Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 061757
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1257 PM CDT MON JUL 6 2015

.UPDATE...
ISSUED AT 627 AM CDT MON JUL 6 2015

NEW DEVELOPMENT OVER THE LAST HALF HOUR TO HOUR HAS SET UP IN MORE
OF A WEST TO EAST FASHION WITH SLOWER STORM MOTIONS ACROSS MUCH OF
CENTRAL IOWA. EXPECT THIS ACTIVITY TO CONTINUE FOR THE NEXT FEW
HOURS...AND GIVEN THE EFFICIENT RAIN PRODUCTION AND SLOWER STORM
POSSIBILITY OF TRAINING/BACKBUILDING COULD HAVE SOME POTENTIAL FOR
HEAVY RAIN AND FLASH FLOODING ACROSS PORTIONS OF CENTRAL IOWA THIS
MORNING. HAVE ALSO INCREASED POPS FOR THE NEXT FEW HOURS...WITH
INSTABILITY EXPECTED TO DECREASE TOWARD MID MORNING AND STORM
COVERAGE/INTENSITY EXPECTED TO DIMINISH BEFORE ADDITIONAL
DEVELOPMENT THIS AFTERNOON.

&&

.SHORT TERM /TODAY/...
ISSUED AT 259 AM CDT MON JUL 6 2015

AREA OF LOW PRESSURE CENTERED OVER NORTHWEST IA/SW MN WITH AN
ASSOCIATED COLD FRONT STRETCHING BACK TO THE SSW. STORMS CONTINUE
TO DEVELOP ALONG AND AHEAD OF THE FRONT...WITH ACTIVITY EXPECTED
TO CONTINUE THROUGH THE EARLY MORNING HOURS. ACTIVITY HAS
DIMINISHED IN INTENSITY AND CURRENTLY NOT EXPECTING SEVERE STORMS
IN THE NEAR TERM. ACTIVITY SHOULD LINGER INTO THE MORNING HOURS
WITH THE FRONTAL BOUNDARY SLOWLY SINKING ACROSS THE CWA TODAY.
ADDITIONAL REDEVELOPMENT EXPECTED BY THIS AFTERNOON IN VICINITY OF
THE FRONT. SOME LINGERING POST-FRONTAL RAIN/STORMS POSSIBLE MUCH
OF THE DAY ACROSS THE NORTH/WEST. WITH THE EXTENSIVE CLOUD SHIELD
ALSO ANTICIPATED...HAVE LOWERED HIGHS A BIT. OTHERWISE MAIN CHANCE
FOR SEVERE STORMS WILL BE WITH THE ADDITIONAL REDEVELOPMENT ALONG
THE FRONT TOWARD THIS AFTERNOON. HEAVY RAIN ALSO A POSSIBILITY
WITH VERY HIGH PWATS. CURRENT SPC MESO DATA SUGGESTING PWATS NEAR
2.0 INCHES NEAR THE FRONT...WITH THE SOUNDINGS INDICATING SIMILAR
VALUES ACROSS THE CWA LATER TODAY. THIS SHOULD LEAD TO EFFICIENT
RAINFALL PRODUCTION COUPLED WITH HIGHER FZLVLS. HOWEVER DO EXPECT
STORM MOTIONS TO BE PROGRESSIVE ENOUGH AND NOT TRAINING...THAT ANY
HEAVY RAINFALL WILL BE BRIEF. THIS COUPLED WITH THE PAST WEEK OF
DRIER WEATHER...AND NEARLY MATURE CROPS SHOULD MINIMIZE THE FLASH
FLOOD THREAT.

.LONG TERM /TONIGHT THROUGH SATURDAY/...
ISSUED AT 259 AM CDT MON JUL 6 2015

SURFACE COLD FRONT IS EXPECTED TO BISECT IOWA EARLY THIS EVENING
FROM NORTHEAST IOWA TO SOUTHWEST IOWA. NUMEROUS SHOWERS AND
THUNDERSTORMS WILL OCCUR NEAR THE FRONT. PRECIPITABLE WATER VALUES
FAVOR A CONTINUED RISK FOR HEAVY RAIN ESPECIALLY NEAR STRONGER
THUNDERSTORM UPDRAFTS. MODELS PROG 0-3KM BULK SHEAR NEAR 35 KNOTS
BRINGING A MARGINAL RISK FOR DAMAGING WINDS WITH MU CAPE AND
LAPSE RATES ALSO SUPPORTING A MARGINAL RISK FOR LARGE HAIL.

THE FRONT WILL PROGRESS SOUTHEAST THROUGH THE STATE OVERNIGHT AND
EXIT EARLY TUESDAY MORNING. SURFACE HIGH PRESSURE WILL BUILD OVER
THE MIDWEST TUESDAY BRINGING THE RETURN OF A COOLER AND DRIER
AIRMASS.

SURFACE HIGH PRESSURE BUILDS EAST WEDNESDAY BRINGING SOUTHERLY
RETURN FLOW TO IOWA. FORECAST MODELS HAVE TRENDED FURTHER SOUTH
WITH A SHORTWAVE MOVING OVER CENTRAL PLAINS WEDNESDAY. THUS HAVE
REFINED PRECIPITATION CHANCES FURTHER SOUTH ACROSS IOWA.

LATE IN THE WEEK MODELS CONTINUE TO SHOW SIGNS OF UPPER RIDGE
BUILDING ACROSS THE PLAINS WITH A LEESIDE TROUGH IN THE NORTHERN
PLAINS. THIS PATTERN FAVORS A WARMING TREND WITH INCREASED
HUMIDITY AND OCCASIONAL CHANCES FOR THUNDERSTORMS WITH SHORTWAVES
ROTATING UP AND OVER THE RIDGE.

&&

.AVIATION...06/18Z
ISSUED AT 1254 PM CDT MON JUL 6 2015

PRIMARY ISSUES WILL BE IN THE FIRST SIX TO NINE HOURS OF THE
FORECAST WITH SCATTERED TO NUMEROUS CONVECTION ACROSS CENTRAL IOWA
PRIOR TO FRONTAL PASSAGE. ANTICIPATE AREAS OF MVFR TO IFR
CONDITIONS THROUGH THE AFTERNOON WITH LOW CEILINGS AND RESTRICTED
VISIBILITIES IN CENTRAL IOWA. A COLD FRONT WILL PASS THROUGH LATE
THIS AFTERNOON AND EARLY EVENING WITH THE THREAT OF PRECIPITATION
ENDING. HOWEVER...SMOKE FROM CANADIAN AND ALASKA FIRES MAY END UP
PRODUCING VISIBILITY PROBLEMS OVERNIGHT BUT HAVE NOT INCLUDED AS
OF YET. WILL CONTINUE TO MONITOR THE LOWER VISIBILITIES PRODUCED
BY THE SMOKE AND ADJUST AS NECESSARY. OTHERWISE...VFR CEILINGS
EXPECTED LATER TONIGHT INTO TUESDAY AS SYSTEM DROPS SOUTH OF THE
STATE.

&&

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

&&

$$

UPDATE...BEERENDS
SHORT TERM...BEERENDS
LONG TERM...ANGLE
AVIATION...COGIL


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