Home > Products > Valid Products > AFD

000
FXUS65 KREV 232128
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
228 PM PDT MON MAY 23 2016

.SYNOPSIS...

Below average temperatures with increasing chances of showers and
thunderstorms are expected through Wednesday as low pressure moves
slowly south across California and Nevada. Snow may produce occasional
travel impacts over higher passes through midweek. Showers and
thunderstorms will remain possible into the Memorial Day weekend,
although overall coverage should decrease.

&&

.SHORT TERM...

A very broad upper low with a series of embedded waves moving
around the low will impact the weather through at least the middle
of the week. Periods of showers enhanced by these embedded waves
will develop with the occasional thunderstorm as well. Cloud cover
will play a large role in the amount of activity we see each day.

Currently...thick cloud cover in the higher levels is limiting low
level heating and resulting in little in the way of convective
activity...but that should change as we move into the late
afternoon and early evening. As the upper low slowly drops south
through the next 48 hours there should be some minor cooling
aloft. This will not be as extensive as the last system to affect
the region this past weekend. With only minor cooling aloft and
limited heating due to cloud cover at the surface...we are more
likely to see scattered to widespread showers and mainly isolated
thunderstorms each day with no thunderstorms overnight. There is
also little in the way of jet support and very limited low to mid
level shear to sustain any thunderstorm activity...or push the
development past garden variety storms.

The best coverage of thunderstorms is likely to be Tuesday...but
even that day could be limited by the development of cloud cover
early. The stronger storms may produce small hail which could
accumulate on higher elevation roads and/or drag snow levels below
7500 feet briefly and produce some minor accumulations. This could
be the primary impact through Wednesday night.

Lastly...cloud cover will also play an important role in our
temperatures...both highs and lows. Cloud cover in the daytime
along with the presence of the upper low and showers will keep
high temperatures below normal through at least Wednesday.
Meanwhile...if clouds dissipate enough at night there could be
areas of lows in the 20s in the Sierra valleys and lower to mid
30s in the lower valleys. However...if clouds remain extensive
overnight low temperatures are not likely to drop out of the 40s
in the lower valleys. While we do not foresee the need for any
freeze watches/warnings at this time...everyone needs to remain
aware that low temperatures could drop 4-8 degrees below the
forecast numbers if skies clear. 20

.LONG TERM...Thursday through the Memorial Day Weekend...

Trimmed back the location/timing of showers and thunderstorms
Thursday afternoon and evening, otherwise no significant changes
to the long term forecast.

Thursday, models show agreement with the general position for
possible showers in/near the Sierra and out in central Nevada.
With no substantial upper forcing, the convection looks tied to
daytime heating so I have cut back timing to the afternoon and
evening. The model location for convection looks reasonable as
well as it matches typical weakly-forced summer-type convection
in the Sierra south of Tahoe and out in the central NV convergence
zone. A few showers or storms could drift out into far western NV
Thursday with west-northwest flow aloft.

Friday through Sunday, a broad trough remains over northeast CA
and western NV in many models. There are some models (00Z EC)
which bring a sharper trough into northern NV Friday night and
Saturday morning which could lead to a more widespread band of
precipitation and lower snow levels, especially north of highway
50. Thusly, I have left the nocturnal showers in for some areas to
cover this possibility. Otherwise, low chances for afternoon and
evening showers and thunderstorms were left intact Friday through
Sunday with at least the broad trough allowing for some diurnal
convection each day.

On Memorial Day, uncertainty rises as some models depict stronger
energy dropping into the baggy trough for higher shower chances
while others do not, which would greatly limit chances. Bottom
line for those heading outdoors late week and through the
Memorial Day weekend...be prepared for afternoon/evening rain and
high elevation (generally above 9000 feet) snow along with
cool/chilly nights. Periodic west to northwest breezes could also
lead to choppy conditions on lakes. -Snyder

&&

.AVIATION...

Thick cloud cover and/or limited mid-level instability is really
limiting cumulus development this afternoon in eastern CA and
western NV, with cumulus spreading into a VFR (~110-140 MSL) cloud
deck north of Pyramid Lake. There is still a low chance for -shra
this evening and overnight, but impacts should be limited to
brief and isolated higher terrain obscuration with snow levels
8,000 to 9,000 MSL.

As far as thunderstorms this afternoon and evening, very low (5%)
chance generally east of highway 395 in Mono and Mineral Counties.
Any thunderstorms would be capable of outflow gusts to around 30 kts
and very small (less than 0.5") hail.

