Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 131123

Area Forecast Discussion
National Weather Service North Platte NE
623 AM CDT Sun Aug 13 2017

.SHORT TERM...(Today and tonight)
Issued at 405 AM CDT Sun Aug 13 2017

Latest satellite imagery shows expanding low stratus across
southwest NEB and the central Sandhills with patchy fog reported
in some areas, notably KOGA and KIML that are reporting 1/2SM at
the present time. Local radar display shows diminishing showers in
far northern Holt county, otherwise rest of the local forecast
area is clear of precipitation. Latest water vapor imagery shows a
short wave trough advancing eastward across the Dakotas with west
northwest flow over the Central High Plains. Elsewhere, a mid-
level ridge extends from the Northern Rockies to Alberta and
Saskatchewan and another mid-level trough exists upstream moving
onto the British Columbia and Pacific Northwest coasts.

The mid-level trough will continue to track across the Dakotas
today and move into the Upper Mississippi Valley by this
afternoon while the upper ridge to the west shifts to the Northern
High Plains. At the surface, a weak surface trough extends from
the Panhandle into the SD Badlands and central SD. This area of
weak low pressure will evolve and shift east to eastern
NEB/southeast SD by late this afternoon. Surface dew points today
will remain elevated and will range from the lower 60s in
southwest NEB to mid 60s in north central NEB. This combined
with decent lapse rates at mid-levels, 7-7.5 C/km at 700-500 hPa,
will contribute to moderate instability over much of the local
forecast area, MLCAPEs at least 1500-2000 J/kg. Meanwhile, 0-6 km
deep layer bulk shear of 35-40 kts in place this afternoon and
evening will be supportive of organized multicells and some
supercells. Initial development is expected near mid afternoon in
north central NEB and in the higher terrain upstream/west of the
local forecast area with additional development then occurring
later in afternoon over the southern Sandhills. Storms will move
east to southeast in the afternoon and early tonight with isolated
to scattered areal coverage expected. Large hail, damaging winds,
and locally heavy rainfall are the main hazards given the
expected environment.

Below normal highs expected again today, generally 5 degrees below
seasonal normals with lower 80s largely forecast across the local
forecast area. Seasonable lows are then expected tonight.

.LONG TERM...(Monday through Saturday)
Issued at 405 AM CDT Sun Aug 13 2017

A fairly active pattern will continue into next week as a series
of shortwaves and fronts move across the region. Thunderstorm
chances will be mainly confined to the afternoon/evening hours
where diurnal heating will combine with instability and the
progressing shortwave. Over the next week, the best chance for
precipitation and thunderstorms will likely occur on Tuesday night
as a well developed low pressure system drags a cold front across
the central Plains. Severe storms will be possible with this
system with hail and winds likely being the main threats.
Otherwise, afternoon storms continue through Thursday evening. A
weak high pressure system will then start to build into the area,
bringing a short reprieve from storms. Afternoon storms return for
next weekend.

Overall, temperatures will remain mild in the 80s through next
weekend. Overnight lows will generally range from the mid-50s
across the Pine Ridge region up to the low 60s elsewhere.


.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 611 AM CDT Sun Aug 13 2017

Fog, mist, and low stratus affecting portions of southwest NEB
into the Sandhills. Visibilities have fluctuated across southwest
NEB with sites KLBF, KIML, and KOGA reporting reductions. Ceilings
range from LIFR to MVFR. Stratus and patchy fog expected to
spread north into the Sandhills through the early morning hours
with improvement expected by mid morning. Otherwise, VFR
conditions and partly to mostly sunny skies anticipated today.
Thunderstorm chances begin in the afternoon and evening with best
chances located from southwest NEB to north central NEB. Less
confidence in thunderstorms affecting northwest NEB and far
northern NEB thus no mention in the KVTN TAF at this time. Chances
for showers and thunderstorms continue into late tonight.




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