Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 311128
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
628 AM CDT FRI JUL 31 2015

.SYNOPSIS...
ISSUED AT 407 AM CDT FRI JUL 31 2015

THE OVERALL H5 PATTERN REMAINS LARGELY UNCHANGED FROM 24
HOURS AGO. LOW PRESSURE WAS NOTED OVER SRN PORTIONS OF HUDSON
BAY...WITH A TROUGH EXTENDING SWD INTO THE EASTERN GREAT LAKES.
UPSTREAM OF THE LOW...WEST NORTHWESTERLY FLOW EXTENDED FROM BRITISH
COLUMBIA...ESE INTO THE UPPER MIDWEST AND MID ATLANTIC STATES.
ACROSS THE SRN CONUS...HIGH PRESSURE REMAINED ANCHORED ACROSS NRN TX
TONIGHT. ON THE WESTERN PERIPHERY OF THIS FEATURE...MONSOONAL
MOISTURE CONTINUED TO PUSH NORTH FROM MEXICO INTO THE FOUR CORNERS
REGION. THUNDERSTORMS...WHICH WERE PRESENT ACROSS WEST CENTRAL AND
SOUTHWESTERN NEBRASKA EARLIER THIS EVENING...HAVE DISSIPATED AS THEY
MOVED EAST. BASED ON THE LATEST SATELLITE IMAGERY...REMNANTS OF THE
THUNDERSTORMS WERE NOW OVER PORTIONS OF NORTHEASTERN KS. ANOTHER
AREA OF THUNDERSTORMS WAS PRESENT OVER NERN NEBRASKA ATTM. THIS
ACTIVITY CONTINUES TO DRIFT TO THE SOUTH SOUTHEAST PARALLEL TO THE
MISSOURI RIVER. ACROSS WESTERN AND NORTH CENTRAL NEBRASKA...SKIES
WERE CLEAR AND TEMPERATURES RANGED FROM 61 AT
VALENTINE...THEDFORD...AND OGALLALA TO 66 AT BROKEN BOW AS OF 3 AM

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 407 AM CDT FRI JUL 31 2015

TODAY AND TONIGHT...OVER THE NEXT 24
HOURS...PRECIPITATION CHANCES LATER THIS AFTERNOON AND TONIGHT IS
THE MAIN FORECAST CHALLENGE. FOR TODAY...ANOTHER ROUND OF ISOLATED
TO WIDELY SCATTERED THUNDERSTORMS IS EXPECTED LATER THIS AFTERNOON
AND THIS EVENING...INVOF A STALLED OUT H85 FRONT. ATTM...THIS
FEATURE IS LOCATED ALONG A LINE FROM SRN SHERIDAN COUNTY...TO SRN
CUSTER COUNTY. BOTH THE LATEST NAM AND GFS SOLNS HAVE THIS FEATURE
ROUGHLY ALONG THIS LINE THIS AFTERNOON...SO CONFIDENCE IN THIS LOW
LEVEL FOCAL POINT FOR CONVECTION IS DECENT ATTM. WITH SURFACE
HEATING...SB CAPES REACH 2000 TO 3000 J/KG DURING PEAK AFTERNOON
HEATING ALONG WITH STEEP LAPSE RATES AND MOISTURE CONVERGENCE ALONG
THE H85 FRONT...THUNDERSTORM CHANCES WILL INCREASE AFTER MID
AFTERNOON. H5 STEERING WINDS ARE ORIENTED PARALLEL TO THE FRONT THIS
AFTERNOON...WHICH WOULD USUALLY LEND SUPPORT TO THE POTENTIAL FOR
HEAVY RAIN...HOWEVER...PWATS ARE ONLY AROUND 1.25 INCHES...AND K
INDEXES ARE UNDER 40...SO DO NOT FEEL CONFIDENT ENOUGH TO MENTION A
HEAVY RAIN THREAT IN THE FORECAST. BULK SHEAR INVOF THE FRONT THIS
AFTERNOON IS 30 TO 35 KTS WHICH WOULD SUPPORT A STRONG STORM OR
TWO...HOWEVER AT THIS TIME...THE THREAT FOR WIDESPREAD SEVERE STORMS
APPEARS LOW ATTM. AS THE BOUNDARY LAYER COOLS AND STABILIZES THIS
EVENING...THE THREAT FOR THUNDERSTORMS SHOULD END TEMPORAIRLY IN THE
VICINITY OF THE FRONTAL BOUNDARY. OVERNIGHT A SECOND ROUND OF
THUNDERSTORMS MAY IMPACT NORTHERN NEBRASKA. THIS CONVECTION IS IN
ASSOCIATION WITH A MID LEVEL DISTURBANCE AND DECENT MID LEVEL WAA
OVERNIGHT. DECIDED TO KEEP POPS IN THE 15 TO 20 PERCENT RANGE AS A
MEAGER LOW LEVEL JET EXISTS AND THERE IS NOT MUCH OF A SURFACE
FOCUS. HIGHS TODAY WILL BE IN THE UPPER 80S TO AROUND 90 AND
UTILIZED A BLEND OF THE MET AND MAV GUIDANCE...WEIGHTED MORE TOWARD
THE COOLER MET GUIDANCE AS IT PERFORMED BETTER YESTERDAY COMPARED TO
THE WARMER MAV GUIDANCE. LOWS TONIGHT WILL BE IN THE UPPER 50S TO
AROUND 60 AND UTILIZED A 50/50 BLEND OF THE MAV AND MET NUMBERS AS
THEY WERE NEARLY IDENTICAL FOR LOWS TONIGHT.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 407 AM CDT FRI JUL 31 2015

