Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 142141
AFDOAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
341 PM CST SUN DEC 14 2014

.SHORT TERM...(TONIGHT THROUGH WEDNESDAY)
ISSUED AT 320 PM CST SUN DEC 14 2014

SHORT TERM FORECAST CONCERNS CONTINUE TO BE
PRECIPITATION/TYPE...CHANGEOVER TO SNOW/AMOUNTS AND WIND WITH
VIGOROUS STORM SYSTEM TONIGHT THROUGH MONDAY EVENING AND
HEADLINES.

IT WAS A VERY MILD SATURDAY WITH RECORD WARM MINIMUMS SET AT
OFK/OMA/LNK. WE WE STARTED OUT MILD AGAIN WITH LOWS AROUND
50...DRIZZLY AND FOGGY TOO.  THE 12Z OAX SOUNDING HAD INCREASED TO
.71 PWAT...WITH MOST OF THE MOISTURE IN THE LOWEST 5K FEET.  THE H3
100KT JET WAS DIVING SOUTHEAST ACROSS ARIZONA. MEANWHILE...THE H5
TROF EXTENDED FROM IDAHO SOUTHEAST TO NEW MEXICO WITH THE MID LEVEL
RIDGE SHIFTING EASTWARD TO THE GREAT LAKES AND TENNESSEE VALLEY. THE
LARGEST HEIGHT FALLS OF 130M WERE NOTED AT KABQ.  THE SYSTEM WAS
NEGATIVELY TILTED WITH H5 LOW PRESSURE OVER NORTHERN NEW MEXICO AND
A SECOND AREA OF LOW PRESSURE BACK TOWARD SOUTHERN IDAHO.

WATER VAPOR SATELLITE IMAGERY SHOWED MOISTURE STREAMING NORTHWARD.
A LARGE SWATH OF +10 DEG H85 DEWPOINTS STRETCHED FROM TEXAS ACROSS
KANSAS WITH +8 DEG DEWPOINTS AT KOMA.  PER VISIBLE SATELLITE AND
RADAR AT 16Z...WE WERE STARTING TO SEE A LITTLE BUMPIER CLOUDS NEAR
HEBRON IN SOUTH CENTRAL AS ELEVATED INSTABILITY WAS INCREASING IN
THAT AREA.  THERE WERE A FEW RANDOM STRIKES NEAR HAYS KS...HOWEVER
THE CONVECTION WAS MORE ORGANIZED IN A BAND FROM EASTERN
COLORADO...TO GOODLAND AND DODGE CITY THROUGH OKLAHOMA. BY
21Z...THE ORGANIZED CONVECTION WAS IN BANDS. A WEST TO EAST BAND
NEAR NORTH PLATTE...AND ANOTHER BAND FROM NORTH OF GOODLAND ACROSS
NORTHERN KANSAS INTO EAST CENTRAL KANSAS.

THROUGH 00Z...THE 998MB SURFACE LOW OVER SOUTHEAST COLORADO TRACKS
TO SOUTHWEST KANSAS...HEADS TOWARD NORTHEAST KS BY 12Z MONDAY AND TO
SOUTHEAST IOWA BY 00Z MONDAY EVENING.  THE H5/H7/H85 TRACKS ARE
SIMILAR. THE H85 PATTERN IS A LITTLE MORE COMPLEX...AS BOTH THE
GFS/NAM HAVE A DOUBLE H85 CIRCULATION...ONE OVER NORTHEAST KS AND A
SECONDARY CIRCULATION FARTHER NORTH TOWARD SUX CITY.  DEEP MOISTURE
WILL STREAM NORTHWARD...SHIFTING INTO IOWA TONIGHT...WITH THE
MOISTURE WRAPPING AROUND THE SYSTEM.

TWO AREAS OF PRECIPITATION SHOULD EXPAND...THE FIRST IS ASSOCIATED
WITH THE INCREASING UPPER LEVEL DIVERGENCE/OMEGA/DPVA AND STEEPENING
LAPSE RATES ON THE NORTHEAST SIDE OF THE LOW AND THE SECOND IS WHERE
THERE IS ASSOCIATED WITH THE AFOREMENTIONED...BUT ALSO ENHANCED
CONVERGENCE ALONG THE FRONT IN NORTHEAST NEBRASKA.  THE LIFT
INCREASES ACROSS THE AREA TODAY...IS MAXIMIZED AT 06Z TONIGHT THEN
LIFTS NORTH AND SHIFTS EAST. THE NAM/GFS BOTH HAVE CONVECTIVE PRECIP
AND ELEVATED INSTABILITY THESE AREAS...SO WILL CONTINUE TO MENTION
THUNDER AS THESE FEATURES TRAVERSE THE FORECAST AREA. CRITICAL
THICKNESS VALUES/TEMPERATURES REMAIN FAVORABLE FOR LIQUID
PRECIPITATION THROUGH 09Z...WITH RAIN CHANGING TO FREEZING RAIN/
SNOW 10-15Z FOR KNOX/CEDAR/ANTELOPE COUNTIES...THE CHANGEOVER
MAKES IT TO A WAYNE/DAVID CITY LINE 18-21Z AND LINCOLN/FREMONT BY
00Z...OMAHA EARLY IN THE EVENING AND NEB CITY TO HARLAN BY 03Z AND
THE REST OF SOUTHWEST IOWA/SOUTHEAST NEB THROUGH 06Z. MOST
LOCATIONS SHOULD SEE A THIRD OF AN INCH OF RAIN WITH POCKETS OF
HIGHER .5 TO 1 INCH WATER EQUIVALENTS.

