Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 202021
AFDCYS

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

.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 behavoir 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, wtih breezy north-northwest winds across the plains on
Tuesday in the wake of the front. Best chacne for precip should be
along and west of hte 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 rouding the base
of the main low will combine with persistent llvl upslope flow in
teh post frontal environment to generate another round of showers
and storms from thelate morning through late aftenroon. 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 failry
potent shortwave diving south into the northern plains/Rockies from
Canada on Friday, inducing stronger southeasterly uplopse 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 18Z TAFS through 18Z Sunday afternoon)
Issued at 1147 AM MDT Sat Aug 20 2016

VFR conditions are expected to prevail for the terminals through
Sunday morning. Could see brief, and very localized fog in the
Laramie Valley once again tonight, but am not confident it will
affect KLAR so left it out of the TAF for now. Gusts around 20 kts
are possible for most terminals this afternoon, except for KBFF
and KCDR.

&&

.FIRE WEATHER...
Issued at 221 PM MDT Sat Aug 20 2016

Not much change from the previous forecast package in our
thinking on the fire desk this afternoon. Tomorrow will see
elevated fire weather concerns west of the Laramie Range for
wyoming zones 303, northern 308, and 302. 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 zones 303, northern 308, 302
and 301. Will let shift take another look at it but thinking is we
will likely have a Fire Weather Watch out and issued within the
next few hours for those zones.

&&

.CYS Watches/Warnings/Advisories...
WY...None.
NE...None.
&&

$$

SHORT TERM...JG
LONG TERM...RJM
AVIATION...RJM
FIRE WEATHER...JG



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