Area Forecast Discussion
Issued by NWS Cheyenne, WY

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

FXUS65 KCYS 240338

Area Forecast Discussion
National Weather Service Cheyenne WY
838 PM MST Thu Feb 23 2017

Issued at 838 PM MST Thu Feb 23 2017

Snow rates have diminished across much of the region as the upper
low steadily weakens overhead, however a few areas of heavier
snow showers remain across the forecast area. Winds have also come
down as the sfc high pressure center moves into our forecast area
from the north. Snow totals so far have been quite impressive
with 1-2 feet reported from Wheatland-Torrington-Scottsbluff-
Alliance and in the mountains, and 6-12" most other locations.
Roughly 1-4" was reported from Pine Bluffs to Sidney as well.
Still looking at another 1-2" of accumulation overnight, with
locally higher amounts across the northern panhandle. Winds should
slowly diminish as well.

With that all said, downgraded the Blizzard Warning to a Winter
Storm Warning since winds are gusting only to 25mph in that region
now. Also brought the Winter Storm Warning down to a Winter
Weather Advisory for Kimball and Cheyenne Counties since these
areas got only 1-2" of snow. However, very icy conditions are
possible here tonight with cold temperatures likely freezing
today`s wet and slushy snow to roads so impacts are still non-
negligible. The remaining Winter Storm Warnings will be left as
is since additional snow combined with plentiful snow from today
will continue to make conditions quite dangerous out there.

Temperatures will be very cold tonight with lows in the teens and
single digits. A few below zero readings are possible in the high
country as well.


.SHORT TERM...(Tonight)
Issued at 244 PM MST Thu Feb 23 2017

Latest water vapor loop was showing a very elongated upper level
trof stretching from the intermountain west east towards the high
plains. This has created a large area of broad scale diffluence
over much of the region this afternoon. Latest surface analysis
was showing surface low continuing to weaken across southwest
Carbon county in response to the jet energy pushing east into the
high plains. Meanwhile, the best low level cyclogenesis has
shifted into southwest Kansas. As this surface low moves to the
northeast this will cause the high pressure ridge to nose down the
lee slope of the Rockies.

The main question will be how much more snowfall will occur
tonight. Based on the latest satellite trends it appears like the
majority of the heavier snowfall was still in east central Wyoming
and the northern Nebraska panhandle. This snowfall is showing some
signs of diminishing with the visibility now starting to climb a
bit in Torrington and Chadron. However, we cannot rule out another
2 to 4 inches in this region before the night is finished due to
plenty of upper level divergence. We have cancelled the Blizzard
Warning in southwest Carbon county due to that area being centered
near the surface low with lack of snow and lower wind speeds.
We may also have to drop temperatures even more tonight due to
the influence of the surface high nosing down the lee slope of the
Rockies. Otherwise, current forecast looks to be in good shape with the
snowfall diminishing during the course of the night.

.LONG TERM...(Friday through Thursday)
Issued at 244 PM MST Thu Feb 23 2017

The upper low deepens over the central Plains Friday with snow
rates diminishing east of the Laramie Range mid to late morning
while persisting through the afternoon out west across Carbon and
Albany counties. Models consistently are diminishing snow for the
lower elevations west of the Laramie Range by Friday night and
diminishing in the higher elevations of the Sierra Madre and
Snowy Ranges Saturday evening. After that, next chance for snow
comes out west in the mountains Monday as a low amplitude
fast moving shortwave moves east across the central Rockies. As
for temperatures, expect Friday and Saturday to be a bit colder
than guidance due to the snowpack, with all areas remaining below
freezing until Monday. Slight warmup expected next week with 30s
and 40s for highs east onto the plains and 20s to lower 30s west
of the Laramie Range.


.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 537 PM MST Thu Feb 23 2017

IFR to LIFR will prevail at most airports through tonight with
MVFR at Laramie closer to the surface to midlevel low pressure
circulation and in downslope flow. Will steadily see snow lighten
in intensity overnight, although llvl moisture should keep fog in
place and thus low vis. Conditions will slowly improve through the
day, with MVFR/VFR returning to the area by late afternoon as the
snow ends.


Issued at 244 PM MST Thu Feb 23 2017

No fire weather concerns are expected due to widespread snowfall.


WY...Winter Storm Warning until 11 AM MST Friday for WYZ101>110-

NE...Winter Storm Warning until 11 AM MST Friday for NEZ002-003-

     Winter Weather Advisory until 11 AM MST Friday for NEZ054-055.



FIRE WEATHER...JG is the U.S. government's official web portal to all federal, state and local government web resources and services.