Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 030406
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
1106 PM CDT WED SEP 2 2015

.SYNOPSIS...
ISSUED AT 322 PM CDT WED SEP 2 2015

H5 ANALYSIS THIS MORNING HAD LOW PRESSURE OVER WEST
CENTRAL PORTIONS OF BRITISH COLUMBIA WITH A TROUGH EXTENDING TO THE
SOUTHWEST INTO THE NERN PACIFIC. SOUTH OF THE LOW 50 TO 60 METER HT
FALLS WERE NOTED OVER OREGON AND WASHINGTION STATE WITH A 50 KT JET
STREAK COLLOCATED WITH THE HT FALLS. EAST OF THE LOW...BROAD WEST
SOUTHWESTERLY FLOW EXTENDED ACROSS THE NRN TIER OF STATES AND SRN
CANADA. SOUTH OF THE LOW AND JET STREAK...TWO SHORTWAVES WERE
NOTED...ONE NEAR LAS VEGAS AND A SECOND OFF THE COAST OF SRN
CALIFORNIA.  AT THE SURFACE...A TROUGH OF LOW PRESSURE EXTENDED FROM
NORTH CENTRAL NEBRASKA INTO SWRN KS THIS AFTERNOON. WINDS BEHIND
THIS FEATURE WERE FROM THE WEST AT UNDER 10 MPH...WHILE EAST OF THIS
FEATURE...WINDS WERE FROM THE SOUTH AT AROUND 10 MPH. TEMPERATURES
AS OF 3 PM CDT RANGED FROM 95 AT ONEILL...TO 100 AT VALENTINE.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 322 PM CDT WED SEP 2 2015

WEAK UPPER HEIGHT RISES ONGOING ACROSS THE AREA AS CENTRAL PLAINS
RIDGE BUILDS IN RESPONSE TO DEEPENING TROUGH ACROSS THE PAC NW.
THE SFC REFLECTION TO THIS IS A WEAK SFC TROUGH ACROSS THE MIDDLE
OF THE WESTERN HALF OF NEB...THOUGH WINDS ARE LIGHT MOST
LOCATIONS. MOST NOTABLE DIFFERENCE ACROSS THE ARE ARE DEW POINT
TEMPS WHICH HAVE DROPPED INTO THE UPPER 40S FROM VTN TO OGA...WITH
MID 60S HANGING ON FROM BBW TO ONL AT THIS HOUR. LOW LEVEL
MOISTURE NOT MIXING OUT AS FAR EAST AS THE NAM SUGGESTED...AND FAR
FROM WHAT THE GFS HAD WHICH IS A KNOWN ISSUE WITH THE GFS. DRY
LINE WILL RETREAT WWD AFTER SUNSET UNDER MAINLY CLEAR SKIES.
OPERATIONAL HRRR AND RAP DEVELOPING A SMALL AREA OF CONVECTIVE
PRECIP LATE THIS AFTERNOON AS WEAK FORCING ALOFT OVERLAYS THE DRY
LINE BOUNDARY. SHORT TERM FCST SOUNDINGS FROM THE HRRR AND RAP
SHOW PRONOUNCED INVERTED V PROFILE WITH VERY LITTLE CAPE ABOVE THE
LFC. HAVE NOT INCLUDED MENTION OF PRECIP NOR QPF THIS EVENING WITH
THE IDEA THAT DRY AIR ENTRAINMENT WILL INHIBIT THE POTENTIAL FOR
DEEP...MOIST CONVECTION SUFFICIENT FOR PRECIP.

