Severe Thunderstorm Warning 95, NWS Des Moines, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
100 PM CDT SUN MAY 6 2001

MAIN CHALLENGE IN 1ST 6 TO 8 HOURS...COVERAGE AND STRENGTH OF
CONVECTION.

UPR LO OVR ERN DAKOTAS CONTINUE TO OPEN UP AND WILL BE MORE
PROGRESSIVE INTO FUTURE.  STRONG S/W OVR MT INTO CEN ROCKIES MAY
PROVIDE FOR SOME SHOWERS LATE MON INTO TUE MAINLY DUE TO COLD TEMPS
ALOFT PER 12Z UA ANALYSIS.  CLOSER TO SFC...LOTS OF MOISTURE AROUND
THIS AFTERNOON...BUT NOTHING YET TO TRIGGER IT.  MID/LO S/W ROTATING
SE ON S SIDE OF DAKOTAS LO AND ASSOC COLD FRONT WITH GOOD PRES RISES
BEHIND.  PRETTY GUST WINDS IN NEB ATTM.  SHOULD SEE A LITTLE
CONVERGENCE IN NW IA AHEAD OF THIS FRONT.  FARTHER SOUTH...IN ERN KS
TO WRN MO...THINGS ARE LOOKING DECENT ALONG DIFF HEATING OR OLD
DRYLINE.  EXPECT TO SEE MORE WIDESPREAD CONVECTION HERE BEFORE LONG.

TONIGHT...MY CWA MAY SEE SPLITSVILLE WITH LOW TOPPED SUPERCELLS PER
MCD IN NW IA.  WHILE MORE LINEAR ACTIVITY FIRES IN ERN KS AND MO.
FOR NOW...HAVE JUST MENTIONED EVENING THUNDERSTORMS CWA WIDE IN WORK
ZONES AND WILL ADJUST AS NECESSARY.  I'M JUST NOT IMPRESSED WITH ALL
OF THE PARAMETERS FOR MY CWA ATTM.  SO...ALL IN ALL...I MAY TONE
DOWN THE WORK ZONES NEAR 4 PM.  HAVE HIT THE GRADIENT WINDS PRETTY
HARD TOO...WITH THEM DIMINISHING BY DAWN SOMEWHAT.

MONDAY THRU EARLY THU...MT SYSTEM SHOULD STAY PRETTY FAR NORTH OF
CWA...THOUGH CYCLONIC FLO AND COLD AIR ALOFT MAY PRODUCE SOME LATE
AFTN SHOWERS N HALF ON MONDAY INTO MON EVENING...AND AGAIN ON TUES.
WED AND EARLY THURS SHOULD SEE SOME S/W RIDGING.

REST OF EXTENDED PRETTY MUDDLED AS EVIDENT IN MRF ENSEMBLES.  4 AND
5 DAY LOOKS LIKE 6 TO 8 DAY USUALLY DOES...ALL OVER THE PLACE.
ECMWF LESS IMPRESSIVE...FARTHER NORTH AND MORE PROGRESSIVE WITH NEXT
SYSTEM IN NRN PLNS.  STILL...IT LOOKS AS THOUGH S/W AND ASSOC FRONT
SHOULD ENTER NW CWA SOMETIME LATE THURS...AND LINGER THROUGH EARLY
FRIDAY.  TEMPS WARMING TO SEASONABLE LEVELS.

SAT/SUN...FLAT RIDGING OR EVEN SLIGHLY NW FLO AS RIDGE BUILDS IN
ROCKIES FOR A SHORT TIME.  SHOULD BE DRY AND SEASONABLE TEMPS.

.DSM...NONE

SEARCY

CENTRAL IOWA THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
255 PM CDT SUN MAY 6 2001

LOW PRESSURE OVER EASTERN SOUTH DAKOTA WILL CONTINUE TO MOVE AWAY
FROM IOWA...BUT A TRAILING PRESSURE TROUGH AND DRYLINE WILL PUSH
THROUGH THE STATE LATE THIS AFTERNOON AND THIS EVENING.
THUNDERSTORMS CAN BE EXPECTED ALONG AND AHEAD OF THIS TROUGH AND A
FEW MAY BE SEVERE.  WIND SHEAR VALUES ARE RELATIVELY WEAK...BUT WEAK
TO MODERATE INSTABILITY MAY BE ENOUGH FOR THE STRONGER STORMS TO
BRIEFLY REACH SEVERE LEVELS.