SOME CHANCE FOR THUNDERSTORMS WILL REMAIN IN THE FORECAST FOR
SATURDAY AS A WEAK COLD FRONT DROPS INTO NORTHWEST NEBRASKA LATE
IN THE AFTERNOON. THE BETTER CHANCES THOUGH APPEAR TO BE EAST OF
THE AREA IN IOWA ALONG A WARM FRONT. NEVERTHELESS WITH THE WEAK
COLD FRONT SERVING AS A FOCUS FOR DEVELOPMENT...WILL MAINTAIN THE
SLIGHT TO CHANCE POPS ALREADY IN THE FORECAST. THE LIMITING
FACTORS FOR WIDESPREAD STORM DEVELOPMENT WILL LIKELY BE WEAK
FORCING ALOFT AND THE MIXING OUT THE LOW LEVEL MOISTURE...WITH DEW
POINTS DROPPING TO THE MID AND UPPER 50S ACROSS MOST OF THE AREA
BY AFTERNOON. SOME LOWER 60S HANGING ON IN PORTIONS OF NORTH
CENTRAL AND CENTRAL NEBRASKA. STEEP MID LEVEL LAPSE RATES MAY
COMPENSATE SOME FOR THE LIMITED LOW LEVEL MOISTURE...AND MLCAPE
VALUES SHOULD RANGE FROM 1000 TO 2000 J/KG DURING PEAK HEATING.
STORMS THAT DEVELOP WILL BE HIGH BASED...WITH 0 TO 6 KM SHEAR OF
35 TO 40 KTS WILL PROMOTE POSSIBLE ROTATING STORMS. ANY STORM
THAT CAN TAKE ON SUPERCELL CHARACTERISTICS WILL HAVE THE POTENTIAL
TO PRODUCE LOCALLY DAMAGING WINDS DUE TO THE WELL MIXED DEEP
BOUNDARY LAYER BENEATH THE CLOUD/STORM BASE. LARGE HAIL WILL ALSO
BE POSSIBLE..BUT LESS OF A THREAT THEN DAMAGING WINDS. THE TORNADO
POTENTIAL IS VERY LOW DUE TO HIGH CLOUD BASES AND UNFAVORABLE LOW
LEVEL WINDS.

