Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 190453
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
1153 PM CDT Mon Sep 18 2017

.SYNOPSIS...
Issued at 309 PM CDT Mon Sep 18 2017

H5 analysis from this morning had a tandem of closed
lows over southern Canada. The first was over northern Ontario and
the second was off the coast of central British Columbia. Across the
lower 48, with the exception of the Pacific Northwest, a low
amplitude pattern was noted. Shortwave energy tracked through the
central plains overnight and led to a broad area of showers and
thunderstorms across the region. After beginning the day with broad
coverage of low cloudiness, skies have gradually cleared this
afternoon. Readings as of mid afternoon across western and north
central Nebraska were generally in the 70s.

&&

.SHORT TERM...(This evening through Tuesday)
Issued at 309 PM CDT Mon Sep 18 2017

In the short term, fog potential tonight, followed by fire
weather concerns Tuesday afternoon are the main forecast concerns.
For tonight: A trough of low pressure will deepen across eastern
Wyoming increasing southerly and southeasterly winds across
western and north central Nebraska. With low level cloudiness just
off to the east and light serly winds tonight, a decent setup
exists for the development of fog/stratus, especially over the
southern half of the forecast area. This notion is supported by
the latest NAM12 and 4KM NAM solns which push moisture west into
central and swrn Nebraska overnight. Did go ahead and insert some
patchy fog for the eastern sandhills and southwestern Nebraska. I
did not push the fog mention to areas of fog as the numerical
guidance and HRRR soln didn`t support that just yet. The surface
trough will slide east into the panhandle and northwestern
sandhills Tuesday morning. With surface heating, the fog and
stratus will push east and dissipate by noontime. By afternoon,
low pressure will begin to deepen over nern Colorado, producing
southwesterly winds and forcing a dry line into portions of
southwestern Nebraska. As of 21z Tuesday, the dryline, will lie
down roughly along highway 25 from Sutherland to Palisade. West of
this feature, temps will reach the lower to middle 90s with
minimum RH`s falling to 10 to 15 percent. East of the dryline,
RH`s will fall off to 15 to 25 percent across the eastern
panhandle and western sandhills. Winds on Tuesday will be
strongest east of the panhandle where a nice pressure gradient
will lead to breezy conditions across most of the forecast area.
Across the panhandle and western sandhills, winds will be lighter
as they will be under the influence of a pre frontal trough of low
pressure. With winds of 10 to 20 MPH and some gusts approaching
25 MPH and minimum RH`s of around 15 percent, decided to hoist a
red flag warning for zone 210 which will run from noon to 6 PM
MDT.

.LONG TERM...(Tuesday night through Monday)
Issued at 309 PM CDT Mon Sep 18 2017

Active pattern coming our way as a large upper level trough digs
south through the western portions of the United states. Our region
will remain on the eastern periphery of the upper trough with
southwest flow aloft to dominate through midweek. Then as the trough
digs farther south into the southwest Conus, a more south-southwest
flow aloft will develop for the last half of the week including the
weekend.

Still a small chance for thunderstorms Tuesday night across far
northern Nebraska along a cold front, but the better focus will
remain north in the Dakotas where better dynamics associated  with the
upper level wave will be located. SPC has shifted the threat for
severe mostly out of our area, and agree with the better chances
remaining  to the north.

The cold front will scour out the moisture for Wednesday through
Thursday night and expect dry conditions during this time. For
Friday into the weekend, rain/thunder chances will increase, as both
quality low level moisture and upper level dynamics become favorable
for precipitation development. As the flow aloft becomes near
meridional, south-southwest aloft, potential for several rounds of
showers and thunderstorms training over the same locations through
the weekend. WPC indicates the potential for up to 1.25 inches
across the panhandle, with near 4 inches possible farther east
across northern into central Nebraska. Will have to monitor for
potential heavy rain this weekend.

Highs will be warm through the end of the week, and then cool off
for the weekend as clouds and the threat for rain increase.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1130 PM CDT Mon Sep 18 2017

Satellite imagery shows mostly clear skies, except some high
clouds moving eastward across northern NEB. KLNX VWP winds (at
1136 PM CDT) at 250 m/~820 ft AGL and 500 m/~1640 ft AGL were 34
kts and 29 kts, respectively. Winds at low levels are expected to
increase attributable to a developing low-level jet across the
eastern Panhandle and far western NEB into western SD. This will
prompt LLWS conditions across portions of the north and far west.
LLWS conditions mentioned only in the the KVTN TAF at this time.
Upper height of the wind shear layer is forecast about 1500 ft AGL
with speeds at the top of the wind shear layer near 45 kts.

Fog still a concern, however, confidence has decreased some with
respect to impacts over southwest NEB. Current thinking is fog
will be patchy. Otherwise, stratus/fog is expected to develop
westward from northeast NEB into north central NEB and parts of
southwest NEB. Not as confident in impacts at the KLBF terminal
thus modified weather groups to lessen fog effects. Conditions are
anticipated to improve mid-late morning.

Otherwise, cold front advancing tomorrow late afternoon and
evening will prompt wind shift from southerly to northwesterly.
Slight chances for thunderstorms tomorrow, confined at this time
mainly to far north central NEB in the evening.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from noon to 6 PM MDT Tuesday for NEZ210.

&&

$$

SYNOPSIS...Buttler
SHORT TERM...Buttler
LONG TERM...Taylor
AVIATION...ET



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