Severe Thunderstorm Warning 52, NWS Des Moines, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
230 PM CDT TUE MAY 30 2000

...SEVERE AND HEAVY RAIN THREATS CONTINUE IN THIS FORECAST PACKAGE...

1ST CLUSTER OF SUPERCELLS THAT WERE AROUND DSM AREA HAVE FINALLY
EVOLVED INTO A MORE LINEAR MCS IN THE DVN CWA, WITH ADDITIONAL
ELEVATED STORMS FROMING AROUND THE ALO AND TAMA AREAS.  THIS IS
OCCURRING AS LLJ WEAKENS AND VEERS TO A SW DIRECTION.  FLOW IS
BECOMING MORE SOUTHERLY IN KS, ESPECIALLY AT 850-700 MB IN RESPONSE
TO ANOTHER SHORTWAVE.  SYNOPTIC SURFACE BOUNDARY HAS BECOME
STATIONARY OVER IA WITH SOME PUSH S INTO KS.  JET DYNAMICS ARE
AIDING CONVECTIVE DEVELOPMENT IN SD, WHILE THE CAP IS INHIBITING
CONVECTION SOMEWHAT IN NEBR AND WESTERN KS SO FAR.  THIS WILL LIKELY
CHANGE AS THIS MOVES INTO IA WHERE CAP IS WEAKER.  MESOETA HANDLING
SURFACE BOUNDARY RATHER WELL AT THIS TIME, AND SHOULD LIE ALONG OR
JUST S OF I-80 AGAIN BY EARLY AFTERNOON.  SIMILAR SEVERE CONVECTIVE
PARAMETERS WILL BE IN PLACE AGAIN THIS AFTERNOON WITH CAPES
EXCEEDING 3000 J/KG AND HELICITIES ABOVE 300 OR 400 ALONG AND N OF
THE BOUNDARY, AND EHI'S OF 6-8 ALSO, SO SUPERCELL POTENTIAL IS AGAIN
PRESENT.  SOME EVIDENCE OF A TROPICAL CONNECTION MAY EVEN ENHANCE
OUR PWAT'S THIS EVENING TOO, WITH 2-3 MCS'S LIKELY ONGOING TONIGHT OVER
THE CENTRAL PLAINS INTO THE UPPER MIDWEST.  FOR OUR CWA, AN MCS
LOOKS MOST LIKELY TO INITIATE IN THE SUX/FSD AREA AT THE NOSE OF THE
LLJ, TRACKING SE.  AGREE WITH THE 94E AS FAR AS BACKBUILDING AND
TRAINING. GIVEN LOCAL NATURE OF OUR RAINFALL TUE EVENING AND THIS
MORNING, WILL HOLD OFF ON FLASH FLOOD WATCH AT THIS TIME.  DAY SHIFT
MAY NEED TO CONSIDER ONE FOR TONIGHT AS TODAY'S CONVECTION EVOLVES.
WILL MENTION LOCALLY HEAVY RAIN AND SEVERE IN TODAY'S CENTRAL AND N
ZONES.  FOR OUT SOUTHERN ZONES, WILL KEEP A MORE CONSERVATIVE 30 POP
AS SURFACE BOUNDARY MOVES N.  THURSDAY AGAIN LOOKS ACTIVE AS PER SPC
DAY 2 OUTLOOK.  WARM SECTOR WILL BE IN PLACE, SO WIDESPREAD HEAVY
RAIN THREAT MAY NOT BE AS HIGH.  WILL GO WAMER THAN GUIDANCE TODAY
IN SW IA AS NUMBERS SEEM TOO LOW GIVEN TUESDAYS HIGHS.  THIS MAY BE
THE CASE AGAIN ON THURSDAY IN SOUTHERN IA AS WARM SECTOR PUSHES
NORTHWARD.  NO CHANGES PLANNED FOR EXTENDED FORECAST.

.DSM...NONE.
KULA

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-081>086-
092>097-011100-

CENTRAL IOWA THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
443 AM CDT WED MAY 31 2000

HAZARD--LARGE HAIL...DAMAGING WINDS OVER 60 MPH AND TORNADOES.  HEAVY
RAINFALL ON THE ORDER OF 1 TO 2 INCHES...WITH LOCAL AMOUNTS UP TO 5
INCHES OR MORE...MAY LEAD TO LOCAL FLASH FLOODING.

AREA OF CONCERN--ALL OF CENTRAL IOWA...PARTICULARLY NORTH OF
INTERSTATE 80.

TIMING DETAILS--MOST OF TODAY AND TONIGHT.  A NEW SEVERE THUNDERSTORM
WATCH IS BEING CONSIDERED FOR PARTS OF THE STATE THIS MORNING.

METEOROLOGICAL COMMENTS--A STATIONARY FRONT WAS LOCATED FROM DUBUQUE
TO DES MOINES TO SHENANDOAH THIS MORNING.   THUNDERSTORMS WILL
DEVELOP ALONG AND NORTH OF THIS FRONT TODAY AS ANOTHER IN A SERIES
OF UPPER LEVEL DISTURBANCES IN THE JET STREAM TRACK OUT OF THE
CENTRAL PLAINS INTO THE UPPER MIDWEST.  FAST GROWING THUNDERSTORMS
WERE ALREADY OCCURRING IN RESPONSE OVER NORTHEAST AND CENTRAL
NEBRASKA.  ANOTHER SUCH DISTURBANCE WILL ARRIVE TONIGHT IN NORTHERN
IOWA.

