Severe Thunderstorm Warning 137, NWS Quad Cities, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1145 AM CDT SUN AUG 6 2000

UPDATED ZFP TO INCREASE POPS A TOUCH AND ADD MENTION OF SEVERE.
ATMOSPHERE VERY UNSTABLE WITH LITTLE IN WAY OF CIN PER LAPS DATA.
LATEST RUC2 COMPOSITE SHOWS AN AXIS OF CAPES IN EXCESS OF 3000 J/KG
OVER SOUTHEAST IA AND WEST CENTRAL IL...WITH ANOTHER AXIS THRU
WESTERN ZONES AHEAD OF FRONT. LATEST SFC ANALYS SHOWS FRONT ALONG A
LINE FROM WATERLOO TO DES MOINES...CLOSING GAP ON WEAK PRE-FRONTAL
WINDSHIFT FROM CEDAR RAPIDS TO OTTUMWA. MSAS COMPUTED LI/S RUNNING
-5 TO -10 THROUGHOUT CWA. MOISTURE/INSTABILITY PRESENT...ALL THAT/S
NEEDED IS LIFT/FORCING. WE WILL HAVE THAT AS WELL. WATER VAPOR
SHOWED WAVE INTO WESTERN IA WITH IMPRESSIVE DRYING. WAVE NOT HANDLED
WELL BY MODELS AND SHOULD AID IN CONVECTIVE DEVELOPMENT THIS
AFTERNOON. UPPER AIR ANALYS ALSO HAD WAVE WITH 100 KT H250 JET MAX
NORTHERN IA INTO CENTRAL/SOUTHERN MN. NOWCASTING TOOLS POINT TO
CONVECTION DEVELOPING AROUND 2 PM OR SOON THEREAFTER. MAIN FOCUS
WILL BE ALONG FRONT INTO WESTERN ZONES. OTHER CONVECTION TO OUR SOUTH
ACROSS MO ALONG H850 CONVERGENCE ZONE. SPC HAS MOVED SLIGHT RISK
A BIT FURTHER NW. MODERATE RISK BRUSHES FAR EASTERN COUNTIES. THINK
SLIGHT RISK SHUD COME FARTHER NW TO NEAR A LINE FROM DUBUQUE TO IOWA
CITY TO FAIRFIELD. SHEAR SUFFICIENT TO SUPPORT A FEW HP SUPERCELLS WITH
CONVECTION LIKELY EVOLVING INTO SQUALL LINE AS IT EXITS EAST OF CWA.
CONTACTED SPC AND WILL BE DOING A SPECIAL SOUNDING AT 18Z.

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

MCCLURE

IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007-
009-015>018-024>026-034-035-MOZ009-010-071000-

SIGNIFICANT WEATHER OUTLOOK
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1207 PM CDT SUN AUG 6 2000

...SCATTERED STRONG TO SEVERE STORMS POSSIBLE THIS AFTERNOON INTO
EARLY EVENING...

A WEAK COLD FRONT NEAR A LINE FROM WATERLOO TO DES MOINES WILL MOVE
SLOWLY EAST REACHING THE MISSISSIPPI RIVER BY EARLY EVENING.
MEANWHILE...AN UPPER AIR DISTURBANCE MOVING THROUGH WESTERN IOWA
WILL INTERACT WITH THE FRONT TO IGNITE SCATTERED THUNDERSTORMS OVER
THE AREA BY MID AFTERNOON. THE AIR AHEAD OF THIS FRONT IS VERY MOIST
WITH DEWPOINTS WELL INTO THE 70S. THIS COMBINED WITH AMPLE SUNSHINE
HAS LED TO A VERY UNSTABLE AIRMASS WITH CAPES IN EXCESS OF 3000 J/KG
AND LIFTED INDICES OF -5 TO -10. STORMS WHICH DEVELOP WILL CONTAIN
TORRENTIAL RAIN...AND HAVE THE POTENTIAL TO PRODUCE LARGE HAIL AND
DAMAGING WINDS. AN ISOLATED TORNADO WILL ALSO BE POSSIBLE...MAINLY IN
ILLINOIS WHERE SHEAR WILL BE GREATEST. THE AREAS MOST SUSCEPTIBLE FOR
STRONG TO SEVERE STORMS WILL GENERALLY BE EAST OF A LINE FROM DUBUQUE
TO IOWA CITY TO FAIRFIELD.

ALONG WITH THE THREAT FOR SEVERE WEATHER...HIGH HUMIDITY COMBINED
WITH TEMPERATURES IN THE UPPER 80S TO AROUND 90 DEGREES WILL RESULT
IN VERY UNCOMFORTABLE CONDITIONS. AFTERNOON HEAT INDICES ARE FORECAST
TO TOP OUT BETWEEN 90 AND 100 DEGREES. IF SPENDING TIME OUTDOORS...BE
SURE TO SLOW DOWN...DRINK PLENTY OF FLUIDS AND TAKE FREQUENT BREAKS
IN THE SHADE. ALSO IF SPENDING TIME OUTDOORS...BE SURE TO KEEP AN EYE
TO THE SKY...AND MAKE SURE YOU HAVE A WAY OF MONITORING THE LATEST
WEATHER CONDITIONS.

SPOTTER ACTIVATION WILL LIKELY BE NEEDED BY MID TO LATE AFTERNOON
EAST OF A DUBUQUE TO IOWA CITY TO FAIRFIELD LINE. INTERESTED
INDIVIDUALS SHOULD MONITOR NOAA WEATHER RADIO OR THEIR FAVORITE MEDIA
SOURCE FOR FURTHER UPDATES.

MCCLURE