Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 301736
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
1236 PM CDT SAT AUG 30 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 328 AM CDT SAT AUG 30 2014

REMNANT CONVECTIVE DEBRIS WILL CONTINUE TO SLIDE SOUTHEASTWARD
ACROSS SW NEB THROUGH SUNRISE WHILE STRATUS CONTINUES TO DROP
SOUTHWARD ACROSS ERN SD. RAP LOW LEVEL RH PROGS WOULD SUGGEST THE
STRATUS WILL SAG TO NEAR THE NIOBRARA VALLEY BY 12-15Z OR SO AND THE
HRRR HAS LOW CLOUDS EVEN FURTHER SOUTH. HAVE ADJUSTED SKY COVER FOR
THAT. PREVIOUS FCST HAD MENTION OF FOG ALSO IN THE NERN ZONES AS A
RESULT OF PREVIOUS 24 HR RAINFALL AND BELIEVE THAT THIS WOULD ALSO
BE ALONG THE FRINGE OF LOWER CLOUDS WHICH IS A TYPICAL EVOLUTION
ANYWAY. SO HAVE LEFT THE MENTION OF FOG AS IT WAS...MORE PATCHY TWD
THE SWRN PORTION OF THE AREA...ALL OF WHICH SHOULD BURN OFF BY MID
MORNING. ON THE LARGER SCALE...A TRANSITORY UPPER RIDGE WILL
PROGRESS ACROSS THE AREA TODAY AS THE NRN STREAM REMAINS
ACTIVE...WITH LARGE SCALE SUBSIDENCE IN CONTROL THROUGH THE DAY.
NEXT LONG WAVE TROUGH IS DEVELOPING ACROSS THE PAC NW WITH A LEAD PV
ANOMALY MOVING QUICKLY ACROSS THE NRN ROCKIES TODAY. A LEE SIDE SFC
TROUGH WILL DEVELOP FROM WRN SD INTO THE TX PANHANDLE BY LATE
AFTERNOON AND THE RESPONSE WILL BE AN INCREASE OF SRLY WINDS AND
DEVELOPING THERMAL RIDGE ACROSS THE HIGH PLAINS. ON THE ERN EDGE OF
THE THERMAL RIDGE /WHICH WILL BE RETREATING NWD THROUGH THE DAY/
HIGHER DEW POINTS WILL EXIST. THERE IS WEAK CONVERGENCE ASSOCIATED
WITH THIS FEATURE AS IT RETREATS DURING THE DAY...BUT DEEP LAYER
LIFT DOES NOT LOOK EVIDENT. MAX TEMPS SHOULD CREEP A FEW DEGREES
HIGHER TODAY AS A RESULT OF THE DEVELOPING THERMAL RIDGE...MOST
NOTABLY IN THE SOUTHWEST AND EASTERN PANHANDLE.

ATTENTION THEN TURNS TO LOWERING HEIGHTS ACROSS THE NRN PLAINS SAT
NIGHT AND SUNDAY. LEAD PV ANOMALY /WHICH IS BEST DEFINED INITIALLY
BY 30.00Z GFS/ WILL APPROACH THE PANHANDLE BY LATE SAT
AFTERNOON...THOUGH WEAKENING AS IT MOVES INTO THE RIDGE POSITION.
CONVERGENCE ALONG THE LEE TROUGH IS WEAK INITIALLY BUT WILL LIKELY
PROVIDE ENOUGH LIFT ALONG WITH THE HIGHER TERRAIN FURTHER WEST TO
DEVELOP AT LEAST ISOLATED TSRA WHICH WILL MOVE EWD SAT EVE...THOUGH
LOW LEVELS WILL BE FAIRLY DRY AS SUGGESTED BY WRN FCST SOUNDINGS.
HIGH PLAINS NOCTURNAL LLJ DEVELOPS THROUGH SAT EVE WHICH WILL ADVECT
MID LEVEL INSTABILITY INTO THE CENTRAL PORTION OF THE STATE AND
SHOULD MAINTAIN ENOUGH DEEP LAYER LIFT TO SUPPORT ISOLATED TSRA INTO
THE WRN PORTION OF THE FCST AREA LATE EVE AND EARLY MORNING. NAM/GEM
AND GFS SUPPORT THIS THOUGH HIRES CAMS ARE NOT SO EAGER TO DEVELOP
PRECIP. GRIDS WILL INCLUDE ISOLATED TSRA MENTION...PROGRESSING
ACROSS THE AREA THROUGH SAT NIGHT.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 328 AM CDT SAT AUG 30 2014

