Area Forecast Discussion
Issued by NWS Reno, NV

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092
FXUS65 KREV 292130
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
230 PM PDT Sat Apr 29 2017

.SYNOPSIS...

Warmer and drier conditions will continue this weekend as high
pressure starts to build across the area. This high pressure will
weaken slightly allowing breezy winds Sunday and Monday evenings.
The ridge rebuilds by the middle of next week with light winds
and above normal temperatures. By late next week into next weekend
there could be showers over portions of the region.

&&

.SHORT TERM...

A warming trend this weekend is leading to an increase of snowmelt
and cold water flowing into streams and rivers. See the hydrology
section below for discussion and for safety information.

A high pressure ridge aloft is building over CA/NV this weekend from
the west. This will create warming tomorrow afternoon with highs
in the 70s for western NV and mid 60s for most Sierra
communities. A weak disturbance moving over the ridge will bring
some high clouds tomorrow, mainly north of I-80, and will also
enhance evening breezes east of the Sierra. Expect northwest
winds east of the Sierra with peak gusts 30 to 35 mph during a
roughly 6-hour period Sunday evening.

Winds will increase again Monday evening, with northerly gusts
around 30 mph possible in the Surprise Valley and in Mineral,
Mono, Lassen and northern Washoe counties. Wind directions could
vary between northwest to north Monday and then become
northeasterly Tuesday. The north to northeast flow will bring
slightly cooler air into the area and afternoon highs Monday and
Tuesday could be a few degrees cooler than tomorrow. JCM

.LONG TERM...Wednesday through next week...

Ridge axis will be situated across California and Nevada by
Wednesday afternoon resulting in light winds and warming
temperatures. Either Wednesday or Thursday will win out for the
warmest temperatures of the week, but differences in the progression
of the ridge between the operational models leave that as yet to be
determined. The forecast is leaning towards Thursday as the ridge
axis moves just east of the region. Either way we are looking at a
decent midweek warmup with dry conditions and light winds.
Temperatures will likely peak around the 10 degrees above average
mark with highs in western Nevada reaching near 80 degrees, with low
70s possible in the Sierra.

A large-scale trough in the Gulf of Alaska will swing multiple
waves into the Pacific Northwest coast and gradually breakdown the
ridge across the West by late next week. The synoptic pattern
becomes particularly interesting as that trough moves eastward
into British Columbia and drags a southern splitting shortwave
into the West with it. While the finer details are difficult to
pin down this far out, the general agreement with the models and
ensembles is that the ridge will break down late next week.
Forecaster confidence is medium to high that the pattern will
transition to a more progressive flow leading to a trend toward
near normal temperatures and increasing possibilities for
precipitation.

Something to note...ridge breakdown patterns can be associated with
the enhanced probability of thunderstorms. While lightning isn`t
something that we want to be dealing with already, the potential
exists for that at the end of next week going into the weekend.
-Edan

&&

.AVIATION...

VFR conditions and light winds at terminals will continue through
early Sunday afternoon. Surface winds will increase Sunday
evening, especially east of the Sierra where peak gusts up to
30 kts are possible. Winds aloft turn back to the northeast late
Monday into Tuesday with another round of turbulence over the
mountain ridges possible. JCM

&&

.HYDROLOGY...

A warming trend this weekend is leading to increased snowmelt and
higher flows on many area streams and rivers. Flows are already
significantly above normal for this time of year and this
increase in temperature will only exacerbate those conditions. A
slight cool down Monday and Tuesday may slow the runoff a bit but
then warmer afternoon temperatures return for the rest of next
week. There is also a good chance for showers to return late next
week and next weekend. Any additional rainfall could create more
runoff and even higher flows.

Record to near record snow pack in the Sierra will mean a
prolonged period of high flows through the spring and possibly
into early this summer. Peak flow forecasts vary across the region
with the Truckee and Carson system peak forecasts falling in the
middle of May while the Walker and Lower Humboldt systems are
forecast to peak in June. These are peaks for the main river
systems...not the feeder streams. And even after these peaks
occur...flows will remain elevated for an extended period.

A Flood Warning remains in effect above Rye Patch Reservoir on
the Humboldt River. Flood Advisories are in place on portions of
the Truckee River due to high flows from reservoir releases and
snowmelt and in the lower part of the Carson River due to releases
from Lahontan Reservoir.

Remember that these elevated river flows are moving fast and that
water temperatures are cold. The cold waters make hypothermia a
distinct possibility for anyone in the water and the swiftness of
the water can carry someone away rather quickly. In any areas
where flows are high...even areas without warnings or
advisories...bank erosion is possible so keep everyone, especially
children and pets, a safe distance away from the banks.

&&

.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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