Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 302020
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
320 PM CDT THU JUL 30 2015

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 319 PM CDT THU JUL 30 2015

PRIMARY FORECAST CONCERN OVER THE SHORT TERM /THROUGH FRIDAY
AFTERNOON/ WILL BE THUNDERSTORM POTENTIAL. HIGH RESOLUTION
MODELS...INCLUDING HRRR...RAP...AND 4KM WRF...ARE CONSISTENT WITH
DEVELOPING ISOLATED THUNDERSTORMS OVER THE SANDHILLS AND SOUTHWEST
NEBRASKA THIS EVENING. KEPT THE SLIGHT CHANCE OF THUNDER FROM THE
PREVIOUS FORECAST...BUT BROUGHT IT NORTH OF NEBRASKA HIGHWAY 2. MID
LEVEL INSTABILITY IS PRESENT ACROSS THE AREA AS SEEN BY THE
EXPANDING CUMULUS FIELD ACROSS THE CENTRAL SANDHILLS AND A SECOND CU
FIELD ALONG THE COLORADO BORDER THAT FORMED SHORTLY AFTER 19Z. IN
ADDITION...FORECAST SOUNDINGS SHOW LAPSE RATES AROUND 9C/KM UP TO
600HPA. A SURFACE BOUNDARY SITS ACROSS THE NORTHERN FORECAST AREA
WITH 19Z DEW POINTS IN THE 40S AT VTN AND IEN TO NEAR 60 AT TIF AND
ONL. DESPITE SUFFICIENT MUCAPE /AROUND 2000 J/KG/ ACROSS MOST OF THE
FORECAST AREA...STEEP LAPSE RATES...AND THE RIGHT REAR OF A 250HPA
JET OVERHEAD...BULK SHEAR SEEMS TO BE LACKING. THUS SEVERE WEATHER
IS NOT ANTICIPATED. GIVEN A BELOW AVERAGE PWAT VALUE FROM THE 12Z
LBF RAOB AND STORM MOTION VECTOR OF 20 KTS...FLOODING IS NOT
EXPECTED EITHER. ANY THUNDERSTORM ACTIVITY THAT DEVELOPS WILL LIKELY
DIMINISH BY 09Z FRIDAY.

USED A MAV/MET BLEND FOR MIN TEMPS OVERNIGHT...WHICH COOLED SLIGHTLY
ACROSS THE NORTHWEST FOR MAINLY CLEAR SKIES AND NORTHWEST FLOW AND
WARMED SLIGHTLY ACROSS THE SOUTHEAST FOR A BIT MORE CLOUD COVER AND
LOW LEVEL MOISTURE. INCREASED MAX TEMPS A COUPLE DEGREES FRIDAY PER
MOS GUIDANCE AND NAM AND GFS PUSHING 850HPA TEMPS TO 25-27C.

THUNDERSTORMS ARE POSSIBLE FOR FRIDAY AFTERNOON ACROSS MOST OF THE
FORECAST AREA AS WELL. THE HIGHEST DEW POINTS APPEAR TO BE OVER
CENTRAL AND EASTERN NEBRASKA...BUT SOUTHERLY LOW LEVEL FLOW EXTENDS
INTO THE NEBRASKA PANHANDLE AS WELL. NAM FORECAST SOUNDINGS SHOW A
DEEP MIXED LAYER AND A MOIST MID LEVEL...AND THE UPPER JET STILL
EXISTS OVER NORTHEAST NEBRASKA. WITH BETTER BULK SHEAR THAN THURSDAY
AND CONTINUED INSTABILITY AND CAPE...STRONG STORMS CANNOT BE RULED
OUT...ESPECIALLY EAST OF A IML TO BBW LINE.

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 319 PM CDT THU JUL 30 2015

FRIDAY NIGHT THROUGH SUNDAY...WHATEVER CONVECTION DEVELOPS FRIDAY
AFTN SHOULD DISSIPATE IN THE EVENING GIVEN THE WEAK FORCING ALOFT
AND LACK OF LOW LEVEL FORCING IN THE FORM OF AN 850MB NOCTURNAL JET.

