Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 232134

Area Forecast Discussion
National Weather Service Cheyenne WY
234 PM MST Thu Nov 23 2017

.SHORT TERM...(This evening through Saturday Night)
Issued at 233 PM MST Thu Nov 23 2017

Tonight...Primary challenge will be the winds. Winds have already
begun to increase over our wind prone locations and with
strengthening gradients at the surface and aloft, we have decided to
begin the high wind warning early this afternoon. After midnight,
the NAM forecasts 700 mb winds to increase to 50 to 70 knots along
Interstate 25, with boundary layer showing near 50 knots. This
combined with decent subsidence should allow for some of the
stronger winds to mix down to the surface late tonight at Douglas,
Wheatland, Laramie and Cheyenne, so we have upgraded to a high wind
warning for the I-25 corridor and the Laramie Valley.

Friday...Fast moving shortwave trough aloft and its associated cold
front sweep across, producing a cooler day, albeit still relatively
mild for this time of year. With orographics, expect a chance of
showers over and near our Northern Laramie, Snowy and Sierra Madre

Friday night...Cooler night on tap with less wind and in the wake of
the cold frontal passage.

Saturday...Slightly cooler day with some thickness cooling and some
more cloud cover. Gradients suggest breezy to windy conditions
across southeast Wyoming.

Saturday night...Not as cold as Friday night as the airmass
moderates and with slightly more wind.

.LONG TERM...(Sunday through Thursday)
Issued at 233 PM MST Thu Nov 23 2017

Highly amplified upper air pattern returns to start the weekend
with strong ridging building over the Rockies through Sunday.
Southeast Wyoming will flirt with 580 dm heights at H5 and +8 C
temps at H7 by Sunday which should result in near record temps
once again especially over the plains. Still quite a spread
between the operational GFS and EC regarding the next strong upper
trough progged to cross the area from the west early next week.
GFS is much faster with the trough, keeping it an open wave while
driving a strong Pacific cold front through the area on Monday.
The EC is much slower and stronger, actually closing off the mid
level low over southern CO for a time on Tuesday. Don`t see much
support for the EC solution in the ensemble guidance and think the
pattern probably favors the more quickly ejecting and northern
system given the stronger jet energy downwind of the trough axis.
Should have a quick shot of mountain snow with the potential for
yet another wind event on Monday, this time more of a bora type
event with the strong cold frontal passage. Ridging builds in once
again behind this system for mid week, keeping us in a warm and
dry pattern.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1205 PM MST Thu Nov 23 2017

VFR conditions to prevail thru the period. Main aviation concern
will be periodic strong winds anticipated mainly at SE Wyoming
terminals today & tonight and across the entire region on Friday.
Wind gusts of 30-40 knots can be expected, with a periodic gust
upwards of 50 knots at KLAR and KCYS after 09Z.


Issued at 233 PM MST Thu Nov 23 2017

Minimal concerns based on projected winds and humidities.


WY...High Wind Warning until noon MST Friday for WYZ106-110-116-117.

     High Wind Warning from 2 AM to noon MST Friday for WYZ101-107-



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