Severe Thunderstorm Warning 6, NWS Quad Cities, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
245 PM CDT WED APR 19 2000

PLENTY TO LOOK AT TODAY.  WELCOME PRECIP THAT MOVED THROUGH
OVERNIGHT AND EARLY THIS MORNING HAS EXITED INTO NORTHERN ILLINOIS
AND SOUTHERN WISCONSIN.  IMPRESSIVE UPPER LOW HAS MOVED INTO
SOUTH-CENTRAL SOUTH DAKOTA THIS AFTERNOON.  AT THE SURFACE...THE
LOW  IN SOUTHEASTERN SOUTH DAKOTA HAS OCCLUDED AND THE NEW LOW HAS
DEVELOPED IN NORTH-CENTRAL MISSOURI AND SOUTH-CENTRAL IOWA.  WARM
FRONT EXTENDS SOUTHEASTWARD INTO EAST-CENTRAL MISSOURI  WITH A
DRYLINE SOUTHWESTWARD INTO SOUTH-CENTRAL KANSAS.
CLOUDS-DRIZZLE-GRUNGE HAVE KEPT TEMPS IN CHECK ACROSS NORTHERN PART
OF CWFA.  BREAKS IN CLOUDS NOW DEVELOPING ACROSS SOUTHERN COUNTIES
SHOULD PROVIDE JUST ENOUGH HEATING TO DESTABILIZE THE LOWER
LAYERS...THEN AS THE UPPER LOW APPROACHES THE CAP SHOULD WEAKEN
ENOUGH FOR THUNDER TO MOVE IN EARLY THIS EVENING.  REFERENCE THE SPC
DAY 1 OUTLOOK FOR A DETAILED DISCUSSION OF THE REGIONAL THREAT.

WILL KEEP MENTION OF SEVERE FOR THIS EVENING.  STORMS SHOULD BE
MOVING AT 40 TO 50 KTS AGAIN TONIGHT...SO WOULD NOT EXPECT A THREAT
OF FLASH FLOODING.  AREAS TO WATCH ARE NORTHWESTERNMOST COUNTIES
WHERE RAINFALL THIS MORNING EXCEEDED AN INCH IN SPOTS.

MODELS IN GENERAL AGREEMENT ON THE EVOLUTION OF THE UPPER LOW BUT
HAVE SOME DISCREPANCIES ON THE MOVEMENT OF THE SURFACE FEATURES.  AT
THIS POINT PREFER THE ETA SOLUTION WHICH DEFINES THE SURFACE LOW A
LITTLE MORE CLEARLY AT 00Z.

GIVEN THE STRENGTH OF THE SYSTEM...WOULD EXPECT A SIGNIFICANT CLOUD
SHIELD TO BLANKET THE AREA THURSDAY SO TEMPS WILL STRUGGLE TO CLIMB
OUT OF THE 50S.  EXPECT NGM IS TOO OPTIMISTIC CLEARING THINGS OUT
THURSDAY NIGHT SO WILL UNDERCUT GUIDANCE TEMPS FRIDAY BY TWO CATS OR
MORE AND HANG ON TO THE CLOUDS.

ON THE BRIGHT SIDE...THE WEEKEND LOOKS NICE WITH TEMPS WARMING BACK
INTO THE 70S AND LOTS OF SUN FOR EASTER EGG HUNTS.

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

33

IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007-009-
015>018-024>026-034-035-MOZ009-010-200100-

SIGNIFICANT WEATHER OUTLOOK
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
448 PM CDT WED APR 19 2000

...POTENTIAL FOR A FEW SEVERE THUNDERSTORMS LATE THIS AFTERNOON AND
TONIGHT...
...MAIN THREAT WILL BE LARGE HAIL AND DAMAGING WIND ALONG AND SOUTH
OF HIGHWAY 34...

AT 4 PM...LOW PRESSURE WAS CENTERED OVER NORTHERN NEBRASKA...WITH
A WARM FRONT DRAPED ACROSS IOWA AND ILLINOIS FROM ROUGHLY WASHINGTON
TO SOUTH OF THE QUAD CITIES TO NEAR KEWANEE. A DRYLINE WAS NEARLY
STATIONARY FROM SOUTH CENTRAL IOWA INTO NORTHERN MISSOURI FROM WEST OF
OTTUMWA TO NEAR CHILLICOTHE.

