Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 171123 AFDOAX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE OMAHA/VALLEY NE 523 AM CST WED DEC 17 2014 .SHORT TERM...(TODAY THROUGH FRIDAY) ISSUED AT 353 AM CST WED DEC 17 2014 ...SNOW AND FREEZING DRIZZLE POTENTIAL THE MAIN CHALLENGES... SOME COMPLEXITIES WITH THIS FORECAST GIVEN SUBTLE FEATURES... SPLIT UPPER FLOW... EXISTING DRY AIR... AND VARYING MODEL SOLUTIONS. DESPITE THAT...WE ARE SOMEWHAT CONFIDENT THAT LOCATIONS ALONG THE KANSAS BORDER WILL SEE LIGHT ACCUMULATIONS OF SNOW WEDNESDAY NIGHT AND THURSDAY...GENERALLY UNDER 2 INCHES. CONFIDENCE DECREASES MOVING NORTH FROM THE KANSAS BORDER DUE TO THE DRY AIR IN PLACE. ONE IMPORTANT FEATURE THAT WAS ANALYZED EARLY THIS MORNING IS A RELATIVELY STRONG SURFACE HIGH WITH THE RIDGE AXIS EXTENDING ALONG THE MISSOURI RIVER. THIS HIGH IS KEEPING SURFACE DEWPOINTS LOW... RANGING FROM -2F IN YANKTON TO 18F IN BEATRICE. ALOFT... WATER VAPOR LOOP INDICATED THE UPPER FLOW WAS COMPLEX WITH NUMEROUS SHORTWAVES MIGRATING THROUGH THE WESTERN US. MODELS ARE IN REASONABLE AGREEMENT WITH THE IDEA OF BRINGING TWO SHORTWAVES THROUGH THE SOUTHWEST AND INTO THE HIGH PLAINS THIS EVENING AND OVERNIGHT...WITH A PRIMARY SURFACE LOW DEVELOPING OVER NORTHEAST NEW MEXICO AND THEN MOVING NEAR THE RED RIVER. THIS SETS UP AN ISENTROPIC LIFT REGIME AIDED BY DPVA...WITH WEAK MID LEVEL FRONTOGENESIS IN THE MID LEVEL BAROCLINIC ZONE. A LAYER OF INSTABILITY WAS NOTED ON GFS AND NAM AT 06Z TONIGHT...SUGGESTING A FEW AREAS OF FAIRLY STRONG VERTICAL MOTION AT LEAST FOR A FEW HOURS TONIGHT. ALTHOUGH THE LIFT AND INSTABILITY SHOULD BE PRESENT...ALONG WITH MAX VERTICAL MOTION NEAR THE DENDRITIC GROWTH LAYER... THE ABOVE MENTIONED SURFACE HIGH AND ASSOCIATED DRY AIR SHOULD RESULT IN SUBLIMATION OF SNOW FLAKES FOR THE FIRST SEVERAL HOURS OF THE SNOWFALL. AND WITH THE LOWER DEWPOINTS FROM INTERSTATE 80 NORTH...THOSE ARES WILL TAKE LONGER TO SATURATE. ALL OF THESE FACTORS WERE TAKEN INTO ACCOUNT TO COME UP WITH ABOUT 1.5 INCHES OF SNOW FROM BEATRICE TO FALLS CITY...AND CLOSER TO ONE-HALF INCH ALONG INTERSTATE 80. MOST MODEL SOLUTIONS...INCLUDING THE MAJORITY OF SREF MEMBERS... SHOW A FEW HOURS OF SUPER-COOLED FREEZING DRIZZLE SOUNDINGS THURSDAY MORNING AS MID LEVELS DRY OUT...ESPECIALLY IN WESTERN AND SOUTHERN COUNTIES. UNFORTUNATELY THERE IS POOR AGREEMENT ON THE TIMING AND DURATION OF THIS. THIS WAS ENOUGH OF A CONCERN TO INCLUDE IN THE FORECAST AS PATCHY FREEZING DRIZZLE...MAINLY THURSDAY MORNING. THIS LIGHT SNOW AND MARGINAL FREEZING DRIZZLE IS JUST BELOW WINTER WEATHER ADVISORY CRITERIA...BUT IF CONDITIONS TREND TOWARD AN INCREASE IN EITHER SNOW OR FREEZING DRIZZLE...AN ADVISORY MAY BE CONSIDERED MORE CLOSELY. .LONG TERM...(FRIDAY NIGHT THROUGH TUESDAY) ISSUED AT 353 AM CST WED DEC 17 2014 THIS PERIOD APPEARS TO BE MAINLY DRY OTHER THAN A FEW BRIEF PERIODS WHERE THERE IS A SLIGHT CHANCE FOR LIGHT SNOW OR POSSIBLY LIGHT RAIN. AGAIN...THE UPPER FLOW CONTAINS NUMEROUS WEAK WAVES MOVING WEST TO EAST...BUT LITTLE SURFACE REFLECTION IS ADVERTISED BY THE MODELS. A WARMING TREND OF A FEW DEGREES IS EXPECTED...WITH 40S PREDICTED FOR HIGHS BY MONDAY. && .AVIATION...
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(12Z TAFS FOR KOFK...KLNK AND KOMA.) ISSUED AT 517 AM CST WED DEC 17 2014 DECK OF MVFR CIGS IS JUST WEST OF KOFK/KLNK AND SOME OF THIS MAY CONT TO MOV IN AND OUT OF THOSE LOCATIONS FOR A FEW MORE HOURS...BUT THE MAJORITY OF THE DAY SHOULD BE VFR AT ALL 3 SITES. WINDS WILL CONT TO VEER FROM NORTHEAST TO SOUTHEAST THROUGH THE DAY...BUT REMAIN LIGHT. TONIGHT CLOUDS WILL AGAIN INCREASE AS A STORM SYSTEM HEADS TOWARD THE AREA...MAINLY IN THE MID AND HIGH LEVELS. THIS SYSTEM MAY SPREAD MVFR CIGS/VISBY TO KLNK WITH -SN STARTING BY 8-10Z. WE WILL LEAVE KOMA/KOFK DRY FOR THIS TAF CYCLE WITH CONFIDENCE IN TIMING AND PRECIP LOWER THAN AT KLNK.
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&& .OAX WATCHES/WARNINGS/ADVISORIES... NE...NONE. IA...NONE. && $$ SHORT TERM...NIETFELD LONG TERM...NIETFELD AVIATION...

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