Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 210317
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
917 PM MDT SAT AUG 20 2016

.UPDATE...
Issued at 909 PM MDT Sat Aug 20 2016

Critical fire weather conditions probabilities increasing for both
Sunday and Monday. Issued Fire Weather Watches for many of our
zones for both Sunday and Monday. See Fire Weather Discussion
below.

&&

.SHORT TERM...(This evening through Monday)
Issued at 221 PM MDT Sat Aug 20 2016

After a relatively cool-ish Saturday we will see a gradual
warming trend over the next couple of days as the upper trough
moves out to the east and we see high pressure aloft build
westward across the central Rockies. The NAM was the lone model
hinting at some radiation fog by early morning in the Laramie
Valley, however under deep insolation today and a much drier
boundary layer compared to this time yesterday, not thinking fog a
likely bet again tonight over the I-80 Summit into the Laramie
Valley. Otherwise...Models fairly consistent in maintaining a
deeply dry airmass across southeast Wyoming and the western
Nebraska Panhandle through Sunday with some return moisture
working up across the Sierra Madre and Snowy Ranges Monday
afternoon (lower end chance PoPs for afternoon showers and
Thunderstorms). Main concern on the forecast desk for the next 48
hours comes in the fire weather department as we trend toward more
critical fire behavior considerations Monday afternoon (See fire
weather section of this discussion).

.LONG TERM...(Monday night through Saturday)
Issued at 221 PM MDT Sat Aug 20 2016

Models continue to show a potent upper low skirting across the
US/Canadian border Monday night through Thursday. An associated cold
front will drop down across the forecast area Tuesday morning
bringing cooler temps through midweek. Breezy conditions will occur
ahead of the front along and west of the Laramie Range on Monday
night, with breezy north-northwest winds across the plains on
Tuesday in the wake of the front. Best Chance for precip should
be along and west of the Laramie Range as the front convergences
along the Laramie Range, and then slowly works it`s way westward
through the high country. For Wednesday, a shortwave trough
rounding the base of the main low will combine with persistent
llvl upslope flow in the post frontal environment to generate
another round of showers and storms from the late morning through
late afternoon. Looks to be a broader coverage of activity for
the forecast area. Temperatures will remain somewhat moderate
through the end of the week in energetic cyclonic flow, with
continued chances for showers and thunderstorms through the
period. Models then show another fairly potent shortwave diving
south into the northern plains/Rockies from Canada on Friday,
inducing stronger southeasterly upslope flow across our forecast
area, and thus a better shot for convection. May see stratus/fog
return during this time as well.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 500 PM MDT Sat Aug 20 2016

VFR.


&&

.FIRE WEATHER...
Issued at 909 PM MDT Sat Aug 20 2016

Went ahead with a fire weather watch for areas west of the Laramie
range Sunday. Looking at observations today, we were on the verge
of Red Flag criteria at Saratoga, Laramie and Rawlins. Its going
to be warmer and drier Sunday with same upper level winds, so felt
confident enough to issue the watches. Monday looks to be even
more critical with Red Flag Warning conditions looking fairly
probably with gusty winds 20 to 30 mph and relative humidity
values down to around 10 percent for FWZ 301-304, 306, northern
308 and even out into the northern nebraska Panhandle FWZ 311.
Will let next shift take another look at it but thinking is we
will likely need a warning for Carbon and Albany Counties Sunday.

&&

.CYS Watches/Warnings/Advisories...
WY...Fire Weather Watch from Monday afternoon through Monday evening
     for WYZ301>304-306-308.

     Fire Weather Watch from Sunday afternoon through Sunday evening
     for WYZ303-304-306-308.

NE...Fire Weather Watch from Monday afternoon through Monday evening
     for NEZ311.

&&

$$

UPDATE...GCC
SHORT TERM...JG
LONG TERM...RJM
AVIATION...RUBIN
FIRE WEATHER...GCC



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