Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 160734
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
134 AM MDT Mon Apr 16 2018

.SHORT TERM...Today through Wednesday night
Issued at 109 AM MDT Mon Apr 16 2018

In the west, dry conditions are expected with strong gusty
southwest winds. Wind gusts of 45 to 55 mph are expected on the
upper ridges and mountain passes. A Pacific low pressure trough
will bring moisture and instability into the western mountains
Monday night and Tuesday with snow accumulations of 5 to 9 inches
mainly above 8500 feet with rain to a rain snow mix below 8500
feet. The lower elevations should switch to strait snow around
22Z. East of the Continental Divide, Strong gusty wind and low
relative humidity increase fire danger today. Southwest winds of
20 to 30 mph with gusts of 40 to 50 mph from Sweetwater to Natrona
Counties, combined with minimum relative humidity of 12 to 15
percent will produce conditions favorable for fires with rapid
rates of spread and erratic fire behavior from noon to 7 pm MDT
this evening. Late tonight and Tuesday the Pacific trough will
spread showers and a cold front across areas east of the
Continental divide with colder temperatures Tuesday night and
Wednesday. A weak transitional ridge will pass through Wednesday
with dryer conditions and lighter winds.

.LONG TERM...Thursday through Monday
Issued at 109 AM MDT Mon Apr 16 2018

An upper low over the southern Great Basin Thursday is progged to
push into the Four Corners Region by 12Z Friday, then into the
southern High Plains by Saturday morning. An easterly upslope flow
is expected to develop Thursday east of the Divide, but initially
should be relatively dry. However this should change Thursday
night/Friday morning with a decent chance of precipitation
developing over central and south-central areas, while
northwest/western areas look to remain mainly dry. Overall models
are showing a slightly warmer profile than last night with more rain
than snow in the lower elevations. The exception could be across the
Wind River Basin where some cold air damming/upslope effects could
occur allowing for slightly cooler conditions, and a better chance
of a wet snowfall. Also, models are not showing as much low-level
moisture to work with in the easterly upslope flow. This plus the
southerly track should keep the bulk of the significant
precipitation southeast of the forecast area. Dry and warmer
conditions occur next weekend. There is the potential for a quick
moving wave sweeping east across the northern Rockies which could
give a chance of some convection, mainly over the northern part
of the forecast area Monday.

&&

.AVIATION...For the 12Z TAFS through 12Z Tuesday morning
Issued at 109 AM MDT Mon Apr 16 2018

West of the Continental Divide...KJAC, KBPI, KPNA, and KRKS

VFR conditions will prevail through the forecast period at most
terminal sites. The exception will be KJAC where MVFR conditions
will develop around 00Z and continue through 12Z Tue. Scattered rain
and snow showers move into the lower elevations of the far west
around 00Z, changing to all snow showers after 03Z Tue. The western
mountains will see mainly snow after 00Z with MVFR to IFR conditions
and mountain obscuration. Windy conditions at most terminal sites on
Monday ahead of the approaching cold front that moves through from
00Z to 06Z Tue. The wind gradually decreases after 06Z Tue.

East of the Continental Divide...KCPR, KCOD, KRIW, KLND, and KWRL

VFR conditions are expected through the period. Windy conditions at
the terminal sites ahead of a cold front that moves into the central
part of WY around 06Z Tue and into the eastern sections after 09Z.
Scattered rain showers will develop east of the divide after 06Z
Tue.

Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for
the latest information on icing and turbulence forecasts.

&&

.FIRE WEATHER...
Issued AT 109 AM MDT Mon Apr 16 2018

Today will be a bit of a fire threat for Sweetwater, Fremont, and
Natrona Counties. Clearing skies, temperatures around the 70s,
and strong gusting winds are of concern. A Red Flag Warning has
been issued for Natrona County from noon to 7PM this evening.
Smoke dispersal will be very good or better on this afternoon,
decreasing to fair to good on Tuesday as clouds lower and showers
become more widespread and temperatures fall with an increasingly
strong frontal inversion.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from noon today to 7 PM MDT this evening for
WYZ280.

&&

$$

SHORT TERM...Hulme
LONG TERM...Murrell
AVIATION...Ross
FIRE WEATHER...Hulme



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