THE AIR MASS OVER IOWA REMAINS QUITE UNSTABLE AND WILL BECOME EVEN
MORE UNSTABLE THROUGHOUT THE DAY AS HEATING TAKES PLACE.  PLENTY OF
MOISTURE POOLING ALONG THE BOUNDARY...WITH MORE FLOWING NORTHWARD
INTO THE REGION...IS PROVIDING FAVORABLE CONDITIONS FOR HEAVY
RAINFALL.  THUNDERSTORMS TRAINING OVER THE SAME LOCATION IS
POSSIBLE...LEADING TO HEAVY RAINFALL AND LOCAL FLASH FLOODING.  THE
THREAT FOR SUPERCELL THUNDERSTORMS CAPABLE OF LARGE HAIL AND
TORNADOES IS AGAIN PRESENT TODAY...MAINLY THIS AFTERNOON INTO EARLY
EVENING ALONG THE STATIONARY FRONT.

PRECAUTIONS--STAY TUNED TO NOAA WEATHER RADIO...COMMERCIAL TELEVISION
OR RADIO STATIONS...OR YOUR CABLE TELEVISION PROVIDER FOR LATER
STATEMENTS CONCERNING THIS POTENTIALLY DANGEROUS SEVERE WEATHER
THREAT.

SPOTTER ACTIONS--SKYWARN AND AMATEUR SPOTTER GROUPS SHOULD BE READY
FOR ACTIVATION THROUGHOUT TODAY AND TONIGHT.

KULA

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-081>086-
092>097-011100-

CENTRAL IOWA THUNDERSTORM OUTLOOK...CORRECTION
NATIONAL WEATHER SERVICE DES MOINES IA
443 AM CDT WED MAY 31 2000

HAZARD--LARGE HAIL...DAMAGING WINDS OVER 60 MPH AND TORNADOES.  HEAVY
RAINFALL ON THE ORDER OF 1 TO 2 INCHES...WITH LOCAL AMOUNTS UP TO 5
INCHES OR MORE...MAY LEAD TO LOCAL FLASH FLOODING.

AREA OF CONCERN--ALL OF CENTRAL IOWA...PARTICULARLY NORTH OF
INTERSTATE 80.

TIMING DETAILS--MOST OF TODAY AND TONIGHT.  A NEW SEVERE THUNDERSTORM
WATCH IS BEING CONSIDERED FOR PARTS OF THE STATE THIS MORNING.

METEOROLOGICAL COMMENTS--A STATIONARY FRONT WAS LOCATED FROM DUBUQUE
TO DES MOINES TO SHENANDOAH THIS MORNING.   THUNDERSTORMS WILL
DEVELOP ALONG AND NORTH OF THIS FRONT TODAY AS ANOTHER IN A SERIES
OF UPPER LEVEL DISTURBANCES IN THE JET STREAM TRACK OUT OF THE
CENTRAL PLAINS INTO THE UPPER MIDWEST.  FAST GROWING THUNDERSTORMS
WERE ALREADY OCCURRING IN RESPONSE OVER NORTHEAST AND CENTRAL
NEBRASKA.  ANOTHER SUCH DISTURBANCE WILL ARRIVE TONIGHT IN NORTHERN
IOWA.

THE AIR MASS OVER IOWA REMAINS QUITE UNSTABLE AND WILL BECOME EVEN
MORE UNSTABLE THROUGHOUT THE DAY AS HEATING TAKES PLACE.  PLENTY OF
MOISTURE POOLING ALONG THE BOUNDARY...WITH MORE FLOWING NORTHWARD
INTO THE REGION...IS PROVIDING FAVORABLE CONDITIONS FOR HEAVY
RAINFALL.  THUNDERSTORMS TRAINING OVER THE SAME LOCATION IS
POSSIBLE...LEADING TO HEAVY RAINFALL AND LOCAL FLASH FLOODING.  THE
THREAT FOR SUPERCELL THUNDERSTORMS CAPABLE OF LARGE HAIL AND
TORNADOES IS AGAIN PRESENT TODAY...MAINLY THIS AFTERNOON INTO EARLY
EVENING ALONG THE STATIONARY FRONT.

PRECAUTIONS--STAY TUNED TO NOAA WEATHER RADIO...COMMERCIAL TELEVISION
OR RADIO STATIONS...OR YOUR CABLE TELEVISION PROVIDER FOR LATER
STATEMENTS CONCERNING THIS POTENTIALLY DANGEROUS SEVERE WEATHER
THREAT.

SPOTTER ACTIONS--SKYWARN AND AMATEUR RADIO SPOTTER GROUPS SHOULD BE
READY FOR ACTIVATION THROUGHOUT TODAY AND TONIGHT.

KULA

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-081>086-
092>097-011100-

CENTRAL IOWA THUNDERSTORM OUTLOOK...CORRECTION
NATIONAL WEATHER SERVICE DES MOINES IA
443 AM CDT WED MAY 31 20