THE MOST COMPLEX PART OF THE FORECAST ARE THE TEMPERATURES AND MIXED
PRECIP/CHANGEOVER.  THE NAM/GFS AT 17Z HAD A GOOD HANDLE ON THE
GRADIENT IN TEMPERATURES...WITH UPPER 30S AT AINSWORTH...50 AT
ONL...AND 55 AT YANKTON...HOWEVER FOR 18Z...THE COLDER AIR WAS
GETTING INTO ONL QUICKER THAN THE MODELS HAD. THE GFS WAS BETTER
WITH THE DEWPOINT GRADIENT BETWEEN AINSWORTH AND ONL. FOR NOW HAVE
THE HIGHER SNOWFALL AMOUNTS IN THE NORTHWEST PART OF THE FORECAST
AREA. WHERE THE WINTER WEATHER ADVISORY IS...MOST SPOTS HAVE SOME
ICING POSSIBLE...THEN 1-3 INCHES OF SNOW AND VERY STRONG WINDS
WITH BLOWING SNOW. DID ADD KNOX COUNTY TO A WINTER STORM WARNING
AS DO HAVE A RANGE OF SNOW WITH 6 OR MORE INCHES POSSIBLE IN THE
NORTHWEST PART OF THE COUNTY. AS DISCUSSED...THE RAIN TO SNOW
CHANGEOVER WILL AFFECT THE EVENTUAL SNOW AMOUNTS...IF THE SNOW
CHANGES OVER QUICKER...THESE AMOUNTS MAY NEED TO BE RAISED.

STRONG WINDS...MOS GUIDANCE HAS THE FORECAST AREA HITTING WIND
ADVISORY CRITERIA...AS 40 TO 45KT WINDS ALOFT MIX DOWN.  DO HAVE
NORTHWEST WINDS INCREASING BEHIND THE FRONT 22-30KTS SUSTAINED AFTER
18Z THROUGH MONDAY EVENING. DUE TO THE STRONG WINDS AND LINGERING
BLOWING SNOW...EXTENDED THE ADVISORY INTO THE EARLY EVENING.

THE STORM SYSTEM PULLS AWAY FOR TUESDAY WITH COLD HIGH PRESSURE
OVER THE AREA AND HIGHS IN THE 20S/30S TUESDAY AND WEDNESDAY


.LONG TERM...(WEDNESDAY NIGHT THROUGH SUNDAY)
ISSUED AT 320 PM CST SUN DEC 14 2014

WEDNESDAY NIGHT THROUGH FRIDAY NIGHT...SOME SHORTWAVE TROF ENERGY IS
PUSHING INTO THE PLAINS THAT WILL BRING THE CHANCE FOR LIGHT SNOW TO
PARTS OF THE FORECAST AREA BEFORE THE WAVE MOVES EAST INTO THE
OHIO/TENNESSEE VALLEY. THERE ARE STILL SOME STRENGTH...TIMING AND
LATITUDE DIFFERENCES...BUT COULD GENERATE SOME LIGHT DUSTING TO 1
INCH AMOUNTS.

&&

.AVIATION...(18Z TAFS FOR KOFK...KLNK AND KOMA.)
ISSUED AT 1126 AM CST SUN DEC 14 2014

MAINLY IFR CONDITIONS ARE EXPECTED THROUGH THE TAF CYCLE. PERIODS
OF DRIZZLE ARE POSSIBLE TODAY/THIS EVENING...WITH RAIN LIKELY TO
REACH SITES LATER THIS EVENING/TONIGHT. VIS SHOULD REMAIN ROUGHLY
IN THE MVFR RANGE TODAY...WITH FLUCTUATIONS UP AND DOWN.
EAST/SOUTHEAST WINDS WILL SHIFT TO NORTHWESTERLY AND INCREASE ON
MONDAY MORNING.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...WINTER WEATHER ADVISORY FROM 6 AM TO 9 PM CST MONDAY FOR NEZ012-
     017-018-031-032-042.

     WINTER WEATHER ADVISORY FROM 4 AM TO 9 PM CST MONDAY FOR NEZ016-
     030.

     WINTER STORM WARNING FROM 4 AM TO 9 PM CST MONDAY FOR NEZ011.

IA...NONE.
&&

$$

SHORT TERM...ZAPOTOCNY
LONG TERM...ZAPOTOCNY
AVIATION...MAYES


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