Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 250420
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
1120 PM CDT MON AUG 24 2015

.SYNOPSIS...
ISSUED AT 317 PM CDT MON AUG 24 2015

UPPER LEVEL RIDGE ACROSS THE WEST WITH A TROUGH IN THE EAST. THE
RIDGE AXIS IS ACROSS THE ROCKIES...WITH A CLOSED LOW ACROSS THE
NORTHERN GREAT LAKES. AT THE SURFACE ELONGATED HIGH PRESSURE
DOMINATES THE NORTHERN AND CENTRAL PLAINS. A TROUGH/STALLED
BOUNDARY IS POSITIONED ALONG THE FRONT RANGE OF THE ROCKIES.
SUBSIDENCE ASSOCIATED WITH THE CANADIAN HIGH ALLOWING FOR CLEAR
SKIES AND SEASONALLY COOL TEMPS. 3PM CDT TEMPS RANGE FROM 75 AT ONL
TO 85 AT IML.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 317 PM CDT MON AUG 24 2015

SFC HIGH PRESSURE WILL SLOWLY DRIFT EAST WITH LIGHT SOUTHERLY FLOW
TO GRADUALLY BRING AN INCREASE OF BL MOISTURE. DEW POINTS TODAY IN
THE 40S...AND SHOULD RISE INTO THE 50S TO NEAR 60 TOMORROW. THE
ADDED MOISTURE WILL LIMIT COOLING TONIGHT...EVEN THOUGH SKIES WILL
BE CLEAR. LOWS STILL BELOW NORMAL...HOWEVER NOT NEAR THE RECORD COLD
OF THE LAST COUPLE OF NIGHTS. LOWS EXPECTED TO BE CLOSER TO 50.

TOMORROW THE SOUTHERLY WINDS PICK UP AND WARM AIR ADVECTION WILL
BRING IN WARMER TEMPS. SFC HIGH STILL IMPACTING PORTIONS OF NORTH
CENTRAL...WHERE HIGHS TOP OUT AROUND 80. THE WESTERN ZONES WILL BE
MORE SEASONAL...IF NOT ABOVE AVERAGE IN THE MID TO UPPER 80S. LITTLE
MOVEMENT OR IMPACT WITH THE LEE SIDE TROUGH.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 317 PM CDT MON AUG 24 2015

TUESDAY NIGHT THROUGH EARLY THURSDAY...MOISTURE RETURN BEGINS IN THE
HIGH PLAINS TUESDAY NIGHT AS THE HIGH PLAINS LLJ DEVELOPS IN
RESPONSE TO DRIER AIRMASS ACROSS THE HIGHER TERRAIN COOLING MORE
RAPIDLY UNDER THE RIDGE AXIS. HOWEVER UPPER FORCING REMAINS FURTHER
WEST. THIS INCREASING LOW LEVEL MOISTURE AND LEE TROUGH POSITION MAY
BE PATTERN THAT WOULD FAVOR STRATUS DEVELOPMENT ON THE PLAINS
ADJACENT TO THE TROUGH...BUT MODELS ARE NOT INDICATING THIS YET.
MEANWHILE...UPPER PV ANOMALY ROUNDS THE CENTRAL ROCKIES RIDGE AND
EMERGES OUT ONTO THE HIGH PLAINS WEDNESDAY LATE EVENING. MODELS HAVE
SIGNIFICANT TIMING AND LOCATION DIFFERENCES WITH THIS PV ANOMALY
WHICH DICTATES EACH QPF LOCATION AS EXPECTED. CANADIAN MODEL IS AN
OUTLIER IN ITS DEVELOPMENT OF ELEVATED STORMS IN THE WARM SECTOR
WEDNESDAY NIGHT...THOUGH THIS SEEMS PLAUSIBLE GIVEN THE STRENGTH OF
THE UPPER SYSTEM. BASED ON INTERROGATION OF MODEL FCST
SOUNDINGS...OTHER MODELS ARE APPARENTLY DEVELOPING A STRONG MIDLEVEL
CAP SUCH THAT...DESPITE A DEVELOPING LLJ IN RESPONSE TO THE UPPER
FORCING...WOULD BE INSUFFICIENT FOR DEEP MOIST CONVECTION ABOVE THE
CAP. SOME ELEVATED INSTABILITY WOULD EXIST SHOULD PARCELS BE ABLE TO
MAKE IT TO THE LFC. FOR NOW THE PRECIPITATION FCST WOULD BE LIMITED
TO NEAR AND AHEAD OF A SFC TROUGH IN THE ERN PANHANDLE AND CLOSER TO
THE BETTER UPPER FORCING. TEMPS AHEAD OF THE MAIN UPPER FEATURE WILL
WARM HOWEVER BEST DOWNSLOPE WARMING WOULD LIKELY BE FURTHER WEST AND
WITH INCREASING LOW LEVEL MOISTURE ON SERLY WINDS...HAVE LIMITED MAX
TEMPS A LITTLE AS THIS IS NOT A TOTAL BREAKDOWN OF THE UPPER RIDGE
WHICH WOULD BE A MORE FAVORABLE PATTERN FOR SIGNIFICANT WARMING
AHEAD OF A COLD FRONT.

