Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 122341
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
641 PM CDT SAT APR 12 2014

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 354 PM CDT SAT APR 12 2014

FORECAST CHALLENGES THROUGH SUNDAY ARE WITH THUNDERSTORM/RAIN/SNOW
CHANCES TONIGHT AND SUNDAY AS WELL AS WINDS TONIGHT AND SUNDAY.

AT 19Z...NOTED A FAIRLY BROAD UPPER LEVEL SHORTWAVE TROUGH FROM
SOUTHERN CALIFORNIA INTO THE FOUR CORNERS...WHILE A SECOND SHORTWAVE
TROUGH WAS SEEN OVER THE PACIFIC NORTHWEST. DOWNSTREAM OF THESE
SYSTEMS...FLOW WAS FAIRLY ZONAL ALOFT ACROSS THE EASTERN HALF OF THE
COUNTRY.

AT THE SURFACE...LOW PRESSURE WAS OBSERVED OVER WESTERN KANSAS WITH
A WARM FRONT EXTENDING INTO NORTHERN IOWA. LOW LEVEL MOISTURE WAS
CONFINED TO AREAS SOUTH OF THE FRONT WITH DEWPOINTS IN THE 50S.
MEANWHILE WESTERN AND CENTRAL NEBRASKA SAW MUCH DRIER AIR WITH
DEWPOINTS IN THE UPPER 20S AND 30S. HAVE BEEN WATCHING ACTIVITY
INCREASE THROUGH THE AFTERNOON ON RADAR ACROSS WYOMING...COLORADO
AND THE WESTERN NEBRASKA PANHANDLE. THERE IS INSTABILITY IN THE MID
LEVELS AHEAD OF THE SOUTHWEST UPPER LOW WHICH HAS LED TO QUITE A BIT
OF LIGHTNING OVER THE FOUR CORNERS REGION THIS AFTERNOON.

THE UPPER LEVEL SYSTEM OVER THE SOUTHWEST WILL QUICKLY PROGRESS EAST
OVER THE NEXT 24 HOURS...WHICH WILL PROVIDE THE UPPER LEVEL DYNAMICS
FOR ACTIVITY ALONG THE WARM FRONT TONIGHT AND SUNDAY. WITH THE
MOISTURE IN PLACE THERE WILL LIKELY BE THUNDERSTORMS...BUT WITH THE
SURFACE FRONT WELL SOUTH AND EAST OF THE LOCAL AREA...DO NOT
ANTICIPATE ANY THUNDERSTORMS ASSOCIATED WITH THIS SYSTEM LOCALLY.

THE NORTHWEST SYSTEM WILL DIG TOWARDS THE FOUR CORNERS THROUGH THE
TONIGHT AND SUNDAY PERIODS. THIS WILL PULL A STRONG COLD FRONT
ACROSS NEBRASKA TONIGHT...WITH WINDS INCREASING AND A PRETTY DRASTIC
COOL DOWN. THE WIND DIRECTION WILL NOT CHANGE...BUT THE COLDER
AIRMASS MOVING IN WILL BRING ABOUT A TIGHTER PRESSURE GRADIENT WHICH
WILL INCREASE THE WINDS BEGINNING LATE TONIGHT. THE STRONGEST WINDS
LOOK TO BE BETWEEN 12Z AND 21Z...WITH SUSTAINED WINDS AT 25 TO 35
MPH AND GUSTS TO AROUND 45 MPH. ALTHOUGH IT IS MARGINAL IN TERMS OF
WIND ADVISORY...BELIEVE WE WILL GET THE SUSTAINED WINDS IN PORTIONS
OF THE AREA SO WILL ISSUE A WIND ADVISORY FOR AREAS WITH HIGHEST
CONFIDENCE IN THIS OCCURRING. IT IS POSSIBLE THAT THIS MAY NEED TO BE
EXTENDED WITH THE NEXT FORECAST PACKAGE BUT FELT THIS IS A GOOD
STARTING POINT.