Late tonight and Tuesday a weak, elongated trough will still extend
through CA and NV. This will bring continued chances for -shra,
with very isolated (less than 10% chance) afternoon thunderstorms
possibly bringing occasional higher terrain obscuration in the
Sierra. -Snyder

&&

.REV Watches/Warnings/Advisories...
NV...None.
CA...None.
&&

$$

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





000
FXUS65 KREV 230906
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
206 AM PDT MON MAY 23 2016

.SYNOPSIS...

Below average temperatures with increasing chances of showers and
thunderstorms are expected today through Wednesday as low
pressure moves slowly south across California. Snow may produce
occasional travel impacts over higher passes through midweek.
Showers and thunderstorms will remain possible into the Memorial
Day weekend, although overall coverage should decrease.

&&

.SHORT TERM...

After a rather quiet Sunday in terms of shower activity, the
southward progression of an upper low along the northern CA coast
will lead to increasing instability by this afternoon. The best
overall chances for showers and thunderstorms today appear to
favor areas near the Sierra and northeast CA, then pushing slowly
into far western NV later in the afternoon. Snow levels are
expected to average around 7500 feet today in the Sierra, which
could produce travel impacts over higher passes if persistent
stronger cells or shower bands occur.

For later tonight, several runs of model guidance have indicated
a more persistent area of showers and possible thunderstorms over
portions of Mono, southern Lyon and Mineral Counties. These areas
are within a deformation zone with enhanced upper level forcing
as the upper low center moves over the San Francisco Bay area. We
have increased shower chances over areas south of US-50 although
by this time we may be dealing with an area of steady light to
moderate rainfall with a marginal threat of thunder.

On Tuesday, overall instability continues to increase with latest
guidance generating some convection by late morning. The most
favored areas continue south of US-50, with a secondary focus for
increased coverage north of Susanville and Gerlach. However, as
the day progresses and cells continue to develop with subsequent
outflow interactions, any portion of eastern CA-western NV is
fair game for receiving showers and thunderstorms. Stronger and
more persistent storms capable of producing accumulating hail are
possible, with potential for snow affecting travel on higher
passes mainly above 7500-8000 feet. Later Tuesday night, areas
south of US-50 could again receive another area of rain showers
with a slim possibility of embedded thunder.

Wednesday is also likely to be active as the low tracks inland
across southern CA, with overall instability again sufficient for
another early start to convection. Once again, nearly any portion
of eastern CA or western NV is at risk for shower and thunderstorm
activity, although by later in the day the best forcing and
instability are projected to shift to areas east of Gerlach-Reno-
South Tahoe line. The same potential for hail accumulation and
longer duration storms will apply with stronger cells Wednesday,
although snow levels should edge upward to near 8500 feet during
the afternoon.

By Wednesday night as the low pulls into the Desert Southwest,
the best forcing will also exit western NV so most shower and
thunderstorm activity should diminish during the evening. MJD

.LONG TERM...Memorial Day weekend into the start of June...

No big changes in the models over the last couple days. Another low
pressure over the Gulf of Alaska will drop into the region by
Friday then linger over the Great Basin through the Memorial Day
weekend. This will maintain a threat of showers and a few
thunderstorms with afternoon highs in the 60s and 70s and overnight
lows in the 30s and 40s. For those heading outdoors for an
extended period of time, be prepared for rain, high elevation snow
and chilly nights. Breezy west to northwest winds will also lead
to choppy conditions on lakes.

Looking beyond the holiday weekend, simulations leave a persistent
trough along the west coast into the start of June. This supports
additional lows dropping south from the Gulf of Alaska and western
Canada. No significant warm up or summer like weather is in sight
for now. Brong

&&

.AVIATION...

Showers and thunderstorms will develop along the Sierra Crest around
20-21z, then slowly drift east toward a line from Susanville to Reno
to Mono Lake by 23z-01z. While the instability isn`t overly
impressive, the proximity of an upper low along the California coast
will allow showers and storms to produce moderate to heavy rain,
small hail and snow near and above 7500 feet MSL. Mountain
obscurements are also likely today. The threat of showers and
thunderstorms will continue into Wednesday the low drifts inland
over southern California.

Another low may lead to additional showers and thunderstorms for a
portion of the Memorial Day weekend. Brong

&&


.REV Watches/Warnings/Advisories...
NV...None.
CA...None.
&&

$$

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





000
FXUS65 KREV 211031
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
331 AM PDT SAT MAY 21 2016

.SYNOPSIS...

Low pressure persisting over northern California will keep below
average temperatures with chances for showers and a few
thunderstorms through much of the upcoming week. Snow may still
produce occasional travel impacts today between 5000 and 6000
feet...then become more limited to higher passes after today.

