Severe Thunderstorm Warning 194, NWS Des Moines, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
704 PM CDT MON JUL 22 2013

.UPDATE...
ISSUED AT 704 PM CDT MON JUL 22 2013

LINE OF STORMS ACROSS THE HIGHWAY 20 CORRIDOR MOVING SOUTH. HAVE
UPDATED TO REFLECT LATEST RADAR AND TRENDS AND INCREASE POPS TO
THE SOUTH OF THE LINE. ALSO EXPANDED THE SEVERE THUNDERSTORM WATCH
A ROW OF COUNTIES SOUTH.

&&

.SHORT TERM.../TONIGHT /...
ISSUED AT 326 PM CDT MON JUL 22 2013

COLD FRONT EXTENDING FROM TWIN CITIES TO SIOUX CITY WILL SWEEP SE
ACROSS IOWA THIS EVENING. MAIN DYNAMICS WILL BE ACROSS MN/WI BUT
ISOLATED TO SCATTERED STORMS ARE EXPECTED TO CONTINUE DEVELOP SOUTH
INTO IA. SURFACE FLOW IS FROM THE WEST-SOUTHWEST AHEAD OF THE FRONT
WEAKENING CONVERGENCE BUT INSTABILITY IS STRONG. STORMS THAT DO
DEVELOP WOULD INITIALLY HAVE A HAIL THREAT...AND THEN DUE TO HIGH
BASES AND DRIER AIR ALOFT COULD BECOME GUSTY. EXPECT QUITE A BIT OF
OUTFLOW WITH STORMS THAT DO DEVELOP...WHICH SHOULD KEEP THE LINE
PUSHING ALONG. OUTFLOW SHOULD EVENTUALLY PUSH OUT AHEAD AND CUT OF
INFLOW TO STORMS...SO INTENSITY AFTER AROUND 7 PM SHOULD DIMINISH.
VIRTUALLY ALL OF ACTIVITY SHOULD BE OUT OF CENTRAL IOWA BY MIDNIGHT.
BEHIND THE FRONT A MODERATE PUSH OF COOLER AND DRIER AIR DROPPING
TEMPERATURES BELOW 60 IN THE NORTH.

.LONG TERM.../TUESDAY THROUGH MONDAY/...
ISSUED AT 326 PM CDT MON JUL 22 2013

IN WAKE OF THE COLD FRONT TRAVERSING THE AREA THIS
EVENING...COOLER TEMPERATURES ARE FORECAST FOR THE NEXT WEEK.
IOWA WILL REMAIN BENEATH NORTHWESTERLY FLOW ALOFT AT LEAST THROUGH
THE WEEKEND. ON TUESDAY THE LOWER LEVELS WILL BE PRETTY SCOURED
OUT BEHIND THE FRONT...BUT ALOFT FORECAST SOUNDINGS INDICATE
SUBSTANTIAL SATURATION DURING THE DAY AS A SHORTWAVE MOVES THROUGH
THE FLOW ACROSS NEBRASKA AND SOUTHWEST IOWA INTO MISSOURI. THIS
WILL GENERATE A CONSIDERABLE MID LEVEL CLOUD DECK AND POSSIBLY A
FEW SHOWERS AND STORMS IN THE SOUTHWEST...AND HAVE INCLUDED SOME
SLIGHT CHANCE POPS IN THAT AREA. CONTINUED RECENT TREND OF
FORECASTING MAX TEMPS ABOVE GUIDANCE...BUT DECREASED THE MARGIN ON
TUESDAY TO ACCOUNT FOR THE COMBINED EFFECTS OF COLD AIR ADVECTION
AND ANTICIPATED CLOUD COVER. FROM TUESDAY NIGHT THROUGH THURSDAY
BENIGN AND PLEASANT WEATHER IS FORECAST WITH CONTINUED COOL
TEMPERATURES AND LITTLE TO NO CHANCE FOR RAINFALL.

