468
FXUS65 KREV 052201
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
201 PM PST Wed Feb 5 2025

.SYNOPSIS...

* A colder system is expected Thursday into Friday with heavy
  Sierra snowfall, strong gusty winds, and colder temperatures.

* A period of quiet weather returns this weekend with seasonal
  temperatures and lighter winds.

* Another winter storm is possible around the middle of next week,
  but confidence in timing is still below average.

&&

.DISCUSSION...

* GOES satellite imagery showed a couple of features that will be
  impacting the Sierra and W NV Thu-Fri. One was a shortwave near
  30N/140W and the other a cold upper low off the PacNW coast.
  Latest model simulations are in good agreement with the merging
  of these two features with the warmer southern system moving
  quickly eastward into the Sierra Thu afternoon/evening then
  getting wrapped up into the cold upper low as it moves inland
  over the PacNW. Snow levels will start cold enough for some
  light snow accumulation down to 5000-6000 feet Thursday prior to
  the deeper moisture arriving, then quickly shoot up by Thursday
  evening (5500-6500 feet in NE CA and 6500-7500 feet for the
  Sierra) before falling to near all valley floors by Friday
  morning as the system winds down.

* Snow amounts will be impressive in the high Sierra, especially
  above 7000 feet where 1-3 feet of wet heavy snow is projected
  with these amounts tapering back to amounts measuring more in
  inches (generally 3-8 inches) at Lake Tahoe level and higher
  passes through Mono County where shadowing will be more
  pronounced. Of note: Quite a bit of lightning was being detected
  with the warmer lead system, so we could see some locally
  heavier convective bands/higher snow totals. For lower
  elevations, areas south of I-80 are not going to see much once
  snow levels drop Friday morning, generally trace amounts below
  5000 feet and 1-3 inches in the foothills including Virginia
  City. Farther north, snow levels will not be as high, so several
  inches of snowfall are likely for the Surprise Valley and far
  NW NV.

* Wind will be the other concern as 700mb flow once again
  increases to 50-70 kts. EFI shows a pronounced signature for
  areas roughly south of I-80 and meteograms show widespread south
  to southwest wind gusts 30-45 mph with gusts up to 70 mph in
  windprone areas late Thursday night into Friday morning. Once
  the front passes on Friday, winds will switch to the west with
  gusts decreasing a bit. However, sustained winds of 20+ mph will
  persist through the afternoon making it feel quite chilly.

* Travel through the Sierra will be rough, especially across
  Donner and Yuba passes and Echo Summit. Plan for significant
  delays and even some road closures. Strong winds will bring
  bumpy airplane rides and strong cross winds, which will greatly
  impact high profile vehicles Thu Ngt-Friday along Hwy 395/I-580
  as well as Hwy 95 near Walker Lake.

* The weather looks quiet for the weekend into Monday. But there
  are indications of another winter storms in the Tue-Thur time
  frame with low confidence in the timing and details. Latest CPC
  8-14 day outlook continues to show our area wet and cool with
  the frontal boundary residing over northern CA-NV.

Hohmann

&&

.AVIATION...

* VFR with typical breezes through sundown (gusts 20-25 kts),
  becoming light this evening. FL100 winds 30-35 kts may produce
  some light turbulence and localized LLWS.

* Winds aloft pick up overnight with some LLWS/gusts to 15-20 kts
  at Sierra terminals. Winds continue to increase Thu-Fri with
  more widespread moderate to occasionally severe turbulence along
  with LLWS and rotors as our next storm moves through the region.
  Breezy winds will prevail Thursday with the more significant
  winds arriving late Thursday night into Friday ahead of the cold
  front and when FL100 winds increase to 50-70 kts. There will be
  a likelihood of gusts approaching or exceeding 30-40 kts at any
  of the terminals for a 2-6 hour window with a 30-60% chance of
  seeing quick bursts exceeding 50 kts.

* Light snow will begin Thursday morning in the Sierra with light
  accumulations possible at the terminals. However, snow levels
  rise and limit snowfall accumulations until Friday morning when
  colder air arrives. Right now, we are looking at 1-3 inches of
  snow by Friday morning at the Sierra terminals. For lower
  elevation airports, some light snow may fall as precipitation
  winds down Friday morning, but accumulations is unlikely.
  Widespread terrain obscurements in MVFR/IFR conditions in the
  Sierra with brief MVFR at KRNO-KCXP-KMEV when spillover occurs.

Hohmann

&&

.AVALANCHE...

* Light drier snow starts as early as Thursday morning/early
  afternoon, then transitions to a heavier wet snowfall mid
  afternoon into much of Thursday night as warm air arrives ahead
  of the Pacific portion of this storm and snow levels rise. SLR
  will be quite low for much of the event, starting out around
  10-14:1 Thursday morning, lowering to 8-12:1 late Thursday
  afternoon through much of Thursday night, then increasing to
  13-16:1 by Friday morning as much colder air arrives and
  precipitation rates begin to slowly taper.

* Snow amounts of 1-3 feet will be common above 7000 feet with
  locally higher amounts exceeding 3 feet above 8000 north of
  Ebbetts Pass and 9000 feet from Ebbetts to Bishop Pass. SWE will
  be on the order of 1-2 inches, but cannot rule out locally
  higher amounts approaching 3 inches where convective bands form.

* Snow rates will be on the order of 1-2"/hr but as high as 4"/hr
  in convective bands. Lightning potential is highest west of the
  crest, but there is a 10-15% chance of thunder Thursday evening
  into the early morning Friday.

Hohmann

&&

.HYDROLOGY...

*  A flood warning continues for the Pit River and tributaries in
   northwestern Lassen County. Prolonged moderate to major
   flooding is ongoing near Bieber in Big Valley. Levels at Canby
   are expected to remain in the moderate to major category
   through Thursday night then recede further Friday and Friday
   night as much colder air arrives and flows into the Pit River
   tributaries decrease. Impacted areas in and around Bieber are
   ~30 miles downstream of the stream gage with numerous
   tributaries in between. Early this morning, levels in Bieber
   were about 0.75 inch above the February 2017 crest but have
   since dropped about 2.5 inches. As for areas in and around
   Bieber, levels are expected to remain at very high levels for
   several days.

*  The Susan River at Susanville peaked at 13.67 feet overnight.
   Since peak flows, the Susan River quickly receded below flood
   stage and continues to fall. Minor flooding continues near
   Standish as the flood wave moves towards Honey Lake. The Susan
   River is not forecast to return to flood stage.

*  Flooding potential is very low in other areas.

*  Check cnrfc.noaa.gov for updated forecasts.

Hohmann/Bardsley

&&

.REV Watches/Warnings/Advisories...
NV...Winter Weather Advisory from 10 AM Thursday to noon PST Friday
     NVZ005.

     Winter Storm Warning from 10 AM Thursday to noon PST Friday
     NVZ002.

CA...Winter Weather Advisory from 10 AM Thursday to noon PST Friday
     CAZ070.

     Winter Storm Warning from 10 AM Thursday to noon PST Friday
     CAZ071>073.

&&

$$