Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 241651

Area Forecast Discussion
National Weather Service Riverton WY
1050 AM MDT Tue Apr 24 2018

.SHORT TERM...Tuesday through Thursday night
Issued at 300 AM MDT Tue Apr 24 2018

There are still a few snow showers out there this evening as some
moisture continues to rotate around an upper level low slowing
moving away to the east. Most areas should be largely dry by
sunrise today with only a few spotty snow showers leftover. These
will decrease in coverage and should be over by around noon. At
this time, we are not buying the models keeping showers over the
mountains since the models overdue the orographics and building
heights should stabilize the atmosphere. Clouds may hold tough for
much of the day however in eastern areas, keeping conditions
rather chilly for many areas. A few areas in the northeast could
even see an appearance from the dreaded fog monster, but it would
be brief and likely not that thick. Temperatures will be warmer
the further west you go with more sunshine expected. The big
difference will be much less wind so it will feel much warmer.

Mainly dry weather will then rule from tonight through Wednesday.
With southwest flow and plenty of sunshine temperatures will rebound
nicely with highs in the 70s in some locations. With low humidity,
enhanced fire conditions may develop in the normally breezier areas,
mainly Natrona and southeastern Fremont Counties. It is borderline
however, so we will let the day shift make the final decision on any
fire watches.

Another cold front will then drop southward into the area for
Wednesday night and early Thursday. We like the slower timing right
now, since the GFS is doing it`s usual Speed Racer imitation in
bring things in too fast. In addition, the models look to be
overdoing the QPF despite decent dynamics given the continental
origin of the system and non existent return flow. As a result,
we will keep amounts light for now. This should exit stage
southeast by Thursday afternoon, with sunshine returning fairly
quickly. Temperatures will be knocked down a several degrees, but
not too chilly. Thursday night at this point looks dry and cool.

.LONG TERM...Friday through Tuesday
Issued at 300 AM MDT Tue Apr 24 2018

Friday now looks dry for all areas. Very isolated showers or
storms in the far west late in the day or early Friday evening
cannot be ruled out. 00Z Models have backed off on this
convection for now. The forecast issue continues to be this
developing trough over the western U.S. Saturday into next week.
The first upper level storm system moves into California Saturday
and progresses east into the Great Basin Sunday per the ECWMF and
Canadian models. Then these two models bring the upper low toward
western WY Sunday night into Monday. The 00Z GFS is real quick
bringing this system toward WY on Saturday night. Do not see this
happening and have gone with the slower timing. The weather
pattern remains unsettled Monday and Tuesday with the potential
for weather disturbances moving through or near WY. All the models
vary on placement and timing this far out. The forecast will be
for a chance of showers and thunderstorms over the west Saturday
afternoon and night. Then a chance for showers and storms Sunday
and Monday in the west and north with less coverage over the
central and south. Tuesday could see isolated showers and storms
over the whole area. Overall, the potential for an unsettled
weather pattern from Sunday through much of next week is
increasing. As for temperatures, warm days on Friday and Saturday.
Then a cooling trend for Sunday through Tuesday.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday)

Improving conditions all locations. However, VFR/local MVFR
conditions will persist into the early afternoon period with KCPR
most likely to keep MVFR/near MVFR conditions longest and not going
VFR until late afternoon. Generally light winds expected for most
locations with KRKS seeing the gustiest winds this afternoon/early
evening (northeast 15G20-25kt)


Issued at 300 AM MDT Tue Apr 24 2018

Today will be a cool day with clouds gradually giving way to
sunshine from west to east. Any showers would be restricted to the
morning hours and mainly in the higher elevations. There will be
much less wind than yesterday. Relative humidity will be lower but
remain well above critical levels. Mixing and smoke dispersal
will be generally fair to good. Elevated fire conditions will be
possible in portions of Natrona and southeastern Fremont Counties
Wednesday afternoon with a combination of a gusty southwest wind
and humidity falling into the teens.





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