Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 191749
AFDOAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
1149 AM CST FRI DEC 19 2014

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 303 AM CST FRI DEC 19 2014

DRY BUT CLOUDY APPEARS TO BE THE THEME FOR THIS PERIOD. THE
SOUNDING FROM 00Z LAST EVENING AT OAX HAD A SATURATED CLOUD LAYER
APPROXIMATELY 5000 FEET THICK...FROM 1500 FEET UP TO 6500 FEET.
SURFACE HIGH WAS ANALYZED IN EASTERN IOWA WITH LIGHT SOUTH FLOW
OVER THE REGION. HEIGHT GRADIENT AT 850MB WAS LOOSE WITH WEAK FLOW
FROM THE SURFACE UP TO 700 MB...THEREFORE ADVECTING THE THICK
STRATUS LAYER DOESNT SEEM LIKELY ANYTIME SOON. MODEL CLOUD COVER
FROM SHORT TERM MODELS ALSO FAVOR KEEPING THE OVERCAST INTO
SATURDAY.

LOCATIONS NEAR THE WESTERN EDGE OF THE CLOUDS WILL BE A CHALLENGE
IF THERE IS EROSION OR CLOUD ADVECTION IN THOSE AREAS...YIELDING
THE POTENTIAL FOR MORE WARMING DURING THE DAY AND COOLING AT
NIGHT. FORECAST TEMPERATURES HAVE SOME HINT OF THIS POSSIBILITY
BUT GENERALLY THINK CLOUDS WILL KEEP DIURNAL FLUCTUATIONS LIMITED.

REGARDING THE CHANCES FOR FOG...DRIZZLE...OR FREEZING DRIZZLE...
ONE LACKING INGREDIENT FOR DRIZZLE/FREEZING DRIZZLE IS VERTICAL
MOTION TO GENERATE THE PRECIPITATION. THERE IS NO OBVIOUS LIFTING
MECHANISM...SO UNTIL THERE ARE SIGNALS FOR MORE VERTICAL WE THINK
CHANCES ARE QUITE LOW FOR THAT. LIGHT FOG MAY OCCUR AS CLOUDS
LOWER...BUT DENSE FOG DOES NOT LOOK LIKELY.

.LONG TERM...(SUNDAY NIGHT THROUGH THURSDAY)
ISSUED AT 303 AM CST FRI DEC 19 2014

A POTENT SHORTWAVE WILL HAVE A SIGNIFICANT IMPACT ON OUR WEATHER
SUNDAY NIGHT INTO MONDAY NIGHT. MODEL SOLUTIONS ALWAYS HAVE SOME
SPREAD AT THIS TIME FRAME OF 72+ HOURS...BUT GIVEN HOW DYNAMIC
THIS SYSTEM APPEARS AND THE PROGRESSIVE FLOW...MODELS ARE RATHER
SIMILAR WITH THE MAIN UPPER FEATURES AND TRACK OF THE SURFACE LOW.
THIS IS A NORTHERN STREAM WAVE THAT DEEPENS AS IT DROPS SOUTHEAST
THROUGH THE DAKOTAS AND INTO IOWA...CUTTING OFF AND DIGGING WHILE
THE UPSTREAM UPPER RIDGE OVER THE WEST COAST BUILDS. SURFACE LOW
MOVES FROM NORTHEAST MONTANA SUNDAY EVENING INTO IOWA BY 18Z
MONDAY. COLD FRONT WILL MOVE THROUGH THE FORECAST AREA ON MONDAY.

ALTHOUGH NOT NECESSARILY A HEAVY PRECIPITATION SYSTEM...IT DOES
WARRANT LIKELY POPS FOR MONDAY ESPECIALLY IN EASTERN COUNTIES.
THE WARM SECTOR AREA AHEAD OF THE FRONT WILL HAVE RESPECTABLE
MOISTURE AND WARMTH WITH SURFACE DEWPOINTS AROUND 40 AND
TEMPERATURES IN THE 40S. COLUMN UP TO 850 MB WILL ALSO BE ABOVE
FREEZING SO MUCH OF THE PRECIPITATION WILL FALL AS RAIN.
EVENTUALLY THE COLUMN COOLS BEHIND THE FRONT FOR A MIX OR CHANGE
TO SNOW...BUT ANY SNOW WOULD BE BRIEF AND LIGHT.

ANALOGS INDICATE THAT THESE SYSTEMS TYPICALLY BRING STRONG WINDS
BEHIND THE FRONT...AND THIS SYSTEM LOOKS TO BE NO EXCEPTION. 850
WINDS ON ECMWF AND GFS ARE 50 KNOTS LATE MONDAY...WITH GFS
ENSEMBLE PROBABILITY OF 850 WINDS GREATER THAN 40 KNOTS AT 100
PERCENT.

IN THE WAKE OF THIS LOW...A QUIETER RIDGE PATTERN SETTLES IN FOR
TUESDAY AND WEDNESDAY. THURSDAY IS MORE QUESTIONABLE WITH SOME
MODELS BRINGING ENERGY FROM A WESTERN US LONGWAVE INTO THE
PLAINS...BUT SOME DO NOT. SMALL POPS ARE IN THE FORECAST FOR
THURSDAY BUT CONFIDENCE IS VERY LOW. IF THERE IS PRECIPITATION...
SOUTHERN AREAS MIGHT BE WARM ENOUGH FOR RAIN.

&&

.AVIATION...(18Z TAFS FOR KOFK...KLNK AND KOMA.)
ISSUED AT 1135 AM CST FRI DEC 19 2014

REGIONAL OBS REPORTING WIDESPREAD MVFR CONDITIONS CURRENTLY ACROSS
ERN NEB THIS AFTN. HOWEVER...FALSE COLOR SATL IMAGERY REVEALING
BACK EDGE OF CLEARING OVER CNTRL NEB WAS MAKING ITS WAY EWD. GIVEN
TRENDS THE LAST SEVERAL HOURS...APPEARS THAT ALL SITE WILL SEE
CONDITIONS IMPROVING TO VFR BY MID AFTN. DETERIORATING CONDITIONS
THOUGH EXPECTED TO RETURN LATER TONIGHT WITH FLGT CAT DROPPING
INTO THE IFR RANGE AT KOFK AND KOMA...AND MVFR AT KLNK BTWN 10Z-
14Z SAT MORNING. SHOULD SEE QUICK IMPROVEMENT THEN TO VFR SHORTLY
AFTER.

&&

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

$$

SHORT TERM...NIETFELD
LONG TERM...NIETFELD
AVIATION...DEE


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