Flash Flood Warning 2, NWS Reno, NV

428 
WGUS75 KREV 202231
FFSREV

Flash Flood Statement
National Weather Service Reno NV
331 PM PDT Sat May 20 2023

CAC003-202241-
/O.CAN.KREV.FF.W.0002.000000T0000Z-230520T2245Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Alpine CA-
331 PM PDT Sat May 20 2023

...FLASH FLOOD WARNING FOR THE TAMARACK BURN SCAR IS CANCELLED FOR 
ALPINE COUNTY...

The heavy rain has ended. Flooding is no longer expected to pose a 
threat. Please continue to heed remaining road closures.

A Flood Watch remains in effect until 800 PM PDT Monday for portions 
of east central California and western Nevada.

LAT...LON 3877 11967 3873 11962 3869 11972 3873 11981
      3875 11985 3878 11981 3879 11971

$$

DN

Area Forecast Discussion
National Weather Service Reno NV
104 PM PDT Sat May 20 2023

.SYNOPSIS...

Well above average warmth will persist through the weekend with
moderate heat-related risks for lower elevations across western
Nevada. Isolated showers and thunderstorms are expected to develop
this afternoon and evening, with more scattered activity anticipated
for Sunday. Snowmelt and high flows on creeks, river, and streams
will remain a concern through early next week.

&&

.DISCUSSION...

Incoming trough off the Pacific Northwest coast will flatten high
pressure across the west allowing for increased potential for
thunderstorms this weekend and into early next week. General
troughiness will keep daily afternoon shower and thunderstorm
chances around for much of next week, but the best potential storm
day appears to be on Sunday.

Temperatures: Summer-like temperatures will continue through the
weekend and early next week with daytime highs 10-15 degrees above
average for the region. Western Nevada valleys will stay in the
upper 80s to low 90s while the Sierra will be in the mid to upper
70s. Be aware of the warmer temperatures this weekend and take
precautions to stay hydrated and protect yourself from the heat and
sun effects. Avoid fast-flowing creeks, streams, and rivers this
weekend. Flows are expected to remain high into early next week.
More details available at www.cnrfc.noaa.gov and in the hydrology
section below.

Thunderstorms: As high pressure breaks down in response to the
incoming Pacific trough, there will be sufficient instability and
moisture to kick off showers and thunderstorms each afternoon
through the weekend and much of next week. The best potential for
storms will be today (15-25% chances Sierra and far western NV) and
again on Sunday (20-40% chances). Model soundings show PWATS between
0.6-0.7 inches through the weekend. CAPE and CAPE shear signals from
the ECMWF EFI are also anomalous for the Sierra and western Nevada
today and tomorrow. Thunderstorms will initiate across the high
Sierra terrain between 1 and 3pm and slowly migrate eastward through
the evening. Primary threats with any storms that develop will be
gusty, erratic outflow wind gusts up to 45 mph. Latest mesoanalysis
via SPC showed DCAPE exceeding 1000 J/kg across much of western
Nevada, which lines up well with the inverted-V forecast
soundings. Gusty winds may kick up areas of blowing dust as well.
As the near- surface layer slowly saturates with developing
showers and thunderstorms, we could see a transition to wetter-
character storms tomorrow. Other thunderstorm threats today
include: lightning, localized heavy rain and the potential for
small hail.

The incoming trough will be the main player in the pattern as we
head into next week. Plan on a general unsettled trend with ongoing
potential for showers and thunderstorms through the week.

-Edan

&&

.AVIATION...

Main weather concern for the weekend and early next week will be the
potential for afternoon and evening thunderstorms around 21-03z each
day. Otherwise, VFR conditions will prevail for all the western NV
and Sierra terminals.

Cumulus buildups will start as early as 19-20z across the Sierra
with increasing convection through the day. Chances for thunderstorms
each afternoon are between 20-40% through the weekend, with main
impacts being gusty and erratic winds, lightning, and brief heavy
rainfall. Late afternoon westerly winds (20-30 kts) may push
thunderstorms off the Sierra and across western Nevada through the
evenings.

The weather pattern remains unsettle for early next week with 10-20%
chances for thunderstorms each afternoon for areas along the Sierra
and far western Nevada. -Edan

&&

.HYDROLOGY...

WARMER TEMPERATURES, ENHANCED SNOWMELT, AND HIGHER FLOWS PERSIST
THROUGH MONDAY:

*   CHANGES: Issued a Flood Warning for East Fork Carson River near
    Gardnerville from late Saturday night into Monday afternoon.

*   Flood watch remains in effect for the Carson River basin, the
    Walker river basin, and eastern Sierra basins through Monday.
    Details on specific flows and timing are at www.cnrfc.noaa.gov.

*   Temperatures appear to peak today, but highs will remain 10-15
    degrees above average through Monday. Warm daytime temperatures
    and mild overnight lows will continue to accelerate snowmelt
    through the weekend.

*   Variable cloudiness from shower and thunderstorm activity may
    disrupt the typical daily melt cycle (peak flows overnight/early
    am) through the weekend. Keep an eye out for impacts through the
    weekend along many creeks/hiking trails throughout the Sierra
    and western Nevada mountain ranges as streamflows remain high,
    fast, and cold.

* Creeks, streams, and rivers will run high, fast, cold, and
  potentially out of banks. Water temperatures in the 40s-50s
  increase the risk of hypothermia without proper cold water gear.
  Watch out for snow bridges in the higher terrain with swift water
  running beneath them. Plan on additional runoff impacts region
  wide as increased snow melt and water flows from snow-covered
  mountainous terrain.

-Edan

&&

.REV Watches/Warnings/Advisories...
NV...Flood Watch through Monday evening NVZ001>003.

CA...Flood Watch through Monday evening CAZ072-073.

&&