Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 271242
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
642 AM CST THU NOV 27 2014

.SYNOPSIS...
ISSUED AT 400 AM CST THU NOV 27 2014

A SURFACE RIDGE OF HIGH PRESSURE EXTENDS SOUTH FROM EASTERN SOUTH
DAKOTA INTO EASTERN KANSAS AND CENTRAL OKLAHOMA. MID CLOUDINESS
PERSISTS ACROSS MOST OF WESTERN NEBRASKA. TEMPERATURES AT 08Z RANGED
MAINLY IN THE MID 20S. THE PERSISTENT FOG ACROSS PORTIONS OF
DEUEL...GARDEN AND KEITH COUNTIES IS A RESULT OF SNOWFALL FROM
YESTERDAY AFTERNOON AND EARLY EVENING. SOME MELTING HAS LEAD TO FOG
DEVELOPMENT...AS LOW AS A QUARTER MILE AT TIMES. THIS SHOWN BY OGA
METAR AND AREA NDOR WEBCAMS.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 400 AM CST THU NOV 27 2014

THE AREAS OF FOG ACROSS PORTIONS OF DEUEL...GARDEN AND KEITH COUNTY
WILL PERSIST THROUGH SUNRISE..THEN WILL DISSIPATE BY 8 AM MST.
OTHERWISE THERE WILL BE SOME INCREASE IN MID/HIGH CLOUDINESS ACROSS
THE WEST THROUGH MIDDAY THEN CLEARING. EASTERN AREAS TO REMAIN
PARTLY TO MOSTLY CLOUDY.

ACROSS THE CONUS FOR THANKSGIVING DAY...A BROAD UPPER RIDGE WILL
EXTEND ACROSS THE WESTERN HALF AS A BROAD TROUGH EXTENDS ACROSS THE
EAST. H85 TEMPS WARM TO 13C TO 15C ACROSS EASTERN COLORADO AND
WESTERN KANSAS...HELPING TO PUSH HIGHS IN THOSE AREAS INTO THE 60S.
SOME OF THIS WARMER AIR WILL BE SPREADING INTO WESTERN NEBRASKA. A
WARM FRONT WILL MOVE EAST OF VALENTINE THROUGH BROKEN BOW BY LATE
THIS AFTERNOON. WEST OF THE WARM FRONT...HIGHS SHOULD REACH THE
UPPER 50S IN FAR SWRN AREAS...WHILE IN THE NORTHEAST...HIGHS TO
STRUGGLE TO REACH 32 AT ONL. TEMPERATURES VERY NEAR PREVIOUS
FORECAST AND ALSO NEAR LATEST MAV GUIDANCE.

WEAK LOW PRESSURE DUE TO A SURFACE TROUGH WILL RESIDE ACROSS WESTERN
NEBRASKA TONIGHT. SKIES TO BECOME MOSTLY CLEAR OVERNIGHT. A LIGHT
SOUTHWEST TO WEST WIND WILL DEVELOP HELPING HOLD LOWS TO THE UPPER
20S WEST. FROM THE PLATTE VALLEY INTO EASTERN AREAS SLIGHTLY COLDER
IN THE LOWER TO MID 20S. JUST OFF THE SURFACE AT 850MB...TEMPS WILL
RANGE FROM 11C TO 15C BY 12Z. THIS WILL RESULT IN A FAIRLY STRONG
INVERSION NEAR THE SURFACE.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 400 AM CST THU NOV 27 2014

PRIMARY FORECAST CONCERNS OVER THE WEEKEND THROUGH THE MIDDLE OF
NEXT WEEK DEAL WITH TEMPERATURES. FIRST WITH ANOMALOUSLY WARM
TEMPERATURES FOR FRIDAY AND SATURDAY...THEN A SHARP CHANGE WITH A
STRONG COLD FRONT MOVING THROUGH THE AREA SATURDAY NIGHT AND
SUNDAY.

