Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 312105
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
405 PM CDT SUN AUG 31 2014

.SHORT TERM /TONIGHT/...
ISSUED AT 405 PM CDT SUN AUG 31 2014

WEAK ENERGY STILL WRAPPING AROUND THE UPPER LEVEL SHORT WAVE OVER
MINNESOTA AND WISCONSIN AND INTO NORTHEAST IOWA THIS AFTERNOON. THIS
HAS LED TO A FEW SHOWERS TO DEVELOP OVER THAT REGION. THE STRATUS
FIELD CONTINUES TO ERODE OVER CENTRAL IOWA LEADING TO SOME SFC BASED
INSTABILITY TO DEVELOP. HI RESOLUTION SOLUTIONS THROUGH THE
AFTERNOON ARE SUGGESTING ISOLATED THUNDERSTORM DEVELOP ALONG AND
EAST OF INTERSTATE 35 LATE AFTERNOON THROUGH EARLY EVENING AS A
SURGE OF THETA-E ADVECTION MOVES INTO THE STATE. THE LIMITING FACTOR
IS THE VERY DRY MID LEVELS AND ONLY WEAK VERTICAL ASCENT. POSSIBLE
FOR AN ISOLATED THUNDERSTORM TO DEVELOP OVERNIGHT BEFORE ENDING.
IMPRESSIVE UPPER JET MOVING INTO THE WESTERN CONUS WILL BEGIN TO
APPROACH THE MISSOURI VALLEY LATE TONIGHT. A THUNDERSTORM COMPLEX
FROM THE WEST MAY REACH EASTERN NEBRASKA AND POSSIBLY FAR WESTERN
IOWA BY 12Z BUT THE AREA SHOULD REMAIN DRY THROUGH THAT TIME.



.LONG TERM /MONDAY THROUGH SUNDAY/...
ISSUED AT 405 PM CDT SUN AUG 31 2014

COLD FRONT TO MOVE THROUGH TONIGHT AND BE STRETCHED ACROSS THE FAR
SOUTHEASTERN CWA BY MONDAY MORNING. SOME LINGERING STORMS OR
ADDITIONAL DEVELOPMENT ALONG THE FRONT POSSIBLE THROUGH THE
MORNING/EARLY AFTERNOON HOURS AS SOUTHERLY FLOW AND THETA E
ADVECTION IN PLACE. SECONDARY PUSH OF COOLER AIR ALONG WITH ENERGY
ALOFT TO SLIDE THROUGH NORTHERN IOWA/SOUTHERN MINNESOTA. COULD SEE
SOME CHANCES FOR PRECIP WITH THIS ENERGY AS WELL...BUT MAJORITY OF
PRECIP EXPECTED TO REMAIN NORTH/EAST OF THE CWA. STILL SOME WEAK
INSTABILITY AROUND WITH COOLER AIR MOVING IN ALOFT...AND WEAK
BOUNDARY SO HAVE KEPT SOME SMALL POPS ACROSS THE NORTH/EAST FOR
MONDAY AFTERNOON. ADDITIONAL PRECIPITATION CHANCES EXPECTED ACROSS
NORTHERN IOWA FOR MONDAY NIGHT...AS ANOTHER WEAK WAVE MOVES THROUGH
ALOFT...WITH DRY CONDITIONS EXPECTED TUESDAY INTO EARLY TUESDAY
EVENING AS HIGH PRESSURE BUILDS INTO THE REGION BRIEFLY.

