Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 280530
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
1230 AM CDT SUN SEP 28 2014

.SYNOPSIS...
ISSUED AT 310 PM CDT SAT SEP 27 2014

AT 19Z...WATER VAPOR IMAGERY SHOWED A DEEP TROUGH OVER THE WEST
COAST WITH A CLOSED LOW CENTERED OVER CENTRAL CALIFORNIA. MOISTURE
STREAMED NORTHWARD ON THE DOWNSTREAM SIDE OF THE TROUGH WHERE LOTS
OF CLOUD COVER AND THUNDERSTORMS WERE OBSERVED FROM ARIZONA INTO
MONTANA. STRONG RIDGING WAS IN PLACE ACROSS THE REMAINDER OF THE
COUNTRY WHILE A CUTOFF UPPER LOW SPUN OVER WESTERN IOWA.
TEMPERATURES ACROSS THE PLAINS HAVE SOARED TO WELL ABOVE NORMAL
LEVELS AS WARM AIR STREAMS NORTH UNDER THE RIDGE. BY EARLY
AFTERNOON...READINGS IN THE LOW TO MID 80S WERE COMMON FOR MUCH OF
THE DAKOTAS THROUGH THE SOUTHERN PLAINS...WITH LOCAL AREAS RANGING
FROM 80 TO 85 DEGREES.

SLIGHTLY COOLER AIR ALOFT WAS OBSERVED FROM THE VICINITY OF THE IOWA
UPPER LOW DOWN INTO TEXAS. THIS LED TO STEEPER LAPSE RATES...AND
THEREFORE HAVE OBSERVED DECENT CUMULUS FIELD DEVELOP THIS
AFTERNOON.

THE UPPER LEVEL LOW ACROSS CA/NV THIS AFTN WILL LIFT THROUGH THE
ROCKIES AND INTO THE NRN PLAINS BY TUESDAY. A STRONG PACIFIC FRONT
WILL SWEEP THE FCST AREA MONDAY NIGHT AND TUESDAY PRODUCING HEAVY
RAIN ACROSS WRN NEB WITH LIGHTER AMOUNTS EAST. COOLER WEATHER
PREVAILS WEDNESDAY THROUGH SATURDAY.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 310 PM CDT SAT SEP 27 2014

THE UPPER LOW OVER IOWA WILL STAY FAIRLY STATIONARY OR MAY EVEN
MEANDER WESTWARD SLIGHTLY TONIGHT. MODELS ARE SHOWING A WEAK IMPULSE
OF ENERGY ROTATING AROUND THE LOW...WHICH WOULD MOVE ACROSS THE
NORTHEAST PART OF THE FORECAST AREA AFTER 06Z TONIGHT. AT THE SAME
TIME...IT IS PROJECTED THAT THE LOW LEVEL JET WILL BE VEERING TO THE
NORTHEAST INTO THIS SAME AREA WHICH COULD BRING ENOUGH LIFT TO
DEVELOP SOME SHOWERS LATE TONIGHT AND EARLY SUNDAY MORNING.
TIME-FRAME LOOKS TO BE 09Z TO 15Z CURRENTLY. BELIEVE THERE WILL BE
DEVELOPMENT IN A NORTH TO SOUTH LINE SOMEWHERE FROM NORTH CENTRAL
INTO CENTRAL NEBRASKA. CONFIDENCE ISN/T REAL HIGH THOUGH IN
PLACEMENT AND AS COVERAGE WILL LIKELY BE ISOLATED TO
SCATTERED...HAVE SLIGHT CHANCES FOR SHOWERS IN THE FORECAST
CURRENTLY.

ALSO LOOKING AT POTENTIAL FOR FOG TONIGHT OVER THE WESTERN PART OF
THE FORECAST AREA. THE NAM IS HIGHLIGHTING A STRONG INCREASE IN LOW
LEVEL MOISTURE MAINLY WEST OF HIGHWAY 83 WHILE THE GFS IS FURTHER
EAST. THAT BEING SAID...THE RAP KEEPS MINIMAL LOW LEVEL MOISTURE
OVER THE LOCAL AREA...AS IT KEEPS THE POTENTIAL BETTER OVER WESTERN
KANSAS. THESE DIFFERENCES MAINLY RELY ON THE PLACEMENT OF THE
SURFACE LOW. WITH LOWER CONFIDENCE...HAVE NOT ADDED FOG INTO THE
FORECAST AT THIS TIME...BUT WILL PASS ON POTENTIAL TO ONCOMING
SHIFT.

LOOKING THEN INTO SUNDAY...WITH THE THOUGHT THAT ANY FOG AND/OR
CLOUD COVER THAT MAY LINGER INTO THE MORNING HOURS WILL QUICKLY
DISSIPATE...TEMPERATURES ALOFT WILL BE SIMILAR TO TODAY...AND WITH
DEEP MIXING EXPECTED...SHOULD ONCE AGAIN SEE HIGHS IN THE 80S.