THUNDERSTORMS HAVE DEVELOPED OVER CENTRAL AND EASTERN MISSOURI IN
A REGION OF BETTER MOISTURE AND INSTABILITY. THUNDERSTORMS ARE EXPECTED
TO BUILD NORTH INTO SOUTHEAST IOWA...WEST CENTRAL ILLINOIS AND NORTHEAST
MISSOURI OVER THE NEXT SEVERAL HOURS. THE MAIN THREAT FROM THESE
THUNDERSTORMS WILL BE VERY HEAVY RAIN...LARGE HAIL AND DAMAGING WIND.
AN ISOLATED TORNADO WILL ALSO BE POSSIBLE...ALTHOUGH WIND PROFILES ARE
MARGINAL AT BEST.

THE THREAT FOR SEVERE WEATHER DIMINISHES NORTH OF THE WARM FRONT. THIS
INCLUDES IOWA CITY...CEDAR RAPIDS...CLINTON...PROPHETSTOWN AND AREAS TO
THE NORTH. THUNDERSTORMS ARE STILL EXPECTED...BUT THE SIGNIFICANT CLOUD
COVER HAS STABILIZED THE ATMOSPHERE. ANY THUNDERSTORMS WILL JUST BRING
LOCALLY HEAVY RAIN AND PERHAPS SOME SMALL HAIL. ALONG THE WARM FRONT
FROM NEAR WASHINGTON TO THE QUAD CITIES...POTENTIAL STILL EXISTS FOR
A FEW THUNDERSTORMS TO PRODUCE LARGE HAIL. THUNDERSTORM INTERACTION
WITH THE BOUNDARY COULD ALSO LEAD TO A FEW BRIEF WEAK TORNADOES.

THE THREAT FOR SEVERE WEATHER SHOULD END LATE THIS EVENING.

EMERGENCY MANAGERS AND SPOTTERS SHOULD MONITOR LATER STATEMENTS AND
SHORT TERM FORECASTS. SPOTTER ACTIVATION MAY BE NEEDED LATE THIS
AFTERNOON AND TONIGHT...ALOuNG AND SOUTH OF INTERSTATE 80.

MCCLURE

IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007-009-
015>018-024>026-034-035-MOZ009-010-200300-

SIGNIFICANT WEATHER OUTLOOK...CORRECTED TYPO
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
612 PM CDT WED APR 19 2000

...POTENTIAL FOR A FEW SEVERE THUNDERSTORMS LATE THIS EVENING...MAINLY
ALONG AND SOUTH OF HIGHWAY 34...

AT 6 PM...LOW PRESSURE WAS CENTERED OVER SOUTHERN SOUTH DAKOTA WITH
A WARM FRONT DRAPED ACROSS IOWA AND ILLINOIS FROM ROUGHLY IOWA CITY TO
THE QUAD CITIES TO NEAR KEWANEE. A DRYLINE REMAINS NEARLY STATIONARY
FROM SOUTH CENTRAL IOWA THROUGH NORTHWEST MISSOURI INTO EASTERN KANSAS.

SHOWERS AND THUNDERSTORMS WHICH DEVELOPED OVER MISSOURI HAVE MOVED
QUICKLY INTO CENTRAL ILLINOIS. A LAYER OF WARM AIR ALOFT...ALSO KNOWN
AS A CAP...HAS PREVENTED CONVECTION FROM BLOSSOMING ALONG THE DRYLINE.
HOWEVER...COOL AIR ALOFT FROM AN APPROACHING UPPER LEVEL DISTURBANCE
WILL AID IN ERODING THE CAP WITH THUNDERSTORM DEVELOPMENT EXPECTED BY
10 PM OVER WESTERN MISSOURI AND PORTIONS OF EASTERN KANSAS. THESE
THUNDERSTORMS WILL LIKELY MOVE EAST INTO NORTHEAST MISSOURI...SOUTHEAST
IOWA AND WEST CENTRAL ILLINOIS AROUND MIDNIGHT AND CONTINUE THROUGH THE
OVERNIGHT. THE MAIN THREAT FROM THE THUNDERSTORMS WILL BE HEAVY RAIN...
SMALL HAIL AND GUSTY WINDS. A FEW THUNDERSTORMS MAY PRODUCE LARGE
HAIL AND DAMAGING WINDS ALONG AND SOUTH OF A MOUNT PLEASANT TO MONMOUTH
LINE.

EMERGENCY MANAGERS AND SPOTTERS OVER SOUTHEAST IOWA...NORTHEAST MISSOURI
AND WEST CENTRAL ILLINOIS SHOULD MONITOR LATER STATEMENTS AND SHORT TERM
FORECASTS. SPOTTER ACTIVATION MAY BE NEEDED LATE THIS EVENING SOUTH OF
INTERSTATE 80.

MCCLURE