Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 271750
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1150 AM CST THU NOV 27 2014

.SHORT TERM /TODAY/...
ISSUED AT 327 AM CST THU NOV 27 2014

MAIN CONCERN FOR TODAY WILL BE TEMPERATURES ARE SURFACE HIGH
PRESSURE PUSHES SOUTH ACROSS THE AREA. THIS WILL BRING MUCH COOLER
TEMPERATURES TO THE AREA...EARLY MORNING TEMPERATURES WILL BE NEAR
OR BELOW ZERO ACROSS MUCH OF NORTHERN IOWA. GIVEN COLD TEMPERATURES
AND STIFF WINDS EARLY WIND CHILL VALUES WILL BE NEAR -10 TO -25 FOR
A FEW HOURS IN THE MORNING. AM NOT ANTICIPATING WIDESPREAD OR
PROLONGED PERIODS OF WIND CHILL VALUES BELOW ADVISORY
CRITERIA...AND THEREFORE WILL NOT ISSUE FOR NOW. TEMPERATURES WILL
WARM THROUGH THE DAY...THOUGH GIVEN COLD AIR IN PLACE...INCREASING
CLOUDS LATE... AND FRESH SNOW PACK HAVE DROPPED TEMPERATURES A FEW
DEGREES...ESPECIALLY IN THE NORTH.

.LONG TERM /TONIGHT THROUGH TUESDAY/...
ISSUED AT 327 AM CST THU NOV 27 2014

STRONG THETA-E ADVECTION WILL BE ONGOING OVER WESTERN IOWA BY
EARLY THIS EVENING AS THE SFC HIGH PRESSURE DEPARTS QUICKLY TO THE
SOUTHEAST. THE THETA-E ADVECTION SURGE WILL MOVE ACROSS THE STATE
OVERNIGHT. SURFACE WARM ADVECTION WILL COMMENCE OVERNIGHT AS WELL
WITH SOUTHERLY WINDS INCREASING OVERNIGHT RESULTING IN STEADY TO
RISING TEMPERATURES BY MID TO LATE EVENING. THE INCREASING MID
LEVEL MOISTURE IN ADDITION TO A SHORT WAVE PASSING ACROSS THE
DAKOTAS AND MINNESOTA WILL BRING THE POTENTIAL FOR LIGHT SNOW OVER
FAR NORTHERN IOWA AND POSSIBLE FLURRIES SOUTH INTO CENTRAL IOWA
OVERNIGHT.

HIGH TEMPERATURES ON FRIDAY ARE EXPECTED TO REACH THE LOWER 30S
NORTHEAST TO THE LOW TO MID 40S SOUTH. EXPECT GOOD SNOW MELTING
CONDITIONS OVER CENTRAL IOWA AS DEWPOINTS INCREASE LEADING TO A
MORE EFFICIENT MELTING PROCESS. H85 TEMPERATURES BY LATE FRIDAY
WILL REACH 6C TO 10C AND WILL CREATE A STRONG INVERSION ALOFT. THE
INCREASING DEWPOINTS IN ADDITION TO ADDED LOW LEVEL MOISTURE FROM
MELTING WILL BE TRAPPED NEAR SURFACE DUE TO THE ENHANCED
INVERSION. GROUND TEMPERATURES WILL STILL BE RELATIVELY COOL AT
THIS TIME WITH SOME RESIDUAL SNOW LEFT AND LIKELY WILL RESULT IN A
WIDESPREAD FOG DEVELOPMENT WITH AREAS BECOMING DENSE. SOME
UNCERTAINTY ON HOW PERSISTENT THE FOG/STRATUS WILL PERSIST INTO
SATURDAY. MUCH OF SOUTHWEST IOWA SHOULD SCATTER OUT AS SOUTHWEST
WINDS DEVELOP WITH HIGH TEMPERATURES RISING INTO THE 50S AND
CANNOT RULE OUT A 60 OR TWO. THE NORTHEAST WOULD BE THE LAST TO
SCATTER OUT AND THUS WILL KEEP TEMPERATURES NEAR TO JUST ABOVE 40
FOR HIGHS. A SHALLOW ARCTIC BOUNDARY WILL SHIFT SOUTHEAST INTO NW
IOWA AND BEGIN TO UNDERCUT THE UPPER THERMAL RIDGE SATURDAY NIGHT.
WINDS SHOULD BECOME LIGHT IN ADVANCE OF THE BOUNDARY WITH THE
POTENTIAL FOR FOG TO EXPAND ONCE AGAIN IN ADVANCE OF THE BOUNDARY.
THE COLD FRONT WILL SHIFT SOUTH AND DEEPEN THROUGH THE DAY SUNDAY
WITH TEMPERATURES FALLING MUCH OF THE DAY. THE ARRIVAL OF THE
COOLER AND DRIER AIR WILL WASHOUT THE MOIST LOW LEVELS AND BRING
AN END TO THE FOG POTENTIAL. COLD CONDITIONS WILL CONTINUE THROUGH
MONDAY FOLLOWED BY RETURN FLOW AND WARMER CONDITIONS ON TUESDAY.

&&

.AVIATION...27/18Z
ISSUED AT 1146 AM CST THU NOV 27 2014

HIGH PRESSURE OVER IOWA WILL MOVE TO THE EAST WITH FLOW BECOMING
SOUTHEASTERLY TONIGHT. BAND OF VFR STRATUS WILL OVERSPREAD THE
STATE TONIGHT WITH SOME LIGHT SNOW SHOWERS...HOWEVER VFR
CONDITIONS ARE LIKELY TO PREVAIL.

OUTLOOK...STRATUS BAND WILL ADVANCE NORTH AND EAST OUT OF THE
STATE WITH MILD AND DRY CONDITIONS FOR FRI INTO SAT. A COLD FRONT
WILL MOVE THROUGH SATURDAY NIGHT WITH MVFR CONDITIONS IN STRATUS
AND SNOW SHOWERS EXPECTED BY SUNDAY.


&&

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

$$

SHORT TERM...AWB
LONG TERM...DONAVON
AVIATION...MS NOV 14



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