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fxus65 kcys 092100 

Area forecast discussion
National Weather Service Cheyenne Wyoming
200 PM MST Mon Dec 9 2019

Short term...(this afternoon and tonight)
issued at 200 PM MST Mon Dec 9 2019

Broad upper trough encompassed much of Continental U.S. With northwesterly
flow aloft over the County Warning Area. Cold front that pushed through the area
last night extended from the mid-MS valley to the Southern Plains.
Low clouds were gradually thinning across southeast Wyoming with some
drier air aloft filtering into the region. Current temperatures
were 10-20 degrees colder compared to 24 hrs ago. Some light snow
showers will linger this afternoon over the southern Wyoming mountains
due to orographic lift. The leading edge of colder air was entering
northern Montana/ND, and will push southeast through the High Plains
tonight. There will be enough energy aloft to produce some light
snow showers along the boundary north of a line from Douglas Wyoming to
Alliance NE. Elsewhere, it will be dry with low temperatures in
the teens to lower 20s.

Long term...(tuesday through monday)
issued at 200 PM MST Mon Dec 9 2019

No large scale impactful hazards appear on the horizon outside of
periods of localized high wind potential in The Gap areas during
several different time periods and increasing snow chances late
this week and weekend. However, will need to monitor model evolutions
as decent spread remains among ensemble solutions. Confidence is
low in snow potential and impacts at the end of the forecast period.
Temperatures will initially be below normal but moderate towards
average values mid-week before another cool down this weekend.

Strong 700 mb-300 mb northwest flow will persist Tuesday morning with small
embedded perturbations that may generate just enough mid-level
lift to generate light snow showers across parts of Niobrara
County Wyoming and northern NE Panhandle. Typical gap wind areas near
Arlington, I-80 Summit and Bordeaux will need to monitored
Tuesday, Wednesday, and Friday for potential high wind headlines
as southeast Wyoming gets locked into fast near zonal flow aloft. This
pattern will set up a dry period Tuesday through Thursday until
mountain snow returns Thursday night due to favorable orographic
lift. Winter Weather Advisory headlines may be warranted late
Thursday through Friday for the high country.

Late this weekend, multi-model guidance indicates a phasing
trough dynamic near the central rockies to the High Plains.
Positioning and timing of these troughs will be key to how far
north or south the main precipitation area will set up. Current
model envelope favors greater chances of snow near the Wyoming/Colorado and
south. Overall confidence remains low at this time given the
spread of solutions. Stay tuned for details through the week.


Aviation...(for the 18z tafs through 18z Tuesday morning)
issued at 1050 am MST Mon Dec 9 2019

VFR conditions at all area terminals currently and will continue
into early this evening. Few to scattered cloud cover between 5 and 8
kft will linger around southeast Wyoming terminals into early this afternoon.
Recent model guidance has dampened winds for southeast Wyoming terminals this
afternoon, but gusts to 20 kt are possible. NE Panhandle terminals
are currently observing breezy conditions with gusts 20-25 kt out
of the northwest which will continue until Sundown. A cold front
will clip northeastern portions of the County Warning Area tonight which will
bring lowered ceilings and light snow showers near kaia and kcdr
after 06z tonight.


Fire weather...
issued at 200 PM MST Mon Dec 9 2019

Cool temperatures and minimum afternoon humidity values well above
critical levels will preclude fire weather concerns this week. A
cold front will move southeast through the High Plains tonight and
early Tuesday and may produce light snow showers. Otherwise, it will
remain dry through Thursday. It will be windy for much of southeast
Wyoming Tuesday through Friday. Another low pressure system and cold
front will bring more wintry precipitation Friday through Sunday.


Cys watches/warnings/advisories...


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