Area Forecast Discussion
Issued by NWS Cheyenne, WY

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS65 KCYS 310002

Area Forecast Discussion
National Weather Service Cheyenne WY
602 PM MDT TUE AUG 30 2016

.SHORT TERM...(This evening through Thursday night)
Issued at 240 PM MDT Tue Aug 30 2016

Some isolated convection has fired along a weak convergence zone
around the southeast Wyoming/northern Colorado border this
afternoon...on the northern periphery of an elongated upper low
over Colorado. This will persist through late in the afternoon
with some instability but will dissipate early in the evening with
loss of heating. Moist flow on southerly winds may be enough for
some low clouds and fog mainly from far southeast Wyoming across
the southern Nebraska Panhandle later tonight into Weds morning.

An upper high will build over the region Wednesday into Thursday
boding for warm and mainly dry weather across the CWA. Surface
winds will increase especially over the plains Tuesday afternoon
and again Weds as the gradient steepens between a surface high
over the northern and central plains and falling pressures over
the northern Rockys. Atmosphere should be sufficiently capped so
convection should be held off into Thursday. On Thursday the
upper ridge axis will shift east of the area leaving swly flow
aloft. A weak impulse will approach the area and should set off
at least isolated convection Thursday afternoon and
evening...mainly around the mtns.

.LONG TERM...(Friday through Monday night)
Issued at 240 PM MDT Tue Aug 30 2016

Southwest flow will strengthen overhead Friday and on through the
weekend in advance of the upper low moving across the PacNW and
northern Rockies. Models remain fairly consistent showing a number
of weather disturbances moving over the Rockies as the upper trough
stalls over the western CONUS, however differences do exist with
strength and timing of the individual systems. Confidence remains
relatively  high though that gusty south-southwest winds and
showers/storms will occur nearly each day within this flow pattern.
To start, a leeside surface pressure trough will develop in
advance of the system on Friday, shifting to the east on
Saturday. ECMWF/GFS do show some differences in timing of this
feature, but still expect fire weather concerns out to the west
due to gusty southwest winds and dry humidities both Friday and
Saturday. Looking at widely scattered convection in the afternoon
over much of the area as well, with a few strong storms possible
east of the sfc trough. The main cold front associated with this
system doesn`t look to move across the forecast area until
Saturday night or Sunday, and in the wake of the leeside trough.
Will remain active for convection for Sunday and Monday, with some
strong to severe storms possible across the plains on Monday in
the postfrontal, upslope environment. Temperatures will slowly
but steadily cool off through the period, with Monday looking to
be the coolest day as temps should be in the 60s/70s. Stratus and
fog chances will be high Friday night with strong southerly flow
in place, and again on Monday night in strengthening upslope flow.


.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 557 PM MDT Tue Aug 30 2016

A few showers or weak thunderstorms will remain a possibility over
portions of southeast WY and the western NE Panhandle through mid-
evening before diminishing. There is potential for areas of fog or
low ceilings after 08z, mainly for KCYS/KBFF/KSNY. Expect clearing
after 15z with low-level cumulus developing in the afternoon.


Issued at 240 PM MDT Tue Aug 30 2016

Breezy to windy conditions expected to develop over the plains
Weds through Thursday but humidities look to stay well above
critical levels. Concerns increase out west late in the week as
winds there increase and humidities get rather low.


.CYS Watches/Warnings/Advisories...


FIRE WEATHER...RE is the U.S. government's official web portal to all federal, state and local government web resources and services.