Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 221830

Area Forecast Discussion
National Weather Service Cheyenne WY
1230 PM MDT Thu Mar 22 2018

.SHORT TERM...(Today through Friday night)
Issued at 355 AM MDT Thu Mar 22 2018

Quiet weather this morning with relatively mild temperatures in
the mid 30`s to low 40`s, with the coldest areas across the
northern Nebraska panhandle with readings in the upper 20`s. The
warming trend will continue today as the upper level ridge
continues to amplify through the afternoon. This ridge will
eventually shift eastward into the plains resulting in southwest
flow aloft ahead of the next Pacific storm moving onshore today.
Still expect highs in the 60`s across the area with some low 70`s
over the southern Nebraska panhandle. Winds will increase west of
Interstate 25 today with gusts between 35 to 45 mph expected.
Kept POP around 20 percent in the forecast, mainly along and west
of Interstate 25 late this afternoon and into this evening for
some rain shower activity and scattered mountain snow showers. Do
not expect any thunder showers to form due to the warmer air aloft
and midlevel subsidence. The only other minor concern is locally
strong winds across the Elk Mountain and Arlington areas late
tonight. Models do show llvl gradients increasing along the spine
of the Snowy Range with 700mb winds approaching 55 knots and some
700mb subsidence. Increased winds above guidance and also a
little above local wind models, with gusts approaching 55 to 60
mph for a brief time sometime around sunrise Friday. Will hold off
on any wind headlines at this time since gusts are still below

Models indicate another warm day on Friday, but it should be
slightly cooler compared to Thursday due to expected cloud cover
and windy conditions. Afternoon temperatures should still climb in
the 60`s to near 70 east of Interstate 25 into western Nebraska,
with readings in the mid 50`s to low 60`s along and west of
Interstate 25. Model soundings on Friday and convective parameters
suggest a better chance of thunderstorms in the afternoon as a
short wave disturbance aloft moves across the area during the day.
This will bring in some cooler air aloft and help with
instability, so added a 20 pct chance of thunder with the best
chances along the Interstate 80 corridor. Mountain snow will
continue above 8000 feet with 5 to 10 inches of snow expected,
mainly in the Sierra Madre Range. May need a Winter Weather
Advisory over the next 24 hours. Otherwise, expect the upper level
ridge to build over the area Friday night with a decreasing
chance for precipitation and clearing skies.

.LONG TERM...(Saturday through Wednesday)
Issued at 322 AM MDT Thu Mar 22 2018

A warm, but unsettled start to the extended forecast period with a
vigorous short-wave tracking across the Pacific NW. An increase in
moist southwesterly flow aloft should promote potential convection
during the afternoon/evening hours on Saturday/Sunday, but more so
on Sunday as the aforementioned disturbance digs toward the Great-
Basin. Despite limited CAPE and modest LI values, very steep lapse
rates may support thunderstorms. The latest GFS is hinting at what
appears to be a convective complex developing over the High Plains
by late Sunday afternoon/evening, along an inverted surface trough
extending north from a sub-1000 mb low over northeast Colorado. In
addition to the convection, gusty winds will be likely during each
afternoon for areas along/west of the Laramie Range. We will still
need to pay close attention to the evolution of this system as the
models are still in excellent agreement w/a significant closed low
taking shape over southern AZ/NM Monday through Wednesday. It does
not look like this system moves much, but guidance still shows the
pattern splitting over the CWA w/ most of the energy being shunted
north and south. At this time, the best shot of widespread snow is
looking to be Monday into Tuesday w/ the cold fropa, but this most
likely would be quick-hitting. If the pattern does split, this may
not be a high-impact storm for us. However, even a minor deviation
in the evolution of the pattern and storm track could make quite a
difference. Still not comfortable with starting to mention threats
for accumulating snow in public products, but this certainly bears


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1228 PM MDT Thu Mar 22 2018

No significant impacts anticipated to general aviation ops as VFR
conditions anticipated for this TAF cycle. There is an outside
chance of a rogue -SHRA at KCDR this evening, but confidence was
too low to include anything above VCSH. Otherwise, anticipated
gusty southwest winds to develop at KRWL and KLAR with gusts of
30-40 knots expected.


Issued at 322 AM MDT Thu Mar 22 2018

Minimal Fire Weather concerns for the end of this week and into
the weekend with minimum relative humidities between 20 to 35
percent. Winds will begin to increase late today and early Friday
ahead of the next cold front, but temperatures are expected to
lower by Sunday. Widespread precipitation is possible for early
next week, limiting Fire Weather concerns.




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