Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 070505
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
1105 PM CST SAT FEB 6 2016

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 212 PM CST SAT FEB 6 2016

FOR TONIGHT...A CLIPPER SYSTEM WILL BEGIN TO MOVE SOUTHEAST OUT OF
MANITOBA INTO NORTHERN MINNESOTA...WITH A TRAILING COLD FRONT
PUSHING ACROSS THE NORTHERN HIGH PLAINS. IN ADVANCE OF THE COLD
FRONT...A SURFACE TROUGH WILL MOVE FROM WEST TO EAST ACROSS WESTERN
AND NORTH CENTRAL NEBRASKA. THIS SURFACE TROUGH WILL TURN THE
WESTERLY WINDS SEEN DURING THE DAYTIME HOURS...TO THE WEST NORTHWEST
BEFORE THE MIDNIGHT HOUR. THESE WEST NORTHWEST WINDS WILL REMAIN
BREEZY THROUGHOUT THE NIGHTTIME HOURS...WHICH WILL PREVENT THE
BOUNDARY LAYER FROM DECOUPLING OVERNIGHT TONIGHT. DUE TO THIS WELL
MIXED NOCTURNAL BOUNDARY LAYER...LOW TEMPERATURES ARE ONLY EXPECTED
TO FALL INTO THE UPPER TEENS TO 20S ACROSS THE REGION.

FOCUS THEN SHIFTS TO TWO AREAS OF FORECAST CONCERNS/CHALLENGES FOR
THE DAY ON SUNDAY...AS THE STRONG COLD FRONT CONTINUES TO PUSH
SOUTHEAST ACROSS THE NORTHERN HIGH PLAINS AND INTO THE REGION: 1)THE
POTENTIAL FOR BLOWING SNOW...AND 2)WIND SPEEDS/GUSTS.

FIRST TO ADDRESS THE CONCERN FOR BLOWING SNOW ON SUNDAY. CURRENT
THINKING IS THAT A SUFFICIENT SURFACE CRUST HAS BEEN BUILT UPON THE
SNOW PACK THAT RESIDES ACROSS THE REGION...WHICH SHOULD LIMIT THE
AMOUNT OF BLOWING SNOW. WITH THIS BEING SAID...DO BELIEVE THAT
LOCALIZED AREAS OF BLOWING SNOW ARE POSSIBLE DURING THE DAY ON
SUNDAY...ESPECIALLY IN THOSE AREAS THAT HAVE BEEN SHELTERED FROM
DIRECT SUNLIGHT OVER THE PAST FEW DAYS (IE AREAS THAT HAVE BEEN
SHADED BY TREES AND/OR BUILDINGS). IN ADDITION TO THOSE AREAS OF
LOCALIZED BLOWING SNOW WITHIN OUR REGION...AM CONCERNED WITH HOW
MUCH SNOW IS BLOWN IN ACROSS NORTHERN NEBRASKA FROM THE STATE OF
SOUTH DAKOTA. WHILE TEMPERATURES WARMED WELL ABOVE FREEZING TODAY
ACROSS WESTERN SOUTH DAKOTA...THE STATE OF THE SURFACE CRUST OF SNOW
IS STILL IN QUESTION. ALSO...WINDS WILL BE THE STRONGEST ACROSS THIS
REGION...SO ANY LOOSE SNOW WILL EASILY BE BLOWN INTO NORTHERN
NEBRASKA.

