Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 200151 AAA

Area Forecast Discussion...UPDATED
National Weather Service Cheyenne WY
751 PM MDT Tue Sep 19 2017

Issued at 751 PM MDT Tue Sep 19 2017

Been an evening of frequent updates due to narrow zone of high
winds along the I-25 corridor. We issued a High Wind Warning to
highlight occasional gusts from the northwest to near 60 mph
being observed from Cheyenne north to just south of Wheatland
along the Interstate 25 corridor. As the surface cold front moves
farther to the southeast, the mechanism generating the strong west
to northwest flow along and just east of the south Laramie Range
will gradually weaken through midnight...but still expect windy
conditions well into the overnight period across parts of SE
Wyoming. Snow showers to the west are also diminishing with light
rain at the current time being reported at Laramie.


.SHORT TERM...(This evening through Thursday Night)
Issued at 305 PM MDT Tue Sep 19 2017

Cold front moving into the plains currently and will move across
the Panhandle by early this evening. Expect area of rain and some
light snow to continue out west for the rest of the afternoon then
break up this evening as a shortwave lifts north away from the
area. Skies gradually clearing later tonight.

Dry and mild conditions on tap for Weds with breezy conditions
over the plains in the afternoon as decent mid level flow mixes
down. mainly clear Weds night and Thursday as the upper flow turns
southwesterly and advects some drier air over the region. Warmer
Thursday ahead of significant upper trough digging over the
western CONUS.

.LONG TERM...(Friday through Monday)
Issued at 305 PM MDT Tue Sep 19 2017

Models are in rather good agreement at showing a cool and unsettled
period from Friday into early next week.  Unseasonably deep upper
trough will be centered across the Great Basin on Friday.  Little
movement is forecasted through Saturday, and then the trough will
shift eastward slowly into early next week.  This will keep the CWA
in an area of good upper level divergence and large scale lift from
Friday evening into Monday morning, with an extended period of
elevated precip chances.  Wet bulb zero heights and snow levels will
generally remain above 10000 ft through Saturday and then fall by
Sunday night to Monday to around 8000 ft as the colder air aloft
moves overhead.  Current thinking is that lower elevations will be
mostly rain through early next week, with the higher terrain of the
Sierra Madre and Snowy Ranges potentially seeing more significant
accumulations.  Highs will struggle to get out of the low 50s by
Monday, which is 15-20 degrees below normal for late September.


.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 751 PM MDT Tue Sep 19 2017

Mainly a wind forecast next 12 hours with higher winds Cheyenne to
Scottsbluff and Sidney gradually lessening through 06Z. Ceiling
VFR through the night into tomorrow with winds going more
southwesterly (but lighter) tomorrow.


Issued at 305 PM MDT Tue Sep 19 2017

Cold front will sweep across the area late this afternoon into
early this evening bringing much cooler air and a period of gusty
winds behind it. There will be areas of rain and snow over mainly
western districts into this evening before ending. It will be a
little cooler Wednesday. Some elevated fire weather concerns are
expected over the plains Wednesday afternoon as humidities look to
fall to about 15 to 20 percent and winds gust close to 25 mph.
Warm temperatures will occur Thursday then an approaching low
pressure system will bring cooler and wetter conditions by the


WY...High Wind Warning until midnight MDT tonight for WYZ106-117-118.



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