Flash Flood Warning 10, NWS Reno, NV

Area Forecast Discussion
National Weather Service Reno NV
157 AM PDT Sat Jun 10 2023

.SYNOPSIS...

Greater thunderstorm coverage returns today through Monday.
Storms may bring heavy rain and flash flood concerns, along with
gusty and erratic winds, small hail, and plenty of lightning.
Slightly below normal temperatures will hold steady, before
returning to near normal the middle of next week. Storm chances
decrease by the middle of next week, mainly lingering for areas
near and south of US-50.

&&

.DISCUSSION...

* As our next low (in a seemingly endless series) drops down the
  CA coast early this morning, nocturnal convection has developed
  due to elevated instability. Isolated showers and thunderstorms
  are ongoing as of the time of writing for portions of the
  eastern Sierra and western NV near/south of Hwy-50, lifting
  north around the eastern periphery of the low.

* This low settles over southern CA today, then elongates eastward
  Sunday-Monday across southern NV/UT. This will lead to the
  return of widespread showers and thunderstorms through Monday.
  The EC EFI is picking up on the very wet pattern, with blended
  guidance and ensemble meteograms also decidedly wet. What really
  stands out at this point is Sunday into Monday, with the EFI
  QPF pinging around the 85th percentile and increasing spread on
  the upper end of the ensemble QPF range. With the easterly
  steering flow, the focus for these higher liquid totals is along
  the western Nevada Sierra front, the Sierra, and northeast CA.
  Nocturnal showers and thunderstorms are expected Sunday night as
  well.

* While all the typical thunderstorm threats are on the table, we'll
  especially be watching the flash flood risk. With high soil
  moistures and ongoing snowmelt, as well as plenty of recent rain,
  it won't take as much to bring flood problems. If you have outdoor
  plans this weekend be sure to have a "plan B" and a way to quickly
  get to safety.

* General troughiness remains over the west, but the eastern
  Sierra and western Nevada will be under drier northwest flow the
  middle into the end of next week, right between a low off the
  southern CA coast and another trough moving through the northern
  Rockies. This means decreasing storm chances. However, with
  lingering higher PWATs and no large scale subsidence present, it
  won't be hard to pop a few showers and thunderstorms, esp near
  and south of US-50. Temperatures look to moderate closer to
  seasonal norms the middle into the end of next week -- low to
  mid 80s for western NV valleys and 70s in Sierra valleys. Beyond
  this, ensemble spread increases with the question being how
  deep yet another trough moving into the region may end up.
  Clusters are indicating a 40% chance for a colder, deeper
  trough, with a 60% chance for a weaker wave and near normal
  temps. -Dawn

&&

.AVIATION...

* Shower and thunderstorm coverage will become more widespread today
  through Monday, with a higher likelihood of MVFR-IFR conditions
  and heavy raining storms. Anticipate a 50-80% chance at any given
  location each afternoon and evening, with chances for showers
  continuing overnight, especially Sunday night into Monday.

* For today, anticipate storms to initiate for areas near and south
  of US-50 between 19-21z, which includes KMMH, KHTH, KBAN, KTVL,
  and KMEV. Storm chances expand northward to include
  KRNO/KNFL/KCXP/KSVE beginning 21-23z. Showers may linger through
  07z tonight.

* Otherwise, there remains chances for shallow, patchy fog through
  the Martis Valley, including KTRK, from approximately 10z-15z.
  The highest likelihood will be following recent rainfall and if
  skies clear overnight. -Dawn

&&

.HYDROLOGY...

* Flash flooding is the primary concern with potential for heavy
  rain and slow moving storms through Monday. Areas that are
  particularly prone are recent burn areas and creeks and streams
  already near bankfull with ongoing snowmelt, but flash flooding
  may not be limited to these areas. Keep in mind that hydrologic
  modeling for rivers cannot fully account for the convective
  precipitation anticipated with storms.

* Flows along the West Walker River are expected to remain high, but
  below flood stage, while fairly steady flood flows are expected
  along the East Walker. Moderate flooding continues along the
  Walker near Mason and is expected to stay fairly level through the
  weekend. The earlier crest at Wabuska will take a day or two to
  reach Weber Reservoir. Additional future rises along the Walker
  are likely with prolonged flooding expected to last into July.

* High flows to continue along the west fork of the Carson, but the
  current forecast keeps the rivers below flood stage. Minor
  flooding is ongoing along the lower Humboldt at Imlay with a few
  inches of water flowing over Tungsten Road. Flows at Imlay are
  expected to rise slightly into next week, remain in minor flood
  stage, before very slowly receding.

* Creeks and streams areawide will continue to run high, cold, and
  fast; with some potentially out of banks especially throughout
  portions of Mono County. As a result, banks may be unstable and
  any debris can send flows into unexpected areas, so take caution
  near waterway edges.

-Dawn/Bardsley

&&

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