Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 151148

Area Forecast Discussion
National Weather Service North Platte NE
648 AM CDT Thu Mar 15 2018

Issued at 330 AM CDT Thu Mar 15 2018

A high amplitude ridge extended from the High Plains
north northwest into the Yukon this evening. East of this feature,
closed low pressure was located from New England into the Canadian
Maritimes. A trough of low pressure extended south of the low into
the Bahamas. West of the ridge, low pressure was located off the
coast of British Columbia with a deep trough of low pressure
extending south into southern California. At the base of this trough
of low pressure, a strong vort max was present from southern
California into far southern Nevada. At the surface, a stationary
front was located across southern Nebraska overnight. Easterly winds
have commenced across the forecast area overnight. Skies were partly
cloudy as high clouds continued to stream into the forecast area
from the southwest. Readings as of 3 AM CDT were generally in the


.SHORT TERM...(Today and tonight)
Issued at 330 AM CDT Thu Mar 15 2018

Today and Tonight: Surface low pressure will deepen
across eastern Colorado today as a strong shortwave trough tracks
into the four corners. Easterly winds will increase today and windy
conditions are expected by this afternoon. H85 temps will be fairly
warm today and with the expected decent mixing, highs will reach
into the 50s and 60s. By this evening, showers will begin to develop
over eastern Colorado, north of the surface low and in advance of
the shortwave trough. Steep lapse rates and elevated instability
will increase across southwestern Nebraska this evening and may lead
to an isolated thunderstorm or two. CAPE remains very meager this
evening, so storms will be limited and weak in nature. None the
less, went ahead and confined thunderstorms to the southwestern
forecast area, as this is co-located with negative h800 LI`s. This
area shifts into south central Nebraska overnight with the threat
for thunder ending by midnight. After mid evening, boundary layer
temps will begin to reach the freezing mark over northern Nebraska
as cooler air drops south from South Dakota. Forecast soundings
continue to indicate a good freezing rain/sleet setup across
northern Nebraska overnight into Friday morning. This is supported
with the NAM12 soln and to a lesser degree by the GFS soln. The GFS
is warmer in the boundary layer and has a decreased threat for
freezing pcpn and hints more toward a rain to snow changeover, with
a tighter window for freezing pcpn. Even compromising between the
GFS and NAM12 solns, yields a decent threat for freezing
precipitation across northern Nebraska, along with accumulating snow
across the northwestern forecast area. That being said, decided to
hoist a winter storm warning for Cherry and Sheridan county. Further
east, snow accumulations, will be considerably less, however, there
is still a decent threat for icing. After coordinating with FSD, UNR
and OAX, a winter storm watch will be issued for Keya Paha and Brown
counties, east to Boyd and Holt counties. In these areas, there is a
threat for 1 to 2 tenths of an inch of icing which would be
significant. With some uncertainty on snow accums east of Valentine,
and temperature differences in the boundary layer between the NAM 12
and GFS runs tonight, feel a watch is warranted here. Eventually, we
may need an advisory for the next row of counties south (ie. Grant
east to Wheeler), but feel that the threat for significant icing
here is minimal. As for snow accumulations, 4 to 8 inches of snow is
possible from northern Cherry county west to northern Sheridan
county. This is in addition to the potential for around a tenth of
an inch of freezing rain. Lighter amounts are expected east of
Valentine, however the main impacts from this system will probably
end up being from freezing rain where 0.1 to 0.2" of ice
accumulation is possible.

.LONG TERM...(Friday through Wednesday)
Issued at 330 AM CDT Thu Mar 15 2018

While most of the varying deterministic
output is similar in the large scale, thermal fields continue to
suffer from vast differences.  Notably, the GFS and NAM are in some
cases indicating as much as a 10F spread in temperatures on Friday.
Obviously this creates significant differences in ptypes and any
eventual impacts from snow or freezing rain.  We are favoring the
cooler guidance from the NAM at this point given the deep easterly
or northeast flow pulling down Canadian air across the plains.  So
with that, impacts from ice, some of which may be significant, is
becoming more apparent across our northern tier. This cuts down snow
amounts during the day hours Friday slightly, but ice accumulations

The cooler temperatures aloft are shown to arrive Friday, which will
transition the ptype to all snow for our northwest.  Accumulations
across the Pine Ridge and northwest Sheridan County may eclipse 6".
Wrap around will continue through the day with the main upper low
taking a negative tilt Friday, several inches of snow may accumulate
across far northern portions of our north central zones after the
changeover with light snow possible across our far east into Friday

Transitory upper ridge of high pressure will build across the plains
on Saturday allowing for near seasonal temperatures and dry
conditions.  The next potential weather system arrives during the
late Sunday into Monday timeframe.  Significant differences in the
long term models yields low confidence, especially in the finer
details such as ptype.  But it appears more moisture is progged to
impact the region with slightly cooler than average temperatures
into next week.


.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 648 AM CDT Thu Mar 15 2018

For today: High clouds will continue to increase into the
afternoon hours as an upper level trough of low pressure tracks
into the southern and central plains. For the KLBF terminal, ceilings
will lower further this evening, approaching MVFR toward 12z
Friday. Light rain will be possible as well. For the KVTN
terminal, IFR CIGS will be possible through mid morning before
lifting by 15z. Ceilings will lower this evening with the threat
for rain, freezing rain and snow increasing after 05z Friday. IFR
cigs are expected overnight and will range from 300 to 1000 FT


Winter Storm Warning from midnight CDT /11 PM MDT/ tonight to 7
PM CDT /6 PM MDT/ Friday for NEZ004-005-094.

Winter Storm Watch from late tonight through late Friday night
for NEZ006>010.



SHORT TERM...Buttler
LONG TERM...Jacobs
AVIATION...Buttler is the U.S. government's official web portal to all federal, state and local government web resources and services.