AS FLOW BECOMES MORE MERIDIONAL WITH THE DEEPENING UPPER TROUGH IN
THE NW...NEXT PV ANOMALY AND ASSOCIATED PUSH OF MID AND UPPER LEVEL
MOISTURE WILL ROTATE NWD OUT OF THE SWRN UNITED STATES. THIS SHOULD
ALLOW FOR MORE SHOWER AND THUNDERSTORM DEVELOPMENT OVER THE HIGHER
TERRAIN FURTHER WEST WHICH WILL MOVE INTO THE WESTERN PORTIONS OF
THE AREA BY LATE AFTERNOON THURSDAY. SOME LARGE SCALE HEIGHT FALLS
ASSOCIATED WITH THIS FEATURE WILL ALLOW FOR SLIGHT COOLING OF THE
UPPER LEVELS AND WHEN PAIRED WITH SOMEWHAT DEEPER MOISTURE WITH
SERLY SFC WINDS...WILL BE SUFFICIENT FOR POSITIVE CAPE ABOVE THE
LOWER LFC BY LATE IN THE DAY. WEAK SHEAR REMAINS HOWEVER SO ALTHOUGH
BETTER CHANCES EXIST FOR THUNDERSTORMS...LARGE SCALE ORGANIZATION
DOES NOT LOOK FAVORABLE THROUGH 00Z FRI. THE ADDED MID AND UPPER
LEVEL MOISTURE AND ASSOCIATED CLOUDS WITH CONVECTION IN SWRLY
FLOW...WHICH HAS ORIGINS IN THE TROPICS ACCORDING TO ANALYSIS OF
320K MIXING RATIO...WILL ALLOW SLIGHTLY COOLER MAX TEMPS FOR
THURSDAY.

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 322 PM CDT WED SEP 2 2015

THURSDAY NIGHT THROUGH SATURDAY NIGHT...IN THE MID RANGE...THE MAIN
FORECASTING CHALLENGES ARE PRECIPITATION CHANCES THURSDAY NIGHT...AND
AGAIN ON FRIDAY NIGHT INTO SATURDAY. FOR THURSDAY
NIGHT...THUNDERSTORMS WILL BE ONGOING ACROSS SWRN NEBR AND NERN
COLORADO AT THE BEGINNING OF THE PERIOD. THIS ACTIVITY WILL MOVE
NORTHEAST INTO THE NIGHTTIME HOURS THANKS TO DECENT MID LEVEL
WAA...WHICH TRACKS FROM SOUTHWESTERN INTO NORTH CENTRAL NEBRASKA. IN
ADDITION...THE NOSE OF A H85 JET STREAK WILL TRACK FROM SOUTH
CENTRAL INTO EASTERN NEBRASKA OVERNIGHT...ADDING ADDTL SUPPORT FOR
PRECIPITATION. AS FOR CHANCES...DECIDED TO KEEP THESE ON THE LOWER
SIDE OF THE ENVELOP AS TIME SECTIONS ARE INDICATIVE OF A DECENT DRY
LAYER BELOW 10000 FT AGL WHICH WILL LIMIT COVERAGE AS WELL AS QPF/S.
ON FRIDAY...STORMS WILL LINGER INTO THE MORNING HOURS ACROSS NERN
PORTIONS OF THE FORECAST AREA. BY AFTERNOON...TRANQUIL WEATHER CONDS
ARE EXPECTED AS THE FORECAST AREA IS IN BETWEEN SYSTEMS. SLIGHTLY
DRIER AIR WILL PUSH INTO THE NORTHWESTERN CWA FRIDAY WITH A DRYLINE
EXTENDING FROM NORTH CENTRAL INTO SWRN NEBRASKA. UPPER LEVEL FORCING
WILL HOLD OFF UNTIL FRIDAY AFTERNOON...SO MOST LOCATIONS WILL SEE A
DRY FCST ON FRIDAY. PCPN CHANCES WILL BEGIN TO INCREASE FRIDAY
EVENING AS A STRONG UPPER LEVEL DISTURBANCE LIFTS ACROSS EASTERN
COLORADO...APPG WESTERN NEBRASKA FRIDAY EVENING. THE BEFORE
MENTIONED DRYLINE WILL RETREAT WEST DURING THE EVENING HRS. HOW FAR
WEST THIS RETREATS AND THE AMOUNT OF DEEP LAYER MOISTURE AVAILABLE
FRIDAY NIGHT IS SOMEWHAT IN DOUBT ATTM. THE GFS IS MUCH DRIER IN THE
WEST COMPARED TO THE NAM SOLN. IN FACT...LAYER PW/S ARE RUNNING
AROUND A HALF AN INCH DRIER IN THE GFS COMPARED TO THE NAM SOLN. NO
SURPRISE...THE GFS IS DRY WITH ITS QPF FIELD FRIDAY NIGHT AND THE
NAM DEVELOPS CONVECTION INVOF THE DRYLINE. INHERITED FCST HAD A
MENTION OF PCPN FRIDAY NIGHT...AND WITH THE GFS BEING TOO DRY IN ITS
LOWER LEVELS UPON INITIALIZATION THIS MORNING...LEANED TOWARD THE
WETTER NAM SOLN WHICH SEEMED TO DO BETTER WITH THE MOISTURE FIELD.
THAT BEING SAID...PRECIPITATION CHANCES IN THE 20 TO 30 PERCENT
RANGE SEEM PLAUSIBLE FOR NOW. THE THREAT FOR PCPN WILL LINGER INTO
SATURDAY IN THE NORTH DURING THE MORNING HOURS...THEN WITH POSSIBLE
DEVELOPMENT OVER EASTERN AND CENTRAL NEBRASKA SATURDAY AFTERNOON. AS
FOR DEVELOPMENT SATURDAY AFTERNOON...ONCE AGAIN...THE GFS SEEMS TOO
DRY WITH ITS MOISTURE FIELD AND CONTINUE TO LEAN TOWARD THE WETTER
NAM SOLN WHICH INITIATES A LINE OF CONVECTION ACROSS THE CENTRAL AND
EASTERN CWA SAT AFTN. DEEP LAYER WIND SHEAR FINALLY REACHES 30 TO 40
KTS SAT AFTN...SO WOULDN/T BE SURPRISED IF A STRONG TO SEVERE STORM
DEVELOPS SAT AFTN/EVE.

