Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 312016
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
316 PM CDT THU JUL 31 2014

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 315 PM CDT THU JUL 31 2014

A WEAK AREA OF SURFACE LOW PRESSURE WAS CENTERED NEAR ONEILL THIS
AFTERNOON. A WEAK FRONT EXTENDS SOUTH/SOUTHWEST FROM THIS LOW INTO
SOUTH CENTRAL NEBRASKA. IT APPEARS THAT THE BEST CONVERGENCE NEAR
THE FRONT IS ACROSS SOUTH CENTRAL NEBRASKA...AND THIS IS WHERE A
COUPLE OF ISOLATED THUNDERSTORMS HAVE DEVELOPED IN THE LAST HOUR.
CANNOT COMPLETELY RULE OUT THE POSSIBILITY OF AN ISOLATED STORM IN
EASTERN HOLT AND WHEELER COUNTIES...BUT CHANCES ARE LOOKING SLIM.

OVERNIGHT TONIGHT EXPECTING SKIES TO CLEAR COMPLETELY FOR THE MOST
PART...AND WITH A FAIRLY DRY AIRMASS IN PLACE...EXPECTING LOWS IN
MOST LOCATIONS TO ONCE AGAIN DROP INTO THE 50S.

NORTHWEST FLOW ALOFT WILL DOMINATE THE WEATHER FRIDAY. NEARLY ALL
MODELS INDICATE THAT A WEAK WAVE WILL ROTATE SOUTHEAST WITHIN THE
FLOW DURING PEAK HEATING THURSDAY AFTERNOON...AND HAVE ADDED A
SLIGHT CHANCE FOR THUNDER TO ACCOUNT FOR THIS ACROSS NORTH CENTRAL
NEBRASKA. NAM MODEL DOES INDICATE AROUND 1250 J/KG OF MLCAPE AND
0 TO 6 KM SHEAR OF 30 KTS...SO A STRONG STORM CANNOT BE RULED OUT.
OTHERWISE A WARM DAY EXPECTED...WITH HIGHS IN THE MID TO UPPER 80S
AT MOST LOCALS.

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 315 PM CDT THU JUL 31 2014

ALTHOUGH MODELS ARE IN DECENT AGREEMENT ON THE HEMISPHERIC SCALE
WITH LONG WAVE NUMBER AND POSITION...MODELS DIFFER ON THE SRN FRINGE
OF THE MAIN BAND OF WESTERLIES ACROSS CANADA AND THE NRN PORTION OF
THE U.S. THEREFORE THERE ARE TIMING DIFFS WITH INDIVIDUAL SHORT
WAVES IN THE SPLIT FLOW THAT RESULTS FROM THE PREVIOUSLY MENTIONED
WESTERLIES AND THE WEAKER FLOW OVER THE WRN U.S. UNFORTUNATELY THIS
RESULTS IN UNCERTAINTY IN WEAKLY FORCED REGIMES SUCH AS THIS AND
HENCE MAINLY SLIGHT CHCS FOR THUNDERSTORM ACTIVITY DURING THE
WEEKEND.

SPECIFICALLY FOR THE MED RANGE...FRIDAY NIGHT INTO
SATURDAY...WESTERN STATES UPPER RIDGE WILL BUILD EWD INTO THE NRN
HIGH PLAINS AS THE ERN STATES UPPER TROUGH SLOWLY MOVES SEWD. A WEAK
UPPER PV ANOMALY MOVES QUICKLY SEWD ON THE FRINGE OF THE UPPER HIGH
ACROSS THE HIGH PLAINS...WEAKENING AS IT MOVES SOUTH. SHORT RANGE
MODELS DIFFER ON PLACEMENT OF THIS FEATURE AND THEREFORE FORCING
ASSOCIATED WITH IT...ALBEIT WEAK...IS ALSO HANDLED DIFFERENTLY. SOME
WEAK MID LEVEL FORCING DOES RESULT IN TANDEM WITH SOME ELEVATED
INSTABILITY FRIDAY NIGHT INTO THE FIRST PART OF THE DAY SATURDAY.
SMALL THUNDERSTORM CHANCES ARE IN THE FORECAST FOR THIS
SCENARIO...THOUGH CONFIDENCE ON SIGNIFICANT MEASUREABLE
PRECIPITATION IS LIMITED. HIGH TEMPS WILL INCREASE TO AT OR SLIGHTLY
ABOVE AVERAGE VALUES FOR THIS TIME OF YEAR...WITH LOWS DOING MUCH
THE SAME.

