Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 030939
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
239 AM PDT TUE MAY 3 2016

.SYNOPSIS...
A few showers and thunderstorms are possible this afternoon and
evening, then thunderstorm chances increase Wednesday with a few
strong storms possible. More widespread rain and high elevation
snow, with possible thunderstorms will continue Thursday and into
the weekend as low pressure remains over the region.

&&

.SHORT TERM...
Made a few changes to the details, but the overall idea of the
transition to a wet pattern remains on track. High confidence in
a wet week, especially as we get to Wednesday and Thursday. The
main changes were to decrease the thunderstorm potential into
Wednesday and also trim back pops near/east of Highway 95. The
system is moving in slightly slower so snow levels look to remain
above 8-9000 feet at least through the short term.

The upper low that will affect the region into the weekend is near
135W and slowly making its way toward the coast. Moisture begins
to increase today in the Sierra and extreme Western NV. However,
cloud cover increases and there is a nice stable layer around 450
mb. There is enough instability for some showers near the 395
corridor north of Bridgeport, but any thunderstorms look to be
isolated at best. Showers also will not be that heavy today,
although localized amounts up to 1/4" are possible.

The upper low is expected to near the coast Wednesday afternoon.
Instability and moisture increase with the best instability once
again near the 395 corridor. However, compared to previous runs,
it appears less than before. In addition, the upper jet streak is
slower to move east of the Sierra so the forcing does not look
quite as good. Factor in the cloud cover, and we may not see as
many thunderstorms, nor be as strong as it looked yesterday. I
kept the chances of showers near the 395 corridor high, but
trimmed them east of highway 95 where there is less moisture and
instability. I also cut back the thunderstorm potential to
scattered. This is still a decent number, but if the cloud cover
is too much it could be less.

The jet then does move east Wednesday night and the forcing is
better. Loss of heating may limit thunderstorm potential to
isolated, but showers should be quite numerous at least near and
east of the Sierra.

Thursday could be a potentially very active day as instability and
moisture increase even more. In addition, the upper forcing
remains favorable with the jet in a good location and diffluence
in the flow aloft. Kept showers likely for much of the area with a
chance of thunder. Some of these could be rather heavy if the
models are correct with the instability and forcing. The best
chances for these heavy showers continue to be centered on the
Reno-Tahoe area. Wallmann

.LONG TERM...Friday through Monday...

Expansive upper low will be centered over southern CA to begin
period, and move only slowly eastward through the weekend. This
will keep the cool and unsettled weather pattern going with
numerous showers and isolated-scattered thunderstorms. Being on
the north-northwest side of upper low, heavier and more persistent
bands of precipitation are likely to occur although confidence in
exact location/timing remains low-medium. Deterministic runs of
the GFS/ECMWF show two distinct periods where such heavier bands
could develop, late Friday into Saturday morning and again by
Saturday night/Sunday morning. However, these smaller scale
features are difficult to pinpoint so far out. Precipitation
totals overall continue to look impressive and some rises on
streams and creeks can be expected. Snow levels have trended a bit
higher from previous model runs but should still generally be
7000-8000 feet Fri-Sat before rising Sunday. So snow impacts
should remain confined to the highest passes during this event.
Anyone traveling or planning outdoor activities should prepare now
for a very active weather pattern which will include the
possibility of lightning and small hail.

The upper low is forecast to finally depart Monday with decreasing
showers and warmer temperatures. After highs in the 50s and 60s
Friday-Saturday, readings will rise into the 60s and 70s Sunday-
Monday. Model simulations are pointing to even warmer conditions
beyond Monday. Hohmann

&&

.AVIATION...

Scattered showers and isolated thunderstorms are possible this
afternoon and evening along and just east of the Sierra although
probability of a thunderstorm will be low. Showers and
thunderstorms will increase Wednesday through the weekend with
storms capable of heavy rain and small hail. Hohmann

&&

.REV Watches/Warnings/Advisories...
NV...None.
CA...None.
&&

$$

For more information from the National Weather Service visit...
http://weather.gov/reno



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