Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 231011

Area Forecast Discussion
National Weather Service Cheyenne WY
411 AM MDT Fri Mar 23 2018

.SHORT TERM...(Today through Saturday night)
Issued at 410 AM MDT Fri Mar 23 2018

Current obs across the area show pretty mild temperatures for 3 AM
with most locations above 40 degrees, with even a few places in
the lower 50`s. The mountain wave and area of subsidence which
resulted in isolated wind gusts over 75 mph earlier between Elk
Mountain and Laramie has since weakened and pushed east. Gusts are
now between 40 to 50 mph, and if they continue to weaken, may end
up cancelling the High Wind Warning for that area before noon

Another warm day is expected today, but it will likely be slightly
cooler compared to Thursday as a weak disturbance aloft brings
some cooler air to the region. Although partly cloudy skies are
expected early this morning, clouds will increase through noon as
this disturbance moves over the area. This will keep afternoon
temperatures in the 50`s across most of southeast Wyoming with low
to mid 60`s east of I-25. With daytime instability, lift
associated with the shortwave disturbance, and some llvl moisture,
believe there is a good chance for at least widely scattered
thunderstorms across most of the area this afternoon, with the
best chance across western Nebraska and far eastern Wyoming where
the highest moisture content is located. Confidence is high enough
to add scattered thunderstorms to the southern and central
panhandle of Nebraska and far southeast Wyoming late this
afternoon with POP above 40 percent, and as high as 80 percent in
the mountains. Another minor concern is mountain snowfall, which
should increase today. However, SNOTEL obs show temperatures still
above freezing over the Sierra Madre and Snowy Ranges as high as
11000 feet, with a few locations above 40 degrees. Will hold off
on a Winter Weather Advisory since it will take a while for this
layer to cool since the upper level disturbance is relatively
weak. Otherwise, expect the upper level ridge to rebuild over the
area tonight and Saturday with a decreasing chance for
precipitation and clearing skies. Kept POP below 10 percent on
Saturday due to midlevel subsidence, although can not rule out a
few rain showers or sprinkles with highs ranging from the mid 50`s
to mid 60`s across the area.

.LONG TERM...(Sunday through Thursday)
Issued at 323 AM MDT Fri Mar 23 2018

A warm, but unsettled start to the extended forecast period with a
vigorous short-wave tracking across the Intermountain West. Strong
upper-level difluence in advance of this feature should contribute
to surface cyclogenesis over northeastern Colorado, along with the
development of an inverted surface trough extending to the north &
east across the western Nebraska Panhandle. Increasing forcing for
ascent, coupled with moist southwest flow aloft will be supportive
of shower/thunderstorm development by 00z Monday. Convection could
become particularly widespread over the NE Panhandle on Sunday Eve
with enhanced low-level convergence along the surface trough. CAPE
around 500-1000 J/kg per the GFS, coupled w/excellent deep layer &
low level shear with strong veering and 30-40 knot flow at H5, may
be sufficient for an organized albeit marginal threat for possible
severe thunderstorms. On Monday/Tuesday, the models remain in good
agreement w/ a splitting upper-level pattern as a closed low takes
shape over southern AZ/NM. Meanwhile, the majority of the northern
stream energy is shunted to the northeast over the Dakotas. Expect
to see a good chance for snow across much of the area, mainly with
the cold frontal passage. However, a lack of any sustained dynamic
support combined with notable dry air entrainment aloft suggests a
low-impact event (for most areas) at this time. We cannot rule out
several inches of accumulation over northern areas during the late
Sunday Night/Monday Morning time frame, as long as banding is able
to develop invof the surface front before the energy splits. Still
something to pay close attention to, but widespread heavy snowfall
seems unlikely at this time.


.AVIATION...(For the 12Z TAFS through Saturday morning)
Issued at 323 AM MDT Fri Mar 23 2018

Very windy conditions are expected over the southeast Wyoming
terminals today with gusts up to 40 kts expected late this morning
and this afternoon. Lighter winds over western Nebraska, but a
few locations may see gusts as high as 30 knots today. Otherwise,
VFR conditions expected to prevail today with near MVFR CIGS
possible across western Nebraska through this evening as
thunderstorms develop and push northeast. Good chance of
thunderstorms across most locations today, so will likely add VCTS
for the next TAF issuance.


Issued at 323 AM MDT Fri Mar 23 2018

Minimal Fire Weather concerns through the weekend with daytime
relative humidities lowering to 20 to 30 percent each day until
Sunday. There is a good chance for thunderstorms this afternoon as
a disturbance aloft moves across the area. Otherwise, generally
unsettled weather into early next week as another Pacific system
moves across the intermountain west, bringing snow and colder
temperatures to the area Monday and possibly Tuesday.


WY...High Wind Warning until noon MDT today for WYZ110.



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