Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 172000

Area Forecast Discussion
National Weather Service Cheyenne WY
200 PM MDT Mon Oct 17 2016

Issued at 158 PM MDT Mon Oct 17 2016

Update to massage grids for current conditions and to add high
wind warning across the southern panhandle.


.SHORT TERM...(Today through Tuesday)
Issued at 238 AM MDT Mon Oct 17 2016

Today...Inherited gridded forecasts and highlights are in good shape
with some minor adjustments. As far as strong winds go, fast moving
shortwave aloft and cold front will quickly sweep west to east
across our counties with an 80 to 90 knot 500 mb speed max zipping
across, along with a 100 to 140 knot 300 mb jet max. Models,
including their soundings, show enough subsidence and dry adiabatic
layer to help the stronger 50 to 55 knot 700 mb winds mix down to
the surface, especially across southeast Wyoming. We have decided to
expand the high wind warning to include Converse, Niobrara and
Goshen counties based upon the NAM and GFS numerical guidance and
progged soundings. Winds across western Nebraska may get close or
even exceed high wind criteria, though with it being a borderline
situation, we have opted to continue the inherited wind advisory and
advise the day shift to monitor closely. Scattered to numerous
showers expected along and west of I-25 in moist flow aloft.
Guidance high temperatures close on the models and have compromised
between the models. Local wind models also suggest a decent chance
of high winds at Bordeaux and Cheyenne.

Tonight...Fortunately, winds aloft will decrease and surface winds
will mostly decouple, though it will remain breezy at times, with
relatively mild overnight minimum temperatures due to mixing.
Precipitation will end as the low and mid levels dry out.

Tuesday...Next fast moving, low amplitude shortwave aloft moves into
western Wyoming, spreading increasing clouds and rain and snow
showers across our Snowy and Sierra Madre Ranges in the afternoon.
Much less wind expected based on low and mid level gradients and
more cloud cover that will limit mixing. Cooler in the wake of the
cold front, especially east of I-25, and again have compromised
between the NAM and GFS MOS maximum temperatures for highs.

.LONG TERM...(Tuesday night through Sunday)
Issued at 238 AM MDT Mon Oct 17 2016

Tuesday night-Wednesday:
The models are in fairly good agreement in showing a progressive shortwave
moving through the northern Rockies. This shortwave will bring
scattered rain/snow showers to the forecast area. The best focus
at this point appears to be along the sierra/snowy mountain
ranges, but there may be a good chance along the mid level frontal
boundary as it surges southeast through Southern Wyoming and the
southern Panhandle Tuesday night. Not real confident that it will
yield to much precipitation, but there will be some instability
which may yield to some banded rain/snowfall. Colder temperatures
will also accompany this front as it pushes through the area
Tuesday night. These colder temperatures will persist through the
day on Wednesday along with the potential for a few instability

Wednesday night-Sunday:
A strong surface high is expected to settle over western Wyoming
Wednesday night which will allow for a cold start for most of the
area with lows mostly in the 20s. Beyond this timeframe, we should
see a warming trend as the upper level ridge builds across the
southwest U.S. This may keep us in a breezy pattern, but it should
be fairly mild with afternoon highs climbing from the 50s and 60s
on Thursday to the 60s and 70s this weekend.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1159 AM MDT Mon Oct 17 2016

Strong and gusty winds will be the main aviation concern today as
westerly winds gusting 40 to 50 kts will be common at all
terminals. Occasional gusts in excess of 50 kts are likely at the
Wyoming locations as well. Rain and high elevation snow showers
occurring this morning should push south by 20Z with VFR
conditions prevailing thereafter. Winds will slowly diminish with
sunset, and should remain relatively light overnight. Breezy
conditions will return for Tuesday afternoon, but speeds will be
less than today by at least half.


Issued at 238 AM MDT Mon Oct 17 2016

Inherited Red Flag Warning for today looks good especially with
expected winds and humidities nearing 15 percent. Fortunately,
humidities will be higher Tuesday through Thursday, limiting
concerns. Humidities will again lower Friday and Saturday, and we
will closely monitor this.


WY...High Wind Warning until 7 PM MDT this evening for WYZ104>110-

NE...Wind Advisory until 7 PM MDT this evening for NEZ002-003-019-021-

     High Wind Warning until 7 PM MDT this evening for NEZ020-054-055.



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