Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 261148 AFDOAX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE OMAHA/VALLEY NE 548 AM CST FRI DEC 26 2014 .SHORT TERM...(TODAY THROUGH SUNDAY) ISSUED AT 315 AM CST FRI DEC 26 2014 SNOW LATER TODAY AND TONIGHT IS THE PRIMARY FORECAST CONCERN. WINTER WEATHER ADVISORY WILL BE IN EFFECT FOR A GOOD PART OF NORTHEAST NEBRASKA THIS AFTERNOON AND TONIGHT. TOTAL SNOW AMOUNTS OF 2 TO 4 INCHES LOOK LIKELY IN THIS AREA...ALONG WITH WINDS UP TO 20 MPH. AFTER A MOSTLY SUNNY HOLIDAY...LOW CLOUDS HAVE AGAIN INVADED EASTERN NEBRASKA AND WESTERN IOWA THIS MORNING...SPREADING SOUTH BEHIND A COLD FRONT WHICH SHOULD BE SOUTH OF NEBRASKA AND SOUTHWEST IOWA BY OR SHORTLY AFTER SUNRISE. MEANWHILE...MID LEVEL RIPPLES IN SOUTHWEST FLOW ALOFT EMANATING FROM BASE OF UPPER TROUGH IN ARIZONA WAS PROVIDING WEAK LIFT FROM TIME TO TIME...CAUSING PATCHY DRIZZLE OR FREEZING DRIZZLE FROM CENTRAL INTO NORTHEAST NEBRASKA. THIS PHENOMENON APPEARS TO BE ISOLATED ENOUGH TO LIMIT IMPACTS THIS MORNING. ATTENTION THEN TURNS TO STRONGER WAVE EXPECTED TO EJECT INTO THE PLAINS AND BEGIN TO AFFECT OUR AREA THIS AFTERNOON. GFS/NAM HAVE SLOWED TIMING OF THIS FEATURE A TAD FROM EARLIER RUNS...AND APPEAR A LITTLE MORE ROBUST WITH FORCING. AS WAVE MOVES INTO CENTRAL NEBRASKA THIS AFTERNOON...ISENTROPIC UPGLIDE WILL INCREASE MARKEDLY ALONG 290K THETA SURFACE...MAGNIFYING FRONTOGENETICAL FORCING IN THE 600- 550MB LAYER OVER NORTHEAST NEBRASKA. BEST LIFT IS FORECAST NEAR OR JUST AFTER 00Z...AND IS MAXIMIZED WITHIN DENDRITIC TEMPERATURE REGIME OF FORECAST SOUNDINGS SUGGESTING EFFICIENT SNOW-MAKING. NEGATIVE THETA-E LAPSE RATES AND EQUIVALENT POTENTIAL VORTICITY SUGGEST AT LEAST CONDITIONAL INSTABILITY WILL LEAD TO BANDING OF PRECIPITATION AS WELL. LESS FAVORABLE ENVIRONMENT IS FORECAST ACROSS THE REST OF EASTERN NEBRASKA AND SOUTHWEST IOWA...BUT BROAD ASCENT IN WARM ADVECTION REGIME WILL STILL BRING PRECIP TO THESE AREAS. AS WAVE MOVES NORTHEAST OVERNIGHT...ASSOCIATED LIFT WILL TAPER AS WE HEAD TOWARD 06Z. HOWEVER MOISTURE WILL REMAIN IN A DEEP DENDRITIC TEMPERATURE LAYER ACROSS NORTHEAST NEBRASKA THROUGH OR PAST 12Z...SO WE WILL LIKELY SEE PERSISTENT LIGHT SNOW THERE ADDING TO ACCUMULATION. AN ENSEMBLE APPROACH TO SNOWFALL AMOUNTS USING A VARIETY OF MODEL OUTPUT POINTS TO SNOWFALL POTENTIAL IN THE 3 TO 4 INCH RANGE OVER A GOOD