Severe Thunderstorm Warning 92, NWS Des Moines, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
340 PM CDT SAT MAY 5 2007

.DISCUSSION...

BLOCKING PATTERN REMAINS OVER THE CONUS THROUGH AT LEAST 48 HOURS.
THE CONTINUED SLOW PROGRESSION OF THE TROUGH OVER THE CENTRAL PLAINS
REMAINS THE FOCUS FOR THIS FORECAST.  UA ANALYSIS THIS A.M. SHOWED A
WARM AND DRY SLUG OF AIR OVER WESTERN IOWA AT 850 MB.  FURTHER EAST
WE ARE STILL UNDER SOME INFLUENCE OF THE HIGH OUT EAST.  SOUNDINGS
INDICATE DECENT CAP OVER IOWA LOCATIONS THROUGH 03Z.  AFTER 03Z THE
CAP WEAKENS AND WE COULD SEE SOME THUNDER DEVELOP THOUGH A MORE
LIKELY SCENARIO IS THE ACTIVITY TO OUR WEST WILL MAKE ITS WAY INTO
OUR WESTERN PERIPHERY. SOME HEAVY RAIN LIKELY TONIGHT OVER THE
WESTERN QUARTER OF THE CWA MAINLY AFTER MIDNIGHT.  ONLY SEVERE
THREAT...AND ITS A CONDITIONAL ONE...REMAINS OVER SOUTHWEST IOWA
NEAR THE WARM FRONT.  IF THE CAP WEAKENS OR BREAKS WE SHOULD HAVE NO
TROUBLE LIGHTING THINGS UP IN THE SOUTHWEST.

FOR SUNDAY...SCENARIO REMAINS INTERESTING.  105KT SPEED MAX ROUNDS
THE UPPER LEVEL SYSTEM THEN RETROGRADES SOME AS IT HEADS INTO THE
DKTAS.  THIS CAUSES A BACKING FLOW OVER IOWA AND PULLS THUNDER
CHANCES BACK WEST.  THE UPDATED SWODY2 CAUGHT THIS AS WELL AND
PULLED THE SLIGHT CHANCE OUT OF CENTRAL IOWA.  IF THAT SCENARIO PANS
OUT THEN WE MAY BE IN ANOTHER HURRY UP AND WAIT MODE TOMORROW.  I
WILL LET THE EVENING/MID SHIFT GET A LOOK AT ONE MORE RUN BEFORE WE
MAKE ANY BIG CHANGES TO THE HWO AND GRIDS.  THE SYSTEM FINALLY MOVES
EAST LATE SUNDAY AND MONDAY.  A POTENTIAL HEAVY RAIN SCENARIO
SETTING UP FOR SUNDAY NIGHT/MONDAY.  SOME SEVERE POTENTIAL MONDAY
WITH 2500-3000 CAPES OVER SRN IA. THERE IS FAIRLY BIG DIFFERENCES
BETWEEN THE 06Z AND 12Z RUNS FOR BEYOND MONDAY SO NO MAJOR CHANGES
WERE MADE AT THIS TIME BEYOND MONDAY.

&&

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

&&

FAB

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
836 PM CDT SAT MAY 5 2007

IAZ004-005-015-023-024-033>035-044>047-057>059-070>072-081>083-
092>094-061100-
EMMET-KOSSUTH-PALO ALTO-POCAHONTAS-HUMBOLDT-SAC-CALHOUN-WEBSTER-
CRAWFORD-CARROLL-GREENE-BOONE-AUDUBON-GUTHRIE-DALLAS-CASS-ADAIR-
MADISON-ADAMS-UNION-CLARKE-TAYLOR-RINGGOLD-DECATUR-
836 PM CDT SAT MAY 5 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA.

.DAY ONE...TONIGHT
THUNDERSTORMS WILL CONTINUE THROUGH THE NIGHT WITH SOME OF THEM
PRODUCING HIGH WINDS AND LARGE HAIL. A TORNADO IS ALSO POSSIBLE
WITH SOME OF THE STORMS. THE BEST CHANCE IS FOR AREAS WEST OF A
MT. AYR TO ROCKWELL CITY LINE..

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

THE THREAT OF THUNDERSTORMS WILL CONTINUE SUNDAY INTO EARLY NEXT
WEEK. AN ISOLATED SEVERE THUNDERSTORM IS POSSIBLE SUNDAY NIGHT WITH
A BETTER CHANCE ON MONDAY.  THE MAIN THREAT WILL BE LARGE HAIL AND
DAMAGING WIND. HEAVY RAINFALL MAY ALSO OCCUR FROM SUNDAY NIGHT AND
MONDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL LIKELY BE NEEDED UNTIL AFTER MIDNIGHT
SUNDAY MORNING...AGAIN SUNDAY EVENING...AND AGAIN ON MONDAY.

IAZ006-007-016-017-025>028-036>039-048>050-060>062-073>075-
084>086-095>097-061100-
WINNEBAGO-WORTH-HANCOCK-CERRO GORDO-WRIGHT-FRANKLIN-BUTLER-BREMER-
HAMILTON-HARDIN-GRUNDY-BLACK HAWK-STORY-MARSHALL-TAMA-POLK-JASPER-
POWESHIEK-WARREN-MARION-MAHASKA-LUCAS-MONROE-WAPELLO-WAYNE-
APPANOOSE-DAVIS-
836 PM CDT SAT MAY 5 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA.

.DAY ONE...TONIGHT

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

THE THREAT OF THUNDERSTORMS WILL EXIST SUNDAY AFTERNOON INTO EARLY
NEXT WEEK. AN ISOLATED SEVERE THUNDERSTORM IS POSSIBLE SUNDAY NIGHT
WITH A BETTER CHANCE ON MONDAY.  THE MAIN THREAT FROM THE STORMS
WILL BE LARGE HAIL AND DAMAGING WIND. HEAVY RAINFALL MAY ALSO OCCUR
SUNDAY NIGHT AND MONDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED SUNDAY NIGHT AND MONDAY.