Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 311810
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
110 PM 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 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 108 PM CDT FRI JUL 31 2015

ANOTHER WARM AFTERNOON EXPECTED WITH ISOLATED THUNDERSTORMS
EXPECTED. AT THIS TIME THE THUNDERSTORMS LOOK TO BE FOCUSED ON AN
EAST/WEST BOUNDARY ACROSS CENTRAL NEBRASKA. THIS PLACED BOTH TAF
SITES IN A LESS THAN FAVORABLE LOCATION AND DID NOT INCLUDE IN THE
TAF. THUNDERSTORMS EXPECTED TO DIMINISH AFTER SUNSET. HOWEVER THE
BOUNDARY REMAINS ACROSS THE AREA...AND WILL LIFT NORTH. CANNOT
RULE OUT SOME ISOLD STORMS ACROSS NORTHERN NEB OVERNIGHT. COVERAGE
DOES NOT WARRANT MENTION IN THE KVTN TAF YET.

&&

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

&&

$$

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



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