Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 261150
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
650 AM CDT TUE MAY 26 2015

.SHORT TERM /TODAY/...
ISSUED AT 348 AM CDT TUE MAY 26 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.

.LONG TERM /TONIGHT THROUGH MONDAY/...
ISSUED AT 348 AM CDT TUE MAY 26 2015

PRECIP TRENDS WILL REMAIN THE PRIMARY CONCERN THROUGH THE FORECAST
PERIOD. CURRENT POTENT SHORT WAVE ALONG THE ERN OK/KS BORDER WILL
PUSH A SHARP LOBE OF THERMODYNAMIC AND KINEMATIC FORCING THROUGH IA
TODAY.  MUCH OF THIS SYNOPTIC SCALE FORCING WILL BE THROUGH THE
GREAT LAKES BY 00Z...HOWEVER LINGERING WEAK LOW LEVEL CONVERGENCE
MAY BE SUFFICIENT FOR A FEW ISOLATED SHOWERS OR STORMS DURING THE
EVENING CENTRAL AND SOUTHEAST.  ANY PRECIP THREAT THEN LOOKS TO FADE
WITH LOSS OF HEATING LEADING TO A BREAK THROUGH AT LEAST WED NIGHT
WITH SHORT WAVE RIDGING AND LITTLE IN THE WAY OF LIFT OR MOISTURE.

THE NEXT PRECIP WINDOW WILL BE ASSOCIATED WITH SUBTLE REMNANTS OF
CURRENT CA/NV TROUGH.  ITS APPROACH INTO THU WILL REBUILD DEEPER
MOISTURE AND INSTABILITY STARTING ANOTHER PROLONGED PERIOD OF POPS.
FORCING WILL INITIALLY BE DRIVEN BY WEAK/MODERATE ISENT LIFT AND
MOISTURE TRANSPORT FROM THU INTO THU NIGHT. MODEL DIFFERENCES
THEN ARISE INTO FRI HOWEVER WITH 00Z GFS SPINNING UP A MUCH
STRONGER MID LEVEL WAVE THAN THE 00Z ECMWF. THIS RESULTS IN A
DEEPER SURFACE REFLECTION AND NOTED QG FORCING LINGERING OVER
IA...ESPECIALLY NRN SECTIONS...FROM FRI NIGHT THROUGH SAT NIGHT.
ALTHOUGH THE 00Z DETERMINISTIC ECMWF SUGGESTS A WEAKER
SOLUTION...ITS 12Z ENSEMBLE RUN IS MORE GFS-LIKE WITH THE CMC/GDPS
HINTING TOWARD A STRONGER SOLUTION AS WELL. PWATS AND WARM CLOUD
DEPTHS ARE NOT EXTREME DURING THIS PERIOD...BUT STILL WELL ABOVE
NORMAL AND CAPABLE OF PRODUCING MODERATE TO HEAVY EFFICIENT RAINS
CONSIDERING THE SLOW SYSTEM MOVEMENT. GFS QPF THROUGH SAT IS FOUR
TO SIX INCHES OVER NRN IA AND WHILE IT IS LIKELY OVERDONE DUE TO
BEING THE STRONGER OUTLIER....IT IS INDICATIVE OF HIGHER END
POTENTIAL. THIS WILL CERTAINLY NEED TO BE MONITORED CONSIDERING
THE NARROW SWATH OF TWO TO THREE INCH RAINS THAT OCCURRED SINCE
MON ACROSS PORTIONS OF CRAWFORD...CARROLL AND CALHOUN COUNTIES.

REGARDLESS OF HOW THE MAGNITUDE OF THIS SYSTEM PLAYS OUT...ALL
SOLUTIONS SUGGEST SOMEWHAT DRIER WEATHER AND CONTINUED COOLER
TEMPERATURES TO START THE NEXT WEEK. POPS WILL BE ON THE DECREASE
WITH HIGHS STAYING NO BETTER THAN THE 60S.

&&

.AVIATION...26/12Z
ISSUED AT 650 AM CDT TUE MAY 26 2015

SHOWERS WITH A FEW THUNDERSTORMS TO CONTINUE TO IMPACT THE TAF
SITES THROUGH THE MORNING HOURS...WITH REDEVELOPMENT EXPECTED
THROUGHOUT THE AFTERNOON INTO THE EARLY EVENING HOURS.
PRECIPITATION SHOULD COME TO AN END DURING THE EVENING...WITH
DRY CONDITIONS INTO WEDNESDAY. CIGS WILL REMAIN THE IN THE LOWER
VFR TO MVFR RANGE TODAY. DIPS INTO LIFR ARE POSSIBLE THIS MORNING
IN THE PRECIPITATION. MAINLY LOW VFR TO HIGHER MVFR CIGS POSSIBLE
FOR TONIGHT...WITH WINDS SHIFTING TO THE WEST/NORTHWEST THIS
AFTERNOON INTO TONIGHT.

&&

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

&&

$$

SHORT TERM...BEERENDS
LONG TERM...SMALL
AVIATION...BEERENDS


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