Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 161731

Area Forecast Discussion
National Weather Service Cheyenne WY
1031 AM MST Thu Feb 16 2017

.SHORT TERM...(Today through Friday night)
Issued at 303 AM MST Thu Feb 16 2017

Main concern for the short term period will continue to be the
potential for strong winds along I-25 near Bordeaux. Gradient
progs are very marginal along the Laramie Range and I-25 corridor
for high winds, so maintained the idea that west-northwesterlies
will be sustained roughly 35 to 40 mph from later this morning
through early afternoon today in this area. Winds at the 800mb
level are expected to be around 40 kts over this area by mid
morning, so likely to see a few gusts around 55 mph as mixing
commences. Temperatures across the forecast area will be very warm
today, roughly 15 to 25 degrees above normal along and east of
the Laramie Range. Think we`ll see another round of high
temperature records broken today, mainly across the plains. The
combination of moderate downslope winds and very warm temperatures
will produce very low humidities across the plains, spanning from
the single digits over Laramie County into the mid teens
elsewhere across the plains. Thus, fire weather conditions will be
conducive to fire spread if any fires develop, however fuels are
still not critical so this may preclude fire development.

A few rain and high elevation snow showers are possible tonight
over the Sierra Madre and Snowy Range mountains as a shortwave
trough and Pacific cold front approach from the west. Moisture
will lessen as the system approaches so not anticipating much more
than just light showers. Ahead of the front, looking at the
potential for another round of strong winds near Bordeaux and
perhaps even further south along the southern Laramie Range.
Gradient progs are only around 50 meters, but winds in the 800-750
mb are looking to be in the 45 to 50 kt range. A cross section of
winds and lapse rates across the Laramie Range shows a decent sfc
inversion setting up overnight so not confident the stronger
winds will reach the sfc. Therefore, will hold off on any High
Wind highlights for now due to low confidence, but did maintain
gusts of 50 to 55 mph in the forecast from Bordeaux into the
southern Laramie Range. Friday will be cooler as the front moves
eastward across the area midday, with more widespread breezy
northwest winds across the forecast area in the post frontal
environment. Flow aloft will turn to the southwest on Friday
night, and another shortwave trough with Pacific moisture could
bring a chance for rain/snow showers to the high country through
early Saturday morning.

.LONG TERM...(Saturday through Wednesday)
Issued at 303 AM MST Thu Feb 16 2017

Mainly dry and quite mild conditions across the CWA Saturday
through most of Sunday but becoming somewhat windy around the
southeast Wy mtns Sunday as lee troughing develops over the high
plains. Some rain and snow showers should then move across the CWA
later Sunday through Sunday night in association with an upper
trough that will move across the region at that time. Dry and a
little cooler in the wake of this system Monday but still on the
mild side. Looking windy again for Tuesday around the southeast Wy
mtns as surface pressures fall over the high plains. Should see
some increase in rain and snow shower activity mainly out west
Weds ahead of a large upper trough that will move onto the west
coast region.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1027 AM MST Thu Feb 16 2017

VFR conditions through the taf period under mostly clear skies.
Southwest winds will gust to 20-25 kts at RWL through the
afternoon. Expect west northwest winds to increase at CYS after
06Z. Winds will become more northwesterly across the Nebraska
Panhandle by early Friday morning.


Issued at 303 AM MST Thu Feb 16 2017

Elevated fire weather conditions are expected again this
afternoon with many areas across the high plains of southeast
Wyoming and western Nebraska seeing very warm temperatures and RH
values dropping into the low teens. A few spots across Laramie
County could even see RHs drop into the upper single digits. Wind
gusts along the I-25 corridor from Wheatland to the Colorado
border are expected to range from 25 to 35 MPH, with locally
higher speeds near Bordeaux. Further east, gusts up to 20 mph are
possible. Grass fires, if started, will spread rapidly under
these conditions. Cool down begins Friday with afternoon
humidities back above critical.




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