Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 242140

Area Forecast Discussion
National Weather Service Reno NV
240 PM PDT Fri May 24 2019


Cool, showery weather, with periods of steadier precipitation, and a
few thunderstorms, will continue through the Memorial Day weekend.
Increasing snow levels will keep impacts from snowfall mainly
above 7500 to 8000 feet, except Sunday night when snow may
accumulate down to 6500 to 7000 feet in Mono County. A slow
warming trend takes hold late next week. Showers and thunderstorms
are still expected next week, but with decreasing coverage as we
move through the week.



The forecast reasoning has changed little over the last few days.
The upcoming weekend appears cool and damp with increasing
chances for showers through Sunday. Through much of next week, we
will see a very slow warming trend with a chance of showers each
day and possibly a few thunderstorms...but there will be a
decrease in coverage as we move into the latter part of the week.

Convection has started forming across the forecast area this
afternoon well ahead of an approaching upper level area of low
pressure. As this low drops south we expect an increased chance
for thunderstorms into the evening hours. It is not out of the
question for isolated storms to continue through the night as
instability associated with low-to mid-level forcing is

Earlier forecast runs saw less instability for Saturday as we were
anticipating increased cloud cover and cooler temperatures. Now
the forecast soundings are indicating more instability for
Saturday. This is in response to less anticipated cloud cover and
slightly decreased temperatures aloft. We already had slight
chance of thunder in the forecast; this was maintained...but it
would not be outside the realm of possibility for greater
thunderstorm coverage east of Highway 95.

Another low drops south through California and deepens early
Sunday. This low then curls east toward southern Nevada. Our
position...initially on the east side of the low then on the north
side...should lead to increased instability early Sunday with
continued thunderstorm chances...then the development of more
steady rain/snow as a deformation axis develops through the day.
The core of the low has become a bit colder through the past few
model cycles. This means snow levels lower from around 8000-8500
feet in Mono County to around 6500-7000 feet by late Sunday. We
have been steadily increasing QPF for the Sunday time frame. The
increase in QPF and decrease in snow levels opens Mono County up
to the possibility of 3-7 inches of snow by late Sunday night for
elevations above 7500 feet. We do not anticipate any advisories
yet as most of this will above the bulk of the populated
areas...but certainly Mammoth Lakes could pick up snow.

Farther north into the Tahoe basin...snow levels will remain high
enough through Sunday night to limit snow accumulations to areas
above most of the passes.

Lingering showers...and possibly afternoon thunderstorms...
continue into Monday and Tuesday as this main low slowly lifts out
and is replaced by another shortwave trough.

Yet another shortwave trough rotates into the region Wednesday
with more showers and thunderstorms. With all of this shower
activity around...even with periodic breaks...high temperatures
will remain below normal through at least Wednesday.

A slow warming that starts Thursday...with highs reaching around
normal for Friday. Some model solutions try to get the broad
upper level trough east of the region by Friday while others hold
it in the region. As long as the southeast U.S. ridge remains in
place...we are not likely to see this broad upper trough
completely go away; it may just shift east a bit. While the
forcing will decrease...increased daytime heating Thursday and
Friday will allow showers and thunderstorms to continue
developing. The coverage will just not be as great as the day
leading up to the end of the forecast. REV



Showers are developing along the Carson Range and other terrain
around the region. Expect hit-or-miss showers to continue to develop
with a few thunderstorms mixed in for this afternoon for area
terminals. MVFR/IFR conditions will be possible should a shower or
thunderstorm move over a terminal. Some light-moderate icing will be
possible this afternoon/evening with the freezing level generally
8500-9500 ft MSL.

Another round of stratus/fog is likely for KTRK especially if any
showers occur over the airfield. Otherwise, conditions will be
largely VFR tonight for other sites with low potential for ragged
stratus around terrain.

Wetter weather is expected for the weekend with Sunday being the
wettest day. Saturday will be more hit-or-miss, but most terminals
will have showers or steadier rain by Sunday with a deformation axis
forming over the region. Outside of surface precipitation, mountain
obscurations and some light-moderate turbulence/icing will be other
aviation hazards. Boyd


.REV Watches/Warnings/Advisories...


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