Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 142020

Area Forecast Discussion
National Weather Service North Platte NE
320 PM CDT Wed Mar 14 2018

.SHORT TERM...(This evening through Thursday)
Issued at 320 PM CDT Wed Mar 14 2018

Upper level ridging will dominate across the region tonight ahead
of long wave trough that is located along the west coast. The
base of the long wave trough will pivot toward southern Colorado
by Thursday afternoon. As this happens surface low pressure will
deepen across eastern Colorado. This will cause easterly winds to
increase Thursday afternoon across much of the area, with gusts
nearing 30 mph in spots by late Thursday afternoon. A warm front
will sharpen across northern KS Thursday afternoon, with highs
well into the 80s across southwest KS to the south of the front.
Just north of the front, highs in the 60s are expected for
portions of central and southwest Nebraska. Farther north upper
40s and 50s can be expected across northern Nebraska. Some
increase in mid level clouds can be expected Thursday afternoon,
but any precipitation from the approaching storm system should
hold off till Thursday night.

.LONG TERM...(Thursday night through Wednesday)
Issued at 320 PM CDT Wed Mar 14 2018

We continue to monitor the progress of a strong spring storm to
affect wrn and ncntl Neb Thursday night and Friday. The models
continue to show convectively enhanced bands of rain changing to
freezing rain, sleet and snow as they lift north into nrn Neb.
Heavy precipitation is expected in the bands and in fact, the NAM
shows around 500 J/KG of CAPE Thursday evening. This would support
thunderstorms. The 750-400mb Shear appears weak in the model with
500mb winds just 25kts so hail sizes will be small, likely pea-

Sfc low pressure over Nwrn KS will help draw arctic air into ncntl
Neb Thursday night causing rain and freezing rain initially, then
sleet as the cold air gets deeper late Thursday night. The arctic
high, currently centered across nrn Manitoba is quite cold; below
0F, but today`s morning runs of the GFS and NAM are somewhat slower
to pull the cold air south into ncntl Neb. Once the cold air is in
place, a deep h700mb low across Swrn Neb will move east Friday
cooling temperatures aloft and a changeover to snow will occur.

Mostly to all snow is expected across Nwrn Neb, west of highway 83,
where a winter storm watch is in place. Median QPF in this region is
over 0.75 inches which would support the storm watch given a 10-12
to 1 snow-water ratio. The forecast in this area is 3 to 8 inches of
snow; WPC suggested 6 to 12.

Given the rain-snow mix elsewhere, it is uncertain if a watch will
be needed farther east through Brown, Rock and Holt counties,
including areas north. The models may be lifting the deformation
zone too far north as the h700mb low tracks east along the KS-Neb
border which favors a more southern solution to the heavier rain and
snow, but the timing of the changeover is uncertain. Also, note that
the models are showing a run-to-run diurnal warm and cold bias which
is affecting the temperatures and snowfall amounts. Last night`s
forecast was on the warm side, yesterday and today it is colder.

The models show a cold pool driven area of moderate snow developing
on the west side of the h700mb low which could prompt winter weather
advisories elsewhere north of I-80.

The forecast uses a blended model approach. The GFS 800mb
temperatures were the basis for the rain-ice-snow weather types
which might be too conservative as the NAM is colder. The NAM 750mb
CAPE was the basis for the thunderstorms chances Thursday night
which line up well with SPC.

A second storm system will be moving through the Cntl Plains Sunday
and Monday. Today`s model runs of the GFS, GEM and GEF suggest the
h700mb low will track through cntl KS which is favorable for rain
changing to snow across Neb.


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1235 PM CDT Wed Mar 14 2018

Clear skies and VFR conditions will prevail through tonight across
all of western and north central Nebraska. A storm system will
begin to intensify across the Rockies Thursday. This will turn
winds to the east Thursday morning with gusts to 25 kt by noontime
Thursday. Mid level clouds around 10000 ft AGL will also begin to
increase Thursday morning.


Winter Storm Watch from late Thursday night through Friday
evening for NEZ004-005-094.



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