Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 260456 AFDOAX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE OMAHA/VALLEY NE 1056 PM CST THU DEC 25 2014 .UPDATE... ISSUED AT 1040 PM CST THU DEC 25 2014 SURFACE LOW PRESSURE OVER CENTRAL KANSAS WILL CONTINUE TO TRACK NORTHEAST ACROSS SOUTHEAST NEBRASKA INTO IOWA BY 12Z. LOW CLOUDS ARE WORKING IN FROM THE NORTH AND THERE HAS BEEN SOME FREEZING DRIZZLE FOR PARTS OF SOUTH DAKOTA. LOCALLY THE UPPER LEVEL SUPPORT IS WEAK...SO WE DO NOT HAVE MUCH PRECIPITATION IN THE FORECAST. FORECAST SOUNDINGS WOULD SUPPORT FREEZING DRIZZLE/SNOW OVERNIGHT MAINLY IN FAR NORTHEAST NEBRASKA. THE STORM SYSTEM OVER ARIZONA WITH 80M HEIGHT FALLS IS STILL ON TRACK TO PUSH INTO THE PLAINS FOR FRIDAY/FRIDAY NIGHT WITH LIGHT MIXED PRECIPITATION POSSIBLE INITIALLY(DRIZZLE/FREEZING DRIZZLE/SNOW)...THEN ACCUMULATING LIGHT SNOW AS THE COLDER AIR BECOMES DEEP ENOUGH. THE 00Z NAM STILL HAS LIGHT SNOW WITH THE 1 TO 2 INCH AMOUNTS IN NORTHEAST NEBRASKA AND THIS WAS SIMILAR TO THE 12Z EC. THE 00Z GFS HAS COME IN A LITTLE MORE AGRESSIVE WITH HIGHER 2 TO 4 INCH AMOUNTS...ESPECIALLY FROM CENTRAL INTO NORTHEAST NEBRASKA. THERE IS A STRONG MID LEVEL THERMAL GRADIENT/FRONTOGENESIS WITH OMEGA THRU THE SATURATED DENDRITIC ZONE ALONG WITH OTHER FACTORS...SO HIGHER AMOUNTS MAY BE SUPPORTED. && .SHORT TERM...(TONIGHT THROUGH SUNDAY) ISSUED AT 320 PM CST THU DEC 25 2014 FAIRLY COMPLEX FORECAST THROUGH FRIDAY NIGHT. THE MAIN FORECAST CONCERNS ARE HOW FAST LOW CLOUDS MOVE IN FOR TONIGHT INTO FRIDAY...THEN PCPN TYPE AND PCPN AMOUNTS FRIDAY THROUGH FRIDAY NIGHT. AN IMPRESSIVE TROUGH WAS OVER THE ROCKIES THIS MORNING. 12 HOUR HEIGHT FALL MAX AT 500 MB WAS 210 METERS OVER SOUTHERN NEVADA. A 115 KNOT JET MAX WAS DIGGING SOUTHEAST ALONG THE CALIFORNIA COAST. SHORT RANGE MODEL INITIALIZATION IN COMBINATION WITH WATER VAPOR SATELLITE IMAGERY LOOP SHOWED A CLOSED LOW ALONG THE NEVADA/UTAH BORDER AT MID AFTERNOON. SURFACE ANALYSIS AT 21Z SHOWED A COLD FRONT CURVING FROM NORTHEAST MINNESOTA INTO NORTHEAST NEBRASKA THEN INTO NORTHWEST KANSAS. THIS FRONT WILL PUSH SOUTHEAST THROUGH ALL OF THE FORECAST AREA OVERNIGHT...TURNING WINDS TO THE NORTHWEST OR NORTH. JUST HOW FAST LOW CLOUDS WILL FILL IN BEHIND THE FRONT IS A CHALLENGE. 18Z NAM WAS USED MAINLY FOR THIS...BUT BLENDED IN SOME OTHER GUIDANCE. THE RESULT IS A FORECAST THAT LOW CLOUDS SHOULD MOVE INTO THE OMAHA AND LINCOLN AREAS IN THE EARLY MORNING HOURS. FORCING AND MOISTURE DEPTH ARE NOT IMPRESSIVE ENOUGH TO CREATE MUCH PCPN TONIGHT...BUT DID KEEP SOME LOW POPS GOING IN ABOUT THE NORTHWEST HALF OF NORTHEAST NEBRASKA TONIGHT. FRIDAY...THE CLOSED LOW AT 500 MB SHOULD BE OVER THE FOUR CORNERS REGION AT 12Z...MOVE TO CENTRAL COLORADO BY 00Z SATURDAY THE KICK NORTHEAST AND OPEN UP BY 12Z SATURDAY. BY THAT TIME...LIFT HAS MOSTLY ENDED WITH PCPN SHIFTING OUT OF THE FORECAST AREA. DURING THE DAY FRIDAY...MAINLY USED A BLEND OF THE 12Z GFS AND THE 12Z ECMWF FOR DETAILS. PCPN SHOULD INCREASE IN THE AFTERNOON OVER ABOUT THE NORTHWEST HALF OF THE