Severe Thunderstorm Warning 295, NWS Des Moines, IA

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE DES MOINES IA
932 PM CDT THU AUG 17 2006

.DISCUSSION...

WIDELY SCATTERED STORMS HAVE DEVELOPED OVER NORTHEAST KS AND THE
DAKOTAS THIS EVENING. ISOLATED SHOWERS DEVELOPED NORTH OF THE WEAK
FRONTAL BOUNDARY OVER NORTHERN IA AS WELL. PROFILER WINDS SHOW
DIVERGENT LLJ OVER IOWA TONIGHT WITH BEST INFLOW OVER THE SOUTHERN
COUNTIES OF THE STATE. PWATS STILL ABOVE 2 INCHES OVER N MISSOURI
ACROSS TO HIGHWAY 30. BEST LLJ PROGGED TO BE WEST OF REGION THROUGH
12Z ALONG WITH SOME WEAK COMPONENT ALONG THE BORDER. HAVE TRIMMED
POPS NORTH A BIT AND LEFT CHANCES FOR SOME HEAVY RAINERS TOWARD
MORNING SOUTH AS DYNAMICS STILL PROGGED TO INCREASE BY THAT TIME.
LOWS BUMPED UP FAR NORTH. LOW ST AND FOG WILL KEEP DIURNAL RANGE
RATHER LOW...5 TO 7 DEGREES IN SOME CASES./REV

.PREVIOUS DISCUSSION...

MONSOONAL MOISTURE FLOW HAS WEAKENED A LITTLE TODAY AS FLOW OUT OF
MEXICO IS NO LONGER STREAMING TO THE NORTHEAST. THE MOISTURE FEED IS
HOWEVER BECOMING MORE FAVORABLE FROM THE GULF OF MEXICO TONIGHT AND
FRIDAY. CURRENTLY A COUPLE OF BOUNDARIES ARE EVIDENT ACROSS THE AREA
WITH ONE ACROSS CENTRAL IOWA AND ANOTHER MORE SIGNIFICANT WARM FRONT
OVER NORTHERN MISSOURI. EXPECT SHOWERS AND THUNDERSTORMS TO DEVELOP
TONIGHT OVER SOUTHEAST NEBRASKA INTO SOUTHWEST IOWA AND THEN
PROGRESS EAST NORTHEAST TOWARD MORNING AS ANOTHER PUSH OF MOISTURE
ADVECTION ARRIVES. THE PRIMARY BOUNDARY IS NOT EXPECTED TO MOVE MUCH
OVER NORTHERN MISSOURI ON FRIDAY AND EXPECT IT TO REMAIN ACTIVE
ALONG AND NORTH OF THIS AREA WITH A FOCUS ON SOUTHERN IOWA.
CONDITIONS STILL LOOK FAVORABLE FOR TRAINING AND BACK BUILDING OF
STORMS WITH THE FLOW BECOMING PARALLEL TO THE FRONT. PW VALUES WILL
REMAIN ABOVE 2 INCHES THROUGH AT LEAST FRIDAY NIGHT AND POSSIBLY
LINGERING INTO SATURDAY. WITH THIS AMOUNT OF SATURATION...HIGH
FREEZING LEVELS AND AND THIN CAPES THROUGH OUT THE COLUMN...THE
SEVERE THREAT LOOKS MINIMAL WITH THE GREATER THREAT BEING HEAVY
RAINFALL WITH WARM RAIN PROCESSES LOOKING FAVORABLE. ADDITIONAL 2 TO
4 INCH AMOUNTS REMAIN POSSIBLE MAINLY ALONG AND SOUTH OF HIGHWAY 92
THROUGH SATURDAY MORNING. RAIN CHANCES NORTH OF HIGHWAY 20 HAVE BEEN
REDUCED WITH DRIER AIR AFFECTING THIS REGION AND WITH THE SYSTEM SET
UP A LITTLE FARTHER SOUTH THAN PREVIOUSLY EXPECTED.

