Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 251744
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1243 PM CDT MON MAY 25 2015

...UPDATED FOR 25/18Z AVIATION DISCUSSION...

.SHORT TERM /TODAY/...
ISSUED AT 320 AM CDT MON MAY 25 2015

ANOTHER COMPLEX DAY AHEAD...THOUGH SYSTEM HAS NOT EVOLVED EXACTLY AS
LAST NIGHTS MODELS SUGGESTED FOR 06-12Z MONDAY...UPPER LEVEL WAVE
OVER NORTHEAST KS AND NORTHWEST MO BECOMING MORE ACTIVE AT 07Z.
SHOWERS AND ISO THUNDER BEGINNING TO DEVELOP OVER THOSE AREAS
HEADING INTO SOUTHERN IOWA NOW. HAVE UPDATED THE OVERNIGHT INTO
MORNING POP GRIDS TO REFLECT THE INCOMING PRECIPITATION. FORTUNATELY
PRECIPITABLE WATER VALUES HAVE DROPPED TO NEAR ONE INCH AND WARM
CLOUD DEPTHS ARE SLIGHTLY UNDER 10KFT SO RAINFALL EFFICIENCY WILL
NOT BE AS PROLIFIC AS SUNDAY MORNINGS SHOWERS AND MORE WELL DEFINED
MCV THAT CROSSED THE AREA. SUBJECTIVE H850 00Z ANALYSIS CONTINUES TO
SHOW SUBTROPICAL ANCHOR HIGH OFF THE SOUTHEAST US WITH BROAD AREA OF
LOW PRESSURE OVER THE ROCKIES...LOW NEAR DENVER AT 00Z. THE MAIN
MOISTURE CHANNEL HAS MOVED EAST OF IOWA NOW BUT THE LOW AND
APPROACHING FRONT LATE THIS EVENING WILL STILL IMPACT THE REGION
WITH MORE CHANCES FOR STORMS. AS THE UPPER LEVEL DISTURBANCE OVER KS
TRACKS NORTHEAST...IT SHOULD EXIT EAST/NORTHEAST AREAS BETWEEN 15-
17Z. SOME BREAKS IN CLOUDS LIKELY SOUTHEAST THIRD...ALLOWING HIGHS
TO BUILD INTO THE LOWER 80S THIS AFTERNOON. OVER THE NORTH LOWER TO
MID 70S MORE LIKELY WITH THICKER CLOUD COVER. BETWEEN 20-00Z WILL BE
LOOKING FOR MAIN H500 WAVE OVER THE ROCKIES TO EJECT NORTHEAST
TOWARD IOWA. THIS WILL SET THE STAGE FOR INCREASING THUNDERSTORM
DEVELOPMENT. BUFR SOUNDINGS SHOW 1200-1900 J/KG MLCAPE BY 21Z THIS
AFTERNOON MOST AREAS. WIND FIELDS ALOFT NOT OVERLY IMPRESSIVE THIS
AFTERNOON...BUT CERTAINLY ENOUGH TO ORGANIZE STORMS WITH THE
POTENTIAL FOR SEVERE STORMS. CURRENTLY OUR AREA HAS BEEN UPDATED TO
SLIGHT RISK FOR LATE AFTERNOON AND EARLY EVENING. MAIN THREATS
APPEAR TO BE WIND AND HAIL AND A FEW TORNADOES. ACTIVITY LIKELY TO
CONTINUE INTO THE EARLY EVENING. RAINFALL TODAY MAY STILL APPROACH
.25 TO .75 INCHES WITH THE COMBINATION OF THIS MORNINGS
PRECIPITATION AND THIS AFTERNOONS EXPECTED STORMS OVER THE
WEST /NORTHWEST.

.LONG TERM /TONIGHT THROUGH SUNDAY/...
ISSUED AT 320 AM CDT MON MAY 25 2015

ACTIVE PATTERN TO CONTINUE THROUGH MUCH OF THE PERIOD...WITH THE
MAIN WESTERN US TROUGH TO LIFT NORTHEASTWARD THROUGH TUESDAY. THIS
UPPER WAVE WILL APPROACH THE REGION TONIGHT AND MOVE THROUGH THE CWA
TUESDAY BEFORE PUSHING INTO THE GREAT LAKES REGION TUESDAY NIGHT.
SOUTHERLY FLOW AHEAD OF IT WILL CONTINUE TO PUSH MOISTURE NORTHWARD
INTO THE AREA...WITH AN ELONGATED AREA OF LOW PRESSURE AND
ASSOCIATED WARM FRONT STRETCHED NORTHEASTWARD ACROSS THE CWA TONIGHT
INTO TUESDAY. AN UPPER VORT MAX CURRENTLY OVER CNTRL/NW TEXAS WILL
LIFT NORTHWARD TOWARD THE REGION AS WELL...AND WITH ENERGY FROM THE
MAIN UPPER TROUGH AND THIS SECONDARY SHORTWAVE TROUGH LIFTING
THROUGH THE REGION LATE TONIGHT...EXPECT AN AREA OF THUNDERSTORMS TO
DEVELOP ACROSS THE CWA MAINLY DURING THE EVENING/LATE NIGHT HOURS.
DEEP LAYER SHEAR STRONGER IN THE EVENING THEN WEAKENS INTO THE
OVERNIGHT HOURS...WITH INSTABILITY WANING THROUGH THE OVERNIGHT
HOURS AS WELL. GIVEN THE AMOUNT OF SHEAR/INSTABILITY SOME SEVERE
STORMS POSSIBLE WITH THE LATEST SPC OUTLOOK SHOWING A SLIGHT RISK
ACROSS MUCH OF THE CWA FOR TONIGHT. LARGE HAIL AND DAMAGING WINDS
WOULD BE THE MAIN THREATS...WITH AN ISOLATED TORNADO THREAT AS WELL
HOWEVER IT LOOKS SLIGHTLY BETTER FURTHER SOUTH AND WEST OF THE CWA.

