Area Forecast Discussion
Issued by NWS Reno, NV
FXUS65 KREV 291256 AAA
Area Forecast Discussion...UPDATED
National Weather Service Reno NV
556 AM PDT Thu Sep 29 2016
No changes were made this morning to the fire weather watch in
effect for Friday afternoon and evening. Winds will increase
today, but other than a couple localized areas of critical
conditions, winds will be less than 30 mph. On Friday, winds will
increase north of Highway 50 with peak gusts 35-40 mph. However,
RH will increase as well with a slug of moisture moving in ahead
of the cold front. With the cooler temperatures, it is
questionable that Red Flag conditions will be hit. The moisture is
also a bit more north of I-80 with RH above 60% at ridge level.
Some of this was already taken into account yesterday by leaving
extreme NE California out of the watch. Still, the moisture in the
model suite looks to have increased compared to 24 hours ago. My
gut feeling is there is only 30% chance of a hit for zone 458, 50%
for 272/450 with 453 having the best chance at 80-90%. It will be
warmest out in zone 453 with the moisture not quite making it
there, thus the highest confidence there. Will let the day shift
continue to assess the trends.
Beyond Friday, Saturday will also be a bit breezy with gusts 25-30
mph. In addition, a dry slot moves in with the descending air mass
behind the front. RH will be lower Saturday near and south of
I-80, but with winds diminishing during the day, it looks to
remain below critical at this time.
Another breezy day Sunday ahead of the upper low with some wetting
moisture possible late in the afternoon into the evening. Much of
this will fall as snow above the 6-7000 foot level.
.PREVIOUS DISCUSSION... /Issued 300 AM PDT Thu Sep 29 2016/
High pressure over northeast California and western Nevada will
exit the region today with a few showers possible over southern
Mono and western Mineral Counties. A cold trough moves into the
West Coast this weekend bringing breezy and much cooler
conditions. More widespread precipitation and even some Sierra
snow showers are expected Sunday and Monday.
Some modest adjustments were made to the wind forecast primarily
Friday evening into very early Saturday morning. Otherwise,
adjustments only reflect model differences in trends which were
rather insignificant from previous runs. The largest impacts for
the short term forecast through Saturday continue to be breezy to
gusty winds with implications for aviation, area lakes, and fire
Models continue to favor isolated showers and thunderstorms for
southern Mono/Mineral Counties this afternoon as upper due to
some lingering instability coupled with relatively warm surface
temperatures. Elsewhere conditions will be dry through Saturday
The pressure gradient will begin to tighten as low pressure drops
down the Pacific coast. Upper level flow becomes increasingly
amplified into the weekend as well. Expect winds to begin to
increase this afternoon with gusts around 25 mph. A further
increase on Friday is expected which continues to be projected as
the windiest day. Gusts Friday will be generally be 30 to 40 mph
with some wind prone locations approaching 50 mph. With gusts
around 40 mph, we expect some fire weather concerns for the Sierra
Front as well as the Basin and Range despite humidity that will
be around to slightly above critical thresholds.
Forecast winds were increased overnight Friday into early
Saturday morning. 700 mb wind speeds remain around 40kts
suggesting that breezy conditions would continue for Sierra
locations including Lake Tahoe and along the Sierra Front. These
gusts will likely continue well into the evening and into very
early Saturday morning. Saturday remains breezy, but fire weather
concerns will be mitigated by rising humidity. Boyd
LONG TERM...Sunday through Wednesday...
The main story will continue to be the deep trough forecast to move
through Sunday night. As mentioned earlier, this trough is not that
unusual for the time of year, but it will be the coldest we have
seen so far this autumn.
The models have changed slightly, which is expected 4 days out.
Instead of showing a band of precip along and behind the main cold
front, they now show it as more showery with the cold pool overhead.
Aside from that, little has changed with some breezes during the day
Sunday and gusts up to 30 mph, stronger over ridges. The greatest
threat for precip will be late Sunday afternoon into Sunday evening.
I have increased the pops in the Sierra to near 60% along the crest
from Tahoe north and also expected the chance of precip to include
almost all of Western Nevada Sunday night. The low itself will move
overhead to the threat of light showers will be present just about
As far as precip amounts, they overall look to be light and less
than 1/4". Snow levels will start near 7000 feet Sunday afternoon
and fall to near 5000 feet Monday morning. With these snow levels a
couple inches of wet snow is possible in the higher elevations above
6000 feet, including around Lake Tahoe. Still, given the showery
nature it won`t be widespread, but there are possible travel impacts
over the passes.
Monday, the low will slowly pull away, but it will be cold with
highs in the 40s and 50s. Tuesday morning could be quite cold with
some hard freezes possible for many areas outside of the main urban
centers in Western Nevada. Tuesday and Wednesday will see a warming
trend, but it will be slow with temperatures still remaining below
average in the valleys due to the northeast flow while the mountains
rise closer to average.
VFR conditions through Friday. Increasing SW winds today with peak
gusts to 25 kts north of I-80. Stronger SW winds Friday 18-03Z with
peak gusts to 35 kts north of Highway 50 and to 25 kts south. Some
mtn wave turbulence is possible in the morning before mixing helps
to alleviate some of it.
Friday night, mtn wave turbulence will be stronger as 700 mb winds
increase to 40-50 kts. This could create areas of LLWS for higher
elevation terminals such as KMMH and KTVL, with a lower probability
for KRNO/KCXP. Saturday`s winds will weaken with less turbulence
expected. The next chance of precip is late Sunday into Monday
morning with some restrictions to CIGS/VIS in the Sierra.
NV...Fire Weather Watch from Friday morning through Friday evening
CA...Fire Weather Watch from Friday morning through Friday evening
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