Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 262319 AAA
AFDLBF

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE NORTH PLATTE NE
519 PM CST THU FEB 26 2015

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 336 PM CST THU FEB 26 2015

HIGH PRESSURE WILL BUILD SOUTH TONIGHT FROM THE DAKOTAS INTO EASTERN
NEBRASKA TONIGHT. THIS WILL CAUSE WINDS TO SWITCH AROUND FROM NORTH
TO THE SOUTH AS THE HIGH BUILDS SOUTH. AS THIS OCCURS...WINDS WILL
BE LIGHT AND VARIABLE. THERE WILL BE CLOUD COVER OVER THE SOUTHWEST
PORTION OF THE FORECAST AREA OVERNIGHT WHERE THERE WILL BE SOME
MOISTURE RETURN CONTINUING IN THE SOUTHERLY FLOW FROM WESTERN TEXAS
INTO THE HIGH PLAINS. TEMPERATURES ACROSS THE FORECAST AREA TONIGHT
WILL BE WARMEST WHERE THE CLOUDS REMAIN IN PLACE...AND ALTHOUGH THE
COLDEST -20C 850MB AIR WILL HAVE MOVED EAST OF THE
AREA...TEMPERATURES AT THIS LEVEL WILL REMAIN AT -15C TO -18C SO
EVEN WITH THE CLOUD COVER...THESE AREAS WILL SEE LOWS IN THE LOW
SINGLE DIGITS. THE REMAINDER OF THE FORECAST AREA WILL OBSERVE
MOSTLY CLEAR SKIES AND LIGHT WINDS LEADING TO A STRONG RADIATIONAL
COOLING NIGHT AS THE BOUNDARY LAYER DECOUPLES. MOST OF THIS AREA
SHOULD SEE LOWS DROP BELOW ZERO. THE LIGHT WINDS WILL LIMIT WIND
CHILLS...THOUGH EVEN A FEW KTS OF WIND WILL DROP WIND CHILLS INTO
THE TEENS BELOW ZERO.

WITH THE MOISTURE RETURN INTO FAR SOUTHWEST NEBRASKA AND THE
SOUTHERN PANHANDLE TODAY HAVE SEEN A FEW FLURRIES IN SOME LOCATIONS.
THIS IS EXPECTED TO CONTINUE TONIGHT INTO FRIDAY MORNING SO HAVE
CONTINUED THE MENTION OF A SLIGHT CHANCE FOR LIGHT SNOW WEST OF A
LINE FROM OSHKOSH TO IMPERIAL. THINK THE LIKELIHOOD OF ANY
MEASURABLE SNOW WILL BE SMALL THOUGH.

THE SURFACE HIGH WILL BUILD EAST ON FRIDAY...BRINGING SOUTHERLY FLOW
ACROSS MUCH OF NEBRASKA...WITH INCREASING WINDS AS THE DAY
PROGRESSES DUE TO AN INCREASING PRESSURE GRADIENT AND DAYTIME
BOUNDARY LAYER MIXING. FORECAST SOUNDINGS INDICATE MIXING TO NEAR
800MB IN SOME LOCATIONS ALTHOUGH THAT SHOULD BE THE MAXIMUM MIXING
HEIGHT WITH MANY AREAS NOT MIXING QUITE TO THAT LEVEL. THERE WILL BE
WARM AIR ADVECTION ONGOING IN THOSE LEVELS WITH MANY PLACES SEEING
RISES IN TEMPERATURES OF 5 TO 8 DEGREES. SO DO EXPECT WARMER
TEMPERATURES THAN HAVE BEEN EXPERIENCED TODAY...GENERALLY IN THE 20S
SO REMAINING WELL BELOW NORMAL.

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 336 PM CST THU FEB 26 2015

...MIDDLE PERIODS /FRIDAY NIGHT THROUGH SUNDAY/...

THE MAIN SYNOPTIC PATTERN OVER THE WEEKEND IS CHARACTERIZED BY AN
UPPER LEVEL TROUGH DIGGING OVER THE WESTERN U.S. WITH THE CENTER OF
500HPA LOW PRESSURE NEAR KLAX BY 00Z MONDAY. THE AMPLIFICATION OF
THE TROUGH RESULTS IN A SPLIT FLOW REGIME OVER THE FORECAST AREA
SATURDAY AND SUNDAY.

DID NOT ADJUST TEMPERATURES MUCH EXCEPT TRENDED A LITTLE BIT TOWARD
MAV GUIDANCE. KEPT FRIDAY NIGHT MIN TEMPS ABOVE GUIDANCE TO ACCOUNT
FOR INCREASING CLOUD COVER...MAINLY ACROSS THE SOUTHERN HALF OF THE
FORECAST AREA.

