Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 201139
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
539 AM CST Tue Feb 20 2018

.SYNOPSIS...
Issued at 344 AM CST Tue Feb 20 2018

H5 analysis from earlier this evening, had an elongated area of
low pressure which extended from far northern Quebec, west
southwest to northern Saskatchewan. A trough of low pressure
extended from northern Saskatchewan, south to around Las Vegas
Nevada. Strong high pressure was dominant across the eastern
CONUS. This high was located north of the Bahamas and a ridge
associated with this feature, extended north into the Mid Atlantic
states. Current satellite imagery, has the trough axis roughly
from western Wyoming south into far northeastern Utah. At the
surface, an arctic cold front extended from southeastern Wisconsin
to southeastern Kansas and the northern Texas panhandle. High
pressure was located over eastern Montana this morning. Across
western and north central Nebraska, light to moderate snow was
occurring and readings were in the single digits above zero.

&&

.SHORT TERM...(Today and tonight)
Issued at 344 AM CST Tue Feb 20 2018

Temperatures will be the main forecast challenge over the next 24
hours. Through daybreak, the latest HRRR, and NAM12 soln end the
threat for light snow for most of the forecast area. The exception
will be in the far northeastern forecast area where snow may
linger through the mid morning hours. With respect to winter
headlines, will hold onto these for the time being as snow
continues through sunrise. Could see these being cancelled
sometime this morning, as snow ends. Wind will be fairly limited
today, so a blowing snow threat will be minimal. Also, wind
chills, especially across northwestern Nebraska will be in the -10
to -20 range through mid morning, before increasing to around
zero by mid afternoon. Some clearing will take place this
afternoon as subsidence increases behind the exiting shortwave
trough. However, with arctic air entrenched across the central and
high plains, highs will struggle to get out of the teens. Arctic
high pressure will build into north central, then east central
Nebraska overnight. Lows will bottom out below zero across the
board, with some -5 to -15 degree readings across northern
Nebraska. Fortunately, winds will be fairly light, so wind chills
should bottom out in the -20 to -30 degree range across northern
Nebraska tonight. Based on the current forecast, a wind chill
advisory will be needed for Sheridan and western Cherry county.
Will pass this onto the day crew for issuance after the current
winter headlines expire or get cancelled this morning.

.LONG TERM...(Wednesday through Monday)
Issued at 344 AM CST Tue Feb 20 2018

Nebraska remains in southwest flow aloft into the weekend with an
Intermountain West trough, Hudson Bay low, and a Bermuda high.
The pattern turns more zonal after the Western U.S. trough passes
through the Plains. At the surface, a 1040mb+ high scoots across
the northern Plains midweek and is replaced by a late week lee
side low emerging onto the southern Plains. The low deepens as it
cuts across Kansas over the weekend.

Wednesday... Return sfc flow, notable WAA (H85 temps rising 10C in
24 hrs), and fair skies help moderate temperatures somewhat, albeit
still much cooler than normal. Kept highs generally in the mid to
upper 20s, which is on the cooler end of guidance to account for a
fresh snowpack.

Thursday... A pronounced shortwave pushes northeast across the
Plains, bringing the next shot at precip. Low levels are slow to
saturate, but strengthening forcing at H5-7 in the afternoon should
speed up precip efficiency. NAM and GFS forecast soundings still
show the temp profile primarily -5 to -10C. This is cold enough for
all snow but too warm for the best dendritic growth, which will
limit SLR`s. However, the soundings (and isentropic analysis at 275-
295K) also show strong lift, and X-sections suggest a little theta-E
folding and weakly negative EPV. The potential for bursts of higher
snowfall rates will overcome relatively low SLR`s to result in light
accumulations, mainly across north central Neb.

Friday and Saturday... The progression of the longwave trough along
with a mid level wave (or closed low as shown by the GFS) raises
precip chances again. This system has better moisture with decent
flow ahead of the sfc low and steady moisture advection at H5-7.
Temps may play a big role as current forecast highs are in the 30s
each day. As of now, the greatest chance of precip occurs overnight
which supports all snow (lows in the teens and H85 temps around
-5C). Forcing and lift appear rather impressive in the soundings,
and a 100kt+ H3 jet adds to the upper level dynamics. The potential
exists for at least light accumulations across the area and will
need to be watched.

Sunday and Monday... Temps return to near seasonal averages with
quasi-zonal flow aloft and downslope flow in the low levels. H85
temps should reach freezing, translating to upper 30s to lower 40s
at the surface. A small chance of rain/snow exists Monday with a
weak shortwave passage.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 539 AM CST Tue Feb 20 2018

Expect gradual clearing today across western and north central
Nebraska as an upper level system tracks northeast of the area.
Through mid morning however, there will be a continued threat for
light snow at the KVTN terminal with visbys as low as 2SM.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until noon CST /11 AM MST/ today for NEZ004-
094.

Winter Weather Advisory until noon CST /11 AM MST/ today for
NEZ005>010-022>026-036-037.

&&

$$

SYNOPSIS...Buttler
SHORT TERM...Buttler
LONG TERM...Snively
AVIATION...Buttler


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