Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 201737

Area Forecast Discussion
National Weather Service Cheyenne WY
1137 AM MDT Tue Mar 20 2018

.SHORT TERM...(Today through Wednesday night)
Issued at 240 AM MDT Tue Mar 20 2018

Overall fairly quiet weather regime for the next 36 hrs. We will
see some isolated snow showers across our northeastern zones
through the morning that are developing along the southern edge of
a passing upper shortwave moving southeast across eastern Wyoming
and South Dakota. Not expecting much in the way of QPF from these
brief showers. To the southwest, we will see some snow shower
activity in the higher elevations of the Sierra Madre and Snowy
Ranges today into tonight as a weak shortwave moves down the
west/northwesterly fast flow aloft, but overall maybe 1 to 2
inches of new snow with that at most. Shortwave ridging tomorrow
should lead to drier and warmer conditions for Wednesday.

.LONG TERM...(Thursday through Monday)
Issued at 315 AM MDT Tue Mar 20 2018

Medium Range models in reasonable agreement Thursday and Friday,
showing the upper level ridge weakening and translating eastward
into the Great Plains. This will likely result in a higher chance
of unsettled weather for the weekend, but before that, pleasant
weather is expected with high temperatures in the 60`s to mid 70`s
across the eastern plains Thursday and Friday afternoon, with
50`s west of Interstate 25 as a cold front begins to impact Carbon
and Albany counties. May see some very windy conditions with some
potential for strong wind gusts ahead and along this front on
Friday. Models are struggling to come into agreement with llvl and
700mb gradients along I-80 during this time, so only increased
winds by 5 to 10 mph for now, mainly in the wind prone areas. Rain
showers are possible each afternoon with marginal instability,
mainly near the mountains. Can not rule out a few thunder showers
as well on Friday.

For the weekend and early next week, models and ensemble forecasts
are out of phase with regards to shortwave energy and the main
Pacific upper level trough forecast to push onshore late this week
and early in the weekend. Believe conditions will become
unsettled sometime late Saturday through next Monday, but due to
considerable differences in timing with not, can not pin down
anything specific at this time. Expect it to become cooler Sunday
and Monday with lows below freezing and highs struggling to reach
45 to 50 across most locations. Kept POP between 10 to 20 percent
outside the mountains mainly due to large differences in timing of


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1134 AM MDT Tue Mar 20 2018

Breezy northwest winds at 15 to 25kts will continue to dominate
the area this afternoon. In addition, we will see more snow
showers, due to decent instability in place. However, these snow
showers will not be as widespread as yesterday, due to less
boundary layer moisture and more subsidence building from the
upper level ridge. Wind speeds are expected to be lighter
tomorrow, but it will still be breezy in KRWL.


Issued at 240 AM MDT Tue Mar 20 2018

We will see some breezy conditions today across parts of
southeast Wyoming, however relative humidity values will be above
critical thresholds around 25 percent most locations. Winds still
look to be lighter on Wednesday except across portions of Carbon
county, although min RH values 30 to 50 percent depending on site




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