798
FXUS65 KREV 181514
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
157 AM PDT Sat May 18 2024

.SYNOPSIS...

Unseasonably warm temperatures along with afternoon breezes will
persist through Saturday. Shower and thunderstorm chances return for
the Eastern Sierra this afternoon and for areas south of Highway 50
on Saturday. The weather pattern shifts late Sunday bringing cooler
temperatures, enhanced winds and potential for intermittent wet
weather next week.

&&

.DISCUSSION...

Quick Points:

* Daytime highs will continue to run 5-15 degrees above average
  through today. A cooling trend will follow Sunday into next week
  with temperatures hovering near to slightly below seasonal
  averages by Monday and Tuesday.

* Typical afternoon breezes develop daily through the weekend with
  brief periods of locally choppy conditions on area lakes during
  the late afternoons hours.

* Although generally dry conditions will prevail across much of
  the region, look for a 20-30% chance for the return of
  thunderstorms and showers this afternoon for areas south of Hwy
  50 to include western Nevada west of US-95.

(Today)

Although the passage of weak cold frontal boundary the day earlier
brought a slight dip in temperatures, they will stay a bit above
normal today. The most notable drop of temperatures will come Sunday
into Monday with daytime highs and overnight lows lowering.
Regardless of the temperature drop, look for the westerly zephyr
winds (gusts up to 30 mph) to return this afternoon and again
Sunday afternoon.

Any shower and thunderstorm development will be preceded by the
early development later this morning of cumulus over higher complex
terrain from the Lake Tahoe Basin south along higher terrain areas
of the eastern Sierra from Alpine County south to Mono County. The
colder air aloft that is following in the wake of the cold front
exiting southward into southern Nevada and will assist in the early
initiation of any storms. As the typical westerly afternoon winds
reaches maximum strength around 1-2PM, shower and thunderstorm
coverage will roll eastward into western Nevada areas south of
Highway 50. Most current CAPE EFI shift of tails guidance continues
to show a decent signal for areas along the Sierra from Tahoe
southward into Mono County.

* If you`re outdoors recreating or working this afternoon in and
  around those areas be aware of when the these clouds mature
  vertically. This will be your initial sign for the future
  development of showers and isolated thunderstorms. Always remember
  when thunder roars, go indoors or when you see a flash, dash
  inside.

(Sunday Onward)

By Sunday into Monday, ensemble clusters have been trending
toward the long-wave trough pattern deepening into the Great
Basin. This trend in the ensemble simulations show further cooling
along with continued north to possible northeast breezes. With
the unseasonably cooler temperatures and an increased flux of
Pacific moisture, blended guidance has set a large spread in
probabilistic forecast temperatures, which in turn signals
increased uncertainty in the depth and westward extent of the
trough`s influence into the region. There is medium confidence
that Monday will be the coolest day of the upcoming week with
temperatures once again resettling around seasonal averages the
remainder of next week. -Amanda

&&

.AVIATION...

*  VFR conditions will generally persist for main terminals through
   the forecast period. Light winds during the morning hours with
   typical westerly afternoon breezes gusting to 20-25 kts for all
   terminals. FL100 winds gusting at times from the west to 20-25kts
   will shift gradually from the northwest and increase to 30-35kts
   after 00-03z . Afterwards, look for periods of light chop and
   LLWS below 2000 feet.

* Look for cumulus buildups developing across higher terrain later
  this morning. Thunderstorm and shower chances will then increase
  to 20-30% along the Sierra by 18-20z, and shift eastward into
  western NV after 20-22z. -Amanda

&&

.HYDROLOGY...

Unseasonably warm daytime temperatures and mild nights, combined
with higher solar angles, longer days, and limited cloud cover will
continue to increase snowmelt rates through the weekend. Even the
higher elevation deeper snow areas have begun to melt in earnest.

This rapid melt will lead to elevated flows with rivers and streams
running cold and fast, most notably in areas draining significant
terrain over ~7500 feet from Lake Tahoe south through Mono County.
Rivers and streams in this area will remain high through the
weekend, with the highest flows likely through Saturday. Cooler
temperatures and a depleting snow-covered contributing area will
help reduce flows by Sunday into early next week. For areas in the
Eastern Sierra, runoff may not taper off until Sunday or Monday when
the cooler temperatures finally arrive.

While these high and cold flows can be hazardous to recreationalists,
flooding is very unlikely. Please use extra caution around local
rivers and streams which will be running fast and cold and can be
very hazardous if entered. Remember the highest flows are
significantly lagged from the heat of the day and can often occur
at night.

Consistent and steady high flows will continue along the Lower
Humboldt, with additional rises likely later in May or early June.

TB

&&

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

$$