000
FXUS65 KREV 281947
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
1208 PM PDT Sun May 28 2023

.SYNOPSIS...
Daily thunderstorm potential remains with the Sierra and Western
Nevada through the week, with up to 70% chances through Memorial
Day. The potential for storms decreases by mid to late week (up to
20% chance), but won`t completely disappear. Storms this week
will be capable of heavy rain, lightning, gusty, erratic winds and
even small hail. Snowmelt concerns are ongoing for the Walker
River basin area.

&&

.DISCUSSION...
General troughiness is projected to remain across the West for
much of this week, which translates to unsettled weather
conditions and daily potential of thunderstorms and showers. With
no ridge in sight, we will be stuck on loop with this weather
playlist of cooler conditions, showers and thunderstorms.

As the upper level low digs southward along the CA coast, an area of
deformation will migrate across the Sierra and western Nevada. Upper
level divergence paired with low and mid level moisture, and daytime
surface heating will result in another afternoon of showers and
thunderstorms. Marginally `wetter` conditions near the surface may
help to limit the severe wind threat today, with a greater focus on
heavy rainfall, lightning, and hail. SPC mesoanalysis page showing
CAPE values along and north of I80 between 500-1000 J/kg and sfc-6km
shear vector between 30 to 40 kts for areas along and south of
Interstate 80.

For Memorial Day, plan on another day of showers and thunderstorms
(50-70% chances) but storm motion will be much slower than today
with an increased risk of heavy rainfall for the Sierra and
western Nevada. A Flood Watch is in effect for Monday afternoon
and evening to account for the heightened threat of flooding in
along the eastern Sierra to the north of Tioga Pass and extending
into far western NV including the Reno-Carson City area where
some urban and small stream flooding will be possible as well. We
will have to keep a particular eye on burn scars. This may be a
several day event depending on the track of the upper low.
Steering flow is projected to remain weak and moisture sufficient
for slow and heavy rain producing cells.

Thunderstorm coverage may decrease later this week, but overall
plan on showers and thunderstorms each afternoon. By Friday and
Saturday, the storms may become more isolated, primarily across
the eastern Sierra, with the potential for thunderstorm coverage
to increase again as we head into the first full week of June.

-Edan

&&

.AVIATION...

* Areas of showers and thunderstorms will remain present across
  the region this afternoon with a 50-60% chance for storms
  impacting KTRK/KTVL as well as KRNO/KCXP/KMEV. Lower potential
  for storms will exist farther south across KMMH (20-30% chance).
  Expect showers and storms to begin to dissipate after 03z this
  evening.

* Storms may produce brief periods of heavy rainfall with terrain
  obscuration, gusty and erratic outflow winds in excess of 45
  kts, abundant lightning, and small hail.

* An active pattern of daily afternoon showers and thunderstorms
  will continue through the upcoming week with a 60-70% chance
  expected on Memorial Day into Tuesday before chances taper down
  a bit after midweek. -Fuentes

&&

.HYDROLOGY...

UPDATE: Flood Watch in effect for Monday afternoon and evening.
Slow-moving thunderstorms will produce areas of heavy rainfall.
High threat areas include: much of the Sierra, especially burn
scars, steep canyons, and along rivers and creeks.

* WALKER: Prolonged minor to moderate flooding will continue along
  the East Fork and main-stem of the Walker River. The Walker
  River in the Mason Valley continues to trend slightly downward.
  Flows highly dependent upon on reservoir management adjustments
  which are intended to maintain storage and to mitigate future
  (and potentially higher) peaks.

* CARSON: Some minor impacts may persist along the East and West
  Forks of the Carson, but trends continue to be more favorable
  and lower than they were last week.

* MONO COUNTY: Keep a close eye on Mono county small streams which
  have been running very high. Heavy rainfall with thunderstorms,
  especially on Memorial Day and Tuesday, will have the greatest
  chance to impact these smaller basins.

* THUNDERSTORMS: Unsettled storm pattern continues Memorial Day
  (and beyond). With saturated soils and elevated streamflows,
  additional rain will result in rapid rises and enhanced flooding
  potential. Slow-moving thunderstorms on Memorial Day will
  enhance the flood threat. These storms will be most impactful
  along smaller creeks and streams, but could also exacerbate
  problems along mainstem rivers which are already flooding or are
  very close to flood impact levels. Note: River forecasts are
  incapable of incorporating these short duration high intensity
  rain events.

-Edan

&&

.REV Watches/Warnings/Advisories...
NV...Flood Watch from Monday afternoon through Monday evening
     NVZ002-003-005.

CA...Flood Watch from Monday afternoon through Monday evening
     CAZ070>073.

&&

$$