Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 161527 AAB
AFDREV

Area Forecast Discussion...UPDATED
National Weather Service Reno NV
827 AM PDT Sun Jul 16 2017

.UPDATE...
Good Sunday morning. A few items to mention:

* We will be continuing Red Flag Warnings for wind and low
  humidity Monday and upgrading to RFW for Tuesday as guidance
  indicates a similar scenario then for much of the region. It is
  important to note that the RFW conditions are likely be much
  more prolonged Monday compared to Tuesday, on the order of 9-12
  hours Monday, 3-6 hours Tuesday. These winds will have a large
  impact on ongoing fires including Long Valley and MM155 near
  Winnemucca. Grass loads are 2-3x normal, so this could turn into
  a Particularly Dangerous Situation for communities near these
  fires. This includes Palomino Valley, Sutcliffe, and areas south
  of Winnemucca.

* Thunderstorm forecast looks on track today with most storms in
  the Eastern Sierra of Mono County over into Central Nevada,
  following recent HRRR guidance. However based on 12z sounding
  and GOES-16 stability measures, the airmass even up to RNO is a
  touch more unstable than yesterday. So it wouldn`t shock me to
  see a cell or two develop up to Hwy 50 or even I-80, but overall
  main storm areas will be similar to yesterday. We did have some
  pre-dawn lightning in S Mono Co, so we`ll need to watch that for
  holdover fires tomorrow and Tuesday.

* With that said, our radar KRGX is inoperable as of 7 AM this
  morning. Not ideal. There appears to be a significant hardware
  issue that our techs will have to visit the radar to address.
  That may not happen in time before afternoon storms. So we have
  to rely on distant data from other radars or frequent GOES-16
  products and lightning networks to monitor storms today.

-Chris

&&

.PREVIOUS DISCUSSION... /Issued 537 AM PDT Sun Jul 16 2017/

UPDATE (Aviation)...

The thick smoke from the Long Valley Fire north of Reno is acting
like a ceiling deck with bases around 035-050 AGL. This is
creating terrain obscuration from around Doyle south to Carson
City, including KRNO and KCXP. Smoke and haze will clear out of
the region by around noon. Otherwise please see original aviation
section below for the forecast. -Dawn

PREVIOUS DISCUSSION... /Issued 511 AM PDT Sun Jul 16 2017/

UPDATE...

With light northerly flow overnight, smoke and haze have moved
into the Reno/Sparks area this morning from the Long Valley fire.
A few storms did finally pop up in Mono County the last few hours
with around 35 lightning strikes noted southeast of Mammoth
Lakes. Updated the forecast to add smoke, haze, and a few more
hours of isolated thunderstorms. -Zach

PREVIOUS DISCUSSION... /Issued 252 AM PDT Sun Jul 16 2017/

SYNOPSIS...

Isolated thunderstorms remain possible today with the best
chances in the eastern Sierra and central Nevada. Low pressure
approaching the west coast will increase winds Monday and Tuesday,
leading to critical conditions for rapid fire spread. Winds will
decrease a little each afternoon with hot temperatures expected
for the balance of the week.

SHORT TERM...

Weak upper level wave moving through the area this morning is
keeping high level clouds draped over the region with a few light
showers possible. No thunderstorms have have popped up yet, but
an isolated storm or two will remain possible the next few hours.

Ridge of high pressure over the area is flattening in response to
an incoming trough moving through the Pacific Northwest. This
will have a few implications for our weather the next few days
including pushing thunderstorm activity out of the region and
increasing dry southwest winds. It will also cool afternoon high
temperatures starting Monday, albeit only by a few degrees.

Today should be the last day of thunderstorms in the area this
week with storms expected to be limited today mainly to Mono,
Mineral, and southern Lyon counties.

Winds will begin to pick up today with the windiest day of the
week expected to be Monday and only a slight decrease in wind
speeds Tuesday. A Red Flag Warning is in effect for Monday with a
Fire Weather Watch out for Tuesday. See the Fire Weather Section
below for more on the critical fire weather conditions expected
for the start of the week. -Zach

LONG TERM...Wednesday onward...

