Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 230252
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
852 PM MDT Wed Mar 22 2017

.UPDATE...
Issued at 845 PM MDT Wed Mar 22 2017

Updated forecast for this evening and overnight, mainly with
precip coverage and snow levels. Isolated thunderstorms this
evening should be mostly finished across Niobrara and Converse
counties. As the first upper level disturbance ejects northward
tonight, can not rule out some heavier showers and a few rumbles
of thunder across Carbon county. This disturbance will mainly
impact central Wyoming, but may clip northwestern Carbon and
Converse counties with some brief moderate rainfall as well.

As for the storm system Thursday through Friday morning, 00Z model
data is starting to come in and shows a similar solution as the
earlier 12z and 18z runs. The storm may be positioned a little
further north over east central Colorado compared to the 12z
position. Still expect a steady rainfall to spread east into the
I-25 corridor by Thursday afternoon with a few isolated
thunderstorms. Rain will change to snow Thursday night down to
around 5000 feet for southeast Wyoming. Some dynamic cooling may
result in snowlevels down to 4000-4500 feet across western
Nebraska early Friday morning. The position of the storm, and how
quick it moves eastward, will be key in determining where the
heaviest precip bands set up Thursday through Thursday night and
how long they stick around. For now, did not make any changes to
the previous forecast although there is some concern of moderate
travel impacts for locations outside the current Winter Storm
Watch.

&&

.SHORT TERM...(This evening through Friday night)
Issued at 357 PM MDT Wed Mar 22 2017

Main focus will be with the storm system that will affect the CWA
mainly late Thursday into Friday. Difficulty will be with snowfall
amounts. Models have nudged the track of this system a little
farther south again and are not quite as cold thus snow amounts look
to be a little less overall. Over the plains snowfall likely will be
greater than what accumulates given warm ground and marginal
temperatures. The worst conditions look like they will be later
Thursday evening into Friday morning over the South Laramie Range
where combination of snow and stronger winds may make for quite
difficult driving conditions. Have opted to post a Winter Storm
Watch for that area as a general 4-6 inches of snow looks a decent
bet along with winds gusting to around 40 mph at that time. Some
accumulating snows should also extend east along the I-80 corridor
into the far southwestern Neb Panhandle but amounts less with a
little warmer temperatures. Will still have to watch that area as
heavier snow could occur if temperatures turn out a little cooler
than expected.

Conditions will improve during the day Friday as the surface/upper
lows move into the Kansas/Oklahoma area with clearing skies and
subsiding winds. Short upper ridge moves across Friday and Friday
night boding for clear and dry weather.

.LONG TERM...(Saturday through Tuesday)
Issued at 404 PM MDT Wed Mar 22 2017

A series of upper level low pressure systems will keep the weather
relatively active for southeast Wyoming and western Nebraska
Panhandle through the weekend. The first system will track across
the Desert Southwest Saturday into Sunday with a mix of rain/snow
possible across our forecast area Saturday evening through
Sunday. Monday looks mostly dry, but the next system will track
across the Great Basin and into the Rockies Monday night and
Tuesday, bringing increased chances for precipitation through this
time. Temperatures overall will remain slightly above normal for
this time of year. Winds will remain quite tame across the area as
well.

&&

.AVIATION...(For the 00Z TAFS through Thursday afternoon)

South to southwest winds will remain breezy early this evening, but
will gradually diminish shortly after sunset. VFR conditions
expected overnight over southeast Wyoming, with MVFR CIGS and VIS
possible across western Nebraska as some fog may extend northwest
across the panhandle. Added lower VIS from KAIA to KSNY. The next
storm system will bring more widespread chances for precip and gusty
winds on Thursday.


&&

.FIRE WEATHER...
Issued at 404 PM MDT Wed Mar 22 2017

No concerns expected for the most part through the weekend with
cooler and more moist conditions expected. Conditions may approach
critical levels briefly Thursday afternoon over the southern Neb
Panhandle as humidities may lower into the 10-15% range but winds
look too low at that time.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Storm Watch from Thursday evening through Friday morning
     for WYZ116-117.

NE...None.
&&

$$

UPDATE...TJT
SHORT TERM...RE
LONG TERM...RJM
AVIATION...TJT
FIRE WEATHER...RE



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