Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 251000
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
400 AM CST TUE NOV 25 2014

.SHORT TERM /TODAY/...
ISSUED AT 301 AM CST TUE NOV 25 2014

THE STRATUS DECK THAT HAS COVERED THE AREA FOR THE PAST DAY OR SO IS
SLOWLY CLEARING TO THE EAST...NOW AFFECTING ONLY OUR FAR EASTERN
COUNTIES...AHEAD OF A BROAD SURFACE RIDGE APPROACHING FROM THE WEST.
THIS RIDGE AND ITS ASSOCIATED CLEARING SKIES WILL ALLOW TEMPERATURES
TO DROP SEVERAL DEGREES FURTHER YET BEFORE SUNRISE THIS
MORNING...BUT THEN AS ITS AXIS PASSES BY MIDDAY SOUTHWEST WINDS WILL
ALLOW FOR A RAPID IMPROVEMENT IN TEMPERATURES THIS AFTERNOON. AREAS
FROM AROUND THE DES MOINES METRO SOUTH AND WEST WILL BE PARTICULARLY
PLEASED AS TEMPERATURES WILL APPROACH 40 DEGREES. THE ONLY FLY IN
THE OINTMENT IS A LARGE DECK OF MID LEVEL CLOUDS SLOWLY DRIFTING
TOWARD OUR FORECAST AREA FROM SOUTH DAKOTA...HOWEVER...FORECAST
SOUNDINGS INDICATE THAT THESE CLOUDS SHOULD GRADUALLY THIN OUT AS
THEY REACH CENTRAL IOWA AND SHOULD HAVE A MINIMAL EFFECT ON WARMING
THAT WILL BE LARGELY DRIVEN BY LOW LEVEL ADVECTION MORE THAN
INSOLATION. A LARGE LOW PRESSURE SYSTEM AND ATTENDANT CLOUDS AND
SNOW WILL ALSO BE MOVING TOWARD IOWA FROM THE WEST LATE IN THE
DAY...BUT WILL NOT REACH OUR AREA BEFORE 00Z AND THIS SYSTEM IS
DISCUSSED IN THE LONG TERM SECTION BELOW.

.LONG TERM /TONIGHT THROUGH MONDAY/...
ISSUED AT 301 AM CST TUE NOV 25 2014

INTENSE PV ANOMALY CURRENTLY OVER ALBERTA WILL MOVE QUICKLY
SOUTHEAST TODAY THROUGH MONTANA AND THE WESTERN DAKOTAS BEFORE
ARRIVING OVER EASTERN NEBRASKA THIS EVENING. THE ASSOCIATED
KINEMATIC AND THERMODYNAMIC FORCING WILL ARRIVE OVER NORTHWEST
IOWA BY MID TO LATE EVENING AND SPREAD INTO CENTRAL IA LATE
EVENING INTO THE OVERNIGHT. PROFILES SATURATE DURING THIS TIME
WITH SNOW DEVELOPING. THERE IS POTENTIAL THAT THE INITIAL ACTIVITY
COULD BE CONVECTIVE WITH STATIC STABILITY LOWERING AND STEEPING
MID LEVEL LAPSE RATES WITH THE APPROACH OF THE UPPER PV ANOMALY.
THEREFORE A PERIOD OF MODERATE SNOWFALL RATES IS POSSIBLE. THE
SURFACE REFLECTION CLIPPER WILL BE MOVING INTO WESTERN IOWA
OVERNIGHT. WARMER DOWNSLOPE FLOW WILL BE MOVING JUST WEST TO
SOUTHWEST OF THE SFC LOW AND MAY BRING RISING TEMPERATURES NEAR TO
ABOVE FREEZING FOR A SHORT PERIOD OVER SOUTHWEST IOWA. THE PRIMARY
PRECIPITATION TYPE WILL BE SNOW BUT POSSIBLE THAT INITIAL WARMING
OF ROAD SURFACES COULD LEAD TO A MELTING THEN ICING ON PAVEMENT. A
PROLONGED PERIOD OF LIGHT SNOW IS EXPECTED TO LAST THROUGH MUCH OF
WEDNESDAY BEFORE ENDING FROM WEST TO EAST DURING THE AFTERNOON.
A STRIP OF 2 TO 4 INCHES STILL LIKELY THROUGH CENTRAL IOWA BY LATE
WEDNESDAY. NORTHWEST WINDS WILL INCREASE BEHIND THE LOW AS COLD
ADVECTION MOVES IN BY WEDNESDAY AFTERNOON AND WILL CREATE SOME
AREAS OF BLOWING SNOW. MIXED LAYER WINDS NOT TOO IMPRESSIVE OF
22-25 KTS AND GOOD PRESSURE RISES OVER THE DAKOTAS RELAX AS IT
ARRIVES INTO WESTERN IA WITH THE LOW FILLING FURTHER DURING THE
PERIOD. NONETHELESS...A FEW GUSTS TO 35 MPH MAY OCCUR AND CREATE A
FURTHER TRAVEL HAZARD. LIKELY WILL NEED HEADLINES ESPECIALLY
CONSIDERING THE HOLIDAY TRAVEL.

THE WIND WILL REMAIN BREEZY WEDNESDAY NIGHT AS COLD ADVECTION
CONTINUES AND SHALLOW MIXING MAINTAINS. COLD HIGH PRESSURE WILL
MOVE ACROSS THE STATE ON THURSDAY FOLLOWED BY A QUICK RETURN TO
WARM ADVECTION THURSDAY NIGHT AS THE SYSTEM DEPARTS. TEMPERATURES
WILL BE STEADY OR RISING ALREADY BY MID EVENING THEN CONTINUE TO
RISE THROUGH FRIDAY WITH ALL LOCATIONS AT OR ABOVE FREEZING BY
FRIDAY AFTERNOON. THE 850 MB THERMAL RIDGE CLIPS THROUGH THE STATE
FRIDAY NIGHT INTO EARLY SATURDAY. HIGH TEMPERATURES ON SATURDAY
CONTINGENT ON TIMING OF COLD FRONT ARRIVAL AND AMOUNT OF SNOW
COVER REMAINING. FORECAST HIGHS FOR SATURDAY ARE LIKELY
CONSERVATIVE AND WILL BE MUCH WARMER IF SNOW COVER IS GONE. THE
REMAINDER OF THE EXTENDED WILL BRING BOUTS OF COLD AND WARM
ADVECTION WITH SUNDAY AND MONDAY BELOW NORMAL TEMPERATURES
FOLLOWED BY A WARMER TUESDAY.

&&

.AVIATION...25/06Z
ISSUED AT 1116 PM CST MON NOV 24 2014

MVFR CEILINGS WILL PUSH EAST OF SITES...LINGERING AT EASTERN SITES
KMCW/KALO/KOTM THROUGH BEGINNING OF PERIOD. CONDITIONS WILL THEN BE
VFR THROUGH REMAINDER OF PERIOD. WINDS WILL DECREASE NEAR
12Z...BECOMING MORE EASTERLY...THEN BECOMING SOUTHERLY LATE IN
PERIOD. WINDS MAY BECOME GUSTY AGAIN BEYOND 00Z. ANOTHER SYSTEM
WILL PUSH INTO THE REGION BEYOND PERIOD...BRING POTENTIAL FOR SN
AND REDUCED VISIBILITIES AND LOWER CEILINGS.


&&

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

$$

SHORT TERM...LEE
LONG TERM...DONAVON
AVIATION...AWB


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