Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 171012

Area Forecast Discussion
National Weather Service Reno NV
312 AM PDT Mon Jul 17 2017


Low pressure approaching the west coast will increase winds
Monday and Tuesday, leading to critical conditions for rapid fire
spread. Breezy afternoon winds will linger the remainder of the
week, though will not be as strong as Monday and Tuesday. Warm and
dry conditions are anticipated through the work week.


.Short Term...

The main forecast concern for this week is going to be strong gusty
winds accompanying very dry air today and tomorrow that is expected
cause an increase in fire behavior in the area. Increasing winds
will also create dangerous boating conditions today and tomorrow

This is a particularly dangerous situation downwind of the Long
Valley Fire and MM155 Fire which could both be pushed towards local
communities. Ridgetop winds are expected to pick up Monday afternoon
through Tuesday along with tightening surface gradients causing an
extended period of critical fire weather conditions, especially on
the mid-slopes and ridges. For more details about on the critically
dry and windy conditions see the Fire Weather section below.

Haze and smoke from the fires could also be significant throughout
much of western Nevada the next few days. Smoke forecasts can be
challenging since it depends heavily on fire activity, but
considering the expected conditions over the next few days, smoke
and haze were added to the forecast. Strong west/southwest flow
will likely create hazy to smokey conditions from around Pyramid
Lake east into Central Nevada and from around Gerlach south to
around Fallon. The westerly flow should keep smoke mostly out of
the Reno/Carson City areas the next few days, at least from the
current fires burning in western Nevada. -Zach

.LONG TERM...Thursday onward...

The trough that had been sitting of the Pacific Northwest coast much
of the week is finally kicked eastward Thursday into Friday by
another weak wave. This will help to decrease the wind speeds aloft,
but will also increase the surface gradient Thursday and Friday
afternoons. While wind speeds do not look to be nearly as strong as
Monday/Tuesday, expect a slight enhancement to the typical afternoon
winds. Lighter winds speeds are likely for the weekend, with a brief
period of northeasterly winds Saturday night into Sunday morning.

The dry southwest flow across the region will keep thunderstorms
limited to southern and eastern Nevada for the end of the week and
into the weekend. Previous model runs indicated chances for a
monsoonal surge as early as the weekend, however this has been
getting pushed back the past couple of days and latest guidance
would suggest no earlier than Tuesday or Wednesday next week.
If/when this surge occurs it would lead to an increase in
thunderstorm coverage across the region. -Dawn



Winds are already beginning to increase across Sierra ridges early
this morning and are a precursor to the stronger southwest winds
forecast for today and Tuesday. Widespread gusts of 30-35 kts are
likely to bring localized areas of turbulence and wind shear. The
increased winds may also be a concern for aviation support for
ongoing wildfires. Winds will decrease for valley locations tonight,
but will remain gusty across ridgelines.

Widespread VFR conditions are likely today outside of areas near and
downwind of active wildfire. The worst conditions are likely to be
near the Long Valley Fire just west of Pyramid Lake, MM155 Fire just
southwest of Winnemucca, with some concerns for the Draw/Bravo 17
Fires east of Fallon. Near/downwind of these locations expect
reductions to visibility and terrain obscuration. Smoke/haze may
carry farther today and Tuesday due to increased wind speeds with
slantwise visibility reductions possible in an area between Pyramid
Lake-Lovelock-Fallon. The southwest wind direction should limit the
extent of haze into KRNO and KCXP.

Thunderstorms are not expected for the eastern Sierra or western
Nevada through the week. -Dawn



A particularly dangerous situation is shaping up today into Tuesday
for ongoing wildfires, especially the Long Valley and MM155 fires
and the communities downwind. Increasing southwest winds with
gusts in the 35 to 40 mph range will combine with an extremely dry
air mass (single digit minimum humidity values) to create a long
period of critical fire weather conditions. The greatest risk is
from noon to 9 pm today and 2 pm to 8 pm on Tuesday. Wind speeds
on Tuesday have trended upward in the latest guidance and it is
possible they may be similar to speeds today. Red Flag Warnings
remain in effect today and Tuesday and we need to stress that
there is an increased risk of fires jumping containment lines.
Please heed any evacuation orders as the rate of fire spread may
exceed fire protection ability.

Winds will remain gusty across ridges and upper slopes tonight into
Tuesday morning with abysmal humidity recoveries tonight and Tuesday
night (only into the 20-35% range for midslopes, ridges, and the
central Nevada Basin and Range). This will only further heighten
the fire danger the next several days.

Winds will decrease from the middle into the end of the week,
however will remain stronger than the "typical" afternoon breezes.
The dry air mass lingers over the region through the end of the week
as well, so the enhanced fire concerns will continue for much of the
week. Despite the fact that conditions may only be marginal for a
watch or a warning the remainder of the week, we have seen that
fires involving grasses and sage are very active even in marginal
conditions. -Dawn


.REV Watches/Warnings/Advisories...
NV...Red Flag Warning from noon today to 8 PM PDT this evening

     Red Flag Warning from noon to 8 PM PDT Tuesday

     Lake Wind Advisory from noon today to 8 PM PDT this evening

CA...Red Flag Warning from noon today to 8 PM PDT this evening

     Red Flag Warning from noon to 8 PM PDT Tuesday CAZ270-271-278.

     Lake Wind Advisory from noon today to 8 PM PDT this evening



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