Tornado Warning 1, NWS Des Moines, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
242 PM CDT MON APR 5 1999

PLENTY GOING ON TODAY WITH MAIN FORECAST CHALLENGES BEING IN THE
FIRST PERIOD WITH THUNDERSTORMS...WIND AND ENDING TIMES.
CURRENTLY...LARGE AREA OF SHOWERS AND THUNDERSTORMS WHICH WERE
LOCATED OVER MUCH OF THE CWA HAVE MOVED RAPIDLY NORTH.  THERE HAS
BEEN ONE LINE OF PERSISTENT CONVECTION OVER THE WESTERN CWA THAT HAS
LAID DOWN A COUPLE INCHES OF RAIN BUT NO WATER PROBLEMS AS OF YET.
INITIAL DRY GROUND HAS REALLY SOAKED UP THE RAIN.  AS OF 19Z...
CONVECTION DOWN IN MO IS RAPIDLY MOVING NORTH INTO SOUTHERN IOWA
WHICH IS THE LOCATION OF OUR PRIMARY SEVERE THREAT.  CLOUDY SKIES AND
LOW DEWPOINTS HAVE REALLY NOT HELPED OUR CASE FOR SEVERE CONVECTION
AND MOST IF NOT ALL CONVECTION WILL REMAIN ELEVATED.  BEST THREAT
REMAINS HIGH WINDS SINCE FORWARD PROGRESS ON THESE STORMS REMAINS
AROUND 50 TO 60 MPH...BUT CAN GUSTS PENETRATE COLD AIR NEAR SURFACE.
EITHER WAY...WILL MENTION POSSIBLE SEVERE IN EXTREME SOUTHERN ZONES.
IN ADDITION...GRADIENT WINDS HAVE INCREASED SUBSTANTIALLY THIS
AFTERNOON WITH GUSTS UP TO 50 MPH.  AFTER DISCUSSION WITH SEVERAL
SURROUNDING OFFICES...WILL ISSUE WIND ADV FOR NORTHERN CWA NORTH OF A
FOD-CAV-MCW LINE.

THE SYSTEM WILL BLOW THROUGH TONIGHT CLEARING MOST PLACES BUT WILL
KEEP CLOUDS FAR NORTHEAST.  CALM WEATHER TO PREVAIL INTO WEDNESDAY
WITH INCREASING CLOUDS BY WEDNESDAY NIGHT IN ADVANCE OF THE NEXT
SYSTEM.

.DSM...WIND ADVISORY IAZ004>007-015>017-023>025-033>035.

COGIL

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-081>086-
092>097-061100-

CENTRAL IOWA THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
1150 AM CDT MON APR 5 1999

HAZARD -WIDESPREAD RAIN WITH SCATTERED THUNDERSTORMS.  SOME STORMS
MAY BE SEVERE WITH DAMAGING WINDS AND LARGE HAIL.  THERE IS ALSO THE
POSSIBILITY OF A TORNADO BUT IT IS NOT THE PRIMARY THREAT.  MODERATE
TO HEAVY RAINS WILL ALSO OCCUR WITH THE THUNDERSTORMS WITH AN INCH OR
MORE OF RAIN POSSIBLE.

AREA OF CONCERN -THUNDERSTORMS COULD OCCUR ACROSS ALL OF CENTRAL
IOWA.  THE PRIMARY THREAT OF SEVERE WEATHER WILL BE SOUTH OF
INTERSTATE 80.  THE BEST CHANCES FOR HEAVY RAIN WILL BE OVER NORTHERN
AND WESTERN IOWA.

TIMING DETAILS -THUNDERSTORMS COULD OCCUR ANYTIME THIS AFTERNOON AND
INTO THE EVENING HOURS.  THE BEST CHANCES FOR SEVERE WEATHER WOULD BE
LATE AFTERNOON AND EARLY THIS EVENING.  THE THUNDERSTORM THREAT
SHOULD DIMINISH AFTER MIDNIGHT.

METEOROLOGICAL COMMENTS -LOW PRESSURE OVER CENTRAL KANSAS WILL LIFT
INTO EASTERN NEBRASKA BY LATE THIS AFTERNOON.  A WARM FRONT SHOULD
EXTEND EASTWARD FROM THE LOW INTO ILLINOIS...WITH A TRAILING COLD
FRONT INTO MISSOURI.  SHOWERS AND STORMS WILL CONTINUE TO MOVE
ACROSS MUCH OF IOWA THIS AFTERNOON...ESPECIALLY IN THE NORTH AND
WEST.  ANOTHER SQUALL LINE MAY ALSO DEVELOP SOUTHWEST OF IOWA BY
LATE AFTERNOON AND BE JUST AHEAD OF THE COLD FRONT AROUND SUNSET.

