Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 251126

Area Forecast Discussion
National Weather Service Cheyenne WY
526 AM MDT Sun Jun 25 2017

.SHORT TERM...(Today through Tuesday)
Issued at 234 AM MDT Sun Jun 25 2017

Our area remains under the influence of northwesterly flow aloft
through Monday. At the surface, cool high pressure remains in
place over the high plains with light easterly to southeasterly
flow developing today and continuing through Monday. Models
continue to show some low level moisture trying to work its way
back to the Laramie Range today and instability will be a bit
higher than the past few days so can`t rule out an isolated
thunderstorm this afternoon. Forcing mechanisms remain negligible
other than heating over the higher terrain and upstream soundings
show a subsidence inversion aloft which will probably inhibit much
in the way of convection. Upper ridge shifts eastward on Monday
so while there will be boundary layer moisture in place east of
the Laramie Range, subsidence aloft and lack of a significant
shortwave trigger will once again keep most areas dry.

Upper shortwave will flatten the ridge on Tuesday and drive a
pacific front across the area during the day.  For now, models are
showing the best moisture and instability getting shunted to the
east of our CWA so kept the best chances for precipitation in our NE
counties.  Should the front and shortwave be a bit slower, we could
see more in the way of significant convection but think the best
chances for anything strong to severe would be east of our area at
this time.  Breezy conditions will develop in the wake of the front
with deep mixing expected Tuesday afternoon so could see winds
gusting to 40-45 mph west of the Laramie Range.

.LONG TERM...(Tuesday Night through Saturday)
Issued at 234 AM MDT Sun Jun 25 2017

A somewhat active zonal west to east mid/upper flow will continue
across our region through late week, although a deeper tap of
moisture is not evident in the models hence is why we keep PoPs
for showers/thunderstorms in the slight chance to low end chance
range through the week. Strongest shortwave looks to move across
eastern Wyoming and western Nebraska late Wednesday into
Thursday, when we have chance PoPs for thunderstorms across east
central Wyoming into the northern Nebraska Panhandle.


.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 526 AM MDT Sun Jun 25 2017

Taking a look at the latest higher resolution convective allowing
models, we note that most of them initiate isolated showers and
thunderstorms across the south Laramie Range between Cheyenne and
Laramie around 22Z today and move that activity through the
Cheyenne area before crossing into northern Colorado during the
evening hours. While coverages of showers and thunderstorms won`t
be much along that stretch of I-80 Laramie to Cheyenne, we feel a
bit more confident to at least mention a thunderstorm in the
vicinity of Cheyenne 22Z-02Z. We are not carrying a mention of
showers or thunderstorms elsewhere in the aviation area with VFR
conditions expected overnight with the exception of possibly
Sidney where southeasterly flow will be a bit more moist and we
could see some MVFR reduced visibility due to fog over there
towards tomorrow morning.


Issued at 234 AM MDT Sun Jun 25 2017

Generally dry forecast through mid week with just a chance of
widely scattered high-based convection on Tuesday. Afternoon RH
values will fall to 10 to 15 percent each afternoon east of the
Laramie Range. Breezy to windy conditions will also develop on
Tuesday so could see some elevated conditions especially in Carbon
County. A check of the fuel status still reveals the area being
in green up for now though so significant fire concerns are not




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