THUNDERSTORM CHANCES CONTINUE INTO TUESDAY AS THE UPPER WAVE MOVES
THROUGH THE CWA...AND THE SFC TROUGH AXIS TO PUSH EAST BY LATE
TUESDAY/TUESDAY NIGHT. WEAK COLD FRONTAL BOUNDARY TO SAG SOUTH OF
THE STATE FOR WEDNESDAY/WEDNESDAY NIGHT BEFORE LIFTING BACK
NORTHWARD THURSDAY. HIGH PRESSURE TO BRIEFLY BUILD INTO THE STATE AS
WELL WEDNESDAY SO EXPECT MAINLY DRY CONDITIONS WEDNESDAY/WEDNESDAY
NIGHT. NAM TRIES TO HANG THE BOUNDARY ACROSS THE SOUTH...WITH SOME
ADDITIONAL THUNDERSTORM DEVELOPMENT BUT THE MAJORITY OF THE MODELS
PUSH IT SOUTH OF THE CWA. THUS HAVE GONE WITH THE CONSENSUS AND
STUCK WITH DRY CONDITIONS FOR WEDNESDAY NIGHT. ANOTHER UPPER TROUGH
TO BUILD INTO THE WESTERN US FOR THURSDAY INTO NEXT WEEKEND...WITH
SOUTHWESTERLY FLOW SETTING UP AGAIN AND CHANCES FOR THUNDERSTORMS
RETURN FOR LATE WEEK. A STRONGER COLD FRONT TO DROP THROUGH THE AREA
NEXT WEEKEND WITH A LARGE AREA OF HIGH PRESSURE EXPECTED TO BUILD
INTO THE AREA FOR SUNDAY INTO MONDAY. TEMPERATURES TO REMAIN NEAR
AVERAGE FOR THE FIRST FEW DAYS OF THE PERIOD WITH A TURN TOWARD
COOLER THAN AVERAGE TOWARD THE WEEKEND AND INTO EARLY NEXT WEEK.

&&

.AVIATION...25/18Z
ISSUED AT 1243 PM CDT MON MAY 25 2015

CHANCES OF SHRA/TSRA RETURN LATER THIS AFTN INTO THIS EVE ESPECIALLY
FOR THE KFOD...KDSM AND KMCW TERMINALS. MVFR FLIGHT CONDITIONS
EXPECTED AT WORST DUE MAINLY TO CIGS...WHICH ARE EXPECTED TO REMAIN
ABOVE IFR THRESHOLDS. WINDS WILL INCREASE THIS AFTN AND THEN
DIMINISH AFTER SUNSET.

&&

.HYDROLOGY...
ISSUED AT 320 AM CDT MON MAY 25 2015

RAIN EXPECTED ONCE AGAIN TODAY...BUT THREAT FOR ANY FLASH FLOODING
REMAINS LOW. RAINFALL RATES EARLY TODAY NOT EXPECTED TO BE HIGH
ENOUGH AND RAINFALL PERSISTENT ENOUGH. LATER TODAY...SCATTERED
NATURE OF STORMS SHOULD NOT LEAD TO ANY WIDESPREAD COVERAGE UNTIL
THE EVENING HOURS. MAIN CONCERNS ARE ADDITIVE EFFECTS OF YESTERDAYS
THROUGH TUESDAYS RAINFALL...AND SUBSEQUENT EVENTS. SOME URBAN
RUNOFF AND PONDING OF WATER MAY BE POSSIBLE WITH STRONGER STORMS.

IN TERMS OF RIVER FLOODING...MINOR TO MODERATE WITHIN-BANK RISES ARE
EXPECTED AT MULTIPLE LOCATIONS ESPECIALLY WITHIN THE MIDDLE TO LOWER
DES MOINES RIVER BASIN...AS WELL AS THE LOWER RACCOON RIVER BASIN.
IF RAINFALL OVER THE NEXT 24-36 HRS COMES IN HEAVIER THAN
EXPECTED...THEN MINOR FLOODING COULD BE EXPECTED AT SOME
LOCATIONS.

&&

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

$$

SHORT TERM...REV
LONG TERM...BEERENDS
AVIATION...REV
HYDROLOGY...ZOGG/REV



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