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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS63 KOAX 272304
AFDOAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
504 PM CST FRI FEB 27 2015

.SHORT TERM...(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.

&&

.AVIATION...(00Z TAFS FOR KOFK...KLNK AND KOMA.)
ISSUED AT 500 PM CST FRI FEB 27 2015

VFR CONDITIONS EARLY IN THE PERIOD WITH THICKENING MID CLOUDS.
COULD SEE MVFR CONDITION AT KLNK BY 13Z WITH SNOW CHANCES
INCREASING BY 16-19Z...WITH PREVAILING SNOW DEVELOPING BY 19Z.
SNOW CHANCES LIKELY NOT DEVELOPING AT KOMA UNTIL ABOUT 19Z. NOT
SURE SNOW WILL MAKE IT TO KOFK...THUS LEFT THAT LOCATION DRY.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&

$$

SHORT TERM...DERGAN
LONG TERM...DERGAN
AVIATION...DEWALD