Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 170953
AFDOAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
353 AM CST WED DEC 17 2014

.SHORT TERM...(TODAY THROUGH FRIDAY)
ISSUED AT 353 AM CST WED DEC 17 2014

...SNOW AND FREEZING DRIZZLE POTENTIAL THE MAIN CHALLENGES...

SOME COMPLEXITIES WITH THIS FORECAST GIVEN SUBTLE FEATURES...
SPLIT UPPER FLOW... EXISTING DRY AIR... AND VARYING MODEL
SOLUTIONS. DESPITE THAT...WE ARE SOMEWHAT CONFIDENT THAT LOCATIONS
ALONG THE KANSAS BORDER WILL SEE LIGHT ACCUMULATIONS OF SNOW
WEDNESDAY NIGHT AND THURSDAY...GENERALLY UNDER 2 INCHES.
CONFIDENCE DECREASES MOVING NORTH FROM THE KANSAS BORDER DUE TO
THE DRY AIR IN PLACE.

ONE IMPORTANT FEATURE THAT WAS ANALYZED EARLY THIS MORNING IS A
RELATIVELY STRONG SURFACE HIGH WITH THE RIDGE AXIS EXTENDING ALONG
THE MISSOURI RIVER. THIS HIGH IS KEEPING SURFACE DEWPOINTS LOW...
RANGING FROM -2F IN YANKTON TO 18F IN BEATRICE.

ALOFT... WATER VAPOR LOOP INDICATED THE UPPER FLOW WAS COMPLEX
WITH NUMEROUS SHORTWAVES MIGRATING THROUGH THE WESTERN US. MODELS
ARE IN REASONABLE AGREEMENT WITH THE IDEA OF BRINGING TWO
SHORTWAVES THROUGH THE SOUTHWEST AND INTO THE HIGH PLAINS THIS
EVENING AND OVERNIGHT...WITH A PRIMARY SURFACE LOW DEVELOPING
OVER NORTHEAST NEW MEXICO AND THEN MOVING NEAR THE RED RIVER. THIS
SETS UP AN ISENTROPIC LIFT REGIME AIDED BY DPVA...WITH WEAK MID
LEVEL FRONTOGENESIS IN THE MID LEVEL BAROCLINIC ZONE. A LAYER OF
INSTABILITY WAS NOTED ON GFS AND NAM AT 06Z TONIGHT...SUGGESTING A
FEW AREAS OF FAIRLY STRONG VERTICAL MOTION AT LEAST FOR A FEW
HOURS TONIGHT.

ALTHOUGH THE LIFT AND INSTABILITY SHOULD BE PRESENT...ALONG WITH
MAX VERTICAL MOTION NEAR THE DENDRITIC GROWTH LAYER... THE ABOVE
MENTIONED SURFACE HIGH AND ASSOCIATED DRY AIR SHOULD RESULT IN
SUBLIMATION OF SNOW FLAKES FOR THE FIRST SEVERAL HOURS OF THE
SNOWFALL. AND WITH THE LOWER DEWPOINTS FROM INTERSTATE 80
NORTH...THOSE ARES WILL TAKE LONGER TO SATURATE. ALL OF THESE
FACTORS WERE TAKEN INTO ACCOUNT TO COME UP WITH ABOUT 1.5 INCHES
OF SNOW FROM BEATRICE TO FALLS CITY...AND CLOSER TO ONE-HALF INCH
ALONG INTERSTATE 80.

MOST MODEL SOLUTIONS...INCLUDING THE MAJORITY OF SREF MEMBERS...
SHOW A FEW HOURS OF SUPER-COOLED FREEZING DRIZZLE SOUNDINGS
THURSDAY MORNING AS MID LEVELS DRY OUT...ESPECIALLY IN WESTERN
AND SOUTHERN COUNTIES. UNFORTUNATELY THERE IS POOR AGREEMENT ON
THE TIMING AND DURATION OF THIS. THIS WAS ENOUGH OF A CONCERN TO
INCLUDE IN THE FORECAST AS PATCHY FREEZING DRIZZLE...MAINLY
THURSDAY MORNING.

THIS LIGHT SNOW AND MARGINAL FREEZING DRIZZLE IS JUST BELOW WINTER
WEATHER ADVISORY CRITERIA...BUT IF CONDITIONS TREND TOWARD AN
INCREASE IN EITHER SNOW OR FREEZING DRIZZLE...AN ADVISORY MAY BE
CONSIDERED MORE CLOSELY.

.LONG TERM...(FRIDAY NIGHT THROUGH TUESDAY)
ISSUED AT 353 AM CST WED DEC 17 2014

THIS PERIOD APPEARS TO BE MAINLY DRY OTHER THAN A FEW BRIEF
PERIODS WHERE THERE IS A SLIGHT CHANCE FOR LIGHT SNOW OR POSSIBLY
LIGHT RAIN. AGAIN...THE UPPER FLOW CONTAINS NUMEROUS WEAK WAVES
MOVING WEST TO EAST...BUT LITTLE SURFACE REFLECTION IS ADVERTISED
BY THE MODELS. A WARMING TREND OF A FEW DEGREES IS EXPECTED...WITH
40S PREDICTED FOR HIGHS BY MONDAY.

&&

.AVIATION...(06Z TAFS FOR KOFK...KLNK AND KOMA.)
ISSUED AT 1102 PM CST TUE DEC 16 2014

MVFR CEILINGS WILL CONTINUE AT KLNK AND KOFK. MVFR CEILINGS ARE
EXPECTED TO OCCUR AFTER 08Z AT KOMA. CEILINGS WILL IMPROVE TO VFR
AFTER 15-16Z AS A RIDGE OF HIGH PRESSURE SLOWLY MOVES EASTWARD
ACROSS THE AREA.


&&

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

$$

SHORT TERM...NIETFELD
LONG TERM...NIETFELD
AVIATION...SMITH


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