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000
FXUS63 KDMX 230356
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1056 PM CDT WED MAY 22 2013

.UPDATE...
ISSUED AT 814 PM CDT WED MAY 22 2013

TROUGH AND COOL FRONT CONTINUE TO SPIN UP MORE SHOWER ACTIVITY.
HAVE INCREASED POP ACROSS MUCH OF EAST THROUGH JUST AFTER
MIDNIGHT. LOWS ADJUSTED UPWARD A FEW DEGREES ALONG WITH PERSISTENT CLOUDS.

&&

.SHORT TERM.../TONIGHT/
ISSUED AT 353 PM CDT WED MAY 22 2013

UPPER LOW IS MOVING VERY SLOWLY TO THE EAST TONIGHT AND AS A RESULT
WILL LIKELY SEE LIGHT SHOWERS ACROSS THE NORTH THIS EVENING AND FAR
EAST MUCH OF THE NIGHT.  STILL EXPECTING SOME LIGHT SHOWERS OR
SPRINKLES ELSEWHERE AS WELL BUT THESE WILL BE MUCH LIGHTER AND MUCH
MORE HIT AND MISS THAN NORTH AND EAST.  THE NAM12 SHOWS ANOTHER WAVE
OF THETA-E ADVECTION PUSHING SOUTH ACROSS THE CWA THIS EVENING BUT
FORCING IS WEAK IF THERE AT ALL.  THIS SHOULD PROVIDE FOR A BRIEF
PERIOD OF BETTER SHOWER ACTIVITY ACROSS THE NORTH THROUGH MID
EVENING BEFORE EVERYTHING FINALLY PUSHES EAST OVERNIGHT.  WITH
EXPANSIVE CLOUD SHIELD IN PLACE AND LOW CEILINGS IN PLACE...I WOULD
EXPECT THE LOWER CLOUDS TO LINGER FOR A FAIR PART OF THE NIGHT WITH
CLEARING EXPECTED ACROSS THE NORTH LATE.  TEMPS WILL NEED TO BE
MONITORED IF WE CLEAR OUT A LITTLE QUICKER AS THE AIRMASS IN PLACE
IS PRETTY COOL FOR LATE MAY.  TEMPS COULD FALL QUICKER AND FARTHER
WITH A FASTER CLEARING SKY.

.LONG TERM.../THURSDAY THROUGH WEDNESDAY/
ISSUED AT 353 PM CDT WED MAY 22 2013

PRIMARY CONCERN WILL BE CONVECTIVE TRENDS AND PRECIP FROM THE
WEEKEND RIGHT ON THROUGH THE MIDDLE OF NEXT WEEK.  PERIOD WILL BEGIN
WITH A FEW DAYS OF FAIR WEATHER HOWEVER AS CURRENT SYSTEM EXITS AND
IA REMAINS UNDER THE INFLUENCE OF UPPER LEVEL RIDGE.  PROGRESSION OF
RIDGE AND INTRODUCTION OF PROLONGED INTERMITTENT WARM/THETA-E
ADVECTION WILL BEGIN FRI NIGHT HOWEVER AND LAST FROM THE MEMORIAL
DAY WEEKEND RIGHT INTO THE MIDDLE OF NEXT WEEK.  WITH HEIGHTS
GRADUALLY LOWERING IN PERSISTENT WSW FLOW BETWEEN SLOW MOVING WRN
TROUGH AND DEPARTING MS/OH VALLEY RIDGE...THIS WILL PLACE IA INTO
WHAT LOOKS TO BE A NOCTURNAL MAX PATTERN WITH SOUNDINGS SHOWING
ONLY MINIMAL POTENTIAL FOR SURFACE BASED CONVECTION.

DIFFICULT TO PROVIDE TOO MANY DETAILS YET...BUT SAT NIGHT INTO SUN
MORNING IS ONE PERIOD OF CONCERN WITH REGARD TO SEVERE WEATHER AND
HEAVY RAINS WITH LOW LEVEL JET AND 300K INFLOW RIGHT INTO WRN IA.
GFS ELEVATED CAPES APPROACHING 1500 J/KG WITH SEASONALLY HIGH PWS
AND WARM CLOUD DEPTHS UP TO 12KFT WILL PROVIDE FAVORABLE
ENVIRONMENT FOR EFFICIENT RAINFALL. STORM MOVEMENT WILL NOT BE
MUCH EITHER WITH MEAN WIND 20KTS OR LESS.

DO NOT EXPECT MCSS EVERY NIGHT BUT PATTERN REALLY CHANGES LITTLE
INTO THE MIDDLE OF NEXT WEEK WITH H85 FLOW REMAINING FOCUSED FROM
SRN PLAINS INTO IA. THUS HAVE KEPT PROLONGED PERIOD WITH CHANCE
WORDING AND...UNFORTUNATELY...LITTLE CONFIDENCE IN WHEN TO
HIGHLIGHT PARTICULAR PERIODS WITH HIGHER OR LOWER POPS AT THIS
POINT. ELEVATED CAPES ARE NOT AS IMPRESSIVE AS SAT NIGHT FOR
FOLLOWING NIGHTS...BUT STAGNANT PATTERN WILL KEEP POTENTIAL FOR AT
LEAST WEAK MCS ACTIVITY IN THE FORECAST. CUMULATIVE RAINFALL WILL
KEEP THINGS WET WITH LITTLE HYDROLOGIC RECOVERY AND AT LEAST SOME
POTENTIAL FOR ADDITIONAL FLOODING.

&&

.AVIATION...23/06Z
 ISSUED AT 1055 PM CDT WED MAY 22 2013

MAIN CONCERNS CONTINUE THROUGH 12Z WITH MVFR/IFR CIGS AND DZ/-SHRA
CROSSING THE AREA WITH LAST UPPER LEVEL TROUGH AND SFC TROUGH NOW
HEADING SOUTHEAST ACROSS CENTRAL IOWA. UPPER LEVEL SYSTEM OVER
KMKE BUT STILL HAS WRAP AROUND MOISTURE EXTENDING BACK INTO
SOUTHERN MN AND NORTHERN IA AFFECTING MOST OF THE EASTERN TAF
SITES INCLUDING KMCW...KALO...KOTM AND TO A LESSER EXTENT KFOD AND
KDSM THOUGH BOTH OF THOSE SITES WILL SEE PASSING -DZ OR -SHRA
THROUGH 12Z. FINALLY THE LOW DRIFTS EAST AND VFR CONDITIONS
EXPECTED TO RETURN TO AREA AFT 12-15Z AS WEAK RIDGE OF HIGH
PRESSURE BUILDS SOUTHEAST. SOME CONCERN WITH EXTENT OF CLEARING...
HOWEVER AS SUBJECTIVE H850 ANALYSIS SHOWS TROUGH AXIS BACK TO NEXT
UPSTREAM SYSTEM OVER UTAH. WITH BRIEF RETURN TO NORTHWEST FLOW ALOFT...
CLEARING STILL MORE LIKELY TO OCCUR THAN NOT DUE TO LATE MAY SOLAR
INFLUENCE.

&&

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

$$

UPDATE...REV
SHORT TERM...FAB
LONG TERM...SMALL
AVIATION...REV