Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 07/26/21
Area Forecast Discussion
National Weather Service Reno NV
128 PM PDT Sun Jul 25 2021
.SYNOPSIS...
Light westerly winds will continue to pour smoke into the region
from the large Dixie Fire through at least Monday. Monsoon moisture
will overspread the region leading to an increase in thunderstorm
chances each afternoon much of this coming week. After a hot day
Monday, temperatures will cool notably Tuesday before warming back
up again late week.
&&
.DISCUSSION...
* Smoke: Well, earlier there was some hope we`d see a (very)
gradual improving trend in the smoke out our window. That`s
pretty much dashed with worsening AQI as a likely smoke layer
aloft mixes down into the valley around Reno. Super light
westerly winds should kick in later today but the temperature
gradient to drive those winds will be made even weaker by the
thick smoke over W Nevada. In the end, based on HRRR Smoke Model
there may be some evening improvement but extra-low confidence
on extent.
* Similar situation Monday with light W/NW flow at night bringing
in Dixie Fire smoke to much of the region by daybreak, with
mixed confidence on improving conditions for late day, modulated
by t-storm outflows. The one area that escapes the thick smoke
is the E Sierra with more S/SE wind monsoonal trajectories
developing Monday.
* Thunderstorms: Respectable monsoon moisture push into the
region this week with a large high centered over the Four
Corners and Rockies. Thunderstorm probabilities will remain
elevated with precipitable water values rising to near 1" by
Tuesday afternoon in most ECMWF EPS members. Monday afternoon
looking active with slow moving storms in latest HRRR and HREF
guidance, and a wave lifting north out of SoCal could keep
faster moving t-storms going into the pre-dawn hours Tuesday.
Some possibility subsidence behind this wave + "too high PW"
could keep storm coverage down Tuesday PM but low confidence on
that this far out.
* We`ll really need to be on our toes with flash flood and debris
flow risks on the newer burn scars such as Beckwourth, and even
the ongoing Tamarack Fire especially on steeper slopes just west
of Hwy 395 + steep terrain of Alpine County. It only takes 5-10
minutes of heavy rain to cause major flooding on recent high
intensity burns. Will defer to the overnight shift to decide on
flash flood watch issuances each day, as flood flood
environments have limited predictability in our region more than
12-18 hours out.
* Most of the EPS guidance has drier air working in Wednesday
while some members keep moisture values high enough for a
continued storm risk. PW values rise again Thursday into the
weekend so better confidence of storms there. GEFS has a rather
robust QPF signal for Thursday, something to watch. We`re
definitely in a pattern over the coming week where at some point
over the next seven days, most areas will see some rainfall and
some could see rather heavy downpours. Now`s a good time to
ensure drainages are cleared out, and people near recent fires
are prepared for possible flooding.
-Chris
&&
.AVIATION (through Monday)...
Widespread smoke covering the area today mainly from the Dixie
Fire in NE California. Some aircraft holds into RNO due to low
visibility this afternoon. Any improvements will be very gradual
due to afternoon westerly winds being on the light side. HRRR
smoke shows some late afternoon and evening improvements for
TVL/TRK and possibly RNO/CXP/MEV, though confidence is only medium
as there is just a ton of smoke both at the surface and aloft to
move around.
Air flow turns more W/NW again tonight with smoke coming back in
overnight into Monday morning - MVFR to IFR conditions again well
into Monday. Highest risk of thick smoke is for SVE-RNO-NFL-CXP
areas, with less risk for TRK/TVL. Main exception to this will be
MMH where wind trajectories favor only minimal smoke or haze
impact through Monday.
Thunderstorms become more of a factor starting today with a solid
monsoon push working north into the region. Based on NBM and HREF
guidance, the best chances through this evening are between
TVL/MEV and MMH in the E Sierra. Somewhat slow moving storms with
areas of MVFR-IFR in heavy rain and outflows to 35 kts. For Monday
afternoon t-storms are more expansive ahead of an approach wave
aloft, including RNO and TRK/TVL and NFL vicinities. Outflows in
HREF look stronger, possibly up to 50 kts. T-storms of at least
isolated coverage will last into the evening and possibly
overnight to daybreak Tuesday.
-Chris
&&
.FIRE WEATHER...
The main concern for fire weather this week will be the increase in
thunderstorm activity that is expected to last throughout the week
as increasing monsoon moisture moves into the region from the
southeast. New fire starts in very dry fuels, along with gusty
erratic outflow winds and the potential for flash flooding on
current/recent fires are all hazards that could create issues
with the ongoing fire fights.
Today looks like a fairly typical thunderstorms day with build ups
beginning to develop late this morning along the higher terrain of
the eastern Sierra, with continued development and a few relatively
weak storms, expected through early evening.
Monday is a little more concerning as an upper-level wave brings
additional forcing while increasing moisture continues to flow
into the region. Stronger thunderstorms will be likely tomorrow
with the with elevated nocturnal convection possible lasting
overnight. Overnight storms are not clear cut at this point, but
the enough forcing and instability could be left over from to
keep some storms going after dark. Currently expecting a mix of
wet and dry storms tomorrow with the best chances for drier storms
north of highway 50 along the edge of the better increasing
PWATs, where storm motions will be faster with less available
moisture.
Storms will continue to transition to the wetter variety on Monday
(south of I-80), and throughout the region later in the week.
This will create flash flooding concerns, mainly in the more
vulnerable areas with fresh burn scars, especially near on the
Tamarack fire where considerable amounts of complex terrain has
burned near and above roadways.
Storms will continue throughout the week with varying degrees of
coverage and intensity. As moisture levels increase chances for more
widespread wetting rains will be possible this week, with the best
chances from Tahoe southward. -Zach
&&
.REV Watches/Warnings/Advisories...
NV...None.
CA...None.
&&
$$
For more information from the National Weather Service visit...
http://weather.gov/reno