ANOTHER OPPORTUNITY FOR THUNDERSTORMS DEVELOPS SATURDAY BEGINNING
NEAR ONEILL AND SPREADING SOUTH AND WEST AS A WEAK COLD FRONT DROPS
SOUTH. INSTABILITY ISNT THE GREATEST...NEAR OR BELOW 2000 J/KG
MLCAPE...BUT K INDICES SOAR INTO THE 40S WITH AMBIENT PWAT AROUND
1.33 INCHES. THERE IS ALSO A 60 TO 70 KT JET AT 300 MB WITH BULK
SHEAR NEAR 40 KT CALCULATED TO 400 MB. IF A FEW STORMS CAN BUILD
INTO THE 300 MB WINDS THEN STRONG SHEAR WILL DEVELOP SUPPORTING A
STRONG OR SEVERE STORM. POPS ARE LIMITED TO 30 PERCENT SATURDAY AND
ACTIVITY SHOULD DIMINISH IN THE EVENING.

LOW PRESSURE WILL SLOWLY MIGRATE SOUTH THROUGH THE NRN HIGH PLAINS
AN INTO SOUTH DAKOTA. THIS WILL OBVIOUSLY DRAW WARM AIR OFF THE
ROCKIES. SUNDAY APPEARS DRY AND WARM WITH HIGHS IN THE LOW TO MID
90S. A WEAK COLD FRONT DROPS THROUGH SATURDAY NIGHT AND LIFTS BACK
NORTH SUNDAY AFTERNOON. HIGHS SATURDAY RISE INTO THE LOWER 90S.

SUNDAY NIGHT THROUGH THURSDAY...LOW PRESSURE WILL CONTINUE ALONG THE
NRN AND CNTL HIGH PLAINS BUT IT APPEARS HIGH PRESSURE WILL BACK INTO
NCNTL NEB FORMING A STATIONARY FRONT DRAPED NORTH AND SOUTH ACROSS
WRN NEB. THIS FRONT AND THE UPPER LEVEL FORCING IN THE AMPLIFIED
NORTHWEST FLOW WILL BE THE CATALYST FOR THUNDERSTORM DEVELOPMENT
MONDAY NIGHT THROUGH THURSDAY. THE ECM IS LEADING THE WAY AND THE
GFS IS FOLLOWING THE MORE WESTWARD ECM. IN FACT THE ECM KEEPS HIGH
DEW POINTS ACROSS NCNTL NEB AND PRODUCES 1 TO 2 INCHES OF RAINFALL
WITH LESS THAN AN INCH ACROSS WRN NEB.

HIGHS MONDAY IN THE LOWER 90S FALL BACK INTO THE 80S TUESDAY AND
BEYOND EAST OF HIGHWAY 83. IT IS POSSIBLE THAT THE FRONT COULD BE
POSITIONED A BIT FARTHER TOWARD THE GFS WHICH WOULD PRODUCE 90S
ACROSS WRN NEB AND 80S EAST. THIS IS CLOSE TO THE OFFICIAL FORECAST
VS THE ECM WHICH INDICATES 80S THROUGHOUT THE FCST AREA.

POPS ARE LIMITED TO 30 PERCENT MONDAY AND BEYOND.  THIS FOLLOWS THE
CLIMATOLOGY OF JULY RAINFALL PATTERNS...SPOTTY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1223 PM CDT THU JUL 30 2015

VFR CONDITIONS WILL CONTINUE ACROSS WESTERN NEBRASKA THROUGH
FRIDAY AFTERNOON. ISOLATED THUNDERSTORMS ARE POSSIBLE THIS EVENING
ACROSS SOUTHWEST NEBRASKA...INCLUDING KLBF. ANY THUNDERSTORM
ACTIVITY SHOULD BE DISSIPATED BY 09Z.

&&

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

$$

SHORT TERM...DS
LONG TERM...CDC
AVIATION...DS



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