Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 221143
AFDOAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
543 AM CST MON DEC 22 2014

.SHORT TERM...(TODAY THROUGH WEDNESDAY)
ISSUED AT 341 AM CST MON DEC 22 2014

COMPLEX FORECAST THIS MORNING AS RAIN/SNOW MOVES OVER THE REGION
THROUGH THE NEXT 36 HOURS.

00Z UPPER AIR ANALYSIS SAMPLED A STRONG 150KT 300MB JET OVER SEATTLE
AND THIS WILL CONTINUE TO DIG A MID/UPPER LEVEL TROUGH MOVING INTO
THE THE CENTRAL STATES. THERE WAS A BROAD AREA OF 50-70M HEIGHT
FALLS AT 500MB WITH WATER VAPOR IMAGERY SHOWING A POTENT LITTLE SHORTWAVE
DIGGING ACROSS COLORADO WHERE A FEW LIGHTNING STRIKES SHOWED UP
LAST EVENING. AHEAD OF THIS...AN UPPER LEVEL TROUGH AXIS EXTENDED
FROM WESTERN NORTH DAKOTA INTO EASTERN NEBRASKA. THE SFC LOW
REFLECTION WAS CENTERED OVER THE CENTRAL DAKOTAS WITH THE TROUGH
AXIS EXTENDING INTO CENTRAL NEBRASKA. WIDESPREAD LIGHT RAIN OR
DRIZZLE CONTINUES OVER THE CWA THIS MORNING IN SOUTHERLY FLOW
AHEAD OF THIS SFC TROUGH. WE DO EXPECT WIDESPREAD RAIN TO
CONTINUE THROUGH THE MORNING AND INTO THE AFTERNOON HOURS AS THE
UPPER TROUGH CONTINUES TO DIG INTO THE CENTRAL CONUS. THERE MAY BE
A BREAK IN ACTIVITY ACROSS OUR WEST EARLY THIS EVENING AS THE SFC
TROUGH SLIDES EAST OF THE AREA BY 00Z.

THE PAST TWO TO THREE MODEL RUNS HAVE DEEPENED THE MID LEVEL TROUGH
AS IT EVOLVES INTO A CLOSED LOW OVER CENTRAL/ERN NEBRASKA AND
INTO NORTHWEST MISSOURI TONIGHT. THE SFC LOW PIVOTS FROM EASTERN
NEBRASKA ACROSS NORTHERN MO THIS EVENING AND THEN LIFTS NORTH
ACROSS EASTERN IOWA TUESDAY MORNING. A SECONDARY SURGE OF PCPN
WILL DROP SOUTH OUT OF SOUTH DAKOTA OVERNIGHT ALONG THE BACK SIDE
OF THE UPPER LOW. THIS IS WHERE TEMPERATURES WILL BE COLDER FOR A
LONGER PERIOD TO SUPPORT ACCUMULATING SNOW OF NEAR 1-2"...MAINLY
ASSOCIATED WITH THE DEFORMATION ZONE BEHIND THE UPPER LOW. THERE
IS ALSO POTENTIAL FOR AN ENHANCED AREA OF HEAVIER PCPN ACROSS EAST
CENTRAL NEBRASKA AND SOUTHWEST IOWA LATE TONIGHT INTO TUESDAY
MORNING...WHERE MODELS HAVE BEEN SUGGESTING VERY STRONG VERTICAL
MOTION FOR ASCENT. SOUNDING PROFILES SHOW RAIN MIXING WITH SNOW
BEFORE EVENTUALLY TRANSITIONING TO ALL SNOW MAINLY AFTER 03Z AT
OMAHA AND 06Z IN OUR FAR SOUTH. THIS SYSTEM IS LACKING ARCTIC AIR
SO A LONG DURATION OF RA/SN MIX IS POSSIBLE THROUGH MUCH OF THE
TIME IN THE SOUTHERN COUNTIES. THIS LACK OF ARCTIC AIR ALSO MAKES
FORECASTING HOW MUCH SNOWFALL ACCUMULATES ON THE GROUND QUITE
COMPLEX. A VERY CONCERNING ISSUE IS THE POTENTIAL FOR HEAVIER
SNOWFALL AMOUNTS FROM NEAR THE OMAHA METRO AREA AND POINTS
SOUTHEAST OVERNIGHT. MODEL QPF CONTINUES TO COME IN HIGHER WITH
EACH CONSECUTIVE RUN AND THE PREVIOUS MENTIONED STRONG FORCING FOR
ASCENT IS CONFINED IN EAST CENTRAL NEBRASKA AND SOUTHWEST IOWA
FROM 03Z-12Z. HAVE INCREASED SNOWFALL AMOUNTS IN THESE AREAS...BUT
AGAIN...SFC TEMPERATURES AND THE POTENTIAL FOR A RA/SN MIX MAKE
THIS FORECAST VERY COMPLICATING AND UNCERTAIN.

