Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 021222
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
722 AM CDT SAT MAY 2 2015

.SHORT TERM /TODAY/...
ISSUED AT 400 AM CDT SAT MAY 2 2015

UPPER LEVEL SHORTWAVE PUSHING EAST OUT OF THE ROCKIES AND CURRENTLY
MOVING THROUGH NEBRASKA...TO CONTINUE TO PUSH EAST THROUGH IOWA
TODAY. WAA AND MOISTURE ADVECTION IN PLACE AHEAD OF THE WAVE...WITH
SOME ASSOCIATED SHOWERS AND THUNDERSTORMS STRETCHING FROM NORTH
CENTRAL NE INTO SE NE/NE KS. NOSE OF THETA-E RIDGE TO BUILD INTO
SWRN/WC IA BY MID MORNING AS THE WAVE PUSHES EAST...BRINGING CHANCES
OF SHOWERS AND THUNDERSTORMS. THESE CHANCES TO SPREAD ACROSS THE CWA
TODAY INTO THIS AFTERNOON AS THE WAVE MOVES OVERHEAD AND WAA
CONTINUES THROUGH THE DAY...AND LAPSE RATES STEEPEN AND INSTABILITY
INCREASES INTO THE AFTERNOON HOURS AS WELL. THEREFORE WENT WITH
STRAIGHT THUNDER MENTION. WITH THE WARMER AIR IN PLACE AND
WAA...TEMPS SHOULD PUSH INTO THE 70S ACROSS THE CWA. WARMEST
READINGS EXPECTED ACROSS THE NORTHERN CWA WHERE LESS CLOUDS/PRECIP
EXPECTED THROUGH THE DAY.

.LONG TERM /TONIGHT THROUGH FRIDAY/...
ISSUED AT 400 AM CDT SAT MAY 2 2015

PRIMARY CONCERN WILL BE PRECIP TRENDS THROUGH THE
PERIOD...DRIVEN BY WARM/THETA-E ADVECTION TONIGHT...CONVERGENCE
AND PROGRESSION OF FRONTAL BOUNDARY LATE SUNDAY INTO TUE...AND
THEN BROADER SCALE LIFT WED NIGHT INTO THU. SCENARIO FOR TONIGHT
SHOULD BE FAIRLY SIMILAR TO WHAT IS ONGOING OVER NE WITH
PERSISTENT WARM ADVECTION ASSOCIATED WITH PROGRESSIVE H85/H7
BAROCLINIC ZONE. CONVECTION ALLOWING HIGH RES MODELS HAVE DEPICTED
LIMITED COVERAGE SO POPS ARE FAIRLY LOW FOR NOW. HIGH CONFIDENCE
SOMETHING WILL BE THERE BUT LOW CONFIDENCE ON HOW MAY PLACES
MEASURE.

BY LATE SUNDAY THE ATTENTION WILL TURN TO CONVERGENCE ALONG A
FRONTAL PASSAGE AS IT DROPS NW-SE THROUGH THE STATE. NAM/GFS BOTH
DEPICT SUFFICIENTLY REDUCED CINH BY PEAK HEATING TO REALIZE A FEW
THOUSAND MLCAPES SO HAVE POPS INCREASING SHARPLY INTO THE EVENING.
EXPECT MCS TO PERSIST INTO THE NIGHT IN SOME FORM... BUT LIKELY
WEAKEN AS IT BECOMES MORE ELEVATED AND LOW LEVEL INFLOW WEAKENS
AND VEERS. PERSISTENT RIBBON OF FORCING WILL LIKELY KEEP PERIODS
OF CONVECTION GOING INTO MON BEFORE EXPANDING ONCE AGAIN INTO THE
NIGHT AND EARLY TUE AS WARM ADVECTION REDEVELOPS WITH BAROCLINIC
ZONE LIFTING NORTHWARD.

ALTHOUGH HAVE CONTINUED CHANCE POPS THROUGH LATER TUE AND
WED DUE TO GENERAL UNFOCUSED INSTABILITY...FEEL THERE MAY BE
SOMEWHAT OF A LULL WITH LOSS OF THERMODYNAMIC
FORCING/BAROCLINICITY AND SURFACE CONVERGENCE AS IA IS
ESSENTIALLY BACK INTO THE UNFORCED WARM SECTOR WITH ONLY SUBTLE
TRIGGERS AT BEST. BETTER POTENTIAL WILL LIKELY HOLD OFF UNTIL WED
NIGHT AND THU AS MATURING WRN LONG WAVE TROUGH EJECTS LOB OF
FORCING INTO THE MO VALLEY.

ALTHOUGH PULSE SEVERE STORMS ARE CERTAINLY POSSIBLE DURING ANY OF
THESE EPISODES...THE OUTLOOK FOR ANY APPRECIABLE SEVERE WEATHER
SEEMS LOW THROUGH THE ENTIRE PERIOD WITH INSTABILITY AT SEASONAL
LEVELS AND MID LEVEL WINDS RELATIVELY WEAK KEEPING EFFECTIVE
SHEAR VALUES OFTEN FAIRLY LOW.

&&

.AVIATION...02/12Z
ISSUED AT 722 AM CDT SAT MAY 2 2015

AREA OF SHOWERS PUSHING INTO SOUTHWEST IOWA...EXPECTED TO SPREAD
ACROSS THE STATE TODAY. MAINLY HAVE VCSH OR -SHRA AT KFOD AND
KDSM...WITH CHANCES LESS CERTAIN AT THE OTHER SITES. SOUTHERLY
WINDS PICKING UP A BIT TODAY...THEN DIMINISHING TONIGHT. MID
CLOUDS SPREADING ACROSS THE CWA TODAY.

&&

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

&&

$$

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



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