Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 272127 AFDOAX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE OMAHA/VALLEY NE 327 PM CST FRI FEB 27 2015 .SHORT TERM...
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(TONIGHT THROUGH MONDAY) ISSUED AT 322 PM CST FRI FEB 27 2015 SNOW OVER THE WEEKEND REMAINS THE PRIMARY FORECAST CONCERN. LARGE AND BROAD TROUGH REMAINED OVER THE CONUS THIS THIS AFTERNOON WITH SIGNIFICANT SHORTWAVE NOTED DROPPING SOUTH THROUGH THE PACIFIC NORTHWEST WHICH WILL CUTOFF AS AN UPPER LOW IN CALIFORNIA ON SUNDAY. THIS LEAVES THE MIDDLE OF THE COUNTRY IN SOUTHWEST FLOW ALOFT THIS WEEKEND. RELATIVELY FAST MID LEVEL FLOW WILL INDUCE LOWERING SURFACE PRESSURES IN THE PLAINS...DRAWING MOISTURE NORTH FOR SATURDAY/SUNDAY POTENTIAL SNOW. HOWEVER SHORTWAVE/ENERGY ROLLING THROUGH MID LEVEL FLOW IS LOOKING LESS AND LESS DEFINED FROM MODEL RUN TO MODEL RUN...AT LEAST FOR SATURDAY INTO SATURDAY NIGHT. GFS IS PROBABLY THE MOST AGGRESSIVE IN SHOWING SHARPER SHORTWAVE...BUT EVEN THAT IS NOT EARTH-SHATTERING... WHILE ECMWF BARELY SHOWS MUCH AT ALL. STILL EXPECT INDUCED ISENTROPIC UPGLIDE TO COMMENCE SATURDAY DURING THE DAY WITH SATURATION OF LOWER LEVELS OCCURRING BY NOON IN OUR SOUTH AND DURING THE AFTERNOON ALONG INTERSTATE 80. LONGER DURATION AND CLOSER PROXIMITY TO MOISTURE SOURCE SUGGESTS SOUTHEAST NEBRASKA INTO SOUTHWEST IOWA COULD SEE AN INCH OR TWO OF SNOW 18Z-06Z WITH MUCH LESSER AMOUNTS HEADING TOWARD INTERSTATE 80. PERHAPS THE BEST FORCING FOR ASCENT WITH THIS EVENT WILL COME LATER SATURDAY NIGHT INTO SUNDAY MORNING AS MID LEVEL TROUGH IN NORTHERN STREAM ROTATES INTO THE PLAINS. THIS WILL AGAIN INDUCE FAVORABLE ISENTROPIC UPGLIDE IN THE SOUTH BEGINNING AROUND 06Z SUNDAY...SPREADING NORTH WITH TIME OVERNIGHT. SOMEWHAT MORE ROBUST SNOWFALL AND A FARTHER NORTHWARD FETCH ARE EXPECTED WITH THIS PART OF THE SYSTEM. IT APPEARS AREAS ALONG INTERSTATE 80 SHOULD SEE THE HEAVIEST SNOWS OCCURRING SOMEWHERE AROUND 12Z SUNDAY...BUT WILL BE A QUICK SHOT BEFORE TROUGH SWINGS EAST BY 18Z OR SO. SO IN TOTAL...WILL HAVE CLOSE TO 3 OR 4 INCHES IN FAR SOUTHEAST NEBRASKA WHERE A COUPLE OF EPISODES OF 1 OR 2 INCHES OF SNOW FALLS...WITH AMOUNTS TAPERING TO AN INCH ALONG THE INTERSTATE AND A FEW TENTHS IN PARTS OF NORTHEAST NEBRASKA. SHORTWAVE RIDGING WILL FOLLOW EXITING WAVE SUNDAY AFTERNOON/NIGHT. BUT A QUICK RETURN TO LOW/MID LEVEL WARM ADVECTION WILL ENSUE BY SUNDAY NIGHT AS BROAD AND SHARPENING WESTERN UPPER LEVEL TROUGH BEGINS TO PUSH SLOWLY EAST. SOME MID LEVEL FORCING IS NOTED BY CONVERGING Q-VECTORS IN 700-300MB LAYER...AND COULD LEAD TO LIGHT SNOW DURING THE DAY MONDAY. HOWEVER AMOUNTS LOOK RELATIVELY LIGHT WITH THIS INITIAL SURGE OF MOISTURE/LIFT...WAITING FOR MORE POTENT SCENARIO TAKING SHAPE FOR TUESDAY. TEMPERATURES THROUGH MONDAY OBVIOUSLY WILL BE AFFECTED BY AFOREMENTIONED SNOW AND ASSOCIATED CLOUD COVER. WE HAVE NOT WARMED MUCH THIS AFTERNOON GIVEN WEAK SOUTHEAST LOW LEVEL FLOW. HOWEVER THAT FLOW WILL INCREASE LATER TONIGHT...HELPING HOLD LOWS FROM CRASHING. STILL EXPECT AN EVENING DROP INTO THE SINGLE DIGITS OR LOWER TEENS MOST AREAS...WITH COLDER READINGS NEAR ZERO IN SNOW- COVERED WEST CENTRAL IOWA. INCREASING SOUTHERLY FLOW SATURDAY WILL HELP PUSH TEMPS BACK INTO THE 