TOWARD THE END OF THE WEEK THINGS STILL LOOK TO BECOME SOMEWHAT
MORE ACTIVE...AND THE PROGNOSTIC MODELS HAVE COME INTO BETTER
GENERAL AGREEMENT ON THE OVERALL EVOLUTION OF A SERIES OF 500 MB
TROUGHS AND WAVES MOVING ACROSS THE CENTRAL U.S. IT APPEARS THAT A
SUBTLE LEADING SHORTWAVE WILL TRAVERSE IOWA LATE THURSDAY AND
THURSDAY NIGHT...WITH A MORE POTENT WAVE MOVING TO OUR SOUTHWEST
ACROSS THE CENTRAL PLAINS AND MISSOURI ON FRIDAY...THEN THE FINAL
AND STRONGEST TROUGH PIVOTING FROM MINNESOTA ACROSS IOWA AND
WISCONSIN ON FRIDAY NIGHT. AT THE SURFACE THIS WILL TRANSLATE TO A
WEAK TROUGH MOVING ACROSS OUR AREA AROUND THURSDAY
NIGHT...FOLLOWED BY A STRONGER COLD FRONT PROBABLY LATE ON FRIDAY.
THE RESULT IS CHANCE POPS FROM THURSDAY NIGHT INTO FRIDAY
NIGHT...WITH SOME UNCERTAINTY AS TO THE ENDING TIME WHEN RAIN WILL
CLEAR OUT RAPIDLY WITH THE FRONTAL PASSAGE...THEN MUCH COOLER
TEMPERATURES FOR THE WEEKEND WITH HIGHS IN THE 70S AND LOWS IN THE
50S TO LOWER 60S MAKING FOR GLORIOUS LATE JULY WEATHER. ALLBLEND
GUIDANCE POPULATED WITH 20 TO 40 POPS FROM SATURDAY INTO EARLY
NEXT WEEK BUT CAN FIND NO SUPPORT FOR THIS IN THE LONG RANGE
MODELS OR EXPECTED SYNOPTIC PATTERN AND HAVE REMOVED THEM FROM THE
FORECAST.

&&

.AVIATION...23/00Z
ISSUED AT 704 PM CDT MON JUL 22 2013

STORMS PUSHING THROUGH WATERLOO ATTM...SHOULD BE OUT WITHIN THE
NEXT HOUR OR TWO...WITH IMPACTS STILL POSSIBLE AT KOTM AND KDSM
THROUGH 03-04Z. OTHERWISE WINDS TO SHIFT AROUND TO THE
NORTHWEST...WITH SOME HIGH CLOUDS FOR TUESDAY.

&&

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

&&

UPDATE...BEERENDS
SHORT TERM...JUNGBLUTH
LONG TERM...JOHNSON/LEE
AVIATION...BEERENDS

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
347 PM CDT MON JUL 22 2013

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>074-232100-
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-AUDUBON-GUTHRIE-DALLAS-POLK-JASPER-
POWESHIEK-CASS-ADAIR-MADISON-WARREN-MARION-
347 PM CDT MON JUL 22 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA.

.DAY ONE...THIS AFTERNOON AND TONIGHT

SCATTERED THUNDERSTORMS WILL CONTINUE ALONG A COLD FRONT INTO
EARLY EVENING. A FEW STORMS MAY BECOME SEVERE WITH GOLF BALL
SIZED HAIL AND 60 MPH OR GREATER WINDS.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

THUNDERSTORMS CHANCES RETURN THURSDAY AND FRIDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED UNTIL 10 PM.

IAZ075-081>086-092>097-232100-
MAHASKA-ADAMS-UNION-CLARKE-LUCAS-MONROE-WAPELLO-TAYLOR-RINGGOLD-
DECATUR-WAYNE-APPANOOSE-DAVIS-
347 PM CDT MON JUL 22 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA.

.DAY ONE...THIS AFTERNOON AND TONIGHT

SCATTERED THUNDERSTORMS ARE THIS EVENING AS A COLD FRONT MOVES SOUTH.
A FEW STORMS MAY BE SEVERE ESPECIALLY BEFORE 8 PM WITH GOLF BALL
SIZED HAIL AND 60 MPH OR GREATER WINDS.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

THUNDERSTORMS CHANCES RETURN THURSDAY AND FRIDAY..

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED THIS EVENING UNTIL AROUND 10 PM.

JUNGBLUTH

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