12Z SUNDAY AND BEYOND. ZONAL UPPER LEVEL FLOW TO PREVAIL ACROSS
MUCH OF THE CONTIGUOUS 48 TO START OFF THE EXTENDED FORECAST
PERIOD...BUT THE PATTERN DOES SHIFT SLIGHTLY SOUTHWESTERLY ACROSS
THE HIGH PLAINS ON SUNDAY WITH THE APPROACH OF AN UPPER
TROPOSPHERIC NORTHERN ROCKIES SHORTWAVE. THE APPROACH OF THE
SHORTWAVE WILL ALLOW AN AREA OF SFC LOW PRESSURE AND ATTENDANT
BAROCLINIC ZONE TO MOVE EAST ACROSS THE REGION THROUGH THE DAY ON
SUNDAY...POTENTIALLY SETTING THE STAGE FOR AN ACTIVE SEVERE
WEATHER PATTERN ACROSS OUR EAST BY LATE AFTERNOON. GUIDANCE
CONTINUES TO FAVOR EAST OF A KLBF TO KANW LINE WHERE THERMAL
ADVECTION IS SHOWN AND CONVERGENCE ALONG THE BAROCLINIC ZONE WILL
BE MAXIMIZED. THE GFS...NAM...AND EC ALL SHOW CONVECTION FIRING IN
THIS AREA...SO GIVEN THE GOOD AGREEMENT OF NOT ONLY THE FINER
DETAILS BUT ALSO THE LARGER SCALE PATTERN...FELT THAT CONFIDENCE
WAS ENOUGH TO INTRODUCE LIKELY/S INTO THE FORECAST ACROSS OUR FAR
EAST /EAST OF A MAYWOOD TO NAPER LINE/...WITH SOLID CHANCE POPS
/40-50%/ FOR LOCATIONS EAST OF THE KANW TO KLBF LINE SUNDAY
AFTERNOON. THE UPPER TROPOSPHERIC FLOW REMAINS FAIRLY
PROGRESSIVE...SO STORMS SHOULD BE LARGELY REMOVED OF THE FORECAST
AREA BY 06Z MONDAY. SFC TD/S ARE PROJECTED TO REBOUND BACK INTO
THE LOWER TO MID 60S ACROSS OUR EAST AND WHEN COMBINED WITH STEEP
LOWER TO MID LEVEL LAPSE RATES WHICH PROMOTE SB POTENTIAL ENERGY
IN EXCESS OF 2500 J/KG...ROBUST UPDRAFTS ARE ANTICIPATED. DEEP
LAYER SHEAR IS SHOWN TO BE QUITE FAVORABLE FOR SEVERE
WEATHER...WITH THE MODELS PEGGING UPWARDS OF 40-50KTS 0-6KM BULK
SHEAR...LARGE HAIL WILL BE POSSIBLE. THE UPDRAFTS SHOULD QUICKLY
CONGEAL ALONG THE BAROCLINIC ZONE INTO A QUASI-LINEAR CONVECTIVE
BAND WHICH WOULD PROMOTE DAMAGING THUNDERSTORM WIND INTO THE
EVENING.

INTO EARLY NEXT WEEK...THERE REMAINS SOME DISCREPANCIES ON THE
TIMING OF THE EXITING TROUGH...MOST NOTABLY...THE EC RETAINS A PIECE
OF ENERGY WEST OF THE FORECAST AREA...BUT BRINGS IT THROUGH MONDAY
NIGHT.  THE EC GENERATES LIGHT QPF ACROSS MUCH OF THE FORECAST AREA
DURING THIS TIME PERIOD.  THE GFS IN COMPARISON IS DRY AND LACKS
MUCH OF THE EVIDENCE SUPPORTING THIS ADDITIONAL TROPOSPHERIC
PERTURBATION.  GIVEN THE UNCERTAINTY...WENT AHEAD AND SCALED BACK
POPS MONDAY EVENING INTO EARLY TUESDAY...BUT WILL KEEP A SLIGHT
MENTION GOING.

BEYOND EARLY TUESDAY...THE CR ALLBLEND PROCEDURE PROJECTED A DRY
FORECAST THROUGH THURSDAY OF NEXT WEEK...AND THERE ARE NO ARGUMENTS
HERE AS AN OVERALL LACK OF OMEGA WOULD BE ANTICIPATED AS THE STORM
TRACK SHIFTS NORTH AND LOW AMPLITUDE RIDGING ENCOMPASSES MUCH OF THE
CONUS.  LATE IN THE EXTENDED THERE MAY BE ANOTHER SHORTWAVE
IMPACTING THE CENTRAL PLAINS...HOWEVER THE MODELS SEEM TO BE BACKING
OFF THIS SOLUTION A BIT...FOCUSING THE BEST POTENTIAL WELL NORTH OF
THE CWA.  WILL KEEP THE PROCEDURE UNCHANGED FOR NOW.

NOT ANTICIPATING ANY VIOLENT TEMPERATURE CHANGES THROUGH THE
EXTENDED PERIODS...BUT WITH EACH FRONTAL PASSAGE...TEMPERATURES WILL
MODERATE SOME.  THE WARMEST DAY APPEARS TO COME MID-WEEK...AS HIGHS
ON WEDNESDAY ARE FORECAST TO APPROACH THE UPPER 80S TO LOWER 90S FOR
MOST LOCATIONS.  OTHERWISE HIGHS IN THE 70S TO LOW TO MID 80S SHOULD
PREVAIL FOR MOST DAYS.  LOWS IN THE 50S AND 60S SEEM TO BE THE NORM
OVER THE NEXT 7 DAYS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1234 PM CDT SAT AUG 30 2014

VFR CONDITIONS WILL PREVAIL ACROSS WESTERN AND NORTH CENTRAL
NEBRASKA THROUGH THE NEXT 24 HOURS. ISOLATED SHOWERS AND STORMS
MAY MOVE EAST OUT OF THE PANHANDLE AFTER 3Z TONIGHT...HOWEVER
LIMITED SPATIAL COVERAGE AND LOW FORECASTER CONFIDENCE DO NOT
WARRANT ANY MENTION OF -TSRA IN THE TAFS AT THIS TIME. A COLD
FRONT WILL MOVE THROUGH THE AREA TOMORROW MORNING...SWITCHING THE
WIND DIRECTION TO THE NORTHWEST.

&&

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

$$

SHORT TERM...JWS
LONG TERM...JACOBS
AVIATION...MARTIN






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