CHUNK OF NORTHEAST NEBRASKA...WITH AMOUNTS TAPERING TO AN INCH OR LESS ALONG AND SOUTHEAST OF INTERSTATE 80. SPECIFIC HUMIDITY CALCULATIONS USING GARCIA METHOD SUGGEST SOME 5 INCH AMOUNTS ARE ALSO POSSIBLE IN NORTHEAST NEBRASKA...MOST LIKELY NORTHWEST OF THE NORFOLK AREA WHERE FRONTOGENESIS IS AT A MAXIMUM. SNOWFALL MAY LINGER PAST 12Z IN PARTS OF NORTHEAST NEBRASKA AND WEST CENTRAL IOWA...OTHERWISE EXPECT DECREASING CLOUDS AND COLD TEMPERATURES. HIGHS WILL LIKELY HOLD IN THE 20S DESPITE SUNSHINE AND LIGHT WESTERLY FLOW. MOSTLY CLEAR SKIES AND SNOWCOVER SHOULD PUSH LOWS INTO SINGLE DIGITS SUNDAY MORNING IN NORTHEAST NEBRASKA...BUT SOUTHWEST LOW LEVEL FLOW AHEAD OF AN APPROACHING COLD FRONT MAY HOLD LOWS IN THE TEENS. THEN WE SHOULD REBOUND INTO THE 20S AND 30S SUNDAY BEFORE CLOUDS THICKEN WITH ARRIVAL OF COLD FRONT LATER IN THE DAY. .LONG TERM...(SUNDAY NIGHT THROUGH THURSDAY) ISSUED AT 315 AM CST FRI DEC 26 2014 BROAD TROUGH IS FORECAST TO SETTLE OVER MUCH OF THE CONUS TO START THE WEEK...BRINGING COLD TEMPERATURES TO MUCH OF THE PLAINS. THE LEADING EDGE OF THAT COLD AIR WILL BE SLIPPING THROUGH THE CWA SUNDAY NIGHT WHEN 850 TEMPERATURES DROP FROM ABOUT 5 BELOW 00Z MONDAY TO NEAR 15 BELOW BY 12Z TUESDAY. WEAK LIFT ACCOMPANYING THIS COLD SURGE COULD SQUEEZE OUT SOME LIGHT SNOW MONDAY AND MONDAY NIGHT...BUT AMOUNTS SHOULD BE LIGHT. THE MAIN WEATHER STORY AT THIS TIME IS THE COLDER TEMPERATURES WITH MONDAY HIGHS IN THE TEENS NORTH AND 20S SOUTH...DROPPING TO THE SINGLE DIGITS AND TEENS ON TUESDAY. OVERNIGHT LOWS BOTH MONDAY NIGHT AND TUESDAY NIGHT WILL LIKELY DROP BELOW ZERO IN MANY AREAS. A SLIGHT WARMING TREND IS FORECAST WEDNESDAY AND THURSDAY AS THERMAL TROUGH SHIFTS TO THE EAST WITH CORE OF MID LEVEL TROUGH. && .AVIATION...
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(12Z TAFS FOR KOFK...KLNK AND KOMA.) ISSUED AT 545 AM CST FRI DEC 26 2014 IFR CONDITIONS ARE EXPECTED TO PREVAIL THROUGH MUCH OF THE PERIOD WITH INCREASING CHANCE OF LIGHT SNOW AT KOFK AFTER 18Z AND AFTER 01Z AT KLNK AND KOMA.
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&& .OAX WATCHES/WARNINGS/ADVISORIES... NE...WINTER WEATHER ADVISORY FROM 2 PM THIS AFTERNOON TO 4 AM CST SATURDAY FOR NEZ011-012-015>018-030>033-042-043. IA...NONE. && $$ SHORT TERM...DERGAN LONG TERM...DERGAN AVIATION...FOBERT

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