Severe Thunderstorm Warning 124, NWS Quad Cities, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
142 PM CDT SAT JUN 27 1998

THE 17Z SURFACE ANALYSIS HAD DEW POINTS IN THE MID AND UPPER 70S
WITH A BOUNDARY ACROSS THE NORTHERN PART OF THE STATE.  THE 700MB
ANALYSIS HAD +13 AT DVN WHILE +10 AT MPX.  BEST DIVERGENCE AT 200MB
ACROSS EASTERN SOUTH DAKOTA INTO SOUTHERN MINNESOTA AND NORTHERN
IOWA.  AT 850MB A BOUNDARY APPEARED TO BE OVER THE SOUTHERN PART
OF THE STATE EXTENDING FROM LOW PRESSURE OVER WESTERN KANSAS.
THE 17Z ADAP ALSO INDICATING BOUNDARY OVER NORTHERN IOWA.  AT 18Z
THUNDERSTORMS WERE BEGINNING TO DEVELOP OVER SOUTHWEST MINNESOTA...
JUST NORTH OF THE BOUNDARY.

THE CHALLENGE THIS FORECAST IS THUNDERSTORM CHANCE AND OVERNIGHT LOW
TEMPERATURES.

NGM AND ETA FAIRLY SIMILAR WITH CURRENT SITUATION.  BOTH SWING A
FRONT INTO WESTERN AND CENTRAL IOWA TONIGHT WITH SOMEWHAT DRIER
AIR BEHIND IT.  DONT EXPECT THIS FRONT TO MAKE MUCH OF A PUSH AS
UPPER LEVEL FLOW SOMEWHAT PARALLEL TO FLOW.  BOTH DEVELOP LARGE
AREA OF 300MB DIVERGENCE OVER NORTHERN IOWA AT 00Z BUT NGM THEN LIFTS
THIS DIVERGENCE INTO WISCONSIN AT 06Z AND ETA SHIFTS THIS DIVERGENCE
INTO CENTRAL IOWA. NGM LOW LEVEL THETA ADVECTION IS ALSO FARTHER
NORTH THAN THE ETA.  BOTH MODELS INDICATING PRECIPITABLE WATER VALUES
OF 150 TO 220 PERCENT OF NORMAL THROUGH THE NIGHT SO HEAVY RAIN WILL
BECOME A MAJOR FACTOR IF THUNDERSTORMS MOVE INTO THE CWA.  STORM
RELATIVE HELICITY VALUES REMAIN HIGHEST ACROSS CENTRAL IOWA THROUGH
MORNING.

700MB TEMPERATURES ALSO A CONCERN WITH +13 TO +14 ACROSS THE
REGION.  COOLER TEMPS AROUND MPX WHICH IS WHERE THUNDERSTORMS ARE
NOW DEVELOPING.  BOTH NGM AND ETA DO SUPPORT COOLER 700MB TEMPS OVER
EASTER IOWA BY 12Z SUNDAY.  850-300 THICKNESS WOULD ALSO FAVOR A
MORE SOUTHEAST DEVELOPMENT OF THUNDERSTORMS AS THEY MOVE INTO THE
EASTERN PART OF THE STATE.

WOULD AGREE ON LEAVING IN THE POPS FOR LATE NIGHT HOURS.  LOW TEMPS
FOR CURRENT FORECAST ALSO LOOK GOOD.

CID 71/40     DBQ 69/50     MLI 72/40     BRL 75/30

WEISSER

IAZ040>042-051-052-063-280830-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
935 PM CDT SAT JUN 27 1998

...SEVERE THUNDERSTORM WATCH IN EFFECT FOR PORTIONS OF EASTERN
IOWA...

A SEVERE THUNDERSTORM WATCH IS IN EFFECT FOR PORTIONS OF EASTERN
IOWA. COUNTIES IN THE WATCH INCLUDE IOWA... BENTON... LINN...
BUCHANAN... DELAWARE AND DUBUQUE. SOME CITIES IN THE WATCH ARE
MARENGO... VINTON... CEDAR RAPIDS... INDEPENDENCE... MANCHESTER
AND DUBUQUE.

A LINE OF THUNDERSTORMS FROM THE SOUTHWEST TIP OF IOWA TO NEAR
DECORAH WILL CONTINUE MOVING EASTWARD INTO A VERY UNSTABLE AIR MASS
SITUATED OVER EASTERN IOWA.

WHEN SEVERE THUNDERSTORMS ARE OCCURRING...MOVE INSIDE A STRONG
BUILDING. DO NOT STAND BY WINDOWS OR USE TELEPHONES OR
ELECTRICAL APPLIANCES UNLESS AN EMERGENCY. MOTORISTS SHOULD NOT
DRIVE INTO LOW WATER CROSSINGS.

TPH

IAZ040>042-051-052-063-280830-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
935 PM CDT SAT JUN 27 1998

...SEVERE THUNDERSTORM WATCH IN EFFECT FOR PORTIONS OF EASTERN
IOWA...

A SEVERE THUNDERSTORM WATCH IS IN EFFECT FOR PORTIONS OF EASTERN
IOWA. COUNTIES IN THE WATCH INCLUDE IOWA... BENTON... LINN...
BUCHANAN... DELAWARE AND DUBUQUE. SOME CITIES IN THE WATCH ARE
MARENGO... VINTON... CEDAR RAPIDS... INDEPENDENCE... MANCHESTER
AND DUBUQUE.

A LINE OF THUNDERSTORMS FROM THE SOUTHWEST TIP OF IOWA TO NEAR
DECORAH WILL CONTINUE MOVING EASTWARD INTO A VERY UNSTABLE AIR MASS
SITUATED OVER EASTERN IOWA.

WHEN SEVERE THUNDERSTORMS ARE OCCURRING...MOVE INSIDE A STRONG
BUILDING. DO NOT STAND BY WINDOWS OR USE TELEPHONES OR
ELECTRICAL APPLIANCES UNLESS AN EMERGENCY. MOTORISTS SHOULD NOT
DRIVE INTO LOW WATER CROSSINGS.

TPH

IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-
007-009-015>018-024>026-281005-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1204 AM CDT SUN JUN 28 1998

...SEVERE THUNDERSTORM WATCH UNTIL 500 AM CDT...

A SEVERE THUNDERSTORM WATCH HAS BEEN ISSUED FOR MUCH OF EASTERN IOWA
AND NORTHWEST ILLINOIS UNTIL 500 AM CDT. A LINE OF SEVERE
THUNDERSTORMS OVER CENTRAL IOWA WILL MOVE THROUGH EASTERN IOWA
THROUGH 300 AM AND INTO NORTHWEST ILLINOIS BETWEEN 200 AM AND 500 AM.

WIND GUSTS TO 80 MPH AND HAIL TO 2 INCHES IN DIAMETER ARE POSSIBLE.

STAY TUNED TO NOAA WEATHER RADIO OR YOUR FAVOURITE MEDIA OUTLET FOR
UPDATES ON THIS DANGEROUS WEATHER SITUATION.

HELGESON

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1206 AM CDT SAT JUN 27 1998

TIME(CDT)  .....CITY LOCATION.....   ST   ...EVENT/REMARKS...
DATE(CDT)  ....COUNTY LOCATION....

1J223 AM    INDEPENDENCE              IL   0.75 INCH HAIL
06/28/98   BUCHANAN