Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 281814
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1214 PM MDT THU JUL 28 2016

.UPDATE...
Issued at 1158 AM MDT Thu Jul 28 2016

Convective complex that affected much of the Nebraska Panhandle
this morning has mostly moved east of the region with cool,
stable airmass in its wake. Southward pushing outflow boundary is
along Colorado border. It`s uncertain how much destabilization
will occur this aftn, thus affecting severe chances. The RAP has
good instability (1500-2000 J/kg) developing by late aftn in areas
along Interstate 80. Current thinking is that areas from the
southern Laramie Range to the southern Panhandle stand the best
chance of svr storms.

&&

.SHORT TERM...(Today through Friday night)
Issued at 300 AM MDT Thu Jul 28 2016

Today...Looks like another active day across parts of southeast
Wyoming and western Nebraska with the Storm Prediction Center
showing marginal risk east of a Douglas to Laramie line with a
slight risk along and east of I-25 and south of a Wheatland to
Alliance line.

A shortwave moves over northern and eastern Wyoming this morning,
producing scattered showers and thunderstorms across our northern
and eastern counties. Then, this afternoon, with a low and mid level
theta-e ridge axis in place, expect scattered thunderstorms along
and east of a Douglas to Laramie line, with progged CAPE from 2000
to 3000 J/kg early in the afternoon and shear of 45 to 50 knots
helping to produce isolated severe storms producing large hail and
damaging winds in the slight risk area. Severe storms are more
likely earlier in the day, compared to yesterday, with the earlier
passage of the shortwave.

Tonight...Scattered strong to isolated severe storms in the evening
across our southeast counties, then clearing skies. Areas of fog and
low clouds developing east of a Lusk to Cheyenne line after midnight
based on the boundary layer progs.

Friday...Afternoon and evening thunderstorm coverage will be more
isolated with less low and mid level moisture availability along
with the absence of a pronounced shortwave overhead.

Friday night...Isolated thunderstorms will mostly end in the evening
with a slight chance of showers and thunderstorms over western
Nebraska into the late night hours along a low level convergence
axis.

.LONG TERM...(Saturday through Wednesday)
Issued at 350 AM MDT Thu Jul 28 2016

Upper ridge builds over the Rockies and high plains this weekend.
Surface trough/dryline will remain nearly stationary along the
east slopes of the Laramie Range. Saturday will be dry with ridge
overhead. Sunday will be a bit more convectively active for the
mountains and adjacent plains of southeast Wyoming with a passing
upper level disturbance and upslope low level flow. Flow aloft
will be west-southwest with ridge rebuilding over the high plains.
Most of the subtropical moisture will remain to the south, with a
few diurnal mountain thunderstorms possible Monday. Mid levels will
warm Sunday and Monday with highs rising into the 80s-mid 90s. A
upper low and associated trough over the Pacific Northwest Tuesday
will track east-northeast across the northern Rockies into
southern Canada Wednesday as the upper high recenters over the
south central Great Plains. Consequently, the flow aloft backs to
the southwest. The ECMWF introduces some subtropical moisture into
the area by midweek, while the GFS depicts little or no QPF. Much
of the CWA will largely be dry, except for isolated diurnal
convection over the mountains and northeast plains. Temperatures
Tuesday and Wednesday will be a few degrees cooler, but still
above average for early August.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1214 AM MDT Thu Jul 28 2016

Initial thunderstorm complex that passed through western Nebraska
Panhandle sites has cleared the area. Cloud cover has been quick
to dissipate north of the North Platte River Valley...less so to
the south. Still think that the main concern to aviation ops will
be the expected redevelopment of thunderstorm activity later this
afternoon. Thunderstorm development and location will be heavily
dependent upon how quickly clouds break-up in the vicinity of the
higher elevations along with lingering outflow boundaries from the
morning convection. Confidence is not high enough to include
anything more than VCTS at this time. After thunderstorm threat
diminishes around 03z...will see low cigs/fog develop again late
tonight at KCYS...KSNY...KBFF...and KLAR.

&&

.FIRE WEATHER...
Issued at 300 AM MDT Thu Jul 28 2016

Minimal concerns the next few days based on expected humidities
and winds.

&&

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

&&

$$

UPDATE...ZF
SHORT TERM...RUBIN
LONG TERM...MAJ
AVIATION...CAH
FIRE WEATHER...RUBIN



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