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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1142 AM CST FRI NOV 28 2014

.SHORT TERM /TODAY/...
ISSUED AT 308 AM CST FRI NOV 28 2014

WEAK BOUNDARY WILL CONTINUE TO LIFT NORTH ACROSS THE STATE THROUGH 
THE DAY TODAY. THIS WILL ALLOW WAA TO CONTINUE...WITH TEMPERATURES 
WARMING ACROSS THE AREA THROUGHOUT THE DAY. GIVEN CURRENT 
TEMPERATURE TRENDS HAVE INCREASED TEMPERATURES...ESPECIALLY IN THE 
WEST...FOR THE DAY. MAIN CONCERN FOR THE DAY WILL BE WITH 
PRECIPITATION CHANCES IN THE NORTH...ESPECIALLY IN THE AFTERNOON. AS 
SHORTWAVE DROPS SOUTHEAST INTO SOUTHERN MINNESOTA...MODELS INDICATE 
ANOTHER BAND OF FORCING ACROSS NORTHERN IOWA. HIGH RES MODELS ARE 
GENERATING PRECIPITATION IN THE AFTERNOON HOURS. WHILE LOW LEVELS 
HAVE AMPLE MOISTURE AND WILL BE SATURATED...BEST FORCING IS JUST 
ABOVE THIS LAYER INTO DRY AIR...AND HAVE LEFT FORECAST DRY ATTM. 

.LONG TERM /TONIGHT THROUGH WEDNESDAY/...
ISSUED AT 308 AM CST FRI NOV 28 2014

FOG POTENTIAL TONIGHT AND AGAIN SATURDAY NIGHT REMAINS THE PRIMARY
FORECAST CHALLENGE DURING THE BEGINNING OF THE PERIOD. HIGHER
DEWPOINTS CONTINUE TO STREAM NORTH TODAY AND BY THIS EVENING
EXPECT DEWPOINTS TO BE NEAR TO ABOVE FREEZING OVER THE SOUTHERN
HALF OF THE STATE. IN ADDITION...EXPECT GOOD SNOW MELT INTO
CENTRAL IOWA THIS AFTERNOON WHICH WILL CONTRIBUTE ADDITIONAL
MOISTURE TO THE NEAR SURFACE LAYER. THIS MOISTURE WILL BE TRAPPED
WITH A STRONG INVERSION ALOFT AND WILL BE RESIDING OVER A COLD
GROUND AND/RESIDUAL SNOW FIELD WHICH SHOULD RESULT IN FOG
DEVELOPMENT OVERNIGHT. BEST POTENTIAL FOR WIDESPREAD
FOG...POSSIBLY DENSE WILL BE ALONG AND NORTH OF AN OTTUMWA TO DES
MOINES TO DENISON LINE. SREF PROBS FOR LESS THAN 1 MILE
VISIBILITIES HAVE REMAINED CONSISTENT WITH THIS DEVELOPMENT. A
WARM FRONT WILL LIFT INTO THE STATE ON SATURDAY AS THE THERMAL
RIDGE MOVES OVER THE STATE. DEVELOPING SOUTHWEST WINDS WILL ERODE
THE FOG AND STRATUS FROM THE SOUTHWEST BUT IT STILL MAY LINGER
OVER THE EAST/NORTHEAST THROUGH MUCH OF THE MORNING. HIGH
TEMPERATURES REMAIN CONTINGENT ON SNOW MELT AND STRATUS SHIELD.
STILL EXPECT HIGHS INTO THE 50S SOUTH OF INTERSTATE 80 AND IN THE
40 TO 45 DEGREE RANGE NORTH AND EAST.

A COLD FRONT WILL MOVE INTO IOWA SATURDAY NIGHT AND WILL BE OVER
SOUTHERN IOWA BY 6 AM SUNDAY MORNING. FOG IS EXPECTED TO REDEVELOP
ONCE AGAIN IN ADVANCE OF THE BOUNDARY AS WINDS VEER AND BECOME
LIGHT. AGAIN THE FOG COULD BECOME DENSE FOR A PERIOD BEFORE
ERODING WITH THE FRONTAL PASSAGE. SOME HINTS AT DRIZZLE
DEVELOPMENT OVER SOUTHEAST IOWA WHERE THE LOW LEVEL MOISTURE WILL
BE THE GREATEST AND WHERE SOME WEAK VERTICAL ASCENT WITHIN THE
PROFILE WILL BE PRESENT WITH MOISTURE ADVECTION STILL ONGOING. THE
OVERALL DEPTH OF MOISTURE IS LACKING FOR PREFERRED DRIZZLE
GENERATION THUS HAVE NOT INCLUDED IN THE FORECAST AT THIS TIME. 

TEMPERATURES WILL BE FALLING THROUGH MUCH OF SUNDAY AS THE NEXT
ARCTIC BLAST MOVES THROUGH . AN UPPER LEVEL PV ANOMALY WILL PASS
ACROSS THE COLD DOME SUNDAY NIGHT AND MAY GENERATE SCATTERED
FLURRIES. THE LOWEST 250 MB WILL BE QUITE DRY AS THE FORCING
PASSES BY RESULTING IN EVAPORATION OF ANY DESCENDING HYDROMETEORS.
HIGH PRESSURE ARRIVES ON MONDAY FOLLOWED BY RETURN FLOW AS THE
SYSTEM PASSES TO THE EAST MONDAY NIGHT AND TUESDAY. ONE MORE BOUT
OF COLD ADVECTION TUESDAY NIGHT BEFORE THE PATTERN TRANSITIONS TO
A MORE MILD ZONAL FLOW FOR THE END OF NEXT WEEK. 

&&

.AVIATION...28/18Z
ISSUED AT 1137 AM CST FRI NOV 28 2014

WARM FRONT FROM NERN NEBRASKA INTO SOUTHEAST IA WILL LIFT NORTH
THIS AFTERNOON AND TONIGHT. A SLY FLOW OF WARM AIR OVER THE SNOW
BACK WILL CONTINUE THROUGH TONIGHT. AVIATION CONCERN IS WITH FOG
TONIGHT OVER THE SNOW PACK MELTING TODAY WILL LEAD TO AN INCREASE
IN LOW LEVEL MOISTURE WITH AREAS TO WIDESPREAD IFR CONDITIONS
EXPECTED TO DEVELOP OVER THE SNOW FIELD...WHICH WILL REMAIN FOR
THE NORTHERN TAF SITES...IN THE 06Z-14Z TIME FRAME CONDITIONS WILL
IMPROVE BY MID TO LATE MORNING SATURDAY.

OUTLOOK...STRONG COLD FRONT WILL MOVE THROUGH THE AREA SATURDAY
NIGHT INTO SUNDAY. VFR AHEAD OF THE FRONT...WITH WIDESPREAD MVFR
IN CIGS AND SNOW SHOWERS BEHIND THE FRONT.

&&

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

$$

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

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