SUNDAY THROUGH WEDNESDAY...IN THE EXTENDED...A STRONG UPPER LEVEL
LOW WILL TRACK ACROSS THE NORTHERN ROCKIES INTO SOUTH CENTRAL CANADA
SUNDAY INTO MONDAY. ON SUNDAY...A PREFRONTAL TROUGH WILL PUSH
THROUGH MOST OF THE FORECAST AREA...FORCING LOW LEVEL MOISTURE INTO
CENTRAL AND EASTERN NEBRASKA. FOR THE BULK OF THE FORECAST
AREA...SUNDAY AND SUNDAY NIGHT WILL BE DRY...HOWEVER...LOCATIONS IN
THE FAR NORTHEASTERN CWA WILL SEE A SLIGHT CHANCE FOR RAIN SUNDAY
AFTERNOON/NIGHT. ON SUNDAY NIGHT...A STRONG COLD FRONT WILL PASS
THROUGH THE FORECAST AREA...AND FOR THE MOST PART...WILL BE A DRY
FROPA WITH THE EXCEPTION OF THE FAR EASTERN CWA WHERE SOME LIMITED
MOISTURE WILL REMAIN IN PLACE. THE FRONT WILL THEN STALL ACROSS FAR
SRN NEBRASKA MONDAY...THEN LIFT NORTH MONDAY NIGHT INTO TUESDAY AS A
SECOND UPPER LEVEL WAVE DEVELOPS OVER THE NRN ROCKIES. WITH THE
FRONTAL BOUNDARY DRAPED ACROSS THE FORECAST AREA TUESDAY INTO
WEDNESDAY...WENT AHEAD AND LEFT IN A MENTION OF PCPN. TEMPERATURES
BEHIND THE FRONT MONDAY...TUESDAY AND WEDNESDAY WILL GENERALLY BE IN
THE 70S TO LOWER 80S WHICH IS RIGHT AT SEASONAL FOR EARLY
SEPTEMBER.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1104 PM CDT WED SEP 2 2015

UNLIMITED CEILING AND VISIBILITY ARE FORECAST TONIGHT...THURSDAY
AND THURSDAY EVENING. SOUTHEAST WIND 5 TO 10 MPH TONIGHT WILL
INCREASE TO 12-14KT AND BECOME MORE SOUTH EARLY THURSDAY
AFTERNOON.

&&

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

$$

SYNOPSIS...CLB
SHORT TERM...JWS
LONG TERM...CLB
AVIATION...SPRINGER



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