Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 171006
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
406 AM CST Sat Feb 17 2018

.SYNOPSIS...
Issued at 404 AM CST Sat Feb 17 2018

An amplified H5 pattern was present across the Conus and Canada
tonight. High pressure was anchored across the Gulf of Mexico.
High pressure was also present off the coast of northern
California with a ridge extending north into the Aleutian Islands.
Across the northern CONUS: A broad trough of low pressure
extended south from a closed low located over northern portions of
Hudson Bay. On the southwestern periphery of the low, embedded
shortwaves extended from Wyoming into the Idaho panhandle and
British Columbia. At the surface: A trough of low pressure
extended from eastern South Dakota into west Central Nebraska.
West of this feature, winds were generally from the west, while
east of this feature, winds were southerly. Further north, an
arctic cold front was present from central Montana into
northwestern North Dakota. Across western and north central
Nebraska overnight, skies were partly to mostly cloudy and
temperatures ranged from 26 at North Platte, to 32 at Thedford.

&&

.SHORT TERM...(Today and tonight)
Issued at 404 AM CST Sat Feb 17 2018

For today, a weak disturbance will track from the Black Hills
into far northeastern Nebraska. Any precipitation in association
with this weak disturbance should remain north of the forecast
area per the latest HRRR, NAM12, and GFS solutions. The weak will
usher in a weak cool front this morning with some limited cold air
advection this morning. Warm air advection will begin to push
into swrn Nebraska this afternoon. In the interim, some gusty
winds will develop this morning behind the exiting front. Mixing
potential looks good as well as steep lapse rates develop behind
the exiting disturbance. Winds were increased accordingly this
morning with highest speeds around midday. Wind speeds will level
off early this afternoon before decreasing late in the afternoon,
as lapse rates decrease and weak warm air advection commences.
Highs today will range from 40 in the north to near 50 in the far
southwest. A warm front will lift across the forecast area
tonight. Temperatures will be fairly mild with lows generally in
the 20s. Some lower 30s are possible in the non-snow covered areas
of the Sandhills.

.LONG TERM...(Sunday through Friday)
Issued at 404 AM CST Sat Feb 17 2018

Western Nebraska spends much of the next week in southwest flow
aloft as a large trough digs across the Western U.S. and the Hudson
Low spins in place. At the surface, the main driver is a strong cold
front that drops south on Sunday, which is followed by a lee side
low cutting across the southern/central Plains on Monday and a
1040mb high over the central/northern Plains midweek.

The primary forecast challenges are precip potential and
temperatures concerning the storm system late Sunday into Monday.
The fropa will likely be dry, which is progged about 18z Sun. along
Hwy 20 and 00z Mon. along I-80. Fair conditions, H85 temps around
10C and efficient mixing ahead of the front will lead to highs in
the 50s (and perhaps 60s far SW Neb). Behind the front, Arctic air
funnels in and drops the H85 temps below -10C by 06z Mon, resulting
in lows in the single digits north and lower/mid teens south. Strong
CAA, blustery north winds, and overcast conditions will limit highs
to the teens/20s Mon. Continued likely PoP Sunday night through
Monday across northern Neb. Mid level fgen strengthens, along with
upper level dynamics in the form of a 110kt+ H3 jet. Forecast
soundings indicate a prolonged period of decent lift H8-5 near the
Pine Ridge. Isentropic analysis shows persistent upglide combined
with nearly saturated air at 280-290K, and H85 flow takes on an
upslope component. The lift and moisture also coincide with the DGZ
for much of the event, supporting an extended period of light to
moderate snow. The potential exists for over 0.25 inch moisture,
SLR`s around 20:1, and brief periods of 0.5-1 in/hr snowfall rates.
Went ahead and issued a Winter Storm Watch for Sheridan County where
widespread 3-6" is likely and locally 7"+ possible along the Pine
Ridge. Snow totals taper south and east with about 1" from Oshkosh
to O`Neill. Blowing snow does not appear to be a primary concern
attm as wind gusts remain generally 25mph and less, but with the
snow probably on the drier side, can`t rule it out completely.

After the event, Tuesday will remain very cold under mostly cloudy
skies and continued northerly flow. H85 temps around -15C results in
teens for highs. Will need to watch for wind chill headlines Tue and
Wed mornings with subzero lows. Best potential lies across northern
Neb, especially with a fresh snowpack. Temperatures moderate
somewhat Wed and Thu as downslope and then return low level flow
resume.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1122 PM CST Fri Feb 16 2018

Winds will be the main aviation concern through the early morning
hours into Saturday. A southerly low level jet will continue over
western Nebraska through the early morning.


&&

.LBF WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from Sunday afternoon through late Monday
night for NEZ004.

&&

$$

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



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