Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 212101

Area Forecast Discussion
National Weather Service Cheyenne WY
301 PM MDT Sat Oct 21 2017

.SHORT TERM...(This evening through Monday)
Issued at 300 PM MDT Sat Oct 21 2017

Tonight...Inherited high wind warning for our wind prone locations
looks on track, although winds may not increase as much this evening
as earlier expected. Still not enough confidence to delay the
warning. Craig to Casper 850/700 mb height gradients strengthen
significantly and reach 69 and 64 meters by 12Z Sunday. Breezy to
windy at other locations based on progged low and mid level

Sunday...Strong and strengthening northwest flow aloft occurs with
the NAM projecting 60 to 70 knot winds at 700 mb from Rawlins to
Laramie to Cheyenne. 850/700 mb height gradients from Craig to
Casper remain high, in the 60 to 70 meter range. In addition, MET
and MAV guidance showing winds in excess of 30 knots during the day,
so with all factors considered, we feel fairly confident that
stronger winds aloft will be able to mix down to the surface, and
thus we have expanded the high wind warning to include Douglas,
Rawlins, Laramie, Wheatland and Cheyenne after 9 am, continuing
through the afternoon. Fortunately, temperatures will be warmer as
the airmass moderates.

Sunday night...Strong winds may continue over our wind prone
locations based on strengthening 500 mb winds, though the 700 mb
gradient weakens, and therefore, we will not extend the high wind
warning at this time. Another shortwave trough aloft moves across
the northern plains states with a cold front entering our counties,
possibly producing a few baroclinic band showers over our northern
counties after midnight. Dry elsewhere.

Monday...Flow aloft continues to veer to north northwest with cold
air advection limiting high temperatures and making for a cooler and
windy day. The lower and mid levels of the atmosphere appear too dry
to support any precipitation.

.LONG TERM...(Monday night through Saturday)
Issued at 300 PM MDT Sat Oct 21 2017

Elevated winds Sunday night before a backdoor cold front moves
into the area from the northeast. 700mb temperatures drop to -7C
across the northern Panhandle, but cold temperature short lived as
westerly winds return Monday afternoon.

Warming temperatures and windy conditions Tuesday and Wednesday as
700mb temperatures climb back to +10C. GFS 700mb winds close to
50kts, so wind prone areas probably seeing warning level winds.

Stronger system set to move into the area Thursday with fairly
widespread rain and snow mix, turning to snow once the colder
temperatures arrive Thursday night.


.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1206 PM MDT Sat Oct 21 2017

VFR conditions will prevail thru the period. Main concern that
will have impact to aviation ops will be strong winds that will
continue for the rest of the afternoon. Winds will become even
stronger at terminals after 15z Sunday, with gusts to around 50
knots at KRWL, KLAR, and KCYS. Winds will be somewhat lighter at
western Nebraska Panhandle sites, though breezy conditions are
still expected.


Issued at 258 PM MDT Sat Oct 21 2017

Minimal concerns through Tuesday based on minimum humidities.
Concerns increase on Wednesday, however, as minimum humidities
approach 15 percent in the afternoon.


WY...High Wind Warning from 7 PM this evening to 6 PM MDT Sunday for

     High Wind Warning from 9 AM to 6 PM MDT Sunday for WYZ101-107-




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