Severe Thunderstorm Warning 86, NWS Des Moines, IA

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-081>086-
092>097-131800-

CENTRAL IOWA THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
615 AM CDT SUN JUL 13 1997

HAZARD--MORE INTENSE THUNDERSTORMS WITH POTENTIAL FOR DAMAGING WINDS AND
TORRENTIAL RAIN WEST OF I-35 LATE THIS AFTERNOON AND EVENING.

TIMING AND AREA OF CONCERN--REDEVELOPMENT OF THUNDERSTORMS IS POSSIBLE
AFTER 300 PM FOR THE AREA NORTHWEST OF AN ALGONA TO DENISON LINE...WITH
THESE STORMS MOVING EAST TO I-35 BY MIDNIGHT.

METEOROLOGICAL COMMENTS--WIDELY SCATTERED THUNDERSTORMS WHICH WERE OVER
THE EASTERN THIRD OF IOWA AT 600 AM WILL MOVE OUT OF THE AREA ON THE
HEELS OF A DEPARTING UPPER LEVEL LOW PRESSURE TROUGH. BEHIND THE
STORMS...THE AIR REMAINED VERY MOIST AND UNSTABLE ALL NIGHT LONG. LOW 70
DEGREE DEWPOINTS ARE EXPECTED TO INCREASE DURING THE DAY AS TEMPERATURES
SOAR INTO THE 90S...DESTABILIZING THE ATMOSPHERE EVEN FURTHER.

THUNDERSTORMS WERE APPROACHING SIOUX CITY FROM THE WEST AT 600 AM. THESE
STORMS WERE TRACKING ALONG AN OUTFLOW BOUNDARY WHICH EXTENDED FROM MASON
CITY TO A SURFACE LOW IN SOUTH CENTRAL NEBRASKA. THE STORMS SHOULD
DISSIPATE THIS MORNING BEFORE MOVING TOO FAR INTO IOWA. THIS WILL SET
THE STAGE FOR REDEVELOPMENT OF THUNDERSTORMS LATE THIS AFTERNOON AND
EVENING AS A COLD FRONT MOVES EAST AND INTERACTS WITH THE OUTFLOW
BOUNDARIES IN NORTHWEST IOWA.

BY THE TIME THUNDERSTORMS REDEVELOP...LIFTED INDICES WILL BE NEAR MINUS
12 ACROSS IOWA. AN INFUSION OF WARM AIR AT MID LEVELS OF THE ATMOSPHERE
SHOULD DELAY REDEVELOPMENT AND LIMIT THE AREAL COVERAGE OF ANY STORMS.
PRECIPITABLE WATER IS STILL EXTREMELY HIGH OVER IOWA...SO THE STORMS
COULD EASILY PRODUCE 2-3 INCHES OF RAIN IN A SHORT TIME. DRY AIR AND
STRONGER MID-LEVEL WINDS WILL REACH THE STORMS THIS EVENING...INCREASING
THE POSSIBILITY OF STRONG DOWNBURST WINDS. SEVERE WEATHER POTENTIAL IS
EXPECTED TO BE ISOLATED OVER IOWA. HOWEVER...IF THE MID LEVELS END UP
COOLER THAN EXPECTED...THUNDERSTORM COVERAGE AND SEVERE POTENTIAL WOULD
BECOME MORE WIDESPREAD.

PRECAUTIONS--THE HEAT AND HUMIDITY WILL BE THE MAIN PROBLEM TODAY...AND
A HEAT ADVISORY IS IN EFFECT ALONG AND SOUTH OF HIGHWAY 20. STORMS
DEVELOPING OVER THE NORTHWEST THIRD OF IOWA WOULD HAVE THE BEST CHANCE
TO PRODUCE SEVERE WEATHER AND SPOTTER ACTIVATION MAY BE NEEDED LATE THIS
AFTERNOON OR EVENING. RUNOFF PROBLEMS ON ROADWAYS AND RAPID RISES IN
SMALL STREAMS MIGHT OCCUR IN ASSOCIATION WITH LOCALLY HEAVY RAINFALL.

JUNGBLUTH

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-081>086-
092>097-131800-

CENTRAL IOWA THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
615 AM CDT SUN JUL 13 1997

HAZARD--MORE INTENSE THUNDERSTORMS WITH POTENTIAL FOR DAMAGING WINDS AND
TORRENTIAL RAIN WEST OF I-35 LATE THIS AFTERNOON AND EVENING.

TIMING AND AREA OF CONCERN--REDEVELOPMENT OF THUNDERSTORMS IS POSSIBLE
AFTER 300 PM FOR THE AREA NORTHWEST OF AN ALGONA TO DENISON LINE...WITH
THESE STORMS MOVING EAST TO I-35 BY MIDNIGHT.