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 310 PM CDT SAT SEP 27 2014

SUNDAY NIGHT THROUGH TUESDAY...THE ECM AND NAM ARE THE SLOWEST SOLNS
WITH THE PASSAGE OF THE PACIFIC FRONT MONDAY NIGHT AND TUESDAY. THUS
RAIN CHANCES ARE DELAYED UNTIL EARLY MONDAY MORNING. IT IS POSSIBLE
THE FASTER AND STRONGER GFS/GEM SOLNS ARE A BETTER FCST BUT GIVEN
THE MODELS HAVE BEEN TRENDING SLOWER OVERALL...THE NAM/ECM APPEARS TO
BE THE BEST FIT.

A SOLID PV ANOMALY WILL BE APPROACHING THE FCST AREA MONDAY AFTN AND
THIS SHOULD PROVIDE AMPLE SUPPORT FOR SCATTERED TO NUMEROUS TSTMS
INTO THE EVENING. COLD AIR ALOFT AND PWS OVER 200 PERCENT OF NORMAL
ARE EXPECTED TO PRODUCE HEAVY RAIN...MAINLY ALONG AND WEST OF
HIGHWAY 61. THE NAM/ECM SOLN PRODUCES 1 TO 1.5 INCHES OF RAIN IN THE
WEST DOWN TO 1/4 INCH IN THE EAST. POPS ARE LIMITED TO THE LIKELY
CATEGORY FOR THIS FORECAST AS MODEL TIMING IS THE MAIN CONCERN FOR
THE FORECAST.

SOUTHEAST WINDS MONDAY INCREASE TO 25 MPH WITH GUSTS TO 35 MPH. THE
GFS/GEM MODELS SUGGEST 30 MPH WINDS GUSTING TO 40 MPH. THE MAX
TEMPERATURE FORECAST COOLS INTO THE UPPER 70S TO LOWER 80S. AN
INCREASE IN MID LEVEL CLOUDINESS IS EXPECTED WITH THE APPROACH OF
THE UPPER LOW.

SPC SUGGESTED AMPLE SHEAR WILL DEVELOP MONDAY AFTN AS SOUTHERLY
H500MB WINDS INCREASE TO 60 KT. THIS IS TRUE BUT COUPLED WITH THE
STRONG LOWER LEVEL SOUTHERLY WINDS...20 TO 30 KT...THE EFFECTIVE
SHEAR APPEARS WEAK NEAR 20 TO 30 KT AND THE NAM SOUNDINGS SUGGEST
NARROW CAPE. THE SIGNIFICANT SEVERE PARAMETER IN ALL SOLNS SEEMS TO
SUPPORT THE 5 PERCENT SEVERE WEATHER POTENTIAL MONDAY.

THE PACIFIC FRONT MOVES THROUGH THE FCST AREA TUESDAY. THE H500MB
COLD POOL CENTERED OVER SD SHOULD CONTINUE TO SUPPORT CONVECTION
ACROSS NRN NEB WITH HIGHS IN THE 60S TO LOWER 70S. THE 500M AGL
WINDS IN THE GFS...ECM AND GEM INCREASE TO OVER 30 KT ACROSS NRN NEB
DURING THE AFTN WHICH WOULD SUPPORT A WIND ADVISORY. THE 12Z ECM HAS
TRENDED TOWARD THE DEEPER GFS/GEM LOW PRESSURE SYSTEM SOLN. THE
STRONG WINDS DEVELOP IN CONJUNCTION WITH THE PV ANOMALY AND H700MB
WINDS OF 45 TO 55 KT SHOWN IN THESE MODELS.

TUESDAY NIGHT THROUGH SATURDAY...STRONG COLD FRONTS MOVE THROUGH
WEDNESDAY NIGHT AND THURSDAY NIGHT. BOTH SUGGEST A CHANCE OF
SHOWERS. THE SECOND COLD FRONT SENDS H850MB TEMPERATURES TO NEAR 0C
FRIDAY MORNING. HIGHS FRIDAY RISE INTO JUST THE 50S TO LOWER 60S
WHICH WOULD SUPPORT FROST SATURDAY MORNING BUT THIS HIGH MOVES OFF
VERY QUICKLY AND WARM AIR RETURNS TO THE FCST AREA FRIDAY NIGHT.
OTHERWISE HIGHS RISE INTO THE 60S AND 70S EACH DAY.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1229 AM CDT SUN SEP 28 2014

VFR CONDITIONS EXPECTED TONIGHT AND TOMORROW. SOME LIGHT
RAINSHOWERS OR SPRINKLES MAY DEVELOP NEAR SUNRISE BETWEEN KBBW
AND KONL. MIFG OR BR IS ALSO POSSIBLE ALONG THE PLATTE RIVER
VALLEY BETWEEN 2912Z AND 2914Z. SOUTHERLY WINDS WILL INCREASE
OVER WESTERN NEBRASKA SUNDAY AFTERNOON.

&&

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

&&

$$

SYNOPSIS...BROOKS/CDC
SHORT TERM...BROOKS
LONG TERM...CDC
AVIATION...POWER




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