Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 120534 AAA

Area Forecast Discussion...UPDATED
National Weather Service Reno NV
934 PM PST Sun Feb 11 2018


The initial cold front and band of showers was moving out of
western NV this evening with clearing noted on the backside across
parts of northeast CA and northwest NV. Snowfall was light over
the Sierra and western NV as there was too much dry air to work
over before rain and snow could reach the surface. Farther east
along I-80 - east of Lovelock to Winnemucca and beyond, an inch
or two of snow has resulted in slick roads as temperatures remain
below freezing. A band of snow is currently moving across central
NV and will impact Highway 50 overnight east of Fallon through
Austin and Eureka.

The clearing will be shortlived as satellite and radar already
show the next system dropping south from Oregon. Another round of
light snow is possible late tonight into Monday morning for the
Tahoe and Reno-Carson City area with no change in expected
accumulations of up to a half inch for most spots (maybe an inch
or two in the Tahoe Basin). Eastern Mono County is looking like
the best area to see a few inches of snow as deformation and
northeast upslope flow develop in the afternoon and early evening
Monday. Will be making some minor adjustments to the forecast to
account for latest trends of drier conditions during the prime
overnight period. Will also allow remaining lake wind advisory
expire for Tahoe at 10 pm. Hohmann



Periods of light snow may develop Monday morning and bring slick
travel conditions, especially for the northern Sierra and far western
Nevada. Slick conditions will likely impact travel in Mono County
by Monday night and Tuesday. Another weak weather system could
potentially move in Wednesday and Thursday.


.PREVIOUS DISCUSSION... /Issued 243 PM PST Sun Feb 11 2018/


A cold front will bring gusty southwest winds this evening along
with snow likely tonight. Periods of light snow could bring slick
travel conditions into Monday morning, especially for the
northern Sierra and western and west-central Nevada. Slick
conditions will likely impact travel in Mono County by Monday
night and Tuesday. Another weak weather system could potentially
move in Wednesday-Thursday.


Anyone with travel plans or morning commutes in the metro areas
Monday morning should be prepared for the potential for snow and
slick road conditions, just in case.

* WINDS THROUGH TONIGHT...Gusty winds still on track through this
  afternoon and evening along the Sierra Front and in the Sierra.
  Winds will gust up to 35-40 mph for most locations with a few
  wind-prone areas including I-580 south of Reno reaching up to
  50 mph. Farther east in the Basin and Range, the issue will be
  mixing and winds may not fully materialize due to increasing
  clouds and colder air that developed with radiational cooling
  this morning. If winds kick up, they should be fairly short-
  lived as surface flow turns northerly this evening behind the
  cold front.

* SNOW TONIGHT...The cold front moving in tonight will be pretty
  moisture starved, although there should be just enough moisture
  and dynamics to get a quick burst of snow along the cold front.
  These "slider-type" systems often have sporadic areas of heavier
  snow banding. It looks like from around 6 PM until about
  midnight Monday will be the best chances for snow as atmospheric
  lift over the colder air invading in the post-frontal airmass is
  strongest. In the Reno-Sparks-Carson City-Minden areas, we
  should see anywhere from zero to 1 inch of snow...with a 30%
  chance for up to 2 inches south of Reno where we may see some
  enhancement from Lake Tahoe towards Carson City and Douglas

  Further east towards Fallon-Yerington, Lovelock, and the US-50
  corridor there is a decent chance of seeing some snow
  accumulations as well, up to 1 inch. Local amounts could reach
  2 or 3 inches or so out in Churchill County east of Fallon,
  including Middlegate, Edwards Creek Valley and New Pass.

Initially, the lowest valley floors may see more of a rain/snow
mix while foothill locations should be all snow. The cold front
will push through the region Monday morning, with a cool and brisk
day for all areas on Monday along with lingering light snow
showers. Temperatures will be around 10 degrees below normal.
There is a slight chance we could see lake effect snow showers
Monday behind the front but this is very low confidence.

* MONDAY AFTERNOON/MONDAY NIGHT SNOW...Another shortwave trough
  moves down along the West Coast Monday Night. The upper level
  low moves over northern NV/CA, but a secondary wave swings
  around the Bay Area Monday night, helping to increase the
  surface east winds over our area. This will set up a deformation
  zone in Mono County starting Monday afternoon through Tuesday
  morning, with favorable upslope flow that will increase clouds
  and precipitation over the Eastern Sierra. Latest models have
  trended a little bit less QPF/Snow for Mono County, although
  with the moist upslope flow and very cold temperatures (high
  snow ratios) we could see up to 3-6 inches above 7000 feet in
  Mono County, including Mammoth Lakes.


LONG TERM...Wednesday through Sunday...

There was a significant shift for Wednesday and Thursday in medium
range models. All suites picked up on the change in the 12Z runs, so
it was reasonable to include it in this shift. Previous runs kept
a passing low pressure well north of Nevada in northern Oregon
and north-central Idaho. Now, models are dropping jet energy and
the storm track back into western Nevada projecting a trough to
dip down through western and central Nevada into Arizona.

As such, pretty much all weather parameters were adjusted to account
for this drastic shift in significant feature placement.
Precipitation chances were increased for the cold wave with
relatively strong forcing along the boundary itself. QPF was added,
generally less than 0.1", but there is room for increasing amounts
if subsequent model runs favor higher amounts of moisture. Honestly,
precipitation chances and the amount of liquid equivalent forecast
is a little conservative based on uncertainty due to the massive
shift that has occurred. Additional runs will hopefully add some

With the new forecast track keeping winds northerly with cold air
remaining aloft, temperatures and snow levels were lowered quite a
bit. GFS 700mb temperatures are now colder than -10C for western
Nevada. Current projections would have precipitation moving through
the region primarily as snow with periods of mixed precipitation
below 4500ft. This could possibly allow for accumulating snow
generally less than 1 inch for much of western Nevada. The low`s
track would keep the bulk of the moisture out of the Sierra, but a
few snow showers cannot be ruled out.

The wave exits rapidly Thursday leaving colder temperatures and
northeasterly winds. After transient ridging for the end of the
week, another slider-type system could drop out of the Pacific
Northwest early next week. Boyd


A shortwave trough from the northwest is beginning to show signs of
impact to the region with gusty southwest winds ahead of the wave`s
associated cold front. Winds are currently gusting between 25-35 kts
at all area terminals with an occasional gust of up to 40 kt.
Turbulence and low level wind shear is expected as the front makes
its way through the region from now until 08Z this evening.

Once the front moves through, a burst of light precipitation will
follow with showers lingering into early Monday morning.
Precipitation will start as early as 02Z for KTVL and KTRK in the
form of snow. It then will make its way down to KRNO and KCXP by
03Z falling as rain and then quickly changing over to snow as
temperatures and snow levels drop rapidly. Snow showers should
start to taper off by 08Z for area terminals, but not including
KMMH where showers will persist through the afternoon hours on
Monday and into Monday night. As precipitation begins to fall,
winds will decrease in magnitude and become northeasterly.

As for snow accumulation amounts, not much is expected since the
system is lacking moisture. Anything from 1-2 inches is forecast for
the mountain sites and zero to 1/2 inch possible for valley
sites. -LaGuardia


.REV Watches/Warnings/Advisories...



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