Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 121732

Area Forecast Discussion
National Weather Service Riverton WY
1132 AM MDT Mon Mar 12 2018

.SHORT TERM...Today through Wednesday night
Issued at 300 AM MDT Mon Mar 12 2018

A large ridge of high pressure will dominate the weather pattern
through the forecast period. A weak shortwave will slowly make its
way over the forecast area this morning, with very isolated
precipitation over the western mountains. Little to no snow
accumulation will occur. Otherwise, a warming trend will begin today,
with temperatures becoming slightly above normal into Tuesday. By
Wednesday, areas east of the Divide could be 15 to 20 degrees
above normal. Gusty SW winds will occur over much of the area,
with the Wind Corridor becoming windy. Lower elevation snow melt
and ground thaw will be a concern through the forecast period,
especially east of the Divide. With the SW flow Wednesday, precip
chances will increase across the far west. Rain (and possibly
isolated thunderstorms) will occur in the lower elevations. Snow
levels will range between 8500 and 9500 feet during the day
Wednesday, before a cold front moves through Wednesday evening.

.LONG TERM...Thursday through Monday
Issued at 300 AM MDT Mon Mar 12 2018

Very complex upper level storm system hangs along the west coast
Thursday and Friday. Then the system moves inland toward the Great
Basin Saturday and into the Rockies Sunday through Sunday night.
The system exits next Monday morning. A potential weather
disturbance is forecast to move through the area Thursday into
Thursday night bringing a chance of rain and snow showers to much
of the region. Models differ on Friday as the GFS shows another
weather disturbance lifting across the area. Meanwhile, the ECMWF
and Canadian models develop an upper level low circulation in NE
Colorado Friday and move it into Nebraska Friday night. Not sure
which scenario will play out at this time and do not want to go
overboard on precip chances Fri into Fri night. For now will keep
the low chances in the forecast. All three models show Saturday
as being fairly dry with some precip moving into the south and
southwest Saturday night. Then the chance of rain and snow on
Sunday into Sunday evening with the rest of the through passing
through the area. Next Monday drys out for most places with
lingering mountain snow showers. High temps Thurs in the 40s and
50s, then 40s to lower 50s Fri and Sat. High temps in the 30s and
40s next Sunday and Monday. Confidence is low on just how this
weather scenario will play out, so expect changes in the forecast
to occur.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1125 AM MDT Mon Mar 12 2018

VFR conditions with light winds are expected through the forecast
period. The only exception will be patchy late night and morning
fog in Yellowstone National Park and in low lying areas of the Big
Horn Basin. KWRL has a small chance of fog in the vcnty early


Issued AT 300 AM MDT Mon Mar 12 2018

Light snow showers, with little to no accumulation, over the
Winds and Absarokas this morning. Otherwise, expect dry conditions
for much of the area today and Tuesday. Generally light wind and
stable air mass will result in poor to fair smoke dispersal until
Wednesday, when winds and warming increases mixing for good smoke
dispersal outside of mountain precipitation. Precipitation will
stay confined to the west, with rain in the valleys and low snow





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