Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 252059
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
159 PM PDT Sun Jun 25 2017

.SYNOPSIS...

Isolated to widely scattered thunderstorms are possible this
evening with the best coverage likely over northeast California.
Critical fire weather conditions are likely Monday as very dry
air combines with gusty winds. Choppy lake conditions are also
likely Monday. Temperatures will cool down to near seasonal
averages through midweek, then slowly warm up again late in the
week with mainly dry weather prevailing.

&&

.DISCUSSION...

Isolated thunderstorms trying to develop in the lee of the Sierra
due to differential heating should be relatively short lived this
evening. Storms may last a little longer east of the Sierra where
a weak zephyr may focus development, along the Pine Nuts, and the
Virginia Range...but are not expected to take on any organized
characteristics. To the north there is greater potential for
loosely organized, longer-lived convection due to the presence of
upper level support in the form of potential vorticity advection.
Areas north of a line from Susanville to Gerlach show the best
potential for any organization. Even so...storms will still be no
more than widely scattered and the support does not last long.
Cells should be moving fast enough to limit the amount of
precipitation...but that increases the chance for dry lightning
strikes.

That brings us to Monday when drier air moves into all but the
very far northern parts of the forecast area...heights and
temperatures decrease and breezes increase. The combination of
breezy winds and drier air will create critical fire weather
conditions in areas where fuels are receptive. We are also
concerned with holdovers from lightning strikes this evening.
More details are in the Fire Weather section. We have issued Lake
Wind Advisories for areas east of the Sierra Front into parts of
the basin and range to account for gusty winds Monday as well.
Forecast guidance does show a little residual moisture interacting
with a secondary vorticity lobe over the far northern forecast
area Monday evening...so a slight chance of thunderstorms was
added there.

Beyond Monday the weather turns generally benign with dry
westerly flow over much of the region. High temperatures should be
closer to normal or just a little above through Thursday.

The GFS persists in bringing a weak upper level low into the
region late Friday. The ECMWF has a similar feature...but is not
as aggressive. There is a lack of moisture...but the mere
presence of the feature along with increasing instability due to
warming temperatures could develop afternoon towering cumulus.
Right now we will leave mention of thunderstorms out of the
forecast.

The models diverge more for Saturday with the ECMWF more
aggressive with a deeper trough by then. The GFS is trying to
start building a ridge again. Both are back to westerly flow for
Sunday. Given the differences between the models and some run-to-
run differences cropping up in each model...we will keep the
explicit mention of storms out of the forecast for next
weekend...but they are not out of the question for Saturday.
Temperatures warm a bit more for Saturday and Sunday...back to
well above average.

&&

.AVIATION...

Convection across western Nevada and the eastern Sierra should
decrease through the evening. Over northeast California and far
northwest Nevada the convection is likely to continue into the
later evening hours. The only terminals likely to see any
thunderstorm activity this evening are KMMH and KSVE.

By Monday...breezy winds develop across the forecast area with
surface gusts east of the Sierra and through western Nevada
reaching 30-35 kts at times. Another breezy day is likely Tuesday
with surface gusts approaching 25-30 kts.

Winds should decrease into Wednesday and Thursday. Friday into
next weekend may see a return to isolated convection along and
just east of the Sierra each afternoon and evening...but right now
the chances are less than 15%.

&&

.FIRE WEATHER...

Thunderstorms are looking less likely along the Sierra Front from
around Susanville through northern Mono County this afternoon and
evening. Clouds are forming, but elements are relatively flat.
Still, a late afternoon thunderstorm is possible (about a 10%
chance) over the Virginia Range. Slight chances of general
thunderstorms remain possible mainly for eastern Mono and western
Mineral Counties where surface convergence is expected to be
stronger. Also, the best chances of dry variety thunderstorms
remain in northern Lassen County with slight chances for far
northern Washoe/Modoc counties. Holdovers from dry strikes will be
a concern heading into Monday. Overall, overnight recoveries will
be poor to moderate for most valleys.

The upper circulation shifts towards the west coast tonight resulting
in a stronger pressure gradient over the region for Monday in the
afternoon and evening. It is expected that winds will increase
across northern Nevada and far northeastern California, sustained 15
to 20 mph with gusts around 35 mph. Coupled with low RH in the
single digits to 14%, critical fire weather conditions will be
likely. As such, the Fire Weather Watches for the Sierra Front and
Nevada interior, including northern Mineral County, have been
upgraded to a Red Flag Warning. Also, fine fuels have been deemed
ready for eastern Lassen County and a portion of zone 458 which
includes Gerlach and the Smoke Creek Desert. Red Flag Warnings
have been issued for these areas as well. Recoveries will
continue to be poor to moderate for most valleys.

Winds remain breezy Tuesday afternoon, but below criteria. Still,
winds will be sufficient to drive any existing fires that may be
occurring in valley locations mainly through nearly continuous
grasses and brush. Afternoon winds become lighter by Wednesday with
slightly cooler temperatures. Boyd

&&

.REV Watches/Warnings/Advisories...
NV...Red Flag Warning from 1 PM to 11 PM PDT Monday
     NVZ450-453-458-459.

     Lake Wind Advisory from 1 PM to 11 PM PDT Monday for Washoe Lake
     in NVZ003.

     Lake Wind Advisory from 1 PM to 11 PM PDT Monday NVZ004.

CA...Red Flag Warning from 1 PM to 11 PM PDT Monday CAZ278.

&&

$$

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


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