Severe Thunderstorm Warning 71, NWS Des Moines, IA

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-081>086-
092>097-192215-

CENTRAL IOWA THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
1109 AM CDT TUE MAY 19 1998

HAZARD--WIDELY SCATTERED SEVERE THUNDERSTORMS CAPABLE OF PRODUCING
LARGE HAIL...HEAVY RAIN AND GUSTY WINDS.

AREA OF CONCERN--SOUTH OF HIGHWAY 20.

TIMING DETAILS--AFTER 200 PM OVER NORTH CENTRAL IOWA...AFTER 700 PM IN
SOUTHERN IOWA.

METEOROLOGICAL COMMENTS--THUNDERSTORMS ARE CURRENTLY PUSHING ACROSS
PARTS OF NORTHWEST MISSOURI AND EASTERN IOWA LATE THIS MORNING AND
HAVE PRODUCED SEVERAL OUTFLOW BOUNDARIES OVER SOUTHERN IOWA. IN
ADDITION...A SLOW MOVING FRONTAL BOUNDARY ACROSS NORTHERN IOWA IS
FORECAST TO BECOME STATIONARY THIS AFTERNOON OVER PARTS OF CENTRAL
IOWA. THE ATMOSPHERE IS ALREADY VERY UNSTABLE WITH TEMPERATURES ALOFT
COOLING JUST ENOUGH TO ALLOW THUNDERSTORM DEVELOPMENT LATE THIS
MORNING OVER PARTS OF SOUTHERN IOWA. MOISTURE CONVERGENCE IS FORECAST
TO INCREASE ALONG THE FRONTAL BOUNDARY BY MID AFTERNOON WHICH WILL
ENHANCE ADDITIONAL THUNDERSTORM DEVELOPMENT ACROSS PARTS OF CENTRAL
AND SOUTHERN IOWA. THE PRIMARY THREAT APPEARS TO BE FROM LARGE HAIL
AND HEAVY RAINFALL...HOWEVER DUE TO THE EXTREME INSTABILITY FORECAST
ALONG THE BOUNDARY THIS AFTERNOON AND EVENING...ONE OR TWO OF THE
STRONGER STORMS MAY PRODUCE WIND GUSTS TO 70 MPH.

PRECAUTIONS--SPOTTER ACTIVATION MAY BE NEEDED LATER THIS
AFTERNOON...ESPECIALLY OVER THE SOUTHERN TWO THIRDS OF THE STATE.
EMERGENCY MANAGERS SHOULD KEEP ABREAST OF LATER CENTRAL IOWA
THUNDERSTORM OUTLOOKS THIS AFTERNOON REGARDING THE SEVERE THUNDERSTORM
POTENTIAL.

SMITH

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-081>086-
092>097-200130-

CENTRAL IOWA THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
228 PM CDT TUE MAY 19 1998

HAZARD--WIDELY SCATTERED SEVERE THUNDERSTORMS CAPABLE OF PRODUCING
HAIL UP TO GOLFBALL SIZE...HEAVY RAIN AND WIND GUSTS TO 70 MPH.

AREA OF CONCERN--SOUTH OF HIGHWAY 20.

TIMING DETAILS--AFTER 400 PM.

METEOROLOGICAL COMMENTS--THE COLD FRONT HAS PRETTY MUCH STALLED OUT
FROM NEAR WATERLOO TO AROUND ATLANTIC. TOWERING CUMULUS CLOUDS WERE
DEVELOPING ALONG AND SOUTH OF THIS FRONT WHICH INDICATED THAT THE
TEMPERATURE INVERSION SUPPRESSING THUNDERSTORM DEVELOPMENT WAS CLOSE
TO BREAKING. IN FAR NORTHEAST IOWA AND SOUTHERN WISCONSIN...THE CAP
HAS ALREADY RUPTURED RESULTING IN A FEW SEVERE STORMS. AS THE EVENING
PROGRESSES AN UPPER LEVEL DISTURBANCE WILL MOVE OUT OF COLORADO...
COOLING THE MID LEVELS AND BREAKING DOWN THE CAP. THUNDERSTORMS SHOULD
THEN BECOME MORE WIDESPREAD ALONG THE BOUNDARY FROM IOWA ALL THE WAY
BACK INTO THE NEBRASKA/KANSAS BORDER AREA. THE DEGREE OF INSTABILITY
AND PRESENCE OF DRY AIR ALOFT INDICATES LARGE HAIL AND DAMAGING
DOWNBURSTS WILL BE THE MAIN HAZARDS. BECAUSE THE FRONT WILL ALSO BE
STATIONARY FOR MUCH OF THE NIGHT...UP TO 2 INCHES OF RAIN COULD FALL
IN A FEW SPOTS BUT PARTICULARLY EXCESSIVE RAIN IS NOT EXPECTED SINCE
GULF OF MEXICO INFLOW IS RATHER WEAK AND THERE IS CONSIDERABLE DRY AIR
ALOFT.

PRECAUTIONS--A SEVERE THUNDERSTORM WATCH HAS BEEN ISSUED FOR EXTREME
EASTERN IOWA AND MAY BE NEEDED FURTHER WEST LATER THIS EVENING.

PYTLAK

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-081>086-
092>097-200130-

CENTRAL IOWA THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
228 PM CDT TUE MAY 19 1998

HAZARD--WIDELY SCATTERED SEVERE THUNDERSTORMS CAPABLE OF PRODUCING
HAIL UP TO GOLFBALL SIZE...HEAVY RAIN AND WIND GUSTS TO 70 MPH.

AREA OF CONCERN--SOUTH OF HIGHWAY 20.

TIMING DETAILS--AFTER 400 PM.

METEOROLOGICAL COMMENTS--THE COLD FRONT HAS PRETTY MUCH STALLED OUT
FROM NEAR WATERLOO TO AROUND ATLANTIC. TOWERING CUMULUS CLOUDS WERE
DEVELOPING ALONG AND SOUTH OF THIS FRONT WHICH INDICATED THAT THE
TEMPERATURE INVERSION SUPPRESSING THUNDERSTORM DEVELOPMENT WAS CLOSE
TO BREAKING. IN FAR NORTHEAST IOWA AND SOUTHERN WISCONSIN...THE CAP
HAS ALREADY RUPTURED RESULTING IN A FEW SEVERE STORMS. AS THE EVENING
PROGRESSES AN UPPER LEVEL DISTURBANCE WILL MOVE OUT OF COLORADO...
COOLING THE MID LEVELS AND BREAKING DOWN THE CAP. THUNDERSTORMS SHOULD
THEN BECOME MORE WIDESPREAD ALONG THE BOUNDARY FROM IOWA ALL THE WAY
BACK INTO THE NEBRASKA/KANSAS BORDER AREA. THE DEGREE OF INSTABILITY
AND PRESENCE OF DRY AIR ALOFT INDICATES LARGE HAIL AND DAMAGING
DOWNBURSTS WILL BE THE MAIN HAZARDS. BECAUSE THE FRONT WILL ALSO BE
STATIONARY FOR MUCH OF THE NIGHT...UP TO 2 INCHES OF RAIN COULD FALL
IN A FEW SPOTS BUT PARTICULARLY EXCESSIVE RAIN IS NOT EXPECTED SINCE
GULF OF MEXICO INFLOW IS RATHER WEAK AND THERE IS CONSIDERABLE DRY AIR
ALOFT.

PRECAUTIONS--A SEVERE THUNDERSTORM WATCH HAS BEEN ISSUED FOR EXTREME
EASTERN IOWA AND MAY BE NEEDED FURTHER WEST LATER THIS EVENING.

PYTLAK