SCATTERED STORMS WILL LINGER INTO THE EVENING HOURS...WITH THE
ECMWF THE MOST AGGRESSIVE IN DEVELOPING AN MCS ACROSS NORTHERN
NEBRASKA AND SLIDING IT EAST INTO EASTERN NEBRASKA OVERNIGHT. THE
GFS AND NAM ARE SILENT WITH THIS SCENARIO...SO WILL NOT GO HIGH
WITH POPS BUT EXPAND THE SLIGHT CHANCES IN CASE THE ECMWF IS
CORRECT. IT APPEARS THAT THE ECMWF IS A BIT STRONGER WITH A
PERTURBATION ALOFT...AND THEREFORE LEADS TO MORE CONVECTION. WILL
CONTINUE TO MONITOR THIS.

THE AFOREMENTIONED WEAK COLD FRONT MOVES THOUGH THE AREA SATURDAY
NIGHT AND STALLS SUNDAY ALONG THE NEB/KS BORDER. SHOULD REMAIN DRY
DESPITE THE WEAK FRONT RETURNING  NORTH ACROSS THE AREA AS A WARM
FRONT SUNDAY NIGHT. RISING HEIGHTS DUE TO THE UPPER LEVEL RIDGE
EXPANDING NORTH FROM THE SOUTHERN PLAINS AND VERY WEAK FORCING
ALOFT SHOULD KEEP THUNDERSTORM ACTIVITY FROM DEVELOPING.

LATER MONDAY A SHORTWAVE ALOFT WILL ATTEMPT TO MOVE INTO THE
RIDGE FROM THE WEST. WHILE NOT DISLODGING THE RIDGE...IT WILL
FLATTEN A BIT WITH HEIGHTS LOWERING SLIGHTLY ACROSS THE AREA.
WILL INCLUDE A SLIGHT CHANCE FOR STORMS AS THIS OCCURS LATER
MONDAY. CENTER OF THE UPPER LEVEL RIDGE THEN APPEARS TO SET UP
SHOP ACROSS THE TX PANHANDLE FOR THE REMAINDER OF THE WEEK. THIS
SETS UP A RING OF FIRE TYPE PATTERN ACROSS OUR AREA...WITH SEVERAL
WEAK DISTURBANCES RIDING EAST THROUGH THE AREA ON THE NORTHERN
PERIPHERY OF THE UPPER RIDGE. AT LEAST A SLIGHT CHANCE FOR STORMS
IS WARRANTED IN THIS TYPE OF PATTERN. LATER FORECASTS WILL BETTER
PINPOINT HIGHER CHANCES AS UPPER WAVES BECOME BETTER DEFINED BOTH
IN STRENGTH AND TIMING.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 624 AM CDT FRI JUL 31 2015

EXPECT MAINLY CLEAR SKIES THIS MORNING WITH INCREASING MID LEVEL
CLOUDINESS LATER THIS AFTERNOON. CIGS IN GENERAL...WILL RANGE FROM
12000 TO 25000 FT AGL LATER THIS AFTERNOON THROUGH THIS EVENING.
SKIES WILL CLEAR OVERNIGHT AT BOTH TERMINALS. ISOLATED
THUNDERSTROMS ARE POSSIBLE ACROSS THE SANDHILLS AND NORTH CENTRAL
NEBRASKA DURING THE AFTERNOON AND EVENING HOURS. COVERAGE OF
STORMS WILL BE ISOLATED AT BEST...SO WILL NOT INCLUDE MENTION OF
THUNDERSTORMS IN THE 12Z KLBF AND KVTN TERMINAL FORECSATS.

&&

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

$$

SYNOPSIS...CLB
SHORT TERM...CLB
LONG TERM...TAYLOR
AVIATION...CLB


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