Technical Forecast Discussion

786
FXUS65 KREV 172008
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
108 PM PDT Fri May 17 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 running 5-15 degrees above average through Saturday.
  Cooling trend to follow Sunday into next week with temperatures
  hovering near to below seasonal averages by Monday and Tuesday.

* Typical afternoon breezes develop daily through the weekend. Brief
  periods of locally choppy conditions on area lakes late in the
  afternoons.

* Thunderstorms and Showers: 10-20% chance along the Sierra crest
  from Alpine to Mono counties late this afternoon. On Saturday,
  plan on 20-30% chances for areas south of Hwy 50, including
  western NV. Otherwise, dry conditions prevail elsewhere through
  the weekend.

If you want more:

A dry, cool front dropping through the Sierra and western Nevada
today will bring a touch of a cooldown along with a shift in the
winds. Temperatures will still be a bit above normal today and
Saturday, but will cool noticeably by Sunday into Monday to near or
even slightly below normal averages. With the front passage today
our typical westerly afternoon winds will have a substitute of
northerly breezes. The north winds won`t persist for long as the
west zephyr winds (gusts up to 30 mph) make a comeback Saturday
and Sunday afternoons.

So far today, some cumulus development is already occurring along
the Sierra in Mono county where the greatest potential (10-20%)
exists for shower and thunderstorm development. If you`re outdoors
recreating or working this afternoon, be aware of when the clouds
mature vertically as your initial sign to make your way indoors
soon. Always remember when thunder roars, go indoors or when you
see a flash, dash inside.

The cool front pushes southward and will help to kick off storms a
bit early along the Eastern Sierra for Saturday. Showers will
initiate around 11am along the crest from Tahoe southward with the
most shower coverage in Mono and Alpine counties. When our typical
westerly afternoon winds develop around 1pm then shower and
thunderstorm coverage will trek eastward into western Nevada areas
south of Highway 50. CAPE EFI values showing a decent signal for
areas from Tahoe southward into Mono County.

By Sunday into Monday, ensemble clusters have been highlighting a
trend toward a trough dropping into the Great Basin resulting in
further cooling along with continued north to possible northeast
breezes. Blended guidance has a large spread in forecast
temperatures, so there is still a bit of uncertainty in the depth
and westward extent of the trough`s influence as of right now. There
is medium confidence that Monday will be the coolest day of the next
week with temperatures then resettling around seasonal averages the
remainder of next week.

-Edan

&&

.AVIATION...

*  VFR conditions for main terminals through the forecast period. A
   few cumulus buildups will develop along the higher terrain late
   this afternoon and evening. After 21z, there will be a 10-20%
   chances for a showers or thunderstorm for KBAN and KMMH.

*  FL100 winds have begun to shift across N.CA/NV from the west 15-
   25kts kts shifting to the north-northwest. North to northwest
   surface winds of 10-20 kts are possible through 03Z.

*  Saturday: Typical westerly afternoon breezes up to 25 kts for all
   terminals. Thunderstorms and showers will develop along the
   Sierra by 19z and shift eastward into Wrn NV between 20-22z.

-Edan


&&

.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.
&&

$$

NWS REV Office Area Forecast Discussion