Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 170859

Area Forecast Discussion
National Weather Service Reno NV
159 AM PDT Tue Oct 17 2017

Hazy conditions will continue today with west flow and fires
ongoing. Warm and dry conditions will persist through early
Thursday. A fast, weak storm will bring gusty winds on Thursday,
with valley rain and mountain snow for Thursday night into Friday.
Warmer and drier conditions are expected for the weekend and into
next week.


Weakened high pressure will allow for inversions to mix out more
easily today and Wednesday. With improved mixing and more breezy
conditions in place, temperatures will warm to well above normal
values. These dry and warm conditions will stick around through
early Thursday.

Primary weather concern for this week will be the approaching storm
system for Thursday and Friday. Model simulations continue to trend
towards less rain/snow and more wind. Ridge winds will increase
significantly with this storm with gusts between 80-100 mph
possible. Wind gusts of this magnitude are pretty typical for
fall/winter storms. A weak moisture feed with this storm will
provide some chances for precipitation across areas north of
Highway 50, but the amounts are looking lower than previous model
runs have shown. Wind gusts along the cold frontal passage
Thursday afternoon/evening will likely be around 40 to 50 mph with
locally higher wind gusts to 60 mph possible. There are fire
weather concerns with the gusty winds too, so be sure to check out
the Fire Weather Discussion below. Downslope enhancement is
feasible, but it would be right along and with the cold front
Thursday evening. Minor changes from day-to-day have made it
difficult to pin down the downslope potential. Just know we are
keeping an eye on it!

Precipitation will likely occur with this storm especially along the
Sierra crest and north of Highway 50, but amounts have been reduced
since we first started talking about the storm. It looks like we
could get between 0.25 and 0.50 inch for northeast CA, Tahoe basin,
and near the Sierra crest (mainly north of Tioga Pass) with lighter
amounts elsewhere. This system is relatively moisture-starved so
some portions of west central NV especially south of Highway 50 and
eastern Mono County could end up with little to no rain/snow. A few
inches of snow may accumulate mainly above 7500 feet, but travel
impacts are likely to be limited to higher passes for only a short
duration. -Edan

.LONG TERM...Friday through next week...
Continued the trend from the short term going drier with the late
week system. Otherwise, made few changes to the going forecast. The
system Friday should be on its way out with some precip in the
morning tapering to isolated showers in the afternoon as the forcing
and showers move east. It will still be a little breezy with much
cooler temperatures, a few degrees below average.

Then, strong high pressure is expected to build in over the weekend
and last through next week. Temperatures will rise a good 10+
degrees above average by midweek. Record highs are possible in the
mountains, but valley inversions may keep the valleys a few degrees
below records. Overall, highs are expected to be in the 70s for all
locations by midweek.


VFR conditions through Thursday with generally light winds. Winds
will gradually increase on ridges into Wednesday, but will still be
light in the valleys. Increasing winds Thursday into Thursday night
with the next storm. Some LLWS is possible Thursday night, with
confidence about 70% that at least one terminal in the Reno-Tahoe
area to be impacted. Some MVFR CIGS are possible in the Sierra with
-RA after 06Z Friday night.


Winds are looking better on Thursday with successive model runs.
Still, the best threat for any critical conditions will be near and
south of I-80. The moisture does look to increase fairly rapidly
north of there. Peak gusts look to be 30-40 mph area wide so they
will be solid, but nothing extraordinary. Min RH has the best chance
of dropping into the teens near and south of I-80.

For now, will issue a watch for zone 273 only, but 450, 453 and 459
may need to be added later. Higher confidence in 273 seeing the
lower RH for longer as well as the stronger winds.

One other concern would be the potential for critical conditions
continuing overnight, at least for 450/273 with potential downslope
winds. There is not a strong signature, but something to monitor.
Even if RH were to rise above 20%, if downslope winds materialize
gusts to 60 mph could occur in the foothills. Based on past events,
RH doesn`t matter much as long as it is dry enough to burn
(generally 30-40%). Will continue to monitor this as well with 273
the best threat with the lowest RH.

.REV Watches/Warnings/Advisories...


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