20S DESPITE THICKENING CLOUD COVER...WITH CLOUDS/FLOW KEEPING LOWS IN THE TEENS OR LOWER 20S SATURDAY NIGHT. SUNDAY IS A LITTLE TRICKIER AS INITIAL SOUTHERLY FLOW BECOMES NORTHERLY BEHIND COLD FRONT IN WAKE OF EXITING MID LEVEL TROUGH. HIGHS WILL LIKELY HOLD IN THE 20S MOST AREAS BUT COULD SNEAK INTO THE LOWER 30S SOUTH. THEN A QUICK SHOT OF HIGH PRESSURE AND ASSOCIATED DECREASING WINDS/CLOUDS WILL ALLOW LOWS MONDAY MORNING IN THE TEENS...OR PERHAPS LOWER NORTH. THEN STRONG SOUTH WINDS AND DECENT WARM ADVECTION MONDAY SUGGESTS HIGHS COULD BREAK FREEZING. .LONG TERM...(MONDAY NIGHT THROUGH FRIDAY) ISSUED AT 322 PM CST FRI FEB 27 2015 TUESDAY REMAINS A COMPLICATED FORECAST SCENARIO AS A STRENGTHENING LOW PRESSURE SYSTEM AHEAD OF APPROACHING MID LEVEL TROUGH DRAWS WARM AIR ALOFT INTO THE PLAINS WHILE SURFACE TEMPERATURES TEETER AROUND FREEZING. GFS AND ECMWF ARE IN DECENT AGREEMENT IN REGARDS TO OVERALL MID LEVEL AND SURFACE PATTERNS...AS WELL AS TEMPERATURE PROFILES TUESDAY MORNING. STRONG SOUTHERLY FLOW WILL CONTINUE MONDAY NIGHT AHEAD OF SURFACE LOW DEVELOPING IN THE HIGH PLAINS. THIS WILL FORCE ABUNDANT MOISTURE AND A WEDGE OF ABOVE-FREEZING AIR INTO THE 950-700MB LAYER AS FAR NORTH AS NORTHEAST NEBRASKA AND WEST CENTRAL IOWA. MEANWHILE SURFACE TEMPERATURES ARE FORECAST BY BOTH MODELS TO RISE ABOVE FREEZING TO AND NORTH OF INTERSTATE 80 FOR A TIME TUESDAY MORNING BEFORE STRONG COLD FRONT SWEEPS THROUGH. ECMWF IS A BIT SLOWER WITH THIS COOLING AND HANGS ONTO ABOVE-FREEZING SURFACE TEMPS INTO THE AFTERNOON. OF COURSE THIS IS STILL MANY DAYS AWAY AND ANY FLUCTUATION IN POSITION OF SURFACE LOW WILL PLAY A BIG ROLE IN TEMPERATURE PROFILE. IN ANY EVENT...A MIXED BAG OF PRECIPITATION TYPES IS POSSIBLE FOR MUCH OF OUR CWA BEGINNING MONDAY NIGHT INTO TUESDAY...WITH ALL EVENTUALLY CHANGING TO SNOW BEFORE SYSTEM EXITS TUESDAY NIGHT. AND CLEARLY SNOW/ICE AMOUNTS WILL BE GREATLY AFFECTED BY CHANGEOVER TIMING. WILL PLAY A BLEND OF GFS/ECMWF FOR NOW...WHICH WOULD PAINT A STRIPE OF POTENTIAL FREEZING RAIN FROM INTERSTATE 80 SOUTH MONDAY NIGHT BEFORE MOST OF THAT CHANGES TO JUST RAIN...THEN TO SNOW AT SOME POINT TUESDAY AFTERNOON. MAINLY SNOW IN FAR NORTHEAST NEBRASKA LOOKS OKAY...WITH A HODGEPODGE OF PRECIP IN BETWEEN. WILL LIKELY KEEP A RAIN/SNOW MENTION IN THESE AREAS UNTIL A MORE DEFINITIVE SCENARIO IS MORE APPARENT. BEYOND TUESDAY...WE SHOULD SEE A COLD DAY TO FOLLOW ON WEDNESDAY BEFORE A SOMEWHAT MORE ZONAL FLOW PATTERN TRIES TO DEVELOP BY THE END OF THE WEEK. AND DARE I SAY A WARMING TREND LOOKS ON TRACK FOR LATE NEXT WEEK...WITH FRIDAY TEMPERATURES AT OR ABOVE NORMAL.
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&& .AVIATION...(18Z TAFS FOR KOFK...KLNK AND KOMA.) ISSUED AT 1141 AM CST FRI FEB 27 2015 VFR CONDITIONS ARE EXPECTED THROUGH MUCH OF THE PERIOD. HIGH CLOUDS WILL MOVE IN OVERNIGHT WITH LOWER CLOUDS MOVING NORTHEAST THROUGH THE EARLY MORNING HOURS. KLNK COULD BE IN MVFR CATEGORY BY MID TO LATE SATURDAY MORNING AS THE NEXT SYSTEM MOVES TOWARD THE AREA. DO NOT THINK ANY SNOW WILL BE AT THE SITES BY 18Z SAT. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...NONE. IA...NONE. && $$ SHORT TERM...DERGAN LONG TERM...DERGAN AVIATION...KERN

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