A COLD FRONT WILL DROP SOUTH ACROSS IOWA ON SATURDAY AND THIS WILL
KEEP CHANCES FOR SHOWERS AND THUNDERSTORMS IN THE FORECAST. THIS
FRONT WILL HAVE A MORE FALL LIKE AFFECT TO IT WITH FALLING
TEMPERATURES EXPECTED BY LATE MORNING AND INTO THE AFTERNOON OVER
PORTIONS OF THE NORTHWEST. CANADIAN HIGH PRESSURE MOVES SOUTH INTO
THE CENTRAL PLAINS ON SUNDAY AND WILL BE THE DOMINANT INFLUENCE
THROUGH MONDAY NIGHT. SOME UNCERTAINTIES TUESDAY THROUGH THURSDAY AS
NUMEROUS SHORT WAVES RIPPLE THROUGH THE NORTHWEST FLOW. THE
GFS/CANADIAN/ECMWF ARE ALL HINTING AT A MORE SIGNIFICANT SHORT WAVE
ARRIVING LATE IN THE PERIOD AND HAVE PLACED POPS ON THURSDAY.
TEMPERATURES NEAR SEASONAL DURING THE EXTENDED.

&&

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

&&

DONAVON/REV

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
347 PM CDT THU AUG 17 2006

IAZ004>007-015>017-023>028-033>039-044>050-181100-
EMMET-KOSSUTH-WINNEBAGO-WORTH-PALO ALTO-HANCOCK-CERRO GORDO-
POCAHONTAS-HUMBOLDT-WRIGHT-FRANKLIN-BUTLER-BREMER-SAC-CALHOUN-
WEBSTER-HAMILTON-HARDIN-GRUNDY-BLACK HAWK-CRAWFORD-CARROLL-GREENE-
BOONE-STORY-MARSHALL-TAMA-
347 PM CDT THU AUG 17 2006

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA
ALONG AND NORTH OF A DENISON THROUGH AMES TO TAMA LINE.

.DAY ONE...TONIGHT

A FEW THUNDERSTORMS ARE EXPECTED OVERNIGHT...MAINLY ALONG THE
HIGHWAY 30 CORRIDOR.  NO SEVERE WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

PERIODS OF THUNDERSTORMS ARE EXPECTED FROM FRIDAY INTO SATURDAY.
THERE IS A THREAT FOR A FEW SEVERE THUNDERSTORMS ALONG WITH AREAS
OF HEAVY RAINFALL. DAMAGING WINDS AND LARGE HAIL WOULD BE THE
PRIMARY THREATS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED ON FRIDAY INTO SATURDAY.

IAZ057>062-070>075-081>086-092>097-181100-
AUDUBON-GUTHRIE-DALLAS-POLK-JASPER-POWESHIEK-CASS-ADAIR-MADISON-
WARREN-MARION-MAHASKA-ADAMS-UNION-CLARKE-LUCAS-MONROE-WAPELLO-
TAYLOR-RINGGOLD-DECATUR-WAYNE-APPANOOSE-DAVIS-
347 PM CDT THU AUG 17 2006

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA
ALONG AND SOUTH OF AN ATLANTIC TO DES MOINES TO GRINNELL LINE.

.DAY ONE...TONIGHT

SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP OVERNIGHT...
ESPECIALLY AFTER MIDNIGHT. HEAVY RAINFALL IS THE MAIN THREAT WITH
ISOLATED ONE TO TWO INCH AMOUNTS POSSIBLE BY FRIDAY
MORNING...MAINLY NEAR THE MISSOURI BORDER.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

ADDITIONAL THUNDERSTORMS ARE EXPECTED FRIDAY INTO SATURDAY.
ISOLATED SEVERE WEATHER IS POSSIBLE WITH THESE STORMS. THE MAIN
THREAT WILL BE FROM LARGE HAIL AND DAMAGING WINDS. IN
ADDITION...THE HEAVY RAIN THREAT WILL CONTINUE WITH AMOUNTS OF 2
TO 3 INCHES POSSIBLE BY SATURDAY MORNING.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NECESSARY ON FRIDAY INTO EARLY SATURDAY.

CC