Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 220538
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1138 PM CST WED JAN 21 2015

.SHORT TERM /TONIGHT/...
ISSUED AT 330 PM CST WED JAN 21 2015

SCATTERED FLURRIES/LIGHT SNOW SHOWERS CONTINUE TO ENCROACH ON ABOUT
THE NORTHERN HALF OF OUR AREA BUT HAVE NOT BEEN ABLE TO MAKE IT
DOWN TO I-80 YET THIS AFTERNOON. WITH THE PARENT SYSTEM PRODUCING
THIS LIGHT PRECIP DEPARTING TO THE EAST THE SNOW SHOULD GRADUALLY
FADE OUT AFTER SUNSET...AND HAVE CARRIED LINGERING POPS BUT WITH
LITTLE TO NO ADDITIONAL ACCUMULATION THROUGH THE EVENING. OVERCAST
SKIES WILL PERSIST THROUGH THE NIGHT...KEEPING TEMPERATURES FROM
FALLING TOO FAR AND HAVE ALSO INCREASED FORECAST OVERNIGHT LOWS
JUST A BIT TO ACCOUNT FOR THIS.

.LONG TERM /THURSDAY THROUGH WEDNESDAY/...
ISSUED AT 330 PM CST WED JAN 21 2015

LONG WAVE PATTERN REMAINS ESSENTIALLY UNCHANGED THROUGH MUCH OF THE
PERIOD. ACTIVE ERN PACIFIC/WRN CANADA FLOW WILL CONTINUE TO
DEVELOP AND REINFORCE ERN CONUS MEAN TROUGH. THIS PATTERN RESULTS
IN A SENSIBLE WEATHER REGIME WITH CONTINUED ABOVE NORMAL
TEMPERATURES AND LITTLE IN THE WAY OF PRECIPITATION. SUBSIDENCE
AND MINIMAL MOISTURE WILL KEEP OUR FORECAST DRY INTO AT LEAST
EARLY FRIDAY. SRN REMNANTS OF SHORT WAVE CURRENTLY OFF THE BC
COAST WILL INCREASE OUR MID LEVEL MOISTURE FOR A NARROW WINDOW
LATE IN THE DAY BUT STRUGGLE BELOW 2KM. FORCING IS WEAK SO
FORECAST IS CURRENTLY DRY. HOWEVER THETA-E ADVECTION CROSS
SECTIONS SHOW A SHARP FRONTAL BOUNDARY THERMODYNAMIC FORCING
COUPLET ALOFT AND WOULD NOT BE SURPRISED TO SEE A VERY BRIEF
PERIOD OF CERTAINLY VIRGA BUT VERY POSSIBLY HIGH BASED LIGHT
PRECIP REACHING THE GROUND DURING THE LATE AFTERNOON OR EARLY
EVENING HOURS.

NEXT AND BETTER CHANCE FOR PRECIPITATION WILL BE SAT NIGHT INTO
SUN. TIMING IS UNCERTAIN BETWEEN THE ECMWF AND GFS...HOWEVER BOTH
MODELS SUGGEST SUFFICIENT FORCING FOR A PERIOD OF PRECIPITATION
SOMEWHERE IN THAT WINDOW. SHARP RISE/FALL COUPLET WITH FAIRLY
BALANCED THERMODYNAMIC AND KINEMATIC FORCING PUSHES THROUGH THE
UPPER MS VALLEY. ECMWF IS FASTER CENTERED 00-06Z OR SO WHILE THE
GFS IS SLOWER FURTHER INTO THE NIGHT AND POSSIBLE VERY EARLY SUN
MORNING. CURRENTLY HAVE MID RANGE CHANCE POPS FOR 12-18 HOURS BUT
THESE WILL LIKELY NEED TO BE RAISED ACROSS A SMALLER WINDOW ONCE
THE TIMING CAN BECOME MORE TARGETED.

THERE IS LITTLE IN THE WAY OF FORCING OR MOISTURE THROUGH
THE REMAINDER OF THE EXTENDED. NW FLOW WILL REMAIN ACTIVE BUT WITH
HEIGHTS GRADUALLY RISING PLACING IA MORE UNDER THE INFLUENCE OF
THE WRN CONUS RIDGE. HAVE HIGHS WELL INTO THE 30S NE/40S SW AND
WOULD NOT BE SURPRISED TO SEE A FEW 50S IN THEIR EITHER.

&&

.AVIATION...22/06Z
ISSUED AT 1135 PM CST WED JAN 21 2015

MVFR CIGS ACROSS NORTHERN IA WITH VFR BREAKS ACROSS THE SOUTH.
WILL HAVE PERIOD OF MVFR THROUGHOUT THE NIGHT THEN GRADUAL
TRANSITION TO VFR ENTIRE AREA BY WED AFTERNOON AND EVENING. BRIEF
IFR IS POSSIBLE AT KALO/KMCW OVERNIGHT. LIGHT NORTHWEST WINDS
TONIGHT BECOMING WEST TO SOUTHWEST ON WEDNESDAY.

&&

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

$$

SHORT TERM...LEE
LONG TERM...SMALL
AVIATION...DONAVON



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