Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 261141
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
641 AM CDT TUE AUG 26 2014

.SHORT TERM /TODAY/...
ISSUED AT 314 AM CDT TUE AUG 26 2014

THUNDERSTORM COMPLEX ACROSS WESTERN CENTRAL AND SOUTHWEST IOWA WILL
CONTINUE TO EXPAND EAST OVER THE NEXT SEVERAL HOURS. THE
THUNDERSTORMS WILL LAST THROUGH MID MORNING AND ARE EXPECTED TO
REMAIN CONFINED TO SOUTH OF HIGHWAY 20. THE STORMS ONCE AGAIN HAVE
EFFICIENT RAIN PRODUCING CHARACTERISTICS AND MAY PRODUCE 1 TO 3
INCHES IN A SHORT PERIOD. OVERALL SHOULD BE ABLE TO AVOID ANY HYDRO
ISSUES UNLESS THIS MOVES THROUGH THE DSM METRO. OTHERWISE IT WILL
ACT MAINLY AS A PRIMER FOR THE REMAINDER OF THE WEEK. HIGH PRESSURE
TO THE NORTH COMBINED WITH A PASSING SHORT WAVE JUST TO THE
NORTHEAST WILL HELP PUSH DRIER AIR IN FROM THE NORTHEAST AND WILL
HELP END THE PRECIPITATION. HAVE DECREASED PRECIPITATION CHANCES
INTO THE AFTERNOON AS FORCING DIMINISHES WITH THE ARRIVAL OF THE
DRIER AIR. THE MOISTURE BEGINS TO SURGE BACK NORTH INTO SOUTHWEST
IOWA BY LATE AFTERNOON AND WILL BRING THE RETURN OF ELEVATED
INSTABILITY AND INCREASING CHANCES FOR THUNDERSTORMS ONCE AGAIN.

TEMPERATURES WILL AGAIN BE CLOUD DEPENDENT BUT OVERALL COOLER THAN
MONDAY WITH HIGHS IN THE 70S NORTH AND CENTRAL TO THE 80S SOUTH.

.LONG TERM /TONIGHT THROUGH MONDAY/...
ISSUED AT 314 AM CDT TUE AUG 26 2014

WILL SEE PROLONGED PERIOD OF WET WEATHER THROUGH EXTENDED. PATTERN
WILL REMAIN FAIRLY STAGNANT WITH SURFACE HIGH OVER SOUTHERN U.S.
KEEPING IOWA IN WET PATTERN AS SURFACE LOW REMAINS ACROSS WESTERN
KS/NE WITH STATIONARY BOUNDARY NEAR/ACROSS IOWA. THIS WILL ALLOW
FOR SEVERAL ROUNDS OF RAIN AS WAVES PUSH THROUGH MOSTLY ZONAL FLOW
ACROSS THE NORTH. LOW WILL SLOWLY BEGIN TO PUSH EASTWARD AS UPPER
LEVEL LOW BEGINS TO PHASE AND HELPS TO PUSH EAST TOWARDS END OF
THE WEEK. EXPECT BEST CHANCES FOR PRECIPITATION TO COME OVERNIGHT
THROUGH FRIDAY...WITH PRECIPITATION LINGERING INTO THE DAYTIME
HOURS...AND ADDITIONAL DIURNAL DEVELOPMENT POSSIBLE. FOR TONIGHT
HAVE CUT BACK ON POPS THROUGH THE EARLY EVENING AS MODELS HAVE
SLOWED PUSH OF THETA-E ADVECTION PUSHES IN FROM NE. ADVECTION WILL
LINGER THROUGHOUT THE DAY AND INTO THE OVERNIGHT HOURS. WITH
ADDITIONAL MUCH STRONGER WAVE PUSHING EASTWARD WEDNESDAY
NIGHT...THIS APPEARS TO BE THE BEST CHANCE FOR PRECIPITATION AND
HEAVY RAINFALL. HOWEVER...LATEST MODEL RUNS ARE BEGINNING TO PUSH
SYSTEM SLIGHTLY FURTHER NORTH...IF NORTHERN TREND CONTINUES...MAY
PULL PRECIPITATION NORTH OF IOWA INTO MINNESOTA. HOWEVER...FOR NOW
EXPECT BEST PRECIPITATION TO BE ACROSS WEST CENTRAL AND NORTHERN
IOWA THROUGH THE OVERNIGHT...ONCE AGAIN WITH PRECIPITATION
LINGER INTO THE DAY THURSDAY. LOW WILL FINALLY BEGIN TO PULL EAST
FOR FRIDAY WITH ADDITIONAL FRONT PUSHES THROUGH IOWA...THOUGH
MODELS HANG UP EASTWARD PROGRESSION WITH LINGERING PRECIPITATION
INTO THE WEEKEND...ESPECIALLY IN EASTERN AND SOUTHERN IOWA.