SEE SITE SPECIFIC DETAILS BELOW FOR MORE INFORMATION.

IAZ005>007-016-017-024>028-035>039-047>050-059>062-072>075-082>086-
093>097-071100-
APPANOOSE-BLACK HAWK-BOONE-BREMER-BUTLER-CERRO
GORDO-CLARKE-DALLAS-DAVIS-DECATUR-FRANKLIN-GRUNDY-HAMILTON-HANCOCK-
HARDIN-HUMBOLDT-JASPER-KOSSUTH-LUCAS-MADISON-MAHASKA-MARION-MARSHALL-
MONROE-POLK-POWESHIEK-RINGGOLD-STORY-TAMA-UNION-WAPELLO-WARREN-WAYNE-
WEBSTER-WINNEBAGO-WORTH-WRIGHT-
INCLUDING THE CITIES OF...ALGONA...AMES...BOONE...CENTERVILLE...
CHARITON...CRESTON...DES MOINES...FORT DODGE...GRINNELL...
INDIANOLA...IOWA FALLS...KNOXVILLE...LAMONI...MARSHALLTOWN...MASON
CITY...NEWTON...OSKALOOSA...OTTUMWA...PELLA...PERRY...WATERLOO...
WAVERLY AND WEBSTER CITY
255 PM CDT SUN MAY 6 2001

* EVENT TIMING... THE REMAINDER OF THE AFTERNOON AND EVENING HOURS

* THREAT CATEGORIES...
     TORNADO.......... NONE
     DAMAGING WINDS... LOW
     LARGE HAIL....... MODERATE
     FLASH FLOODING... MODERATE

* SPOTTER ACTIVATION OUTLOOK... MODERATE

* SEVERE THUNDERSTORM WATCHES MAY BE ISSUED FOR PORTIONS OF CENTRAL
  AND EASTERN IOWA LATER THIS AFTERNOON.  SOME OF THE STORMS MAY
  ALSO PRODUCE LOCALLY HEAVY RAINS OF AN INCH PER HOUR.  THE STORMS COULD
  REPEATEDLY MOVE OVER THE SAME LOCATIONS FROM SOUTH TO NORTH AND
  PRODUCE LOCALIZED FLASH FLOODING.

IAZ004-015-023-033-034-044>046-057-058-070-071-081-092-071100-ADAIR-A
DAMS-AUDUBON-CALHOUN-CARROLL-CASS-CRAWFORD-EMMET-GREENE-GUTHRIE-PALO
ALTO-POCAHONTAS-SAC-TAYLOR-
INCLUDING THE CITIES OF...ATLANTIC...CARROLL...DENISON AND
ESTHERVILLE
255 PM CDT SUN MAY 6 2001

* EVENT TIMING... THUNDERSTORMS ARE NOT EXPECTED.

* THREAT CATEGORIES...
     TORNADO.......... NONE
     DAMAGING WINDS... NONE
     LARGE HAIL....... NONE
     FLASH FLOODING... NONE

* SPOTTER ACTIVATION OUTLOOK... NOT EXPECTED.

SMALL

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THREAT KEY:
    TORNADO.......... ANY TORNADO OCCURRENCE
    DAMAGING WINDS... WINDS >= 58 MPH
    LARGE HAIL....... HAIL >= 3/4 INCH DIAMETER
    FLASH FLOODING... FLOODING CAUSED BY HEAVY RAINS WITHIN 6 HOURS
                      OF RAIN EVENT. POSES THREAT TO LIFE OR
                      PROPERTY.

THREAT CATEGORY KEY:  PROBABILITY OF THREAT OCCURRING WITHIN 25
                      MILES OF POINT WITHIN FORECAST AREA
    NONE....... NOT EXPECTED.  LESS THAN 5% ( 2% FOR TORNADOES)
    LOW........ 5-15% (2-15% FOR TORNADOES)
    MODERATE... 25-35%
    HIGH....... 45% OR GREATER

SPOTTER ACTIVATION OUTLOOK KEY:
    NOT EXPECTED
    LOW........ ACTIVATION POSSIBLE BUT NOT LIKELY
    MODERATE... POSSIBILITIES ABOUT 50-50
    HIGH....... ACTIVATION LIKELY

FOR MORE INFORMATION ON PROBABILISTIC SEVERE WEATHER OUTLOOKS...GO
TO THE STORM PREDICTION CENTER WEBSITE AT
WWW.SPC.NOAA.GOV/PRODUCTS/OUTLOOK/PROBINFO.HTML .