METEOROLOGICAL COMMENTS--WIDELY SCATTERED THUNDERSTORMS WHICH WERE OVER
THE EASTERN THIRD OF IOWA AT 600 AM WILL MOVE OUT OF THE AREA ON THE
HEELS OF A DEPARTING UPPER LEVEL LOW PRESSURE TROUGH. BEHIND THE
STORMS...THE AIR REMAINED VERY MOIST AND UNSTABLE ALL NIGHT LONG. LOW 70
DEGREE DEWPOINTS ARE EXPECTED TO INCREASE DURING THE DAY AS TEMPERATURES
SOAR INTO THE 90S...DESTABILIZING THE ATMOSPHERE EVEN FURTHER.

THUNDERSTORMS WERE APPROACHING SIOUX CITY FROM THE WEST AT 600 AM. THESE
STORMS WERE TRACKING ALONG AN OUTFLOW BOUNDARY WHICH EXTENDED FROM MASON
CITY TO A SURFACE LOW IN SOUTH CENTRAL NEBRASKA. THE STORMS SHOULD
DISSIPATE THIS MORNING BEFORE MOVING TOO FAR INTO IOWA. THIS WILL SET
THE STAGE FOR REDEVELOPMENT OF THUNDERSTORMS LATE THIS AFTERNOON AND
EVENING AS A COLD FRONT MOVES EAST AND INTERACTS WITH THE OUTFLOW
BOUNDARIES IN NORTHWEST IOWA.

BY THE TIME THUNDERSTORMS REDEVELOP...LIFTED INDICES WILL BE NEAR MINUS
12 ACROSS IOWA. AN INFUSION OF WARM AIR AT MID LEVELS OF THE ATMOSPHERE
SHOULD DELAY REDEVELOPMENT AND LIMIT THE AREAL COVERAGE OF ANY STORMS.
PRECIPITABLE WATER IS STILL EXTREMELY HIGH OVER IOWA...SO THE STORMS
COULD EASILY PRODUCE 2-3 INCHES OF RAIN IN A SHORT TIME. DRY AIR AND
STRONGER MID-LEVEL WINDS WILL REACH THE STORMS THIS EVENING...INCREASING
THE POSSIBILITY OF STRONG DOWNBURST WINDS. SEVERE WEATHER POTENTIAL IS
EXPECTED TO BE ISOLATED OVER IOWA. HOWEVER...IF THE MID LEVELS END UP
COOLER THAN EXPECTED...THUNDERSTORM COVERAGE AND SEVERE POTENTIAL WOULD
BECOME MORE WIDESPREAD.

PRECAUTIONS--THE HEAT AND HUMIDITY WILL BE THE MAIN PROBLEM TODAY...AND
A HEAT ADVISORY IS IN EFFECT ALONG AND SOUTH OF HIGHWAY 20. STORMS
DEVELOPING OVER THE NORTHWEST THIRD OF IOWA WOULD HAVE THE BEST CHANCE
TO PRODUCE SEVERE WEATHER AND SPOTTER ACTIVATION MAY BE NEEDED LATE THIS
AFTERNOON OR EVENING. RUNOFF PROBLEMS ON ROADWAYS AND RAPID RISES IN
SMALL STREAMS MIGHT OCCUR IN ASSOCIATION WITH LOCALLY HEAVY RAINFALL.

JUNGBLUTH

IAZ033>039-044>050-057>062-070>075-081>086-092>097-131745-

HEAT ADVISORY UPDATE
NATIONAL WEATHER SERVICE DES MOINES IA
657 AM CDT SUN JUL 13 1997

ADVISORY INFORMATION--A HEAT ADVISORY IS IN EFFECT FOR THE SOUTHERN
TWO-THIRDS OF IOWA TODAY.

FORECAST CONDITIONS AND RECENT REPORTS--HEAT INDICES WILL CLIMB INTO
THE 105 TO 110 DEGREE RANGE TODAY AS ACTUAL AIR TEMPERATURES SOAR INTO
THE LOW TO MID 90S. TO MAKE MATTERS WORSE...TEMPERATURES ACROSS THE
ADVISORY AREA FELL ONLY INTO THE MID AND UPPER 70S OVERNIGHT. WITH
PLENTY OF SUNSHINE EXPECTED ACROSS THE ADVISORY AREA...THE HEAT WILL
BUILD QUICKLY...REACHING HAZARDOUS LEVELS BY LATE MORNING.

PRECAUTIONS--CHECK ON ELDERLY RESIDENTS AND THOSE IN POOR HEALTH TODAY
SINCE THEY ARE MOST SUSCEPTIBLE TO THE HEAT. PEOPLE WHO WILL BE AT
LOCAL CARNIVALS AND FAIRS THIS AFTERNOON SHOULD ALSO TAKE PRECAUTIONS.
STAY OUT OF THE SUN AS MUCH AS POSSIBLE AND DRINK PLENTY OF FLUIDS.
MAKE SURE PETS AND LIVESTOCK ALSO HAVE PLENTY OF WATER.

PYTLAK