Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 191124
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
524 AM MDT Mon Jun 19 2017

.SHORT TERM...(Today through Wednesday)
Issued at 324 AM MDT Mon Jun 19 2017

Models in good agreement and show a benign weather pattern across
the Front Range early this week. A strong upper level ridge, which
is responsible for the heat wave across the southwest United
States, will begin to nudge north and east today. This will result
in high temperatures in the upper 70`s to mid 80`s across the area
with even warmer temperatures on Tuesday. No precipitation is
expected through tonight due to a significant stable/dry layer
around 500mb. Can not rule out a few showers and some isolated
thunder over the mountains and adjacent high valleys and plains
across southeast Wyoming late Tuesday afternoon and evening as
some moisture begins to push back into the region. Models do
indicate a weak shortwave disturbance moving eastward across the
area. Most places will not see any activity due to the strength of
the upper level ridge and associated subsidence aloft.

For Wednesday, Models show a weak cool front moving south and then
backing westward into the Laramie Range, resulting in upslope
east to northeast winds. It may be a few degrees cooler Wednesday
afternoon compared to Tuesday, but the front moves into the area
later in the day, so do not anticipate much of a temperature
change. Believe the models are not handling the boundary layer
moisture and instability, especially further south. Model
soundings do show at least some chance of showers and
thunderstorms depending on the timing of the front with CAPE
values around 1000 j/kg and cooling aloft between 600mb to 400mb.
Increased POP late in the afternoon and towards the evening. Most
of the activity looks to be high cloud-base thunder showers with
maybe a threat of strong gusty winds.

.LONG TERM...Wednesday Night through Sunday...

The models are showing a change to much cooler temps by this
upcoming weekend.  Westerly flow aloft will dominate the pattern
through Friday.  A weak front will push across the region on
Thursday morning with slightly cooler temps.  Convective chances
will be rather small on Thursday aftn, although cannot rule out an
isolated storm especially in areas near the Colorado Border.  All
long range models show a potent shortwave diving southeastward
across the region by late Friday and Saturday.  The 00Z GFS is
around 18 hrs earlier with the fropa on Friday aftn compared to the
Euro (fropa Saturday morning).  Regardless of the soln, temps on
Saturday will be much cooler, perhaps as much as 20 degrees below
normal. The best chance of convection across the plains may occur on
Friday evening/night just ahead of the front.  A much drier and
stable airmass behind the front would tend to stymie tstms over the
weekend.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 513 AM MDT Mon Jun 19 2017

Vfr cigs with bases around 10000 ft AGL are expected across the
Nebraska Panhandle through around 15Z. Winds will remain
relatively light through the period with gusts mostly below 20
kts.  No storms are expected to impact aviation this afternoon.

&&

.FIRE WEATHER...
Issued at 224 AM MDT Mon Jun 19 2017

Warm and dry conditions are expected through the middle of this
week with relative humidities around 15 percent in the afternoon
west of the Laramie Range. Winds are expected to be relatively
light with green fuels, so no impacts are anticipated. A strong
cold front is expected to impact the region later this week and
especially into next weekend with cooler temperatures and a more
favorable chance of precipitation.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&

$$

SHORT TERM...TJT
LONG TERM...ZF
AVIATION...ZF
FIRE WEATHER...TJT



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