Severe Thunderstorm Warning 55, NWS Quad Cities, IA

AREA FORECAST DISCUSSION...CORRECTION TO ADD CODING AT BOTTOM
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
232 AM CDT THU MAY 18 2000

7Z SURFACE ANALYSIS PUTS THE LOW ALONG THE CENTRAL NE-KS BORDER
ABOUT IN LINE WITH 00Z MODEL FORECASTS.  A STATIONARY FRONT EXTENDS
EAST NORTHEAST FROM THE SURFACE LOW ACROSS NORTHERN IA.  STRONG
OUTFLOW FROM STORMS IN THE SUX AREA APPEARS TO BE PUSHING THE FRONT
SOUTHWARD.  WATER VAPOR IMAGERY DEPICTS THE MID-LEVEL CIRCULATION
OVER THE SURFACE LOW...AND THE MODELS DO INDICATE A VERTICALLY
STACKED SYSTEM.

MAIN CONCERN IS COMBINATION THREAT OF SEVERE WEATHER/HEAVY RAIN
TODAY.

00Z MODELS ARE IN GENERAL AGREEMENT ALTHOUGH THE AVN APPEARS A LITTLE
STRONGER AND FASTER THAN THE ETA/NGM.  WILL LEAN TOWARD THE LATTER
WHICH BRING THE SURFACE LOW EAST DURING THE DAY ALONG THE MO-IA
BORDER.  THE SYSTEM IS PROGGED TO DEPART THE REGION TONIGHT.

THE POTENTIAL FOR SEVERE CONVECTION EXISTS ACROSS MOST OF THE CWA
TODAY AND THIS EVENING.  LARGE HAIL WILL BE THE PRIMARY THREAT NORTH
OF THE FRONT. COMBINATION OF MODERATE TO HIGH SHEAR AND CAPE
ENVIRONMENT SUGGESTS POTENTIAL FOR SUPERCELLS AND THUS A TORNADIC
THREAT ALONG AND SOUTH OF THE FRONT.  THE FORECAST TIMING OF THE
SURFACE LOW AND TRIPLE POINT REACHING THE CWA TOWARD MAX HEATING THIS
AFTERNOON SUPPORT THIS.

A HEAVY RAIN THREAT EXISTS MAINLY NORTH OF THE FRONT THIS AFTERNOON
AND EVENING.  PRECIPITABLE WATER VALUES ARE OVER AN INCH AND 100-150
PERCENT OF NORMAL...AND THE FRONT WILL PROVIDE A GOOD FOCUS.
HOWEVER...850MB WINDS ARE PROGGED TO VEER THROUGH THE DAY SO LIFT
OVER THE FRONT WILL NOT BE AS IMPRESSIVE AS THIS MORNING OVER
SOUTHERN MN AND SOUTHERN WI.  SO...WILL MENTION HEAVY RAIN AS A
LOCALIZED THREAT IN THE ZONES/SWO BUT NOT ISSUE A FLASH FLOOD WATCH.

THE EXTENDED LOOKS GOOD AND WILL MAKE NO CHANGES.

WOLF

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

IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007-009-
015>018-024>026-034-035-MOZ009-010-190500-

SIGNIFICANT WEATHER OUTLOOK
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1028 AM CDT THU MAY 18 2000

...SEVERE WEATHER LIKELY ALONG AND SOUTH OF I-30 EXPECTED THIS
AFTERNOON...

A SLOW MOVING COLD FRONT WILL PROVIDE THE FOCUS FOR STORMS TO DEVELOP
BY AFTERNOON.

STORMS THAT DEVELOP ALONG AND NORTH OF US-30 WILL BE NORTH OF THE FRONT
WILL SEE THE POTENTIAL FOR LARGE HAIL OF GOLFBALL SIZE OR LARGER THE
PRIMARY RISK AND LOCALLY HEAVY RAINS.

AREAS ALONG AND ESPECIALLY SOUTH OF I-80 WILL BE ALONG AND SOUTH OF THE
FRONT AND COULD SEE SUPERCELLS DEVELOP WITH ISOLATED TORNADOES...LARGE
HAIL AND STRONG WINDS.  HEAVY RAINS BY LATE AFTERNOON COULD ALSO CREATE
LOCAL FLOODING. THE MOST SIGNIFICANT RISK FOR TORNADOES AT THIS TIME
APPEARS TO RUN ALONG AND SOUTH OF US-34 TIL EARLY EVENING.

THIS SEVERE WEATHER EPISODE IS EXPECTED TO BE SIGNIFICANT AND WIDESPREAD
THIS AFTERNOON WITH SPOTTER ACTIVATION NEEDED THIS AFTERNOON INTO
TONIGHT.

EMERGENCY MANAGERS SHOULD BEGIN PREPARATIONS NOW AND PASS ON ANY SEVERE
WEATHER REPORTS TO QUAD CITIES WFO.

NICHOLS