Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 101746
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1246 PM CDT THU APR 10 2014

.SHORT TERM /TODAY/...
ISSUED AT 339 AM CDT THU APR 10 2014

FRONT CURRENTLY PASSING THROUGH THE STATE WITH LITTLE SENSIBLE
WEATHER.  DESPITE SOME DECENT MID LEVEL QG FORCING...DEEPER
SATURATION REMAINS DIFFICULT WITH RELATIVELY DRY AIRMASS IN PLACE
ACROSS THE STATE.  RADAR CONTINUES TO INDICATE ECHOES ACRS SOUTHERN
MINNESOTA ASSOCIATED WITH MID LEVEL FRONTOGENETICAL FORCING AND THIS
AREA WILL SWEEP ACROSS THE NORTHERN IOWA THIS MORNING.  HAVE LEFT
THE THREAT OF SOME SPRINKLES WITH THIS BAND AS IT MOVES SOUTHEAST...
HOWEVER MEASURABLE PRECIPITATION REMAINS IFFY AT BEST.  BEHIND THE
FRONT...SUBSIDENCE AND DRYING WILL RAPIDLY OVERSPREAD THE FORECAST
AREA FROM NORTH TO SOUTH THIS AFTERNOON.  WITH SUNSHINE APPEARING IN
MANY LOCATIONS BY AFTERNOON...DECENT MIXING IS EXPECTED WITH GUSTY
NORTHWEST WINDS.  TEMPERATURES SHOULD REBOUND...ALTHOUGH THE COLD
ADVECTION WILL LIMIT OVERALL POTENTIAL WITH READINGS NEARLY 15
DEGREES OR SO COOLER THAN WEDNESDAY.

.LONG TERM /TONIGHT THROUGH WEDNESDAY/...
ISSUED AT 339 AM CDT THU APR 10 2014

DIFFICULT TO GET EXCITED ABOUT PRECIP CHANCES AT THIS POINT FOR
FRIDAY AM. MODELS REMAIN IN GOOD AGREEMENT WITH PUSHING A
WEAK...FAST MOVING SHORTWAVE THROUGH THE UPPER MIDWEST. THE SIGNAL
OF THIS SHORTWAVE HAS WEAKENED DRAMATICALLY IN PAST 24 HOURS. THE
MAJOR HINDRANCE FOR THIS SYSTEM IS A LACK OF MOISTURE. THE AREA OF
HIGH PRESSURE WHICH WILL BE PASSING THROUGH THE CWA THURSDAY PM WILL
HAVE PROPAGATED INTO ILLINOIS BY FRIDAY AM AND THE SUBSEQUENT
NORTHEASTERLY FLOW WILL MAKE IT INTO MISSOURI...SERVING AS A BARRIER
OF ENTRY OF GULF MOISTURE INTO IOWA TO SUPPORT THIS SHORTWAVE.
FURTHERMORE...MODEL SOUNDINGS HAVE A LAYER OF SATURATION AT H700
WHICH IS ONLY ABOUT 2KFT THICK. AS A RESULT...HAVE SCALED POPS BACK
SIGNIFICANTLY.

MODELS COMING INTO MUCH BETTER AGREEMENT FOR SATURDAY PM EVENT. A
LARGE TROUGH WILL MOVE EASTWARD ACROSS NORTH CENTRAL MINNESOTA WITH
AN ATTACHED BOUNDARY EXPECTED TO DROP DOWN INTO IOWA. FOR SYNOPTIC
SCALE EVOLUTION...LEANING TOWARDS BLENDED SOLUTION WITH BIG NUDGE
TOWARDS EURO AS THE EURO HAS HAD THE MOST RUN TO RUN CONSISTENCY.
ALL IN ALL...MODELS LOOKING MUCH MORE IMPRESSIVE IN LATEST RUNS
VERSUS 24 HOURS AGO. DEWPOINTS LOOK TO BE IN THE MID 50S TO LOW
60S ACROSS SOUTHERN TO CENTRAL IOWA BY 00Z SUN. PER USUAL...THE
NAM IS THE MOST AGGRESSIVE WITH CONVECTION...MARKETING MUCAPE
VALUES AROUND 2500 J/KG ACROSS SOUTHERN IOWA AT 00Z SUNDAY.
COMPARATIVELY...THE GFS HAS AROUND 1000 J/KG OF CAPE AT THAT TIME.
REGARDLESS OF SOLUTION...THERE SEEMS TO BE A WARM INVERSION TO
KEEP CONVECTION CAPPED PRIOR TO 18Z ACROSS CWA. BOUNDARY TO DROP
SOUTHEASTERLY DURING THE DAY AND THIS WILL LIKELY BE THE FOCUS FOR
CONVECTION. WILL KEEP AN EYE ON FURTHER RUNS TO SEE POSITIONING OF
BOUNDARY DURING PEAK HEATING. 0 TO 6 KM SHEAR LOOKS TO BE IN THE
30 TO 40 KT RANGE WHICH IS CERTAINLY SUFFICIENT. NOTABLE MOISTURE
AND QG VECTOR CONVERGENCE TO HELP PROVIDE LIFT AND SUPPORT FOR
STORM DEVELOPMENT. IN TRYING TO NARROW DOWN CONVECTIVE
MODE...GIVEN LCL...BRN...AND HELICITY LEVELS...MORE SUPPORTIVE OF
SUPERCELLS MORE CAPABLE OF PRODUCING HAIL AND TORNADO THREAT SEEMS
VERY LOW. WILL WATCH TO SEE HOW SUBSEQUENT 12Z THU AND 00Z FRI
RUNS HANDLE SYSTEM.