CURRENT 850MB TEMPERATURES ACROSS NEBRASKA ARE BETWEEN 9C AND
16C...WHICH COOL BEHIND THE COLD FRONT TONIGHT AND SUNDAY. BY SUNDAY
AFTERNOON ALL AREAS WILL BE BELOW 0C AT THIS LEVEL...GENERALLY -3C
TO -5C. COLD AIR ADVECTION WILL BE ONGOING THROUGH THE DAY...AND
WITH GOOD CLOUD COVER WENT WITH A NON-DIURNAL TREND FOR TEMPERATURES
IN MOST AREAS. HIGHS ONLY ARE EXPECTED IN THE 30S AND LOW 40S.

IN TERMS OF PRECIPITATION...THE CURRENT ACTIVITY WILL SLOWLY MOVE
EAST INTO THE PANHANDLE THROUGH THE LATE AFTERNOON HOURS. WITH THE
AMOUNT OF DRY AIR IN PLACE...DID BACK OFF ON THE TIMING OF
PRECIPITATION CHANCES TO MAINLY THIS EVENING...AND SLOWED THE
PROGRESSION EASTWARD. THE FORECAST MODELS DO DEVELOP DECENT
FRONTOGENESIS AROUND 700MB LATE TONIGHT AND SUNDAY MORNING...MAINLY
FROM THE PANHANDLE INTO NORTH CENTRAL NEBRASKA. THIS FORCING DOES
SHIFT SOUTH THROUGH THE DAY...BUT MOVES RATHER QUICKLY SO LOOKING
FOR THE HIGHER QPFS OVER THE NORTHWEST PART OF THE FORECAST AREA.
FROM LOOKING AT SOUNDING PROFILES...THE SWITCHOVER FROM RAIN TO SNOW
WILL OCCUR LATE TONIGHT OVER THE NORTHWEST AREAS...AND LATER IN THE
DAY TO THE SOUTHEAST. WITH THE TIMING OF THE PRECIPITATION COMING IN
THE AFTERNOON...SOME AREAS ACROSS THE SOUTHEAST PART OF THE FORECAST
AREA MAY NOT SEE A COMPLETE CHANGEOVER TO SNOW SO KEPT MENTION OF
RAIN/SNOW OR JUST RAIN IN THE FORECAST THROUGH TOMORROW. SNOW
AMOUNTS ARE EXPECTED UP TO 2 TO 3 INCHES WEST OF A LINE FROM
OGALLALA TO VALENTINE. THERE IS CONCERN FOR THE NEED FOR A WINTER
WEATHER ADVISORY IN THESE AREAS DUE TO THE STRONG WINDS AND FALLING
SNOW...BUT WITH UNCERTAINTY ON SNOW AMOUNTS AND WHAT IMPACT THERE
MIGHT BE WITH THE SNOW FALLING DURING THE DAY /AND WARM SURFACE
TEMPERATURES AT THE MOMENT/ WANTED TO HOLD OFF ON ANY ISSUANCE UNTIL
TIME GETS CLOSER AND THINGS REALLY COME TOGETHER SO WILL LET THE
INCOMING SHIFT CONTINUE TO LOOK AT THE SYSTEM.

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 354 PM CDT SAT APR 12 2014

AS NORTHERN STREAM TROUGH DROPS SOUTHEAST SUNDAY NIGHT...A CHANCE
FOR LIGHT SNOW GENERALLY SOUTH OF INTERSTATE 80. ANY SNOW
ACCUMULATIONS SHOULD BE LIGHT AND LESS THAN A 1/2 INCH. WINDY
CONDITIONS EARLY IN THE EVENING TO DIMINISH TO 5 TO 15 MPH OVERNIGHT.

