Severe Thunderstorm Warning 112, NWS Des Moines, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
927 PM CDT THU MAY 20 2004

.DISCUSSION...
EARLIER FORECAST UPDATES TRIMMED POPS BACK IN SOUTHERN IA.
INTERESTING EVENING AHEAD AS 850 MB BOUNDARY IS NOW UP TO I-80 BASED
ON CLOUD OBS AND ANALYSIS.  LOCAL TRAINED SPOTTER REPORTED SMALL
FUNNELS WITH THE CU CONGESTUS ALONG THIS BOUNDARY IN CASS COUNTY.
STILL PLENTY OF JUICE ABOVE, WITH VERY STEEP LAPSE RATES ABOVE THE
800 MB LAYER.  RUC 850 MB MOIST TRANSPORT NOSE IS RIGHT WHERE NEW
CONVECTION IS FIRING IN SC NEBRASKA.  EXPECT THIS AREA TO EXPAND AND
SPREAD ENE ALONG 850 MB BOUNDARY.  CORFIDI BACKWARD PROPOGATING
VECTORS SUGGEST SOME BACKBUILDING AND HEAVY RAIN AS WELL.  850 MB
MOIST CONVERGENCE AXIS INCREASES BETWEEN 03-06Z IN NW-WC IA, AND
WOULD FAVOR THIS AREA FOR MORE DEVELOPMENT.  SHEAR PROFILES AND CAPE
STILL SUFFICIENT FOR ELEVATED SUPERCELL STRUCTURE AND ASSOCIATED
SEVERE WX.I
&&

.DMX WATCHES/WARNINGS/ADVISORIES...NONE.

&&

KULA

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
942 PM CDT THU MAY 20 2004

IAZ004>007-015>017-023>028-033>039-044>049-057-058-211100-
AUDUBON-BLACK HAWK-BOONE-BREMER-BUTLER-CALHOUN-CARROLL-CERRO GORDO-
CRAWFORD-EMMET-FRANKLIN-GREENE-GRUNDY-GUTHRIE-HAMILTON-HANCOCK-
HARDIN-HUMBOLDT-KOSSUTH-MARSHALL-PALO ALTO-POCAHONTAS-SAC-STORY-
WEBSTER-WINNEBAGO-WORTH-WRIGHT-
942 PM CDT THU MAY 20 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE PORTION OF CENTRAL IOWA
ALONG AND NORTHWEST OF A LINE FROM AUDUBON TO AMES TO WATERLOO.

.DAY ONE...TONIGHT

ONE OR MORE CLUSTERS OF THUNDERSTORMS WILL DEVELOP ACROSS EASTERN
NEBRASKA INTO WEST CENTRAL IOWA BETWEEN 11 PM AND 2 AM.  THESE
STORMS WILL INTENSIFY AND SPREAD EAST ACROSS MUCH OF NORTHERN
IOWA LATE TONIGHT.  INITIALLY...THE STORMS MAY BECOME SUPERCELLULAR
PRODUCING LARGE HAIL...WITH DAMAGING WINDS AND LOCALLY HEAVY RAINS
BECOMING MORE PROBLEMATIC LATE TONIGHT INTO EARLY FRIDAY MORNING.
RAINFALL AMOUNTS MAY EXCEED 2 INCHES IN ONE HOUR IN LOCALIZED AREAS.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

RISKS OF ISOLATED SEVERE STORMS AGAIN EXIST FRIDAY AFTERNOON AND
NIGHT...WITH A HIGHER RISK OF SEVERE STORMS SATURDAY AND SATURDAY
NIGHT.

.SPOTTER ACTIVATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED OVERNIGHT.  SPOTTER ACTIVATION MAY
ALSO BE NEEDED AT VARIOUS TIMES THROUGH NEXT WEDNESDAY.

IAZ050-059>062-070>075-081>086-092>097-211100-
ADAIR-ADAMS-APPANOOSE-CASS-CLARKE-DALLAS-DAVIS-DECATUR-JASPER-LUCAS-
MADISON-MAHASKA-MARION-MONROE-POLK-POWESHIEK-RINGGOLD-TAMA-TAYLOR-
UNION-WAPELLO-WARREN-WAYNE-
942 PM CDT THU MAY 20 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE PORTION OF CENTRAL IOWA
SOUTHEAST OF A LINE FROM TAMA TO DES MOINES TO ATLANTIC.

.DAY ONE...TONIGHT

ONE OR MORE CLUSTERS OF THUNDERSTORMS WILL DEVELOP ACROSS EASTERN
NEBRASKA INTO WEST CENTRAL IOWA BETWEEN 11 PM AND 2 AM.  A FEW
OF THESE STORMS MAY EXPAND SOUTHEAST TO NEAR ATLANTIC THROUGH
DES MOINES TO TAMA BY 4 AM.  CHANCES HAVE DECREASED THAT STORMS
WILL AFFECT AREAS FURTHER SOUTH AND EAST.  THERE REMAINS A
SLIGHT RISK OF SEVERE WEATHER WITH LOCALLY HEAVY RAINFALL.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

RISKS OF ISOLATED SEVERE STORMS AGAIN EXIST FRIDAY AFTERNOON AND
NIGHT...WITH A HIGHER RISK OF SEVERE STORMS SATURDAY AND SATURDAY
NIGHT.

.SPOTTER ACTIVATION STATEMENT...

SPOTTER ACTIVATION IS POSSIBLE OVERNIGHT...BUT MORE LIKELY FRIDAY
NIGHT AND AGAIN ON SATURDAY.

KULA

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE DES MOINES IA
126 AM CDT FRI MAY 21 2004

IAZ004>006-015-016-023>025-033>036-044>047-057>059-211200-

...SEVERE THUNDERSTORM WATCH #228 REMAINS IN EFFECT UNTIL 700 AM CDT
FOR THE COUNTIES OF...

  AUDUBON               BOONE                 CALHOUN
  CARROLL               CRAWFORD              DALLAS
  EMMET                 GREENE                GUTHRIE
  HAMILTON              HANCOCK               HUMBOLDT
  KOSSUTH               PALO ALTO             POCAHONTAS
  SAC                   WEBSTER               WINNEBAGO
  WRIGHT