Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 271130
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
627 AM CDT FRI MAR 27 2015

.SHORT TERM /TODAY/...
ISSUED AT 303 AM CDT FRI MAR 27 2015

CURRENTLY A SHORTWAVE IS PASSING ACROSS IA.  THERE IS SOME LOW LEVEL
MOISTURE ASSOCIATED WITH THIS FEATURE BUT ANY FORCING WITH THIS
FEATURE US OFF TO THE SOUTH AND EAST.  THUS ALL WE HAVE IS SOME
CLOUD COVER WITH CEILINGS RANGING FROM ABOUT 3500-6000FT AGL.  THE
CLOUDS ARE SHIFTING TO THE SOUTHEAST AND SHOULD EXIT THE SOUTHEAST
AROUND 12Z.  FOR THE REMAINDER OF TODAY WEAK HIGH PRESSURE WILL PUSH
ACROSS THE STATE AND THERE IS LITTLE MOISTURE TO SPEAK OF SO IT WILL
BE MOSTLY SUNNY TODAY.  WE WILL STILL BE IN A DEEP NORTHERLY FLOW
ALTHOUGH THE FAR WEST SHOULD SHIFT AROUND TO THE WEST OR SOUTHWEST
VERY LATE IN THE AFTERNOON.  WHILE I KEPT TEMPS ON THE COOL SIDE
TODAY I WENT MORE MIDDLE OF THE ROAD BETWEEN ALL GUIDANCE.

.LONG TERM /TONIGHT THROUGH THURSDAY/...
ISSUED AT 303 AM CDT FRI MAR 27 2015

PATTERN WILL BEGIN TO DECREASE IN AMPLITUDE THROUGH THE WEEKEND
LEADING TO WARMER TEMPERATURES NEXT WEEK AND A FEW PRECIP WINDOWS.
THE PERIOD WILL BEGIN WITH ONE LAST SHORT WAVE DROPPING INTO
DEPARTING ERN CONUS MEAN TROUGH TONIGHT. MID LEVEL KINEMATIC FORCING
WILL CONTRIBUTE SOMEWHAT...BUT NOTED SLOPED FRONTOGENETIC FORCING IN
THE WARM ADVECTION WILL LIKELY BE THE PRIMARY CONTRIBUTER AS WAVE
DROPS DOWN MO VALLEY BAROCLINIC ZONE. STATIC STABILITY IS NOT TOO
LOW BUT SHOULD BE SUFFICIENT TO RESULT IN BANDED STREAKS OF PRECIP
WHICH IS SUPPORTED BY HI RES MODEL PROJECTED REFLECTIVITY. HAVE
KEPT POPS JUST ON THE BRINK OF LIKELIES FOR NOW WITH BANDING
LIKELY KEEPING COVERAGE FROM BEING TOO WIDESPREAD. MUCH OF THE
PRECIP WOULD BE LIGHT SNOW WITH THERMAL PROFILES ONLY ABOVE
FREEZING JUST NEAR THE SURFACE INITIALLY BUT WITH WET BULB TEMPS
BELOW 2KM EVENTUALLY FLIPPING THINGS TO SNOW AS THE COLUMN TRIES
TO SATURATE. MOISTURE ONLY APPROACHES 4KM OR SO...BUT SUFFICIENT
FOR ICE INTRODUCTION AND SNOW.

SUBSIDENCE SHOULD FOLLOW INTO SAT...BUT TEMPS WILL REMAIN SEASONALLY
COOL UNTIL THE NEXT ROUND OF WARM ADVECTION STARTS AGAIN SAT NIGHT.
THIS WILL LEAD TO PRECIP SOMETIME AROUND SUN...HIGH CONFIDENCE IN
THAT...BUT LOW WITH REGARDS TO TIMING. NEARLY ALL OF THE NON-ECMWF
DETERMINISTIC AND ENSEMBLE FORECAST SUITE SPED UP TIMING AROUND SIX
HOURS VS 12Z MODELS...BUT THE 00Z ECMWF REMAINS ON THE SLOW SIDE.
CANNOT FIND MUCH REASON TO CHOOSE A SIDE LOOKING AT INITIALIZATION
OR BIASES AT THIS POINT SO WILL SIDE WITH FASTER CONSENSUS FOR
THE TIME BEING WITH POPS MAINLY SUN MORNING. WHENEVER THE LOBE OF
FORCING COMES THROUGH IS WILL BE AT LEAST MODERATE AND WITH MORE
THAN ADEQUATE MOISTURE SO HAVE HIGH END CHANCE/LOW LIKELY POPS.
HAVE GONE WITH SHOWER WORDING FOR NOW TO BLEND WITH
NEIGHBORS...BUT INSTABILITY PARAMETERS SUGGEST THERE COULD BE
RUMBLES OF THUNDER AS WELL.

MILD TEMPERATURES AND LITTLE IN THE WAY PRECIP ARE THEN EXPECTED
INTO NEXT WEEK. TEMPS SHOULD BE WELL INTO THE 60S AND POSSIBLY
TOUCHING 70 PLUS IN SPOTS. THE NEXT PRECIP WINDOW WILL BE AROUND WED
WITH A SYSTEM SOMEWHAT SIMILAR TO SUN.  TEMPS WILL MODERATE SOMEWHAT
BEHIND THIS...BUT STILL REMAIN ABOVE NORMAL.

&&

.AVIATION...27/12Z
ISSUED AT 627 AM CDT FRI MAR 27 2015

WEAK HIGH PRESSURE WILL PASS ACROSS IA TODAY PRODUCING VFR
CONDITIONS.  WARM AIR WILL PUSH INTO WESTERN IA AFT 00Z AS ANOTHER
SHORTWAVE MOVES INTO THE STATE.  THERE IS SOME FORCING WITH THIS
FEATURE BUT IT IS NOT DEEP OR ORGANIZED...EXCEPT FOR THE FAR WEST.
THE WESTERN HALF OF IA SHOULD SE SOME LIGHT SNOW AFT 28/03Z ALONG
WITH MVFR CONDITIONS.  KDSM WILL BE ON THE FRINGE OR EASTERN EXTENT
OF THE PRECIP WITH THIS SYSTEM.  LOCATIONS TO THE EAST OF I-35 MAY
SEE AN INCREASE AND SOME LOWERING OF CLOUD COVER BUT LITTLE ELSE.

&&

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

&&

$$

SHORT TERM...FAB
LONG TERM...SMALL
AVIATION...FAB


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