RETURN FLOW SETS UP TUESDAY NIGHT...WITH A WARM FRONT ALOFT LIFTING
NORTH NORTHEAST INTO THE CWA TUESDAY NIGHT. THIS FRONT IS ASSOCIATED
WITH A DEVELOPING AREA OF LOW PRESSURE ALONG THE WESTERN HIGH
PLAINS. MOISTURE TO INCREASE ACROSS THE STATE LATE TUESDAY NIGHT
INTO WEDNESDAY AS SOUTHERLY FLOW INCREASE OFF THE GULF. COULD SEE
SOME THUNDERSTORMS DEVELOP ALONG THE BOUNDARY LIFTING NORTH THROUGH
THE CWA LATE TUESDAY NIGHT INTO WEDNESDAY. DEWPOINTS PUSH INTO 70S
WEDNESDAY...WITH HUMID CONDITIONS RETURNING TO THE CWA. UPPER LEVEL
WAVE TO PUSH EASTWARD FROM THE ROCKIES THROUGH THE CENTRAL US LATE
IN THE WEEK. SFC LOW TO TRACK THROUGH THE GREAT LAKES REGION...WITH
TRAILING COLD FRONT EXPECTED TO DROP THROUGH THE CWA LATE THURSDAY
NIGHT INTO FRIDAY. THIS WILL BRING ADDITIONAL THUNDERSTORM CHANCES
TO THE STATE WITH HIGH PRESSURE AND MAINLY DRY CONDITIONS EXPECTED
INTO THE WEEKEND. EXTENDED RANGE TRYING TO BRING A WEAK SYSTEM
THROUGH LATE IN THE WEEKEND...BUT LOOKS LIKE MAIN TRACK OF THE
SYSTEM WILL BE JUST OFF TO THE NORTH AND EAST FOR NOW. AS FOR
TEMPERATURES...EXPECT WARMING TEMPS MONDAY THROUGH WEDNESDAY WITH
TEMPS NEAR OR ABOVE AVERAGE...WITH A COOL OFF TO SLIGHTLY BELOW
AVERAGE TEMPS FOR THE WEEKEND.


&&

.AVIATION...31/18Z
ISSUED AT 1240 PM CDT SUN AUG 31 2014

BREEZY SOUTHERLY WINDS WILL PREVAIL IN ADVANCE OF A COLD FRONT
WHICH WILL PASS ACROSS THE AREA LATE TONIGHT INTO MONDAY MORNING.
THE PRIMARY AVIATION CONCERN WILL BE WIDESPREAD THUNDERSTORMS
MOVING ACROSS THE STATE OVERNIGHT. STORMS WILL LIKELY HAVE STRONG
WINDS ALONG THE LEADING EDGE AND SIGNIFICANTLY REDUCED
VISIBILITIES IN HEAVY RAIN. A PERIOD OF MVFR STRATUS IS POSSIBLE
BEHIND THE STORMS. THE STRATUS SHOULD BEGINS TO SCATTER AS DRIER
AIR ARRIVES BEHIND THE BOUNDARY.


&&

.HYDROLOGY...
ISSUED AT 1241 PM CDT SUN AUG 31 2014

CONCERNS FOR FLOODING CONTINUE VERY LATE THIS AFTERNOON AND
TONIGHT. CURRENT PROFILES REMAIN QUITE DRY BELOW 700 MB HOWEVER
MOISTURE ADVECTION LATE AFTERNOON AND INTO TONIGHT SHOULD HELP
PUSH PWAT VALUES TO NEAR 1.6 INCHES OVER A NARROW CORRIDOR BY THIS
EVENING. RECENT RAINFALL...ESPECIALLY SOUTHWEST INTO THE CENTRAL
COUNTIES...HAVE PRODUCED NEAR SATURATED GROUND ENOUGH TO LOWER
THE THREE HOUR FFG VALUES TO NEAR 1.5 TO 2.5 INCH RANGE AS A
RESULT OF HIGH RUNOFF RATES. A WIDESPREAD ONE TO TWO INCH
RAINFALL WITH SPOTTY THREE INCH AMOUNTS IS LIKELY OVERNIGHT.
GIVEN THE LOW FFG VALUES...LOCAL FLASH FLOODING IS A POSSIBILITY.
CONTINUE TO MONITOR THE NEED FOR HEADLINES OVERNIGHT.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...

FLASH FLOOD WATCH FROM 7 PM CDT THIS EVENING THROUGH MONDAY
MORNING FOR ADAIR-ADAMS-AUDUBON-BOONE-CARROLL-CASS-CLARKE-
CRAWFORD-DALLAS-DECATUR-GREENE-GUTHRIE-MADISON-POLK-RINGGOLD-
STORY-TAYLOR-UNION-WARREN.

&&

$$

SHORT TERM...DONAVON
LONG TERM...BEERENDS
AVIATION...DONAVON
HYDROLOGY...MS AUG 14/DONAVON


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