ALTHOUGH INSTABILITY LEVELS SHOULD BE ON THE LOW SIDE...VERTICAL WIND
SHEAR WILL BE SUFFICIENT TO PRODUCE SEVERE THUNDERSTORMS WITH SQUALL
LINES MAINLY OVER SOUTHERN THIRD OF IOWA...ESPECIALLY SOUTH OF
HIGHWAY 34. DAMAGING WINDS WOULD BE THE PRIMARY CONCERN.  IF STORMS
DID DEVELOP ALONG THE WARM FRONT...DEEP VERTICAL SHEAR WOULD MAKE
TORNADOES ALSO POSSIBLE BUT THE ATMOSPHERE WILL LIKELY NOT BE
UNSTABLE ENOUGH FOR THIS TO OCCUR.

ALTHOUGH WIDESPREAD FLOODING IS NOT EXPECTED...MODERATE TO HEAVY
RAINS FORMING NORTH OF THE LOW MAY PRODUCING PONDING ON ROADS AND
SIGNIFICANT RISES ON STREAMS...RIVERS AND CREEKS.

PRECAUTIONS -SPOTTER ACTIVATION MAY BE NEEDED LATER THIS AFTERNOON
AND THIS EVENING.  IT WILL BE AN ACTIVE WEATHER DAY SO PEOPLE WITH
OUTDOOR CONCERNS SHOULD MONITOR THE LATEST NATIONAL WEATHER SERVICE
FORECASTS AND STATEMENTS FOR UPDATED INFORMATION.

COGIL

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-081>086-
092>097-061100-

CENTRAL IOWA THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
1150 AM CDT MON APR 5 1999

HAZARD -WIDESPREAD RAIN WITH SCATTERED THUNDERSTORMS.  SOME STORMS
MAY BE SEVERE WITH DAMAGING WINDS AND LARGE HAIL.  THERE IS ALSO THE
POSSIBILITY OF A TORNADO BUT IT IS NOT THE PRIMARY THREAT.  MODERATE
TO HEAVY RAINS WILL ALSO OCCUR WITH THE THUNDERSTORMS WITH AN INCH OR
MORE OF RAIN POSSIBLE.

AREA OF CONCERN -THUNDERSTORMS COULD OCCUR ACROSS ALL OF CENTRAL
IOWA.  THE PRIMARY THREAT OF SEVERE WEATHER WILL BE SOUTH OF
INTERSTATE 80.  THE BEST CHANCES FOR HEAVY RAIN WILL BE OVER NORTHERN
AND WESTERN IOWA.

TIMING DETAILS -THUNDERSTORMS COULD OCCUR ANYTIME THIS AFTERNOON AND
INTO THE EVENING HOURS.  THE BEST CHANCES FOR SEVERE WEATHER WOULD BE
LATE AFTERNOON AND EARLY THIS EVENING.  THE THUNDERSTORM THREAT
SHOULD DIMINISH AFTER MIDNIGHT.

METEOROLOGICAL COMMENTS -LOW PRESSURE OVER CENTRAL KANSAS WILL LIFT
INTO EASTERN NEBRASKA BY LATE THIS AFTERNOON.  A WARM FRONT SHOULD
EXTEND EASTWARD FROM THE LOW INTO ILLINOIS...WITH A TRAILING COLD
FRONT INTO MISSOURI.  SHOWERS AND STORMS WILL CONTINUE TO MOVE
ACROSS MUCH OF IOWA THIS AFTERNOON...ESPECIALLY IN THE NORTH AND
WEST.  ANOTHER SQUALL LINE MAY ALSO DEVELOP SOUTHWEST OF IOWA BY
LATE AFTERNOON AND BE JUST AHEAD OF THE COLD FRONT AROUND SUNSET.

ALTHOUGH INSTABILITY LEVELS SHOULD BE ON THE LOW SIDE...VERTICAL WIND
SHEAR WILL BE SUFFICIENT TO PRODUCE SEVERE THUNDERSTORMS WITH SQUALL
LINES MAINLY OVER SOUTHERN THIRD OF IOWA...ESPECIALLY SOUTH OF
HIGHWAY 34. DAMAGING WINDS WOULD BE THE PRIMARY CONCERN.  IF STORMS
DID DEVELOP ALONG THE WARM FRONT...DEEP VERTICAL SHEAR WOULD MAKE
TORNADOES ALSO POSSIBLE BUT THE ATMOSPHERE WILL LIKELY NOT BE
UNSTABLE ENOUGH FOR THIS TO OCCUR.

ALTHOUGH WIDESPREAD FLOODING IS NOT EXPECTED...MODERATE TO HEAVY
RAINS FORMING NORTH OF THE LOW MAY PRODUCING PONDING ON ROADS AND
SIGNIFICANT RISES ON STREAMS...RIVERS AND CREEKS.

PRECAUTIONS -SPOTTER ACTIVATION MAY BE NEEDED LATER THIS AFTERNOON
AND THIS EVENING.  IT WILL BE AN ACTIVE WEATHER DAY SO PEOPLE WITH
OUTDOOR CONCERNS SHOULD MONITOR THE LATEST NATIONAL WEATHER SERVICE
FORECASTS AND STATEMENTS FOR UPDATED INFORMATION.

COGIL