Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 220942

Area Forecast Discussion
National Weather Service Cheyenne WY
342 AM MDT Thu Jun 22 2017

.SHORT TERM...(Today through Saturday)
Issued at 300 AM MDT Thu Jun 22 2017

Warm night so far with the surface low to the east of the Laramie
Range and downslope westerly winds. Models continue to show a
transition to cooler temps behind a cold front that is progged to
push across the plains between 12-15Z. Highs will be 10-15 degrees
cooler to the east of the Laramie Range, back to around normal.
The air mass will be rather stable behind the front, with the
better low level moisture pushed south into Colorado. SPC has
moved the slight risk southward into northern Colorado, and
definitely agree with this as capping will be a problem in areas
near Interstate 80. The HRRR and NCAR models keep the bulk of
convection over northern Colorado, but did keep slight chance PoPs
right along the Colorado border. Increasing ascent and isentropic
lift ahead of a shortwave could actually result in the best chance
of showers by late tonight over the southern NE Panhandle.

Northwesterly flow aloft along with surface high pressure to the
east of the Laramie Range will keep things cool through Saturday.
Highs on Friday/Saturday will mostly be in the 60s to mid 70s over
lower elevations. Models are not as cool for Saturday so bumped
temps up a bit. Overall, Friday and Saturday are looking like
rather pleasant days as winds will be weak and convective chances
minimal in the stable post frontal air mass.

.LONG TERM...(Saturday night through Wednesday)
Issued at 330 AM MDT Thu Jun 22 2017

Minor differences with the 00Z medium range models and their ensembles,
so forecast confidence is moderate to high. CWA will be sandwiched
between a mean eastern CONUS trough and western CONUS ridge, with
northwest flow aloft through Monday. A weak shortwave sliding
southeast across the eastern plains late saturday night may trigger
widely scattered showers. Sunday will be mostly dry with cooler
than normal temperatures. A few late day showers or weak t-storms
may form over the southeast plains and southern Laramie Range.
Dry weather is forecast Monday, with high temperatures warming to
near seasonal normals. The upper ridge flattens Tuesday as shortwave
energy drops south across the north-central CONUS. Isolated convection
will be possible over western NE Tuesday afternoon and east-central
WY Tuesday evening. Seasonal temperatures return Tuesday with highs
in the 70s and 80s. A dry Pacific cool front will pass through the
CWA Wednesday, lowering high temperatures a few degrees.


.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 300 AM MDT Thu Jun 22 2017

A cold front will progress south along and east of the Laramie Range
this morning with northerly winds gusting to 30 kt following its
passage. Winds become northeasterly and remain breezy this afternoon
across the plains, while westerly winds prevail over Carbon and
western Albany counties. Widely scattered t-storms will develop after
18Z from the southern Laramie Range eastward across the Cheyenne Ridge
into the early evening. VCTS at KLAR, KCYS and KSNY between 20Z and
03Z. Gusty outflow winds to 45 kt, small hail and brief MVFR visibility
in heavy rain may accompany the stronger convection. Rain showers will
linger into the overnight hours over the southeast plains.


Issued at 300 AM MDT Thu Jun 22 2017

No fire weather concerns over the next few days.  A cold front will
push across areas to the east of the Laramie Range this morning with
cooler temps and higher humidity values. It will still be quite dry
across western portions of Carbon county, with minimum humidity values
dropping to around 15 percent. Fuels are still green however, thus
no critical fire weather threat is forecasted out there.




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