Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 291158

Area Forecast Discussion
National Weather Service Cheyenne WY
558 AM MDT Sat Jul 29 2017

.SHORT TERM...(Today through Sunday night)
Issued at 214 AM MDT Sat Jul 29 2017

Water vapor imagery continues to show our forecast area within a
fetch of moist air, thus expect persistence with regard to
precipitable water values (1-1.25") for today. Forecast soundings
corroborate this notion by showing a moist column along the Front
Range. The shortwave that is expected to bring another chance for
thunderstorms today is moving into western Wyoming at this hour, and
models show a secondary wave moving up from Colorado later today.
Expect these waves to combine forces to produce another fairly
convective day. Winds up to 500mb are progged to be relatively light
(15kts or less) with an upslope component from sfc-700mb. Therefore,
best likelihood for convection will be over the mountains and
upslope favored locales across the plains of southeast WY and
western NE. Wouldn`t be surprised to see some training of t-storms
or redevelopment along cold pool boundaries due to relatively weak
winds in the steering column especially along the Laramie Range and
into the western row of NE counties. Maintained word for heavy
rainfall in these areas for this afternoon and evening.
Boundary/cold pool amalgamation could also produce gusty outflow
winds, so maintained wording for this hazard as well. The flooding
potential will likely remain very localized as a result of
relatively dry antecedent conditions. Would expect showers/storms to
diminish with sunset, but models show active 500mb flow through the
night so may see some rainfall continue overnight.

Sunday looks pretty similar to today with perhaps slightly stronger
flow at 500mb and above. Maintained similar chances for
showers/thunderstorms in the afternoon and evening, and will have to
keep an eye on perhaps a heightened flooding threat across southeast
Wyoming depending on what happens today. Temperatures both today and
Sunday will be slightly below normal in the 70s and 80s.

.LONG TERM...(Monday through Friday)
Issued at 214 AM MDT Sat Jul 29 2017

A relatively active tstm pattern will continue through at least
the first part of the week. With the upper level ridge centered
across the Great Basin, the CWA will be under weak north to
northwest flow aloft. Daily chances of aftn/evening convection
will occur through Wednesday as PW values remain at around
0.75-1.0 inches. All models show a cold front pushing southward
over the region by Wednesday morning in response to a shortwave
moving through the Northern Plains. Convergence along the front
may serve as the focus for storms on Wednesday. A drier and more
stable airmass is progged across the CWA by Thursday/Friday, so
generally have lower PoPs after midweek. Temps will remain 5-10
degrees below normal through the extended period.


.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 551 AM MDT Sat Jul 29 2017

Ifr cigs are expected to continue across some of the Panhandle
sites through around 14Z. Vfr conditions will prevail through the
remainder of the taf period. Scattered showers and thunderstorms
are expected to develop in areas near the southern Laramie Range
by early afternoon. Brief heavy rain and mvfr vis will be possible
at LAR/CYS. Isolated storms will then move into the Panhandle
around 00Z.


Issued at 214 AM MDT Sat Jul 29 2017

Fire Weather concerns will be minimal this weekend through early
next week. Chances for showers and thunderstorms will be widespread
over southeast Wyoming and western Nebraska this weekend with a
pretty good bet much of this activity will produce wetting rains.
Coverage for showers and storms may progressively lessen through
early next week, but may not see much change in the pattern until
middle of next week.




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