WHERE DEWPOINTS IN LOWER 70S.
LARGE AREA OF TSRA OCCURING ALONG AND NORTH OF WARM FRONT OVER
EASTERN NE AND W CENTRAL IA BEGINNING TO TURN SE AS EXPECTED AND
WILL MAINLY IMPACT AREAS SOUTH OF I-80 THIS MORNING. HOWEVER...
3 HOUR PRESSURE FALL AXIS AT 06Z EXTENDING FROM CENTRAL IA TO NEAR
KORD BEGINNING TO LIGHT UP ON AREA 88DS WITH HIGH BASED CONVECTION
THAT WILL IMPACT AREAS NORTH OF I-80 AS WELL THROUGH SUNRISE. AVN
SHOWS IMPRESSIVE UPPER DIVERGENCE AND MID LEVEL OMEGA OVER SE IA AT
12Z AS H5 SHORTWAVE MOVES THROUGH. PRECIPITABLE H20 OF 1.5 TO OVER 2
INCHES INDICATES HEAVY RAINFALL POTENTIAL THIS MORNING BUT FLOODING
NOT A BIG CONCERN DUE TO RECENT DRY WEATHER AND HIGH FFG VALUES.
SEVERE THREAT LOOKS MARGINAL AS NOCTURNAL JET DIMINISHES AND BETTER
LOW LEVEL MOISTURE AXIS REMAINS TO WEST...BUT CANNOT RULE OUT
ISOLATED LARGE HAIL PRODUCERS. WILL GO WITH LIKELY TO CATEGORICAL
FOR THIS MORNING ALL ZONES...WAITING UNTIL LAST MINUTE FOR
APPROPRIATE WORDING.

AFTER CURRENT COMPLEX MOVES THROUGH...PROBLEM WILL BE WHERE MAIN
FRONT AND OUTFLOW BOUNDARIES LAY OUT IN AFTERNOON FOR REDEVELOPMENT
POTENTIAL. MAIN FRONT WILL LIKELY STAY SOUTH TO SW OF FORECAST AREA
AND WILL KEEP 50 PERCENT POPS IN SOUTH AND CUT TO 40 PERCENT IN
NORTH FOR AFTERNOON AS WEAK SURFACE HIGH BUILDS INTO CENTRAL IA.
TEMPERATURES SHOULD RISE INTO 80S AS SKIES CLEAR BEHIND CURRENT MCS
AND WILL STAY CLOSE TO MAV HIGHS. WEAK COLD FRONT PUSHES SOUTH OUT
OF CANADA INTO NORTHEAST IA LATE TONIGHT AND MAY TRIGGER SOME
CONVECTION AND WARRANT KEEPING LOW SCATTERED POPS IN ZONES. GUIDANCE
ALSO SUGGESTING ANOTHER CENTRAL PLAINS MCS TONIGHT...BUT SHOULD BE
FURTHER TO SOUTH WITH POSSIBLE IMPACT ON SOUTHERN ZONES TOWARD
WEDNESDAY MORNING AND WILL HAVE TO PLACE WORDING FOR LINGERING
MORNING RAIN IN SOUTH...OTHERWISE DRY ON 4TH. H85 TEMPERATURES
INDICATE SLIGHTLY COOLER HIGHS ON WED AND WENT CLOSER TO COOLER MAV.
REINFORCING SHOT OF COOL AIR PUSHES THROUGH LATE WED NIGHT FOR MUCH
COOLER HIGHS ON THURSDAY AND CURRENT EXTENDED FORECAST HANDLES THIS
WELL.

.DVN...
IA...NONE.
IL...NONE.
MO..6.NONE.

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