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fxus65 kriw 120509 

Area forecast discussion
National Weather Service Riverton Wyoming
1009 PM MST Mon Nov 11 2019

Short term...(this evening through Tuesday night)
issued at 119 PM MST Mon Nov 11 2019

Clear skies have presented the extent of snowfall across western
and central WY, with heaviest amounts across most of northern Wyoming.
Satellite imagery shows most snow south of The Divide and for
Fremont County is fading fast, while the Big Horn basin and
Johnson and Natrona counties holding onto snowpack, which in turn
is keeping temperatures in the teens. While the main core of the
last polar airmass has moved off, cold pools in the Big Horn and
Wind River basins will allow temps to fall back into the single
digits tonight, especially in locations that still have a uniform
snow cover. For Johnson County, westerly winds down the Bighorn
range will keep temperatures from falling too far into the teens
overnight. For areas west of The Divide from jac to rks, temps
currently in the middle 30s will only fall to around 20 tonight.
Natrona County will see increasing southwest winds increasing to
15 to 20 overnight, keeping temperatures steady around 20.

For Tuesday, modest west to southwest flow will increase at most
locations. This will help erode some of the cold pools in the
basins, letting temps recover into the 40s. Most areas on the Lee
side of higher elevations, like cod, byg, cpr and jac, could see
downsloping winds helping temperatures reach into the lower 50s
during the afternoon.

Tuesday night another clipper moves across the state. This system
is fairly moisture-starved, so precipitation will be minimal as it
passes. Temperatures will drop to around 30 degrees, aided by
insulating cloud cover with the passing wave.

Long term...(wednesday through monday)
issued at 119 PM MST Mon Nov 11 2019

A fast moving shortwave will transit along the Montana/Wyoming border,
bringing some showers to the northern mountains Wednesday morning.
It will also produce gusty winds along the southern wind corridor
and higher elevations across the entire forecast area. By the
afternoon, winds and snow will diminish and high pressure will build
back into the area. The ridge axis starts along the West Coast
Wednesday evening and will start moving eastward before entering
Wyoming late Thursday night. This will mean mild, dry weather across
the forecast area through Friday morning.

Friday night will see the flow transitioning to a more zonal flow
through the end of the forecast period. A new shortwave will move
into western Wyoming Friday night. Models bring the precipitation
into the northwest starting late Friday evening, before spreading
east of The Divide through Saturday morning. The GFS is much more
robust with this system, showing much higher pops ahead of the
trough so we'll have to monitor the next few model runs. The
precipitation will be mainly snow, but at lower elevations east of
The Divide it will start off as rain before changing over to snow.
This system will clear out late Saturday evening, unfortunately the
zonal flow will allow another shortwave to move in on Monday. His
system could bring snow to southern portions by Tuesday. Confidence
remains low at this point, as models have been having difficulty
with consistency in the latter days of the forecast.


Aviation...(for the 06z tafs through 06z wednesday)
issued at 1000 PM MST Mon Nov 11 2019

VFR conditions will occur at the terminal sites. A gusty wind will
develop at kcpr overnight and this will continue through 00z Wed.
Krks will see a gusty wind develop around 19z through 00z Wed.
Isolated snow showers will form over the northwest Wyoming by 06z Wed.


Fire weather...
issued at 119 PM MST Mon Nov 11 2019

Clear skies and light winds will continue for most areas through
tonight. Higher winds will be limited to areas from Rock Springs
to Casper, where winds will begin to increase to 15 to 20 mph
after midnight. Winds will increase further tomorrow, especially
around Casper, where winds of 25 to 30 mph with gusts to 40 are
expected. Temperatures will recover during the day Tuesday, with
highs rising into the 40s. Some humidity values will fall below 25
percent across Sweetwater County during the afternoon Tuesday.


Riw watches/warnings/advisories...none.



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