MODELS ARE COMING CLOSER TO A SIMILAR SOLUTION FOR THE WEEKEND AND
FOR THE FRONTAL PASSAGE ON SUNDAY...BUT THERE REMAINS ENOUGH
SPREAD TO KEEP CONFIDENCE FROM REACHING A HIGH LEVEL. THAT BEING
SAID...MODEL DISCREPANCIES IN THE FIRST PART OF THE PERIOD HAVEN/T
SWAYED DECISIONS WITH TEMPERATURES BEING QUITE WARM...THEN THERE
IS JUST SOME TIMING DIFFERENCES IN THE PASSAGE OF THE COLD FRONT
AND HOW COLD THE AIR WILL ACTUALLY BE. THEN TOWARDS MID WEEK THE
TREND CONTINUES WITH THE ECMWF/GEM SOLUTIONS BRINGING A FAIRLY
STRONG SHORTWAVE TROUGH ACROSS THE NORTHERN AND CENTRAL PLAINS
WHILE THE GFS STAYS MORE PROGRESSIVE AND WEAKER WITH THE SAME
SHORTWAVE. WILL SHY AWAY FROM THE GFS AS IT CONTINUES TO BE THE
OUTLIER.

FOR FRIDAY AND SATURDAY...A BROAD RIDGE WILL BE IN PLACE ACROSS
THE CENTRAL PART OF THE COUNTRY AS THE TROUGH CURRENTLY OVER THE
EASTERN HALF OF THE CONUS PROGRESSES EAST INTO THE PACIFIC TO
ALLOW THE WESTERN RIDGE TO BUILD EAST. MEANWHILE THE SHORTWAVE
TROUGH SEEN IN WATER VAPOR IMAGERY OVER THE GULF OF ALASKA INTO
NORTHERN BRITISH COLUMBIA WILL MOVE INTO THE PACIFIC NORTHWEST.
WARM AIR ADVECTION WILL BE STRONG THROUGH THIS 2 DAY TIME-SPAN
WITH 850MB TEMPERATURES RISING TO 15-19C ACROSS THE FORECAST AREA.
STANDARDIZED ANOMALIES INDICATE THESE VALUES WILL BE 2-3 STANDARD
DEVIATIONS ABOVE NORMAL...SO AGAIN QUITE ANOMALOUS FOR THIS TIME
OF YEAR INDICATING THE POTENTIAL TO AT LEAST APPROACH RECORD
TEMPERATURES. THE SURFACE FLOW WILL NOT BE REAL STRONG AS THE
SURFACE PATTERN WILL BE RELATIVELY NON- DESCRIPT THROUGH THESE
DAYS. SURFACE WINDS WILL BE FROM THE WEST- SOUTHWEST BOTH DAYS AS
THE SURFACE LOW ASSOCIATED WITH THE SYSTEM MOVING INTO THE
NORTHWEST CONUS DEVELOPS OVER MONTANA. WITH THE PRIMARY SYSTEM
WELL TO THE WEST OF THE AREA THE PRESSURE GRADIENT STAYS QUITE
WEAK SO ALTHOUGH GETTING FAVORABLE WARMING DOWNSLOPE FLOW IT WON/T
BE STRONG. THIS MAY BE WHAT LEADS TO MODEL DISCREPANCIES WITH
HIGHS BOTH FRIDAY AND SATURDAY. THE NAM AND GFS ARE BOTH
INDICATING LITTLE MIXING OF THE BOUNDARY LAYER BOTH DAYS BUT
ESPECIALLY ON FRIDAY. WITH LITTLE IN TERMS OF RELATIVE HUMIDITY TO
WORRY ABOUT SO NOT EXPECTING MUCH FOR CLOUD COVER. BEST GUESS IS
THE LIGHT WINDS ARE LEADING TO THE LACK OF MIXING FROM THE MODELS
BUT REALLY THINKING THAT WON/T HOLD TRUE AND HAVE KEPT FORECAST
HIGHS QUITE WARM WITH 70 DEGREE READINGS CERTAINLY LOOKING
POSSIBLE IN SOME AREAS.