THE OVERALL ERN STATES MEAN TROUGH POSITION REMAINS IN PLACE ALONG
AND EAST OF THE MISSISSIPPI RIVER AS A STRENGTHENING ATLANTIC HIGH
DEVELOPS WWD. THE RESULT OF THE HALTING OF EWD PROGRESSION OF
SIGNIFICANT LARGE SCALE FEATURES WILL BE TO DECREASE THE
AMPLITUDE OF UPPER FEATURES ACROSS THE U.S...THOUGH THE WESTERLIES
REMAIN STRONG ACROSS SRN CANADA. QUICK MOVING UPPER PV ANOMALIES
WILL FLATTEN THE WRN STATES RIDGE WHICH WILL DEVELOP NW FLOW
ACROSS THE HIGH PLAINS BY MID WEEK. GFS SUGGESTS THE MOST
SIGNIFICANT PV ANOMALY WILL TOP THE FLATTENING RIDGE IN CONFLUENT
FLOW TUESDAY EVENING INTO WED AS UPPER HEIGHTS DECREASE ACROSS THE
NRN STATES. THIS WILL PUSH A DECENT COLD FRONT ACROSS THE PLAINS
AND WILL BE ACCOMAPNIED BY GOOD MID LEVEL FGEN SUPPORTING DEEP
LAYER LIFT ACROSS THE AREA. STEEP LOW LEVEL LASPE RATES AHEAD OF
THIS FEATURE TUESDAY AFTERNOON AND EVENING...ALONG WITH AN
INCREASING LLJ BY EVENING RESULTS IN BETTER CHANCES FOR WIDESPREAD
PRECIPITATION ACROSS WESTERN AND NORTH CENTRAL NEBRASKA FOR THIS
PERIOD. TIMING OF THE FRONTAL PASSAGE...ALLOWING UPPER DYNAMICS TO
WORK BEST WITH FAVORABLE THERMODYNAMIC SETUP...WILL BE BEST IN THE
NWRN PORTION OF THE AREA ACCORDING TO THE GFS...BUT TIMING DIFFS
BTWN THE MODELS /AS MENTIONED PREVIOUSLY/ WILL MAKE ALL THE
DIFFERENCE. STILL...FCST HAS BEST OVERALL PRECIP CHANCES IN THE
TUESDAY TO WED TIME FRAME. BEYOND THIS...PRECIP CHANCES LESSEN AS
FRONT CONTINUES TO MOVE SOUTH OF THE AREA. TYPICALLY THE MODELS
DEVELOP TOO MUCH PRECIPITATION ACROSS WRN NEBRASKA IN DAY 2 POST
FRONTAL REGIMES AND HAVE THEREFORE LIMITED CHANCES FOR THE
THURSDAY FORECAST. TEMPERATURES WILL REMAIN QUITE WARM ON MONDAY
ACROSS THE AREA...BUT BEGIN TO FALL BEYOND THIS BACK INTO THE LOW
TO MID 80S BY WED AND THURSDAY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1154 AM CDT THU JUL 31 2014

TRANQUIL CONDITIONS WILL CONTINUE THE REST OF TODAY AND TONIGHT
ACROSS THE REGION. THERE IS A WEAK FRONT WHICH EXTENDS FROM NEAR
KONL TO KBBW. THIS COULD BE THE FOCUS FOR AN ISOLATED THUNDERSTORM
LATE THIS AFTERNOON. OTHERWISE EXPECT VFR CONDITIONS AND NORTH TO
NORTHEAST WINDS 10 KTS OR LESS.


&&

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

$$

SHORT TERM...TAYLOR
LONG TERM...JWS
AVIATION...TAYLOR





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