TROUGH SWINGS EASTWARD FOR SUNDAY AND MAJOR CAA SETS UP FOR UPPER
MIDWEST. ENSEMBLES SHOW H850 TEMPS OF AROUND 10C FOR SATURDAY...
FALLING TO AROUND 0C SUNDAY...AND DOWN TO AROUND MINUS 6C FOR MONDAY
MORNING. VERTICAL PROFILES TO STAY QUITE SATURATED SUNDAY...WITH
DRIER AIR GRADUALLY MOVING IN FROM NORTHWEST TO SOUTHEAST. AS
MENTIONED EARLIER...LEANING TOWARDS EURO SOLUTION...SO WILL HOLD
ONTO MOISTURE AND PRECIP INTO 06Z FOR MUCH OF CWA. AS A RESULT OF
THE ABOVE...WENT WITH A NON DIURNAL TEMPERATURE TREND FOR SUNDAY
AFTERNOON INTO MONDAY MORNING. AS THIS COLDER AIR MOVES IN SNOW
BECOMES A FOCUS FOR LATER SUNDAY INTO MONDAY. RAPIDLY FALLING
TEMPERATURES WOULD HINT AT A VERY SHORT LIVED TRANSITION ZONE.

MODELS HINTING AT HIGH PRESSURE MOVING ACROSS THE MIDDLE OF THE
CONUS MONDAY INTO TUESDAY. THIS SHOULD BRING DRY CONDITIONS AND
SLIGHTLY COOLER TEMPS AS CWA WILL BE IN NORTHWESTERLY FLOW INTO
WEDNESDAY. OUR NEXT PRECIPITATION LOOKS TO MOVE INTO THE MIDWEST IN
THE WEDNESDAY THROUGH FRIDAY TIMEFRAME.

&&

.AVIATION...10/18Z
ISSUED AT 1246 PM CDT THU APR 10 2014

VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD WITH A FEW HIGH
CLOUDS AND NO PRECIP OR OBSCURATIONS FORECAST. TAFS ARE BROKEN UP
FOR CHANGES IN WIND SPEED OR DIRECTION...WITH WINDS DECREASING
RAPIDLY THIS EVENING THEN SWINGING AROUND TO SOUTHWEST AND PICKING
UP AGAIN LATE FRIDAY MORNING.

&&

.FIRE WEATHER...
ISSUED AT 339 AM CDT THU APR 10 2014

CONDITIONS WILL BECOME MORE FAVORABLE FOR FIRES BY MIDDAY INTO THE
AFTERNOON AS SUNSHINE HELPS MIXING TO INCREASE.  THE DEEPER MIXING
WILL ALLOW WINDS TO BECOME GUSTY BY THIS AFTERNOON WITH SUSTAINED
WINDS OF 15 TO 20 MPH FROM THE NORTHWEST ACROSS THE NORTHERN HALF OF
THE FORECAST AREA AND GUSTS OF UP TO 30 MPH.  DEWPOINTS WILL ALSO
FALL NICELY WITH THE INCREASED MIXING AND BY PEAK HEATING THIS
AFTERNOON...RH VALUES WILL DROP INTO THE LOW TO MID 20S ACROSS THE
NORTHWEST HALF OF THE CWA. THESE CONDITIONS ARE JUST A BIT UNDER RED
FLAG WARNING CRITERIA AND WILL HIGHLIGHT ELEVATED FIRE CONDITIONS IN
THE HWO AND POSSIBLY AN SPS.

&&

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

&&

$$

SHORT TERM...COGIL
LONG TERM...KOTENBERG
AVIATION...LEE
FIRE WEATHER...COGIL



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