Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 230020
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
620 PM MDT Sun Oct 22 2017

.UPDATE...
Issued at 608 PM MDT Sun Oct 22 2017

The High Wind Warning were allowed to expire outside of the wind
prone areas in southeast Wyoming since gusts have lowered quite a
bit over the past 2 or 3 hours. High Wind Warning for the wind
prone areas will continue until 4 am since the pressure gradient
along the Snowy and Laramie ranges will be slow to relax tonight.
Still expect gusts over 60 mph at these locations along I-80
between Rawlins and Cheyenne, and I-25 north of Cheyenne towards
Wheatland. A surface cold front, which is still in Montana and
northern South Dakota at this hour, is expected to move southward
tonight. This front will help stabilize pressure gradients across
the area and shift winds into the north by early Monday. Isolated
rain/snow showers are possible across the mountains and eastern
plains as this front moves south.

&&

.SHORT TERM...(This evening through Tuesday)
Issued at 201 PM MDT Sun Oct 22 2017

Tonight...Expect stronger winds at lower elevations of the high
wind warning, to slowly decrease overnight and especially as winds
decouple in the low levels. Craig to Casper 850/700 mb height
gradients remains sufficient tonight to warrant keeping the high
wind warning for our wind prone locations such as Arlington,
Vedauwoo and the I-80 summit.

Monday...Flow aloft continues to veer to north northwest with strong
flow, helping to produce a windy day across our counties. Cooler in
the wake of the cold front that passes early in the day.

Monday night...Colder night in the wake of the cold front.

Tuesday...Slow warming trend develops as the airmass begins to
moderate, though the north northwest flow aloft will retard heating
potential. Continued breezy to windy based on the progged low and
mid level gradients. Continued dry with lack of low and mid level
moisture.

.LONG TERM...(Tuesday night through Sunday)
Issued at 201 PM MDT Sun Oct 22 2017

Fairly active northwest flow over the northern Rockies will send a
cold front through the region about every 3-4 days this week and
next weekend. Wednesday will feature the warmest (& breeziest) day
of the week as afternoon temperatures soar into the 60s west of
the Laramie Range, with 70s across the eastern plains. Would not
be surprised if these need to be bumped up over the coming days
as this is a favorable pattern for warmer conditions east of the
mountains than what models suggest. Wednesday will likely be the
next critical fire weather day too, as the air mass is dry. Low-
level gradients will tighten Wednesday as well, setting the stage
for a potential marginal high-wind event in typical prone areas.
Cold front moves north to south Wednesday night and Thursday,
turning winds northerly, cooling temps, and producing a period of
snow. It`s a quick hitting system, but could see a few inches for
areas west of I-25 on Thursday. Temperatures will be 30 degrees
colder between Wednesday and Thursday with highs only reaching
the 40s. Snow comes to an end Thursday night. Temperatures remain
cold on Friday, with slow moderation back towards seasonal normals
next weekend. Dry conditions are expected Friday through Sunday.

&&

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

VFR conditions will prevail through late this evening. Some lower
CIGS will develop over the western Nebraska panhandle after midnight
as a front moves southward, but expect CIG heights to be just above
MVFR criteria at this time. Otherwise, very windy conditions will
continue tonight with a brief lull before the cold front moves into
Wyoming by early Monday morning. Expect gusts between 30 to 40 knots
at times from KRWL eastward to KCYS.  Winds will shift into the
north and become gusty across the eastern plains early Monday
morning after 08z.


&&

.FIRE WEATHER...
Issued at 201 PM MDT Sun Oct 22 2017

Minimal concerns Monday or Tuesday based on forecast humidities.
However, concerns will increase on Wednesday as the afternoon
humidities approach 15 percent over and near the I-25 corridor.
Concerns decrease after that as humidities will be higher for
Thursday into next weekend.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...

WY...High Wind Warning until 4 AM MDT Monday for WYZ106-110-116-117.

NE...None.
&&

$$

UPDATE...TJT
SHORT TERM...RUBIN
LONG TERM...CAH
AVIATION...TJT
FIRE WEATHER...RUBIN



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