AREA...WITH SOME CHANCE OF LIGHT RAIN...LIGHT SNOW OR FREEZING DRIZZLE FARTHER EAST. MODEL FORECAST SOUNDINGS SHOW THAT PCPN TYPE WILL EVENTUALLY CHANGE TO ALL SNOW AS THE COLD AIR DEEPENS. BULK OF THE ACCUMULATING SNOW FRIDAY AFTERNOON IS EXPECTED IN NORTHEAST NEBRASKA. HEAVIEST PCPN STAYS TO THE NORTHWEST OF OMAHA AND LINCOLN...IN A BAND WHERE MID LEVEL LIFT AND LAYER MOISTURE ARE MAXIMIZED. SOME LIGHT PCPN MAY DEVELOP AHEAD OF THE MAIN AREA OF SNOW...WHICH WOULD BE A MIX...AND BASED ON SURFACE TEMPERATURES MAY FREEZE ON IMPACT. FOR NOW THAT DOES NOT LOOK LIKE IT WILL CAUSE MANY ISSUES...BUT WILL NEED TO MONITOR FOR POSSIBLE UPDATES. BEST LIFT IN THE DEFORMATION ZONE STAYS OVER ABOUT THE NORTHERN HALF OF THE FORECAST AREA FOR FRIDAY NIGHT. THEN LIFTS INTO NORTHERN IOWA AND SOUTHERN MINNESOTA. SNOW AMOUNTS MAY REACH 1 TO 3 INCHES IN NORTHEAST NEBRASKA. SINCE WINDS DO NOT LOOK OVERLY STRONG...OPTED TO NOT HAVE ANY HEADLINES AT THIS POINT. THE PERIOD FROM SATURDAY INTO SUNDAY STILL LOOKS DRY...WITH WEAK HIGH PRESSURE DOMINATING. A COLD FRONT WILL PUSH THROUGH DURING THE DAY SUNDAY...AND THINGS WILL GET GRADUALLY COLDER FROM THAT POINT ONWARD INTO MID WEEK. STRONG MID LEVEL RIDGE WILL BE IN PLACE ALONG 130-140 DEGREES WEST LONGITUDE BY SUNDAY...AND A COLD TROUGH WILL TAKE SHAPE OVER THE NORTHERN CONUS. .LONG TERM...(SUNDAY NIGHT THROUGH THURSDAY) ISSUED AT 320 PM CST THU DEC 25 2014 WILL KEEP SOME CHANCE OF LIGHT SNOW GOING FROM SUNDAY NIGHT INTO MONDAY NIGHT AS AN ARCTIC AIRMASS DROPS DOWN OVER THE NORTHERN AND CENTRAL PLAINS. BEST CHANCES FOR ACCUMULATING SNOW IN THOSE PERIODS REMAINS OVER THE HIGH PLAINS WHERE THERE WILL BE A STRONGER UPSLOPE FLOW COMPONENT. CENTER OF THE ARCTIC HIGH WILL BE OVER WYOMING ON TUESDAY BUT DROP DOWN INTO NORTH TEXAS BY WEDNESDAY. THIS SHOULD HELP ALLOW SLIGHTLY WARMER AIR TO MOVE IN LATER IN THE WEEK. && .AVIATION...(00Z TAFS FOR KOFK...KLNK AND KOMA.) ISSUED AT 538 PM CST THU DEC 25 2014 VFR CIGS FL033 HAVE DEVELOPED AT KOFK WITH MVFR CIGS NEARBY. SURFACE LOW PRESSURE IN NORTHWEST KANSAS WILL TRACK NORTHEAST INTO SOUTHEAST NEBRASKA BY 06Z AND TO CENTRAL IOWA BY 12Z. AS THIS LOW PRESSURE SYSTEM TRACKS NORTHEAST...NORTH WINDS WILL INCREASE AND MVFR/IFR CIGS AND VISIBILITIES WILL MOVE INTO THE TAF SITES THIS EVENING AND OVERNIGHT AND CONTINUE FRIDAY. CONDITIONS WILL DETERIORATE FIRST AT KOFK THEN SPREAD SOUTHEAST. THERE IS NOT A LOT OF LIFT UNTIL LATER FRIDAY...BUT THERE MAY BE SOME LIGHT FREEZING MIST OR FREEZING DRIZZLE AT KOFK TONIGHT AND ONCE THE COLUMN BECOMES COLD ENOUGH...LIGHT SNOW. FARTHER SOUTH AT KOMA AND KLNK...SURFACE TEMPERATURES SHOULD BE NEAR FREEZING AND PRECIPITATION MAY START AS DRIZZLE OR FREEZING DRIZZLE DURING THE AFTERNOON. NORTH WINDS WILL INCREASE AT ALL SITES INTO THE 12-16KT RANGE WITH GUSTS 18 TO 24KTS LATER TONIGHT AND FRIDAY. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...NONE. IA...NONE. && $$ UPDATE...ZAPOTOCNY SHORT TERM...MILLER LONG TERM...MILLER AVIATION...ZAPOTOCNY

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