TIMING DIFFERENCES CONTINUE IN THE MODELS ON THURSDAY...ESPECIALLY
ON HOW FAST THE FRONT MOVES THROUGH THE AREA. ALL MODELS ARE
CONSISTENT IN DEVELOPING PRECIP ALONG AND NORTH OF THE WARM FRONT AS
THE SYSTEM PROGRESSES INTO DEEPER MOISTURE HOWEVER LOCATION OF THE
WARM FRONT AND ASSOCIATED SFC LOW VARIES GREATLY AT THIS POINT. THE
GFS SUGGESTS MID LEVEL FGEN IN THE VCNTY OF THE STRONGEST HEIGHT
FALLS IN THE NWRN PORTION OF THE AREA BY MID DAY...AND NAM/ECMWF
HEIGHT FALLS ARE FURTHER EAST. THE BLENDED PRECIPITATION FCST WILL
FAVOR A MORE SRLY WARM FRONTAL POSITION IN NRN NEBR...AND
THUNDERSTORM CHANCES ALONG THE COLD FRONT AS WELL. CAPE VALUES ARE
LOW IN THE NAM/GFS...BUT FOR DIFFERENT REASONS ALSO. SPC DAY3
OUTLOOK SUGGESTS MRGL POTENTIAL FOR SEVERE WEATHER AND AT THIS POINT
AND THAT LOOKS REASONABLE. HIGHS ON THURSDAY WILL BE LIMITED DUE TO
CLOUD COVER ASSOCIATED WITH THE DEVELOPMENT OF PRECIP.

THE SYNOPTIC AND LARGER SCALE PATTERN FROM LATE IN THE WEEK THROUGH
THE WEEKEND AND INTO NEXT WEEK SIGNALS A TRANSITION TO CROSS-
HEMISPHERIC FLOW AT HIGH LATITUDES. MODELS ARE CONSISTENT IN THIS
DEVELOPMENT...THOUGH EACH HAVE THEIR SMALLER SCALE DIFFERENCES AS
EXPECTED. THIS PATTERN...IN CONJUNCTION WITH A PERSISTENT CENTRAL
PACIFIC RIDGE...MEANS THAT THERE WILL BE A FAIRLY CONSISTENT
PROGRESSION OF UPPER LOW PRESSURE SYSTEMS AND COLD AIR ALOFT TO
MAINTAIN A MEAN TROUGH POSITION ALONG THE WEST COAST AND PACIFIC NW.
DOWNSTREAM RIDGING IN THE CENTRAL PART OF THE COUNTRY...IN THE WAKE
OF THE AFOREMENTIONED UPPER LOW CROSSING THE PLAINS...WILL ALLOW
TEMPS TO REBOUND AFTER A COOLER THAN AVERAGE DAY FRIDAY. NEXT
PRECIPITATION CHANCE COMES SUNDAY AS THE NEXT PIECE OF UPPER LEVEL
ENERGY MOVES EWD IN QUICK SWRLY FLOW ALOFT IN THE NRN PLAINS. STILL
SIGNIFICANT DIFFERENCES IN THE MODELS AT THIS POINT SO CONFIDENCE IN
TIMING AND LOCATION IS LOW AT THIS POINT. THE PREVIOUSLY MENTIONED
CROSS-HEMISHPERIC FLOW MAY ALLOW FOR A MORE SIGNIFICANT CHANGE IN
THE WEATHER PATTERN FOR THE PLAINS BEYOND THIS FCST PERIOD.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1120 PM CDT MON AUG 24 2015

LITTLE CHANGE OVER THE NEXT 24 HOURS AS AN UPPER LEVEL RIDGE OF
HIGH PRESSURE INFLUENCES THE CENTRAL/HIGH PLAINS. WINDS GENERALLY
LIGHT...LESS THAN 7 KNOTS OVERNIGHT WITH SCATTERED HIGH
CLOUDINESS. ON TUESDAY...WINDS LIGHT SOUTHEAST BELOW 10 KNOTS.
ONE CONCERN MAY BE THE RETURN OF ATMOSPHERIC SMOKE WHICH COULD
REDUCE SFC VSBYS TO BELOW 10SM.

&&

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

$$

SYNOPSIS...MASEK
SHORT TERM...MASEK
LONG TERM...JWS
AVIATION...ROBERG


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