Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 171000
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
300 AM MST Sun Feb 17 2019

.SHORT TERM...(Today through Tuesday night)
Issued at 300 AM MST Sun Feb 17 2019

Broad longwave trough extended from the Upper Midwest through the
Great Plains and Intermountain West. Several pieces of embedded
energy or shortwaves continue to rotate through the mean trough.
Some weak reflectivity returns from regional radars indicative of
occasional light snow showers or flurries. Otherwise, skies were
partly to mostly cloudy. A weak surface boundary oriented NW to SE
across WY into SW NE separated W-SW winds from N-NE winds. Gusts
of 25-30 MPH were observed between Cheyenne and Rawlins.

Primary forecast concerns through the short term will focus on the
cold temperatures and wind chills, as well as chances for more snow
showers.

The broad upper trough will be dominant weather feature into early
this week. Migrating shortwaves will be the impetus for periodic
snow shower activity, with more coverage Monday night and Tuesday.
Accumulations through the short term will range from one to two
inches over the southern CWA, with as much as four inches above
8000 feet. It will be breezy across the high plains today with NW
winds gusting to 30 MPH. The combination of the wind and temperatures
in the mid teens to low 20s will drive wind chills to -5 to 10
degrees today. Concerned about low temperatures and wind chills
tonight and Monday night. Coldest areas will be the western valleys
and north of the Platte River where wind chills drop to around -20
degrees. Will postpone the issuance of Wind Chill headlines for
late tonight and Monday morning, and defer this decision to the
next forecast shift. With steadfast 700mb temperatures in the
upper teens below zero early this week, expect high temperatures
in the teens to around 20, and low temperatures from 0 to -10
degrees.

.LONG TERM...(Wednesday through Saturday)
Issued at 300 AM MST Sun Feb 17 2019

Highly amplified large scale pattern will prevail through the long
term. Upper trough over the Rockies translates northeast through
the Great Plains and Upper Midwest Wednesday as more energy aloft
carves out another trough west of the Rockies. Most of the medium
range models develop a cutoff low over the southwest CONUS late
in the week, accompanies by a return of unsettled weather. Winds
intensify with the passage of a shortwave trough Wednesday. CAG-
BRX 850mb gradients peak in the 60-70mtrs between 06Z and 12Z
Wednesday. 700mb gradients are slightly lower, 50-55mtrs, for the
same period. Models have been consistent, so marginal high wind
event is possible late Tuesday night and Wednesday morning for
Arlington and Bordeaux. Winds Thursday and Friday will be lighter,
with breezy conditions returning to southeast WY Saturday. Below
normal temperatures will prevail, with highs in the mid 20s to mid
30s and lows in the single digits and teens.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1027 PM MST Sat Feb 16 2019

Wyoming TAFS...VFR, except MVFR at Laramie and Cheyenne after 00Z.
Wind gusts to 22 knots at Cheyenne until 00Z.

Nebraska TAFS...IFR or MVFR at Chadron and Alliance until 12Z, then
VFR. VFR at Scottsbluff and Sidney. Wind gusts to 30 knots from 11Z
to 01Z.

&&

.FIRE WEATHER...
Issued at 145 AM MST Sun Feb 17 2019

Fire weather concerns will be low with below normal temperatures
through next week. Minimum relative humidities will remain above
critical thresholds. It will be breezy most days, with windy
conditions on Wednesday. There will be chances for snow showers,
mainly early and late in the week.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&

$$

SHORT TERM...MAJ
LONG TERM...MAJ
AVIATION...RUBIN
FIRE WEATHER...MAJ



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