More "typical" summer conditions are anticipated Wednesday into the
start of next weekend with warm and mainly dry conditions. While
wind speeds will begin to decrease by midweek compared to Monday and
Tuesday, afternoon westerly zephyr winds of 10-15 mph with gusts
to 25 mph can still be expected.

Thunderstorm chances will be limited to southern and eastern Nevada
for much of the work week due to the drier and more stable air mass
across the region. The high pressure center begins to weaken and
shift eastward heading into the weekend, allowing for moisture to
slowly creep northward and bring the return of thunderstorms to the
region. As we get toward the latter part of the weekend and into the
start of next week there are indications in the ensemble guidance
that a monsoon surge may work northward. This has the potential to
bring greater thunderstorm coverage to the area, but will also be
battling a trough just off the Pacific Northwest coast. If this wave
arrives slightly further south, the increasing dry southwesterly flow
would push thunderstorm chances farther south. Based on the pattern
so far this summer, we definitely can`t count troughs out! -Dawn

AVIATION...

Mid and high level clouds are moving across the the Sierra and
northern Nevada early this morning, but latest radar signatures
suggest there is hardly any rain associated with them. Otherwise,
widespread VFR conditions early this morning with chances for
thunderstorms this afternoon and evening. Storms are anticipated
mainly south of Highway 50 and will be fairly isolated in coverage.
Isolated storms are possible for KMMH, KHTH, KNFL, and KBAN, but
with chances small of a terminal having a storm pass directly over,
will leave the mention of TS out of the TAF this morning. Outflow
wind gusts of 40 kts and lightning are a possibility with any storm
that does form. Storm bases are likely to be fairly high, leading to
a low risk of terrain obscuration. Chances for storms are near
zero Monday and Tuesday.

Fairly typical westerly winds of 10-15 kts gusting up to 25 kts can
be expected this afternoon and early evening. Stronger winds with
gusts up to 35 kts are likely on Monday, with winds increasing
earlier in the day than usual, around noon local. Breezy
conditions will linger into Tuesday. -Dawn

FIRE WEATHER...

A weak passing wave overnight brought an increase in clouds across
the Sierra and northwestern Nevada, but latest radar trends indicate
little if any rain is reaching the ground. Instability is lacking
and therefore do not think we will see thunderstorm activity now
through morning.

Thunderstorm coverage today looks similar to what we saw Saturday.
Storms should be mainly confined to Mono, southern Lyon, and
Mineral counties and be isolated in coverage. Storms are likely to
be a hybrid of wet and dry as relatively fast storm motions will
limit precipitation totals outside of the main rain core. Dry
lightning strikes could potentially ignite new fires across the
region ahead of Monday`s critical conditions.

Increasing winds on Monday will combine with a significant dry slot
leading to critical fire weather conditions. Winds are expected to
gust 30-40 mph along with single digit to low teen minimum humidity
values for portions of northeast California and northwest Nevada and
Red Flag Warnings continue to be in effect. Winds will remain breezy
on Tuesday with a very dry air mass still over the region. While not
as clear cut of a critical fire weather day compared to Monday, the
continuous and heavy grass crop this year has proven to carry fires
in even typical afternoon winds. With Tuesday`s winds being
stronger than usual, a Fire Weather Watch was issued during the
day shift and will remain in effect for Tuesday afternoon and
early evening.

The dry slot will also lead to poor humidity recovery both Monday
and Tuesday nights, especially for midslopes and ridges. Winds will
remain breezy overnight across ridges Monday night as well.

More "typical" afternoon winds will continue through the week with
afternoon gusts up to 25 mph. -Dawn

&&

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

     Red Flag Warning from noon to 8 PM PDT Tuesday
     NVZ450-453-458-459.

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

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

&&

$$

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



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