PRECIPITATION WILL LIKELY BE HEAVY WITH THUNDERSTORMS THROUGH THE
PERIOD. HIGH PRESSURE ACROSS THE SOUTH WILL KEEP SURFACE FLOW FROM
THE SOUTH WITH AMPLE MOISTURE ACROSS THE STATE. PWAT VALUES WILL
BE GENERALLY NEAR 1.5 TO 1.75 INCHES THROUGH THURSDAY...WITH THE
HIGHEST VALUES NEAR 2 INCHES THURSDAY MORNING. THIS IS SEASONALLY
VERY HIGH. UPPER LEVEL FLOW WILL GENERALLY BE ALONG BOUNDARY WHICH
COULD LEAD TO BACK BUILDING OF STORMS. GIVEN HIGH RAINFALL AMOUNTS
THAT HAVE BEEN SEEN ACROSS MUCH OF THE REGION OVER THE PAST
WEEK...WOULD ANTICIPATE HEAVY RAINFALL TO BEGIN TO LEAD TO A
FLASH FLOOD POTENTIAL...ESPECIALLY TOWARDS MID WEEK...AND A WATCH
MAY BE WARRANTED. IN ADDITION...RIVERS WILL LIKELY BEGIN TO SEE
THE IMPACT OF HEAVY RAINFALL WITH RISES ACROSS THE REGION AS CROP
GROWTH BEGINS TO DIMINISH AT THE END OF THE SEASON. SEVERE THREAT
WILL BE LOW...AND MOSTLY CONFINED TO THE AFTERNOON HOURS WITH
DIURNAL THUNDERSTORM DEVELOPMENT. SHEAR IS LIMITED...THOUGH
MODELS INDICATE AMPLE INSTABILITY WITH HIGH SURFACE BASED AND MU
CAPE VALUES. THEREFORE MAY SEE ISOLATED SEVERE THUNDERSTORMS
THROUGH THE PERIOD.

TEMPERATURES WILL GENERALLY BE COOLER THAN PREVIOUS DAYS
WITH AMPLE CLOUDS AND PRECIPITATION AROUND. HOWEVER...SOUTHERN
IOWA WILL STILL FEEL INFLUENCE OF SOUTHERN HIGH AND WAA.
TEMPERATURES WILL BE HIGHLY VARIABLE THROUGH THE PERIOD THOUGH
WITH IMPACTS FROM OVERNIGHT PRECIPITATION AND LINGERING DAYTIME
PRECIPITATION POTENTIALLY DRAGGING TEMPERATURES DOWN SIGNIFICANTLY
FROM GOING AT TIMES.

&&

.AVIATION...26/12Z
ISSUED AT 641 AM CDT TUE AUG 26 2014

PRECIPITATION WILL BE ENDING ACROSS THE AREA BY 15Z THEN VFR
CONDITIONS WITH LIGHT NORTH TO NORTHEAST WINDS WILL PREVAIL
THROUGH THE DAY. THUNDERSTORMS WILL REDEVELOP TONIGHT WITH THE
GREATEST POTENTIAL AFTER 06Z.

&&

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

$$

SHORT TERM...DONAVON
LONG TERM...AWB
AVIATION...DONAVON


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