Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 221643 AAA
AFDREV

Area Forecast Discussion...UPDATED
National Weather Service Reno NV
943 AM PDT Sat Jul 22 2017

.FIRE WEATHER...Updated
The forecast remains on track with thunderstorms for tomorrow, and
starting out on the dry side. They will turn wetter during the
day, especially for Mono-Mineral. With higher confidence,
upgrading the watches to Red Flag Warnings and adding zones
271/272. Everywhere will see at least isolated thunderstorms with
the threat for new fires.

Will run Mono-Mineral with the early timing as thunderstorms will
start there, but also transition to wet by evening. Further north,
storms will take a little longer to get going, and with the
forcing from the upper low could go well into the evening. With
dry low layers gusts to 50 mph are possible from any storm, and to
60 mph in the deserts.

Monday still looks to be much wetter except north of
Susanville/Gerlach. The models are slower this morning to bring
the moisture that far north so another day of hybrid wet/dry
thunderstorms is possible. All areas will see wetting
thunderstorms Tuesday and the attention will turn to potential
flash flooding as PWAT values increase to 1 inch or more. Wallmann

&&

.PREVIOUS DISCUSSION... /Issued 336 AM PDT Sat Jul 22 2017/

SYNOPSIS...

Areas of haze from the Detwiler Fire could continue this weekend,
mainly for the Mammoth area. After one more day of dry conditions
today, low pressure off the coast will bring increased moisture
for early next week. Thunderstorms will begin Sunday, with some on
the drier side, before more moisture arrives Monday and Tuesday
with wetting rains and localized flash flooding possible.

SHORT TERM...

No significant changes were made to the short term forecast.
Moisture and thunderstorm chances will be on the increase on
Sunday and Monday as flow aloft turns southerly between low
pressure off the California coast and an upper ridge centered
over eastern Nevada and Utah. Heat is expected to peak this
weekend with highs 5 to 7 degrees above average, with cooling to
around average early next week as cloud cover increases and the
upper low brings cooler temperatures aloft.

Today looks like the last day free of deep convection (thunderstorms)
although a few high-based cumulus buildups are possible in Mono
County this afternoon with the very warm to hot temperatures.
Sunday, moisture/PWATs begin to increase with mid-level flow
turning more southerly. The slight cooling (increasing instability)
and moistening aloft is expected to combine with a late-day
zephyr to initiate isolated to scattered thunderstorms, with the
highest concentration in western and west-central NV. As Sunday
will be the first day of increasing PWATs/moistening of the
atmosphere and simulated soundings show around 20 kts of storm-
layer flow, storms are likely to be a mix of wet and dry. With
concern for numerous initial fire starts due to the heavy grass
fuel loading and limited rainfall, a fire weather watch will be
issued with the package.

Monday, moisture continues its slowly increase as flow aloft
remains southerly between the trough and ridge. More areal coverage
of scattered thunderstorms is expected due to the increased
moisture, very warm temperatures, and another weak westerly wind
push (for increased convergence for convection) late in the day.
Storms will have an increased chance of producing heavy rain
versus Sunday with the increasing PWATs and sounding profiles
suggesting the possibility for training cells (unidirectional flow
aloft). High temperatures are expected to come down around 3 to 7
degrees on Monday as clouds increase and temperatures aloft cool.
-Snyder

LONG TERM...Tuesday through Friday...

Low pressure remains along the Northern CA coast on Tuesday,
bringing a vortmax through northern CA/NV on Tuesday afternoon. This
wave will expand thunderstorm coverage and even bring some
organization to the thunderstorms as the exit region of the jet
moves overhead. We have increased chances for thunderstorms on
Tuesday with threats of small hail, gusty winds, and localized heavy
rainfall. Thunderstorms will be on the wet side, with precipitable
water approaching one inch. Flash flooding could be a possibility
especially on recently burned areas.

Low pressure lifts out of the area on Wednesday, with dry southwest
flow returning to the region. Typical breezy afternoon winds will
return with temperatures cooling off a bit to near average mid week.
Temperatures will start to increase again by the end of the week
as the ridge strengthens. Hoon

AVIATION...

VFR conditions today with areas of haze from fires in California.
Typical breezy west winds expected this afternoon and evening with
gusts up to 20kts.

Thunderstorm potential increases Sunday through Tuesday with
scattered showers and storms possible each day. The usual threats of
gusty winds, small hail and locally heavy rains will apply.
Wallmann/Hoon

FIRE WEATHER...

Low pressure off the Northern CA coast moves towards the CA coast
over the next couple days, helping to increase monsoonal moisture
Sunday into next week. Sunday will be the first day of thunderstorms
and also a hybrid thunderstorm day with a mix of wet/dry storms
and numerous new lightning fire starts possible. Even though
moisture will be increasing through the day and localized heavy
rainfall will be possible with the strongest storms, we expect to
see isolated to scattered dry lightning strikes for areas of
western Nevada and northeastern CA, especially along and east of
Highway 395.

We have gone ahead and issued a Fire Weather Watch for Sunday as we
have medium confidence that we will see new fires starts from
lightning. Also, recent above normal temperatures and very dry
conditions have combined for very dry and receptive vegetation ahead
of the anticipated lightning. Gusty outflow winds may also be
possible with these storms with gusts up to 40-50 mph. These factors
will contribute to rapid fire spread and potentially extreme fire
behavior. Hoon

&&

.REV Watches/Warnings/Advisories...
NV...Red Flag Warning from 3 PM Sunday to midnight PDT Sunday night
     NVZ450-453-458.

     Red Flag Warning from 1 PM to 9 PM PDT Sunday NVZ459.

CA...Red Flag Warning from 3 PM Sunday to midnight PDT Sunday night
     CAZ270>272-278.

     Red Flag Warning from 1 PM to 9 PM PDT Sunday CAZ273.

&&

$$

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



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