&&

.SHORT TERM...

Although there will be some day to day variance with shower
potential, the overall unsettled pattern with below average
temperatures will continue through Monday. Today will be the
overall coolest day, followed by a 4-8 degree rise in most areas
Sunday, then little change in max temps between Sunday and
Monday. Winds will not be as strong compared to the previous two
days, although some afternoon zephyr-type west breezes are
probable each day.

For this morning, the snow over Surprise Valley and far northwest
NV will diminish, while much lighter snow and rain showers are
possible southward to near US-50. Later today, a shortwave
rotating into northern CA will lead to more convection developing
across central and eastern CA, then spreading into portions of
western NV especially north of I-80. In addition, Mono and
Mineral Counties will have a better chance for showers and
isolated thunderstorms later this afternoon and evening as the
forcing associated with this shortwave shifts to these areas. Snow
levels rise only a bit from yesterday to near 5500-6000 feet along
the eastern Sierra. Anyone planning travel over the main passes
including Donner and Echo Summits should be prepared for potential
winter conditions. As we saw yesterday over I-80, when convectively
enhanced snow bands develop and persist, they are capable of
producing slick and hazardous road conditions even in late May.

For Sunday, the overall shower potential retreats to areas north
of Susanville-Gerlach and in close proximity to the Sierra crest as
less forcing is expected across the region. There is a small
possibility of a few early evening cells developing east of the
Reno-Carson areas after the zephyr kicks in and provides some low
level convergence. Instability is spotty so most cells that
develop would be short lived with little activity expected later
in the evening.

For Monday, another stronger shortwave drops into northern CA and
brings increased forcing and better shower/thunderstorm potential
again. This wave is projected to keep some diffluence over western
NV, which could keep showers going overnight especially for areas
north and east of a Susanville-Reno-Bridgeport line. Snow levels
are projected to rise, generally ranging from 7500-8000 feet near
the Sierra, which would limit most potential travel impacts to
higher passes. However, snow levels could quickly drop several
hundred feet within heavier convective bands. MJD

.LONG TERM...Tuesday through Friday...

The long term forecast remains on track for below normal
temperatures and chances for showers and isolated thunderstorms
each day through at least the first half of the week. Winds should
be relatively light with some afternoon/evening breezy conditions
possible. For Tue-Wed, model simulations suggest parts of the
eastern Sierra and western NV could see bands of heavier
precipitation under a deformation axis. If these bands develop,
some locations could see daily precipitation totals perhaps in the
0.5 to 1.0 inch range with snow levels 7000-8000 feet MSL. It`s
not possible at this forecast range to know when or where such a
band might develop, but there is some increased potential for
travel impacts due to snow above 7000 ft.

Model consistency run-to-run has been poor for the second half of
next week making forecast confidence lower for that period.
Latest simulations have trended towards developing another cold
upper low over the west by the end of the week. This pattern could
bring another round of strong winds and lower snow levels by the
end of the week into Memorial Day weekend. JCM

&&

.AVIATION...

West surface winds will be breezy today with afternoon gusts
generally in the 15-30 kt range. Mostly VFR conditions except for
local MVFR conditions under scattered showers and isolated
thunderstorms. Expect mountain obscuration today in the Sierra
and also near any showers. Shower coverage Sunday should be
limited mainly to near the Sierra crest and north of Susanville-
Gerlach. A more widespread shower/thunderstorm coverage across the
eastern Sierra and western NV returns Monday and could continue
each day through next week. JCM

&&


.REV Watches/Warnings/Advisories...
NV...Winter Weather Advisory until 9 AM PDT this morning NVZ005.

CA...Winter Weather Advisory until 9 AM PDT this morning CAZ070.

&&

$$

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





000
FXUS65 KREV 210635 AAA
AFDREV

Area Forecast Discussion...UPDATED
National Weather Service Reno NV
1135 PM PDT FRI MAY 20 2016

.UPDATE...

All of the wind headlines were allowed to expire earlier this
evening. Some localized gusty winds in the 30-40 mph range
continued until around 10 pm but overall the speeds should slowly
decrease. Sierra ridge gusts have also begun trending down with
gusts on Slide Mtn. dropping from near 80 mph to 50 mph between 9
and 11 pm.