CHILLY CONDITIONS THEN FOR MONDAY AS HIGH PRESSURE BUILDS SOUTH INTO
KANSAS AND OKLAHOMA. HIGHS IN THE MID 40S EXPECTED ALL AREAS. NW
WINDS TO INCREASE INTO THE BREEZY CATEGORY BY LATE MORNING. LOWS
MONDAY NIGHT WILL BE SUB FREEZING IN THE MID 20S AS LOW DEWPOINTS
DICTATE STRONG COOLING OVERNIGHT.

ON TUESDAY...TEMPERATURES WILL RECOVERY SIGNIFICANTLY TO 60 TO 65
DEGREES AS THERMAL RIDGE BUILDS INTO THE CENTRAL HIGH PLAINS. NEXT
UPSTREAM TROUGH WILL THEN DIG INTO THE PACIFIC NORTHWEST.

LATER IN THE WEEK...QUESTIONS REMAIN REGARDING EVOLUTION OF UPPER
TROUGH LATER WEDNESDAY THROUGH FRIDAY. THE GFS AND GEFS MEAN
CONTINUE TO INDICATE A POTENT SHORTWAVE CLOSING OFF OVER COLORADO
WEDNESDAY NIGHT AND TRACKING INTO SRN NEBR/NRN KANSAS AND EASTERN
NEBRASKA THURSDAY NIGHT. THIS SOLUTION RESULTS IN A NEGATIVELY
TILTED SOLUTION...AND HIGH PRECIPITATION CHANCES. THE AIRMASS IS
EASILY COLD ENOUGH FOR ALL SNOW. THE ECMWF CONTINUES TO BE MUCH
WEAKER WITH THIS FEATURE...WHILE THE GEM WOULD SUPPORT THE GFS/GEFS.
SYNOPTICALLY...THIS SYSTEM HAS THE POTENTIAL TO BECOME A SIGNIFICANT
SPRING SNOW EVENT...SO WILL NEED TO MONITOR MODEL TRENDS CLOSELY.
POPS RAISED TO 30 TO 40 PERCENT WEDNESDAY NIGHT/THURSDAY. RESULTING
FORECAST IS FOR MENTION OF ALL SNOW NORTHWEST AND RAIN/SNOW ACROSS
THE SOUTHEAST. HIGH TEMPERATURES THURSDAY ALSO LOWERED TO THE UPPER
30 AROUND 40 NORTHWEST AND MID 40S SOUTHEAST. IN THE WAKE OF THIS
SYSTEM...TEMPERATURES SHOULD MODERATE INTO THE 50S FRIDAY AND THE
60S SATURDAY.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 640 PM CDT SAT APR 12 2014

A STRONG UPPER LEVEL DISTURBANCE WILL TRACK ACROSS THE CENTRAL
PLAINS OVERNIGHT TONIGHT INTO SUNDAY. THIS FEATURE WILL BRING RAIN
AND SNOW TO WESTERN AND NORTH CENTRAL NEBRASKA LATE TONIGHT INTO
SUNDAY. IN ADDITION...STRONG NORTHERLY WINDS GUSTING UP TO 35 KTS
ARE LIKELY AS WELL. EXPECT MVFR CIGS TO SET IN AT THE KVTN TERMINAL
AFTER 11Z SUNDAY AND AFTER 13Z AT THE KLBF TERMINAL. LIGHT RAIN WILL
CHANGEOVER TO SNOW AFTER 13Z SUNDAY AT THE KVTN TERMINAL AND AFTER
15Z SUNDAY AT THE KLBF TERMINAL. VISBYS MAY DIP DOWN TO 1SM AT KVTN
AND 3SM AT KLBF. CIGS WILL BEGIN TO RISE WITH VFR CIGS EXPECTED
AFTER 22Z SUNDAY.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY FROM 7 AM CDT /6 AM MDT/ TO 7 PM CDT /6 PM MDT/
SUNDAY FOR NEZ022>028-035>038-057-059-071.

&&

$$

SHORT TERM...BROOKS
LONG TERM...ROBERG
AVIATION...CLB






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