Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 202023

Area Forecast Discussion
National Weather Service Cheyenne WY
223 PM MDT Fri Oct 20 2017

.SHORT TERM...(This evening through Sunday)
Issued at 213 PM MDT Fri Oct 20 2017

Tonight...Winds have increased across our western counties this
afternoon, as earlier shifts had predicted. Strong cold front blasts
eastward across our counties this evening with strong cold air
advection all night. Winds aloft increase to near 45 knots and with
downward vertical motion and cold air advection, some locations may
approach high wind criteria after cold frontal passage, though we
feel the strong winds will be rather isolated, thus have held off on
a high wind warning for the overnight. Looks like enough low and mid
level moisture for scattered to numerous showers over and near our
Snowy and Sierra Madre Ranges, especially this evening.

Saturday...Quite windy and much cooler day in the wake of the cold
front and with 700 mb temperatures progged near -6 Celsius, high
temperatures will be in the mid 40s at lower elevations west of
Interstate 25, with 50s east of I-25. Local wind models suggest a
windy day with winds remaining below high wind criteria based on
850/700 mb Craig to Casper gradients.

Saturday night...Inherited high wind watch for our wind prone
locations looks on track as 850/700 mb Craig to Casper gradients
increase significantly. Decent winds and low level mixing will limit
cooling potential for low temperatures.

Sunday...Strong winds look to continue, especially across our wind
prone locations based on the expected low and mid level gradients
and the Craig to Casper 850/700 mb height differences. Warmer
temperatures as the airmass begins to moderate in the wake of the
cold front and with rising 700 mb temperatures. With limited low and
mid level moisture, no precipitation is expected.

.LONG TERM...(Sunday night through Friday)
Issued at 213 PM MDT Fri Oct 20 2017

A weak frontal boundary will move through areas mainly east of the
Laramie Range on Monday which may cool things off a few degrees
compared to Sunday, but very little moisture will be associated
with this front. Therefore, we are not expecting anything more
than a few rain showers along the northern Panhandle. Then a
gradual warmup is expected Tuesday and Wednesday as a weak upper
level ridge noses its way into the region. The bigger changes will
be coming on Wednesday night into Thursday as a powerful cold
surges through the region. This front will bring much colder air
along with the potential for some snow after the front moves
through. Stay tuned to further updates.


.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1147 AM MDT Fri Oct 20 2017

Gusty winds will persist across KRWL this afternoon in advance of
a cold front moving through western Wyoming. This front will pack
quite the punch with strong gusty northwest winds developing
behind it. This front should move through KRWL around 02z and
KLAR/KCYS (03Z-04Z), and the Nebraska Panhandle sites between
05z- 07z. Not expecting much in the way of precipitation with this
boundary, due to a very dry boundary layer.


Issued at 213 PM MDT Fri Oct 20 2017

Some concern for conditions on Saturday with
humidities from 15 to 20 percent in the afternoon along with the
strong winds. Expect humidity recovery Sunday through Tuesday,
limiting concerns, with a decrease in humidities on Wednesday for
increasing concerns.

WY...High Wind Watch from Saturday evening through Sunday afternoon
     for WYZ106-110-116-117.



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