Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 310916

Area Forecast Discussion
National Weather Service Cheyenne WY
316 AM MDT SUN JUL 31 2016

.SHORT TERM...(Today through Tuesday)
Issued at 230 AM MDT Sun Jul 31 2016

Today...Chances for early morning fog appear less than yesterday
based on current temperature and dewpoint spreads. Will watch closely
and paint areas of fog as necessary.

Flow aloft is zonal. Low level convergence axis sets up this afternoon
across our southwest and southern counties where theta-e ridge is
higher. Negative theta-e advection and warm mid level temperatures
should limit thunderstorm coverage elsewhere to isolated. Will
paint highest pops over southern Carbon and southern Albany counties
of Wyoming where moisture will be deeper and convergence greatest.
With relatively weak shear and instability, severe thunderstorms
look quite unlikely.

Tonight...With loss of daytime heating, thunderstorms expected to
end fairly quickly in the evening with clearing skies.

Monday...Low and mid level flow turns northerly with a more stable
airmass in place. Looks like enough moisture and instability to
generate isolated afternoon thunderstorms near the southern Laramie
Range and the Colorado state line. Dry elsewhere. Stuck close to NAM
and GFS MOS guidance temperatures.

Monday night...Influx of low level moisture seen on boundary layer
progs should produce relatively widespread areas of fog along and
east of the mountains and along and east of I-25, though including
the I-80 summit.

Tuesday...Weak shortwave and disturbance progged to move northward
through central Colorado with a decent low and mid level theta-e
ridge axis over our counties. With decent low and mid level moist
upslope southeasterlies, expect isolated to scattered afternoon
thunderstorms erupting over and near the southern Laramie Range and
Snowy Range. Cooler temperatures east of I-25 with increased cloud
cover and lower thicknesses and 700 mb temperatures.

.LONG TERM...(Tuesday night through Saturday)
Issued at 315 MDT Sun Jul 31 2016

The center of subtropical ridge will become situated over the south
central CONUS through the end of the week. A eastern Pacific upper
low will track east along the US-Canadian border mid-week. Another
trough will extend just inland of the Pacific coast Friday. The
flow aloft will remain west-southwest during most of the long term.
While much of the subtropical/monsoon moisture will remain over
the Southwest CONUS, models try to advect some northward into the
central Rockies late in the week. A fairly strong surface front
will push south across the CWA Wednesday night/early Thursday
morning, with southeast upslope flow advecting low level moisture
into the region. Above normal warmth Wednesday will cool back to
slightly below seasonal temperatures Thursday through Saturday.
Best chances for thunderstorms Wednesday and Thursday will be
near the Colorado border and over the eastern high plains. There
will be an increase in convective coverage Friday and Saturday as
a couple of shortwaves track northeast across Wyoming and Colorado,
and interact with increasing mid/upper level moisture.


.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 230 AM MDT Sun Jul 31 2016

Opportunity for patchy early morning fog for the high plains is marginal
at best, so have not mentioned in the 12Z TAFs. Prevailing winds will
be westerly 10-15 kt, with gusts to 20-25 kt across southeast Wyoming.
VFR will prevail outside late day convection. Cannot rule out brief
MVFR visibility in heavy showers, as well as gusty/erratic outflow
winds to 40 kt and small hail. Convection will wane after 03Z.


Issued at 230 AM MDT Sun Jul 31 2016

Relatively low humidities along and west of I-25, though fortunately,
winds will be relatively light the next few days minimizing the risk.


.CYS Watches/Warnings/Advisories...


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