Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 291005

Area Forecast Discussion
National Weather Service Reno NV
305 AM PDT Mon May 29 2017


Above average temperatures will persist through Tuesday with
continued spring Sierra snowmelt leading to cold and swift flows
near creeks, streams and rivers. There will be a low chance for
showers and thunderstorms near the Sierra this afternoon. A weak low
will bring a brief cool down Wednesday with a few showers possible.
Warmer and drier weather returns for late week.



Warm conditions continue today with afternoon high temperatures
expected to near the 90 degree mark across western Nevada valleys
with mid and upper 70s for Sierra valleys. Cooler and near average
temperatures will return by Wednesday as a weak trough approaches
the region. There will be a little better potential for shower and
thunderstorm activity today across the Sierra due to enhanced and
deeper layer instability as capping layers aloft erode due to the
ridging sliding eastward. This increased instability can be seen
with mixed layer CAPE around 600J/kg and LI near -5.

The favored areas for showers and storms to initial form this
afternoon will mainly be areas in the Sierra not deeply covered in
snow pack, that is west of the crest and higher terrain east of the
snowpack through Alpine and Mono counties. However, stronger south
to southwesterly flow aloft may aid in transporting cells initiating
on the west slopes to make it near and over the crest in the eastern
Sierra. Those with recreation plans in the Sierra today should be
mindful for the possibility of lightning strikes, small hail, and
gusty outflow winds near showers and storms.

For Tuesday, a shortwave trough moves inland and will increase winds
during the afternoon with gusts looking to reach into the 30-35 mph
range resulting in choppy conditions across area lakes. Drier
conditions will also arrive with the trough and will knock down
chances for precipitation but an isolated shower or two is still
possible in eastern Mono and Mineral counties. A better potential
for precipitation arrives Wednesday as the the trough axis nears and
diffluence aloft forces better chances for showers across the Sierra
and into far northeast California. Overall, precipitation will still
be on the light side with instability looking too meager to support
thunderstorm development at this time. Fuentes

Confidence in the long term this morning isn`t high. The models
have been struggling with the pattern for next weekend. The GFS
has overall been a little more consistent, but the EC has gone
from the trough to a ridge. While they are both in good agreement
now, there are a few ensemble members that show the trough even
though it is less likely.

For Thursday and Friday, a light west flow is consistent with a
warming trend back above average. Then a ridge builds with
potentially a weak upper low forming near the California coast.
The going forecast was already reasonably in line with the warming
temperatures so made little changes, although the current models
suggest temps 5 degrees warmer.

However, with the upper low we will have to watch for convection.
The GFS, as it has been, is starting as Friday and Saturday while
the EC holds off until Sunday. Given the temps aloft Friday/Saturday
will keep it dry as even the GFS has 500 mb temps near -8 C which
results in a decent cap. Temps aloft are forecast to cool Sunday
so added the threat of thunderstorms south of Tahoe and into the
Pine Nuts. Wallmann


Isolated thunderstorms are possible over the Sierra today.
Terminal most likely to be impacted will be KMMH, but still only
20% or so, otherwise VFR. For Tuesday, SW winds increase with peak
gusts to 25 kts and thunderstorms look much less likely. A few
showers are possible on Wednesday as a weak trough moves in, but
it looks to remain VFR at this time. Wallmann


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