ALTHOUGH THE GFS...NAM...AND EURO PLACE MID LEVEL FRONTOGENESIS AND A
250HPA JET ACROSS THE AREA SATURDAY EVENING...PRECIPITATION SIGNALS
WERE QUITE MESSY. THE NAM KEEPS THE AREA MAINLY DRY WHEREAS THE EURO
AND GFS BRING BETTER MOISTURE INTO THE REGION...PRIMARILY SOUTH OF
HIGHWAY 2. OVERALL...TRENDED POPS DOWN A LITTLE THROUGH SUNDAY DUE
TO LACK OF CONFIDENCE IN MEASURABLE PRECIPITATION. AT KLBF...NAM
SOUNDINGS SHOW A DRY LAYER FROM THE SURFACE TO AROUND 800HPA EXCEPT
BRIEFLY SATURDAY NIGHT. ANY HYDROMETEORS FORMED IN THE MOIST MID
LAYER WILL LIKELY EVAPORATE BEFORE REACHING THE SURFACE. ON THE
CONTRARY...GFS BRINGS THE MOIST LAYER CLOSER TO THE SURFACE EARLY
SATURDAY AND KEEPS THE COLUMN SATURATED FOR A LONGER PERIOD INTO
SUNDAY MORNING. CANNOT IGNORE THE STRONG ISENTROPIC UPGLIDE SIGNAL
IN THE GFS...MOST EVIDENT AT 295K...AND MAINTAINED CHANCE POPS
GENERALLY ALONG AND SOUTH OF INTERSTATE 80. REMOVED POPS EXCEPT FOR
THE SOUTHERN TIER OF COUNTIES BY SUNDAY 12Z AS THE GFS DRIES THE
COLUMN CONSIDERABLY.

...EXTENDED PERIOD /SUNDAY NIGHT THROUGH THURSDAY/...

THE TROUGH SLOWLY MOVES EAST THROUGH THE WEEK...WITH THE AXIS DRAPED
ACROSS THE FORECAST AREA 00Z THURSDAY. ONE 250HPA JET STREAK FORMS
SUNDAY EVENING AND STRETCHES ROUGHLY FROM BROKEN BOW TO
DETROIT...PLACING WESTERN NEBRASKA IN THE RIGHT ENTRANCE REGION. THE
GFS IS A LITTLE MORE AGGRESSIVE WITH THIS WAVE...QUICKLY SATURATING
THE COLUMN MONDAY MORNING. PRECIPITATION TYPE WILL BE A BIT TRICKY
MONDAY AS WARMER AIR WORKS INTO THE REGION. THE GFS BRINGS ABOVE
FREEZING 850HPA TEMPS NORTH TO THE SOUTH DAKOTA BORDER BY 00Z
TUESDAY. THE EURO IS DELAYED ABOUT 12 HOURS AND KEEPS 850HPA TEMPS
ABOUT 5C COOLER MONDAY AFTERNOON AND EVENING. MAX SURFACE TEMPS
BUMPED UP A LITTLE MONDAY WITH MID 30S SOUTH AND UPPER 30S NORTH.
KEPT PTYPE AS SNOW FOR NOW...BUT A PERIOD OF FZRA AND EVENTUALLY
RAIN IS POSSIBLE. THE SECOND 250HPA JET STREAK ARRIVES MONDAY
NIGHT...BUT THE BEST ENERGY APPEARS TO STAY JUST EAST OF THE
FORECAST AREA. IF PTYPE REMAINS ALL SNOW...NOT TOO CONCERNED FOR
ACCUMULATION. THERE IS A CONSIDERABLE AMOUNT OF LIFT...BUT THE
OVERALL TEMPERATURE PROFILE IS TOO WARM AND THE DGZ DOES NOT STAY
SATURATED FOR LONG. TUESDAY...BOTH MODELS BRING A QUICK COOLDOWN AT
850HPA AND DRIER AIR INTO THE REGION AND AM MORE CONFIDENT WITH
LIGHT SNOW BEING THE MAIN PTYPE. THE NEXT SURGE OF MOISTURE ARRIVES
WEDNESDAY WITH THE PASSAGE OF THE MAIN TROUGH AXIS AND COLD FRONT.
THIS TIME AROUND...MUCH COLDER AIR IS PRESENT AND THE SNOW GROWTH
ZONE IS CLOSER TO THE SURFACE...PLACING THE BEST MOISTURE AND LIFT
ABOVE IT. AGAIN...EXPECTING ANY SNOW TO BE RATHER LIGHT WITH
RELATIVELY LOW RATIOS. NORTHWEST FLOW RESUMES THURSDAY...BRINGING A
LULL IN THE SNOW BUT CONTINUING BELOW NORMAL TEMPERATURES.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 519 PM CST THU FEB 26 2015

VFR IS GENERALLY EXPECTED EAST OF HIGHWAY 61 OVERNIGHT AND
FRIDAY. THE MODEL CONSENSUS SUGGESTS THE BANK OF MVFR CIGS AROUND
KONL WILL TO DISSIPATE THIS EVENING. SOME MODELS SUCH AS THE RAP
AND NAM APPEAR TO MAINTAIN THESE CIGS OVERNIGHT THROUGH 15Z FRIDAY
AND THEN MIX THEM OUT.

A BANK OF MVFR CIGS ACROSS ERN COLO IS PROGGED BY THE MODELS TO
LIFT SLOWLY NORTH TONIGHT AND FRIDAY...GENERALLY ALONG AND WEST OF
HIGHWAY 61.

&&

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

$$

SHORT TERM...BROOKS
LONG TERM...DS
AVIATION...CDC





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