THE PACIFIC NORTHWEST SYSTEM MOVES EAST ACROSS THE NORTHERN PLAINS
THROUGH SUNDAY WHICH PUSHES THE COLD FRONT INTO NEBRASKA LATE
SATURDAY NIGHT AND SUNDAY. AGAIN...THERE ARE DIFFERENCES WITH THE
STRENGTH OF THIS SYSTEM BETWEEN THE MODELS WITH THE GFS BEING MORE
PROGRESSIVE AND IN TURN NOT AS COLD. HAVE CONTINUED WITH THE
TIMING COMING FROM THE ECMWF WHICH IS A BIT SLOWER AND STARTS TO
REALLY BRING THE COLD AIR INTO THE FORECAST AREA AROUND 12Z
SUNDAY. MAY SEE A NON-DIURNAL TEMPERATURE TREND IN PARTS OF THE
FORECAST AREA AS THE STRONG COLD AIR ADVECTION PUSHES SOUTH
THROUGH THE DAY. THE CURRENT HIGH TEMPERATURE FORECAST HAS NEAR 20
ALONG THE SOUTH DAKOTA BORDER WITH NEAR 40 OVER THE SOUTHWEST.
WILL NEED TO KEEP A CLOSE EYE ON THIS IN FUTURE FORECAST CYCLES AS
THE SLOWER SOLUTION MAY ALLOW HIGHS TO BE A BIT WARMER IN THE
SOUTHERN AREAS BEFORE THE COLD FRONT PLOWS THROUGH. DID INCREASE
WINDS A BIT BEHIND THE FRONT AS THIS FEELS LIKE A SYSTEM WITH THE
MAKINGS OF A STRONG WIND EVENT. THE STRONGEST PRESSURE GRADIENT IS
DIRECTLY BEHIND THE FRONT BUT GIVEN ANY MIXING OF THE BOUNDARY
LAYER DURING THE DAY SUNDAY WILL KEEP WINDS STRONG DURING THE DAY.
MAY NEED TO INCREASE WINDS FURTHER FOR THIS PERIOD IN LATER
FORECASTS.

SUNDAY NIGHT/MONDAY MORNING WILL BE THE COLDEST OF THE PERIOD BUT
THERE IS CONSISTENCY KEEPING THE SURFACE HIGH FROM NORTH AND EAST
OF THE FORECAST AREA SO MAY NOT BE AS COLD AS MAY HAVE THOUGHT AT
ONE TIME WITH WINDS NOT DROPPING OFF COMPLETELY TO REALLY COOL
THINGS DOWN. HOWEVER...THERE ARE PRETTY BIG DIFFERENCES IN HOW COLD
THE AIRMASS WILL BE WITH A 5C DIFFERENCE BETWEEN THE ECMWF AND
GFS. STILL LOOKING AT LOWS IN THE SINGLE DIGITS AND LOW TEENS.

THEN INTO MID-WEEK A BRIEF AND SLIGHT WARM UP OCCURS THROUGH
TUESDAY BEFORE ANOTHER SYSTEM PUSHES ACROSS THE PLAINS. THIS ONE
WILL NOT BE AS STRONG BUT WILL KEEP TEMPERATURES NEAR NORMAL OR
BELOW NORMAL DEPENDENT ON WHAT MODEL SOLUTION ENDS UP BEING CLOSER
TO CORRECT.

AS A WHOLE PRECIPITATION CHANCES ARE LOW THROUGHOUT THE PERIOD AS
THE SYSTEMS MOVING THROUGH WILL NOT HAVE MUCH MOISTURE TO WORK
WITH. THERE MAY BE SOME BRIEF PERIODS OF LIGHT PRECIPITATION BUT
CONFIDENCE IS LOW ON ANY BEING MEASURABLE TO MORE THAN VERY LIGHT
AMOUNTS AT THIS TIME.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 642 AM CST THU NOV 27 2014

VFR CONDITIONS AT THE KLBF AND KVTN TERMINALS THROUGH TONIGHT.
SOME MID AND HIGH CLOUDINESS WILL TRAVERSE THE AREA TODAY...WITH
ONLY A FEW HIGH CLOUDS TONIGHT. LIGHT SOUTHEAST WINDS THIS MORNING
WILL BECOME SOUTH BY 18Z.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SYNOPSIS...ROBERG
SHORT TERM...ROBERG
LONG TERM...BROOKS
AVIATION...ROBERG







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