THE SECOND CHALLENGE IN THE NEAR TERM WILL BE WIND SPEEDS AND GUSTS
FOR THE AFTERNOON AND EVENING HOURS ON SUNDAY. GIVEN PLENTIFUL
SUNSHINE...STEEP LOW LEVEL LAPSE RATES OF 8+ DEGREES PER KM UP TO
850MB DURING THE 18Z-00Z HOURS...AND MECHANICAL MIXING FROM THE
PASSAGE OF THE COLD FRONT...BELIEVE THAT SUFFICIENT MIXING OF
STRONGER WINDS TO THE SURFACE SHOULD OCCUR ACROSS ALL OF WESTERN AND
NORTH CENTRAL NEBRASKA DURING THE AFTERNOON HOURS ON SUNDAY. THIS
BELIEF IS SUPPORTED BY THIS MORNINGS 12Z BUFKIT SOUNDINGS...WHICH
SHOWS MIXING TO AT LEAST 850MB ACROSS THE REGION. AT THIS TIME...THE
STRONGEST WINDS WHICH WOULD SUPPORT HIGH WIND CRITERIA APPEAR TO BE
CONFINED TO SHERIDAN...CHERRY...KEYA PAHA...BROWN...HOLT...BOYD AND
ROCK COUNTIES.  WILL UPGRADE THESE COUNTIES TO A HIGH WIND WARNING
WITH THIS FORECAST PACKAGE.  THE OTHER COUNTIES THAT ARE CURRENTLY
COVERED IN A HIGH WIND WATCH WILL BE LEFT AS IS AS THERE REMAINS
SOME DOUBT THAT THESE COUNTIES WILL REACH HIGH WIND WARNING
CRITERIA. WFO LBF NO LONGER ISSUES WIND ADVISORIES...SO THE EVENING
SHIFT WILL DECIDE TO UPGRADE THOSE COUNTIES TO A WARNING...OR COVER
THEM WITH A SPS.

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 212 PM CST SAT FEB 6 2016

FOR SUNDAY NIGHT...THE PRECIPITATION FIELDS IN THE 12Z GFS40
INDICATE SOME LIGHT PRECIPITATION IN NORTH CENTRAL NEBRASKA...
NAMELY BOYD AND HOLT COUNTIES. HOWEVER...WITH THE 12Z RUN... NEITHER
THE NAM12 NOR THE CANADIAN NH INDICATE ANY. LOOKING AT THE UPWARD
MOTION IN THE 285-295K LAYER...SOME WEAK UPWARD MOTION IS INDICATED.
THIS GETS SOME SUPPORT FROM THE LOCAL PRESSURE DERIVATIVE ON THE
285K AND 290K SURFACES. SINCE THE LIFT IS WEAK AND OVER A VERY
LIMITED AREA AND TIME SEGMENT...WE WILL KEEP THE PRECIPITATION
PROBABILITY BELOW 20 PERCENT. CLOUDINESS AND SNOW COVER WILL
CONTINUE TO CAP THE DAYTIME TEMPERATURES MONDAY...BUT THE SNOW
SHOULD CONTINUE ERODING FROM THE OUTER EDGES.

DEPENDING ON THE RATE OF EROSION OF THE SNOW COVER...TEMPERATURES
MAY BE CAPPED INTO TUESDAY AND MAYBE EVEN BEYOND THAT. WITH
AFTERNOON WIND AT OR ABOVE 10KT...IT IS POSSIBLE THAT THE WARMER
UPPER TEMPERATURES WILL MIX TO THE SURFACE. IN THAT CASE THEN...IT
WOULD NOT BE OUT OF LINE TO FORECAST TEMPERATURES IN THE 40S TO
LOWER 50S...EVEN WITH SNOW COVER.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1104 PM CST SAT FEB 6 2016

FOR THE KLBF AND KVTN TERMINALS...WINDS WILL BECOME AN AVIATION
CONCERN AFTER 12Z SUNDAY. WINDS WILL INCREASE TO 30027G35KT BY 15Z
AND PEAK NEAR 30034G43KT AFTER 18Z AT KVTN. IN ADDITION...SNOW
SHOWERS ARE POSSIBLE IN THE AFTERNOON IN VICINITY OF THE KVTN
TERMINAL. WINDS AT KLBF SIMILAR PEAKING NEAR 30028G39KT AFTER
18Z. WINDS AT BOTH SITES WILL GRADUALLY LOWER DURING THE EVENING
HOURS.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
HIGH WIND WARNING FROM 9 AM CST /8 AM MST/ TO 8 PM CST /7 PM
MST/ SUNDAY FOR NEZ004>010-094.

&&

$$

SHORT TERM...JACOBS/MOLDAN
LONG TERM...SPRINGER
AVIATION...ROBERG


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