Area Forecast Discussion
Issued by NWS Reno, NV
FXUS65 KREV 010930
Area Forecast Discussion
National Weather Service Reno NV
230 AM PDT SUN MAY 1 2016
Warmer temperatures are expected today through Tuesday with a
chance for showers and a few thunderstorms each afternoon and
evening, mainly near the Sierra. Cooler conditions with more
widespread rain and high elevation snow are possible from
Wednesday through Saturday as low pressure moves slowly across
the western U.S.
Warmer temperatures will finally bring more comfortable weather
for most outdoor activities today through Tuesday. Highs rise to
near 70 degrees in lower elevations today, then push to the mid-
upper 70s by Tuesday. Moderate east winds will prevail today,
which may keep locally choppy conditions along the west shores of
Lake Tahoe, with stronger ridge gusts over the Sierra especially
through this morning.
The trade off - with upper level disturbances over northern or
central CA, a threat of showers and thunderstorms will be present
each afternoon and evening. Today the better forcing and
instability favors the Sierra south of Tahoe to Mono County, and
western NV south of US-50, although a few brief showers can`t be
ruled out farther north to near the I-80 corridor.
By Monday, another shortwave is projected to move northward across
the northern half of CA as flow aloft becomes south. This would
favor more convective development in northeast CA and near the
Sierra, with isolated cells possible into far northwest-western
NV but probably not getting much farther east than Reno or Carson
For Tuesday, stronger low pressure approaching the west coast
could bring a broader area of lift and instability to northeast CA
and far northwest NV, assuming the low moves close enough to the
coast by the afternoon. If this occurs, the more favored areas for
convection look to be similar to Monday, with coverage of showers
and thunderstorms increasing a bit. Some activity could continue
overnight in northeast CA as instability continues along with a
further increase in moisture. There is more uncertainty for the
location of the convective activity Tuesday and Tuesday night as
some guidance scenarios hold the low farther offshore with the
better instability west of the Sierra. Current forecast will
continue to favor the wetter scenario, which is supported by most
of the ensemble guidance. MJD
.LONG TERM...Wednesday through Saturday...
Large scale trough will reach the west coast Wednesday and then
close off as it moves inland during the remainder of the week.
Models continue to depict a very slow eastward movement and this
will provide the region with extensive clouds, periods of showers
and thunderstorms with cooler than average temperatures. For a
closed low in early May, models are showing above average
confidence in track of upper low center, roughly from Los Angeles
to Las Vegas Thu-Sat.
For Wednesday, 250 mb 110+ kt jet in advance of trough may
provide sufficient dynamics to overcome lack of insolation due to
extensive high clouds for scattered showers and thunderstorms,
especially from Tahoe/Sierra Front northward to the Oregon border.
Given the increased flow sfc-aloft and afternoon temperatures in
the 60s to lower 70s, there would be enough shear and instability
present for organized strong storms.
For Thu-Sat, winds aloft decrease and turn east to northeast aloft
as upper low shifts inland. Much of our area will be on the north
and northwest periphery of low. This is where details become harder
to determine, specifically with precipitation banding. Based on
current track, areas near and south of I-80 are favored for best
shower and storm coverage although the broad scale of trough will
warrant good chances farther north as well. We bumped up the
probability to likely at times Thu-Fri south of I-80 where some
locations could see some decent precipitation totals. This is not
a particularly cold storm, so snow levels are going to remain
fairly high. However, deep moist profile suggests stronger storms
will be capable of producing locally heavy rain and lots of small
A general east gradient will prevail today although ridge winds are
expected to come down quite a bit from their strong speeds this
morning. The east flow will keep low levels stable for western NV to
the north of Hwy 50. Lighter winds and sufficient instability will
result in scattered showers and isolated thunderstorms elsewhere
(Sierra south of Portola and Mineral County, including all Sierra
airports). There is about a 25-35% chance of showers at these sites
and 10-15% chance of thunder 21z-02z). KRNO/KCXP/KNFL will most
likely remain dry although there is a 10% chance for a brief shower.
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