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000
FXUS65 KCYS 162053
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
253 PM MDT Tue Apr 16 2024

.KEY MESSAGES...

- Widespread wind gusts 45-55 MPH with occasional gusts to 65
  MPH are expected to persist through late afternoon. High Wind
  Warnings remain in effect until 6 PM MDT this evening.

- Widespread rain and snow showers will return to much of the
  area on Wednesday and Wednesday night. Accumulating mountain
  snow is possible, especially in the Snowy Range with 6 to 12
  inches of new accumulation possible above 9000 feet.

&&

.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 224 PM MDT Tue Apr 16 2024

Isolated to widely scattered (very light) showers may still be a
possibility across southeast WY & the western NE Panhandle given
warming surface temperatures & continued influence from the mid-
level cold core associated w/ the departing surface cyclone. Dry
conditions should prevail for the majority of areas, with little
to no chance for any additional measurable precipitation through
tonight. Strong winds are likely to persist through sunset for a
large portion of the high plains, with widespread gusts 55 to 65
MPH still being observed as of 20z this afternoon. Expect to see
gusts decrease markedly over the next few hours w/ weakening low
level gradients and lapse rates, but occasional gusts to near 50
MPH could still be possible near Arlington and Elk Mountain thru
12z Wednesday as H7/H85 CAG-CPR gradients remain near 45 meters.
High Wind Warnings should expire as scheduled, but will continue
to closely monitor observational trends.

The improved weather conditions will be short-lived as the short
wave ridging aloft quickly gives way to broad, and low-amplitude
troughing over the northwestern CONUS by mid-day Wednesday. Mid-
level westerlies are expected to increase, along with strong sfc
gradients and 35 to 45 knots of 700-800 hpa flow over Carbon and
Albany counties atop steep low-level lapse rates. Wind gusts may
approach or exceed 50 MPH, but confidence in warning-level gusts
is not high enough to warrant any additional headlines with this
forecast package. Numerous rain & snow showers are also expected
to spread across a large portion of the CWA Wednesday afternoon/
evening w/ the passage of the next cold front. Any possible snow
accumulations should be confined to the higher elevations along/
west of the Laramie Range, but overall expect impacts to be very
low. An additional 6 to 12 inches may be possible in the Snowys,
possibly requiring a Winter Weather Advisory w/ future updates.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
Issued at 224 PM MDT Tue Apr 16 2024

The long term forecast includes an active weather pattern for early
spring, with multiple chances of precipitation, large temperature
swings, and, elevated winds at times. The first portion of the long
term forecast includes well below normal temperatures, with a brief
weekend warmup during the weekend, and then returning to slightly
below normal temperatures early next week.

Thursday will start off with our region being under the influence of
a large, negatively tilted H500 trough. The semi-zonal flow will
have just enough of a weak disturbance aloft to keep the
precipitation faucet running in the higher elevations for additional
chances of snowfall. There is also a weak signal for mountain wave
activity over the I-80 Summit, so will need to pay attention to that
in the next couple of days in case additional high wind headlines
seem prudent. At this time of inspection, highest confidence exists
in high levels of CAA occurring from the Canadian Provinces down to
our cwa. Further upstream across CA on Thursday and Thursday night,
another trough will propagate over the Great Basin and Intermountain
West. The Polar Jet and the Subtropical Jet do have a weak signal to
phase together overnight, and into Friday morning. The rear entrance
region of the Subtropical Jet may have just enough "juice" to give
areas along the I-80 corridor of snowfall accumulations. Cold air
will be entrenched across the region due to a cold FROPA, which
leads to higher confidence of snow shower activity being present for
the mountain zones and potentially the high plains. The NE Panhandle
may see a rain/snow mix during the daylight hours. Some of the model
guidance does hint at the subsequent Colorado Low taking a slower
time to eject out toward the Central Plains through Saturday, which
could induce a longer window for light snow showers to remain
present. Overall, expect daytime highs on Thu/Fri/Sat to be 10-20
degrees below normal.

By Sunday, we will begin to see the effects of upper level ridging
aloft. The WAA will bring daytime highs upwards of to 10 to 20
degrees warmer than Saturday. It will be a nice change up to the
recent well below normal temperatures from Thu-Sat. Expect to say
afternoon maximums in the 60s for the lower elevations, and the 40s
for the higher terrain elevations. Breezy winds in the wind prone
corridors are also highlighted in model guidance for Sunday, so we
can expect those wind gusts to mix down to the surface east of the
Laramie Range after atmospheric mixing begins to occur. There does
not appear to be strong enough winds aloft to encourage a watchful
eye for high wind headlines at this time of inspection.

The beginning of next week includes a large spread of deterministic
solutions to what weather and temperatures look like. Quasi-zonal
flow aloft will include nearby shortwave disturbances. Daytime high
temperatures have been nudged down a degree or two to reflect this
as we will be on the fringe of another push of colder air from
Canada. We will also have the chance for additional rain and snow
showers depending on whether the shortwave disturbances trek over
our cwa early next week. Stay tuned for forecast updates in the
coming days as we iron out these smaller details with higher
confidence.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1130 AM MDT Tue Apr 16 2024

A strong storm system and its associated surface low pressure
will move from central Nebraska early this afternoon, to
Minnesota by Wednesday morning.

Wyoming TAFS...Scattered to broken clouds from 3500 to
10000 feet will prevail. Winds will gust from 35 to 52 knots
until 00Z, then gust to 35 knots until 08Z, then from 25 to
35 knots after 15Z Wednesday.

Nebraska TAFS...At Chadron and Scottsbluff, scattered to broken
clouds from 3500 to 10000 feet will prevail. Winds will gust
from 40 to 50 knots until 00Z, then to 35 knots until 03Z.

At Alliance and Sidney, scattered to broken clouds from 4500 to
10000 feet will occur, with occasional light rain and fog
reducing visibilities to 4 miles with ceilings near 2500 feet
until 21Z. Winds will gust to 50 knots until 00Z, then to
30 knots until 03Z.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...High Wind Warning until 6 PM MDT this evening for WYZ102-
     116>119.
     High Wind Warning until 3 PM MDT this afternoon for WYZ101-
     106>108.
     Winter Weather Advisory until 3 PM MDT this afternoon for
     WYZ112-116.
     Winter Storm Warning until 3 PM MDT this afternoon for WYZ114.
NE...High Wind Warning until 6 PM MDT this evening for NEZ019>021-
     054-055-095-096.

&&

$$

SHORT TERM...CLH
LONG TERM...BW
AVIATION...CLH