Severe Thunderstorm Warning 115, NWS Quad Cities, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
214 AM CDT WED JUN 24 1998

06Z SURFACE ANALYSIS HAS WARM FRONT INTO SOUTHERN IOWA/CENTRAL
ILLINOIS WITH A TROF ACROSS NORTHERN IOWA/SOUTHERN WISCONSIN.
MESOSCALE IS VERY NOISY WITH A MESOHIGH AT KMCW AND NUMEROUS OUTFLOW
BOUNDARIES.  PROFILER AND WATER VAPOR IMAGERY HAVE A SHORTWAVE
MOVING THROUGH NORTHERN IOWA AND ANOTHER UPSTREAM IN WESTERN KANSAS.
A 50 KT LLJ RUNS FROM THE TEXAS PANHANDLE INTO IOWA.  ISODROSOTHERM
ANALYSIS HAS LOW 70 DEW POINTS ACROSS ALL BUT FAR NORTHWEST
ILLINOIS.  IR IMAGERY SHOWED WARMING TOPS BUT LAST FEW IMAGES SHOWS
COOLING TOPS AGAIN. DVN 88D ALSO SHOWS REFLECTIVITY GRADIENT HAS
SUDDENLY STRENGTHENED PAST SEVERAL SCANS.

PROBLESM ARE INITIAL SEVERE/PRECIP CHANCES THEN CLOUDS AND HIGH
TEMPERATURES.

ETA/AVN APPEAR TO HAVE INITIALIZED THE BEST OF THE 00Z MODELS IN
OVERALL RESPECT TO THE SYNOPTIC FEATURES.  ETA/AVN PUSH SHIFT THE
LLJ EAST EARLY THIS MORNING AND SLOWLY PUSH WARM FRONT NORTH DURING
THE DAY.  CURRENT STRONG/SVR MCS WILL CONTINUE FOR NEXT SEVERAL
HOURS.  RADAR TRENDS LIKELY THE BEST WAY TO LINE UP PRECIP CHANCES
FOR NEW ZONES.  CURRENT THINKING IS THAT SOUTH OF I80 WILL REMAIN
DRY AS CAPPING ATMOSPHERE BEHIND WARM FRONT IS ALREADY IN PLACE.
NORTH OF I80 CONTINUE MENTION OF SCATTERED TSRA IOWA ZONES AND
CHANCE FOR ILLINOIS ZONES.  IOWA ZONES LIKELY HAVE BEST CHANCES FOR
SEVERE AND SHOULD BE INCLUDED IN ZONES.  DECREASING CLOUDS LATER
THIS MORNING WITH RESIDUAL MOISTURE ALOFT SHOULD BE ENOUGH FOR
PARTLY SUNNY AND HUMID.

TRAJECTORY METHOD GIVES MIXED RESULTS BUT FWC/FAN NUMBERS GIVE
AROUND 90.  BELIEVE SOUTH OF I80 AROUND 90 LOOKS GOOD.  RESIDUAL
CLOUDS FROM MCS A PROBLEM MAINLY NORTH OF I80 BUT ESPECIALLY
NORTHEAST IOWA ZONES.  BELIEVE NEAR 90 MLI AREA LOOKS GOOD WITH
UPPER 80S NORTHWEST ILLINOIS ZONES AND 85 TO 90 NORTHEAST IOWA ZONES.

CID 088/30  DBQ 085/40  MLI 089/30  BRL 091/00

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