Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 180316
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
816 PM PDT Mon Jul 17 2017

.UPDATE...

We let today`s Red Flag Warnings and Lake Wind Advisories expire
as scheduled this evening, but retain all headlines for Tuesday.
Some local gusts above 30 mph, especially in the Basin and Range
could continue for another hour or two but the most widespread
period of stronger wind gusts has passed. Ridge level wind gusts
continue at 35-45 mph, resulting in slow humidity recovery in
higher elevations. Mid slopes will also see poor humidity recovery
overnight due to occasional periods of moderate winds mixing down
from the ridges, and a very dry air mass.

As for the temperature streaks at Reno Airport, the high today
only reached 94 degrees, ending the streak of 95+ degree highs at
17 consecutive days--two days short of the record from 1940. The
streak of 90+ degree highs continues at 32 consecutive days, now
within 3 days of equaling the current record for 90+ degree
streaks. MJD

&&

.PREVIOUS DISCUSSION... /Issued 222 PM PDT Mon Jul 17 2017/

SYNOPSIS...

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

DISCUSSION...

Warm and dry conditions are likely through the entire forecast
period. Gusty winds this evening and Tuesday will decrease
slightly by mid-week. High temperatures are expected to remain
above normal...with the "coolest" days through Wednesday. Lows
should be near seasonal norms.

Dry southwest flow aloft and a strong pressure gradient at the
surface will result in continued gusty winds this evening and
Tuesday...although Tuesday`s winds may be slightly less than this
evening. The very dry air at the surface and aloft will combine
with the gusty winds to create critical fire weather conditions
this evening and again Tuesday. This has the potential to be a
dangerous situation due to the spread of ongoing fires. See the
Fire Weather discussion below for more details.

Slightly less wind Tuesday will mean less chance for gusty lake
winds for the Tahoe Basin and Mono County. We will issue another
Lake Advisory for northeast California...the western Nevada Basin
and Range...and Washoe Lake in the Sierra Front. But we will
leave the Tahoe Basin lakes and the Mono County lakes out of the
advisory for Tuesday.

Flow aloft remains southwest Wednesday through Friday...but
weakens. The low level gradient weakens as well and leads to
typical afternoon zephyr-type winds with gusts in the 25 to 30 mph
range. The southwest flow aloft keeps dry and stable air over the
region as well with no chance for deep convection.

By Saturday the model guidance shows a wave of low pressure moving
through the southwest flow. If there were any moisture this might
pose a problem...but there does not appear to be much moisture.
Another dry day Sunday with weak flow aloft and very warm
temperatures...possibly the warmest of the forecast period...
gives way to developing southerly flow Monday. If this flow
strengthens further we could see thunderstorms develop over the
far southern portions of the forecast area...Mono and Mineral
counties. The forecast models have been trying to redevelop this
southerly monsoon push for a few days...but keep delaying it with
each forecast cycle. Thus we have opted to keep thunderstorms out
of the forecast for now and wait for the models to settle on a
solution.

AVIATION...

VFR conditions persist for much of the forecast area the next few
days. The only areas with limited visibility will be downstream
of current fires where smoke may reduce visibility to 5 miles or
less... depending on how active any of the fires become.

Gusty winds from the west peaking at 25-30 kts will decrease late
this evening...then increase again Tuesday afternoon. Ridge winds
will remain gusty overnight with peak gusts near 40 kt. This could
produce turbulence through the night into Tuesday and possibly
affect air operations on the current fires.

Winds decrease a bit more from mid-week to the weekend as the
overall surface winds and flow aloft decreases.

FIRE WEATHER...

Red Flag Warnings remain in effect for this evening and again
Tuesday afternoon and evening. Winds on Tuesday look similar to
today, with afternoon humidities possibly slightly lower for
northeast CA and far western NV as drier air works down from aloft.
There is an increased risk of fires jumping containment lines with
the gusty winds. It would be wise to heed any evacuation orders as
the rate of fire spread may exceed fire protection ability in the
afternoon and evening.

Winds will remain elevated for ridges and many slopes tonight and
likely Tuesday night as well. With the dry airmass and winds, poor
humidity recoveries are again expected tonight and Tuesday night
(only into the 20-35% range for midslopes and some ridges). This may
allow fires to continue to burn through much of the night (albeit at
a lower intensity) as fine, dead fuels remain below their moistures
of extinction.

Winds are expected to decrease some on Wednesday and Thursday as
thermal gradients decrease slightly. Still, with some breezes and
the very dry air mass lingering over the region, enhanced fire
concerns will continue through at least Thursday as recent fires
have shown a tendency to spread despite much wind. -Snyder

CLIMATE...

As of 220 pm the temperature at the airport in Reno has reached
94 degrees. Normal high temperatures this time of year at the
Reno airport are 93-94 degrees...so the record for consecutive
days with highs of at least 90 degrees is well within reach. The
record for consecutive days with at least 95 degrees may be a bit
harder to reach as we may have mixed to our high temperature
already today. We do have a couple of hours to reach that 95
degree mark.

&&

.REV Watches/Warnings/Advisories...
NV...Red Flag Warning from noon to 8 PM PDT Tuesday
     NVZ450-453-458-459.

     Lake Wind Advisory from noon to 8 PM PDT Tuesday NVZ003-004.

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

     Lake Wind Advisory from noon to 8 PM PDT Tuesday CAZ071.

&&

$$

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



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