Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 152339
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
539 PM CST Wed Nov 15 2017

.SHORT TERM...(This evening through Thursday)
Issued at 330 PM CST Wed Nov 15 2017

The primary focus through Thursday afternoon is the progression of a
surface high pressure and low/mid level ridge. As of 21z, the high
was centered around TIF-BBW, creating southerly flow in the
panhandle and northerly across central Neb. The air has dried
considerably as dew points dropped into the mid/upper 20s.

The center of the sfc high moves out of Nebraska by 06z tonight,
placing the entire forecast area in southerly return flow. Winds
pick up quite a bit due to a rather steep pressure gradient. A low
coming off the Rockies deepens, lowering the MSLP to 1012mb near CDR
while the high maintains 1024mb at OMA. The H85 ridge axis also
pushes east during this time, and flow approaches 50kts by 12z. With
a considerable amount of subsidence and isentropic downglide, some
of the momentum will be translated to the surface overnight. Mixing
will be maximized over the Sandhills, while a slightly stronger
inversion remains in the river valleys. Made little change to min
temps as weak WAA keeps H85 temps above freezing and previous
forecast lows were above guidance. Did bump up Thursday highs as the
stout H85 thermal ridge approaches and pushes temps toward 15C west
and north. Other than some high cirrus, not seeing much in terms of
moisture/cloud cover to keep temps from rising quickly. Highs will
range from mid 50s near ONL (remnant cool air aloft) to upper 60s in
the panhandle. Temps in the far west may still be underdone as MAV
and Met suggest lower 70s at SNY and AIA. Tried to account for that
by adjusting more heavily west of IML-GRN. Winds remain gusty into
the afternoon with a 16mb MSLP difference across the state and
35+kts at H85. The combination of seasonably warm temps, continued
dry air (RH below 25% west of Hwy 61), and gusty winds, will have to
keep an eye on fire weather conditions.

.LONG TERM...(Thursday night through Wednesday)
Issued at 330 PM CST Wed Nov 15 2017

Rain and snow chances during the next 7 days continue to revolve
around an event Friday evening and potentially Tuesday. A positively
tilted trof moves through Friday evening with 1032 mb Pacific high
pressure building through the Cntl Rockies. This will dry out much
of the Great Plains Saturday and Sunday. The models are in excellent
agreement with low pressure circulating through Srn Canada Monday
and a cold front backing in Tuesday. The model consensus falls apart
next Wednesday as the operational GFS brings the coldest arctic high
of the season through the Nrn and Cntl high plains. The GFS
ensemble, Canadian and ECM are less amplified, much more modest, and
just briefly back a cold front through ncntl Neb.

The rain/snow forecast Friday evening leans on the wetter model, the
ECM. The models are in good agreement with warming conditions Friday
ahead of the Pacific cold front. Highs in the 50s and 60s should
develop as h850mb temperatures rise to around 15C. Winds aloft
moisten and increase in speed Thursday night and Friday. This will
probably cause a cirrus shield to develop off the Colorado Rockies
but highs in the 60s should develop, especially since the low level
return flow is dry, and none of the 4 models indicate morning
stratus.

The temperature forecast is a model blend plus the previous forecast
plus bias correction. Bias correction had little impact on the
forecast and tended to increase highs a degree or two and lower
minimum temperatures the same. This suggests a predictable pattern
through Tuesday with warming highs in the 50s and 60s Friday
followed by a cool down into the 40s Saturday. A warming trend
develops Sunday and Monday with highs rising into the 50s to around
60.

The model consensus indicates a back door cold front Tuesday. It is
weak arctic high pressure and the models suggest a bank of clouds
will drape across ncntl Neb which could perhaps support a snow
chance Tuesday night. The forecast Wednesday leans on the warmer
ECM, Canadian and GFS ensemble models for highs in the 40s. The GFS
operational model appeared to be an outlier with a massive arctic
high building through the Nrn plains.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 523 PM CST Wed Nov 15 2017

VFR conditions continue through the forecast period. Winds will
switch to the south overnight. The main concern will be gusty
winds Thursday, mostly across north central Nebraska.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

SHORT TERM...Snively
LONG TERM...CDC
AVIATION...Gomez



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