The band of snow that affected I-80 earlier this evening brought
some impressive totals over 1 foot west of the crest...with some
web camera images near the crest appearing to indicate around 6
inches of new snow. A few inches may have also accumulated down to
near Truckee. Although chain restrictions were still in effect, road
conditions over Donner Summit are improving based on the latest
web camera images. Farther north in the advisory area, satellite
images still show some enhancement although tops have been slowly
warming. Cedar Pass is still snow covered and weather sensors in
the Surprise Valley are reporting temps in the 30s with measured
precip during the evening, which may be yielding some slushy
accumulations down to the 4500-5000 foot level. No changes to this
advisory are planned. MJD

&&

.PREVIOUS DISCUSSION... /Issued 220 PM PDT FRI MAY 20 2016/

SYNOPSIS...
Low pressure will keep the chance for showers and isolated
thunderstorms going through the first half of next week.
Temperatures will start out well below normal this weekend and
then gradually rise to near normal by the middle of next week.

SHORT TERM...

Upper low over northern CA/NV will gradually weaken and lift out
of the of the region on Sunday. The best chances for showers and
isolated thunderstorms will be tonight and Saturday with a
general decrease in activity Saturday night into Sunday. Winds
will also be lighter although typical afternoon/evening breezes
can still be expected Sat-Sun.

For tonight-Saturday, upper trough/area of deformation will swing
through northern areas. The 12z GFS and 12z/18z NAM are in good
agreement and have support from ensemble QPF members regarding a
period of moderate to heavy precipitation overnight and early
Saturday morning across far northeast CA and northwest NV. Some of
the members indicate rather impressive QPF. Snow levels will be
near valley floors and this will promote accumulating snowfall
with several inches likely near Surprise Valley and across
northern Washoe County. So we have hoisted a snow advisory for
snowpacked and slushy roadways north of Gerlach and across far
northeast CA. Some model solutions bring several inches down into
pars of northern and western Lassen County, so that will have to
be watched this evening. A tight westerly gradient will also keep
winds going in these areas which will result in poor visibility
where snow falls.

Isolated-scattered showers will continue across the northern
Sierra and western NV north of Hwy 50 tonight with best chances
north of I-80. We have seen a few lightning strikes so we will
keep a mention of isolated thunder this evening. Where heating has
occurred in the Basin and Range, there could be a few stronger
storms capable of small hail. The gusty winds will gradually
diminish through the night for much of the region south of I-80.

Isolated to scattered showers and thunderstorms will spread to
most areas for Saturday as upper low will be over the region.
Southern areas of Mono-Mineral Counties are in a better position
for showers and thunderstorms as shortwave rotates through upper
low into central NV Sat afternoon-evening. There could be some
brief but light snow accumulations over higher passes along Hwy
395 through Mono County as the sun drops Sat evening. Less shower
coverage and slightly warmer for Sunday as west flow aloft
develops ahead of another trough dropping in from the northwest.
Expect more typical breezy afternoon and evening winds both Sat-
Sun.

LONG TERM...Monday through Friday...
No major changes in the forecast for next week. Still appears that
the Sierra and western Nevada will be in a relatively active weather
pattern. Multiple upper level shortwaves drop out of the Gulf of
Alaska down the west coast which will keep chances for showers and
thunderstorms in the forecast at least for the first half of the
week.

Winds will be relatively light with some afternoon/evening breezy
conditions possible. Temperatures will be relatively cool for the
first part of the week with highs between 60 to 70 degrees for the
lower valleys and in the 50s/60s for the higher elevations. Model
agreement diverges by later in the week with the ECMWF showing a
ridge building in, while the GFS keeps another trough over the west.
Accordingly, forecaster confidence with the chances for continued
showers/thunderstorms beyond Wednesday is low. -Edan

AVIATION...

Gusts up to 30-35 kts will continue through this evening along
the Sierra front range and along the I-80/hwy 50 corridors
including at KRNO/KCXP/KLOL. Wind gusts will be a bit stronger
south of hwy 50 at KMMH/KHTH through this evening.

Mostly VFR conditions expected through Saturday morning except for
local MVFR conditions under scattered showers and isolated
thunderstorms. Our ongoing shower and thunderstorm threat will
continue this weekend and into next week. -Edan

&&

.REV Watches/Warnings/Advisories...
NV...Winter Weather Advisory until 9 AM PDT Saturday NVZ005.

CA...Winter Weather Advisory until 9 AM PDT Saturday CAZ070.

&&

$$

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





    US Dept of Commerce
    National Oceanic and Atmospheric Administration
    National Weather Service
    1325 East West Highway
    Silver Spring, MD 20910
    Page Author: NWS Internet Services Team
Disclaimer
Information Quality
Credits
Glossary
Privacy Policy
Freedom of Information Act (FOIA)
About Us
Career Opportunities