MID LEVEL TROUGH AXIS WILL REMAIN ACROSS IA/NRN MO AND INTO
EASTERN KANSAS THROUGH TUESDAY NIGHT BEFORE FINALLY KICKING OUT
WEDNESDAY. AS A RESULT...HAVE CONTINUED POPS ACROSS THE CWA INTO
TUESDAY EVENING WHEN WE MAY SEE SOME LIGHT SNOWFALL ACCUMULATIONS
AS WELL.

LOOKS LIKE THE AREA MAY ACTUALLY SEE SUNSHINE BY WEDNESDAY AS
UPPER LEVEL RIDGING BUILDS OVERHEAD INTO THURSDAY.

.LONG TERM...(WEDNESDAY NIGHT THROUGH SUNDAY)
ISSUED AT 341 AM CST MON DEC 22 2014

THE NEXT UPPER LEVEL TROUGH WILL ROUND THE FOUR CORNERS REGION 00Z
FRIDAY. AHEAD OF THIS...STRONG WAA IS EXPECTED ON CHRISTMAS DAY
WHICH SHOULD PUSH HIGHS INTO THE 40S. THE GFS AND ECMWF ARE FINALLY
COMING INTO BETTER AGREEMENT WITH THE PLACEMENT AND TIMING OF THE
LARGE SCALE FEATURES INTO EARLY NEXT WEEKEND. THE UPPER TROUGH AXIS
SHOULD QUICKLY SWING THROUGH OUR CWA FRIDAY NIGHT WHICH COULD GIVE
OUR NORTHERN HALF OF THE CWA A BRIEF SHOT AT SNOW FRIDAY.

ANOTHER TROUGH IS FORECAST TO DIG ACROSS THE WEST AND INTO THE
CENTRAL PLAINS EARLY NEXT WEEK.

&&

.AVIATION...(12Z TAFS FOR KOFK...KLNK AND KOMA.)
ISSUED AT 533 AM CST MON DEC 22 2014

IFR CIGS ARE PREVALENT AT THE TAF SITES THIS MORNING WITH LIGHT
RAIN. THE BAND OF LIGHT RAIN IS SWINGING THROUGH NOW AND SHOULD
DECREASE IN INTENSITY FROM WEST TO EAST AS SURFACE WINDS SHIFT
FROM THE SOUTH TO THE SOUTHWEST...THEN NORTHWEST. THIS WIND SHIFT
WILL TRY TO LIFT CIGS TO MVFR AT KOFK AND KLNK. BEHIND THE COLD
FRONT...NORTHWEST WINDS INCREASE TO 10 TO 15KT.  A RAIN SNOW MIX
SHOULD WRAP AROUND LATER TODAY AND TONIGHT. KOFK LOOKS TO TURN TO
ALL SNOW AFTER 00Z...HOWEVER AT KLNK/KOMA...MAY SWITCH BACK AND
FORTH...SO LEFT A MIX IN DURING THE OVERNIGHT HOURS.

&&

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

$$

SHORT TERM...KERN
LONG TERM...KERN
AVIATION...ZAPOTOCNY



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