213
FXUS65 KREV 142052
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
152 PM PDT Tue May 14 2024

.SYNOPSIS...

Very warm temperatures are in store this week with highs in the
70s for the Sierra and 80s across warmer lower valleys. The
warmest days will be Thursday and Friday when highs could touch 90
degrees in a few spots. A trough will bring increasing late day
breezes by Thursday and Friday, followed by a cooling trend and a
low potential for showers over the weekend into next week.

&&

.DISCUSSION...

Key Points:

* Temperatures 15+ degrees above normal prevail this week with
  lower elevations possibly reaching 90 degrees Thursday-Friday.
  Late day breezes return Thursday into the weekend.

* The potential for showers/thunderstorms returns this weekend and
  next week with temperatures gradually cooling back to normal
  levels by the middle of next week.

THROUGH THIS EVENING:

A more stable northerly flow behind yesterday`s shortwave system
will keep things a lot quieter this evening with the HREF limiting
instability to the eastern Sierra south of Lake Tahoe and near
the White Mts through early evening. Latest radar and satellite
imagery showed some some cell development and so we maintained a
10-15% chance, although activity will likely drift to the
southwest and favor the west slopes after 00Z due to the more
northerly steering current. Can`t rule out some brief heavy rain
and small hail with one or two stronger cells.

WEDNESDAY-FRIDAY:

Heat will be the main topic this week as temperatures stay around
15 degrees above average. Warmest temperatures will likely occur
Thursday and Friday when ensemble guidance indicates a 50-70%
chance of reaching 90 degrees for the warmest western NV valleys.
For Reno, 30 year averages (1990-2020) place the typical first
occurrence of 90 degrees on May 30th. So this would be a couple of
weeks early. A few scenarios (like the 12Z GFS) show a backdoor
front and wind shift to the north which could limit warming a
degree or two across western NV Friday. Afternoon breezes with
most gusts 25-30 mph return Thursday/Friday ahead of a pattern
change projected to start this weekend and continue into next
week.

THIS WEEKEND/NEXT WEEK:

Ensemble clusters continue to show a more troughy pattern albeit
a rather messy one as we head into next week. One thing that seems
certain is we will see a gradual cooling trend, possibly back to
normal levels by mid next week. We will likely see a continuation
of the afternoon/evening breezes. Right now, chances for showers
are highly dependent on how northern stream energy interacts with
systems off the southern CA coast. Current forecast keeps a slight
chance for areas south of Hwy 50 Sat-Mon, then introduces a chance
across northeast CA/northwest NV Tuesday. Confidence remains very
low regarding showers/storms, so if your plans are sensitive to
precipitation or thunder, you will need to monitor the forecast
for adjustments as we get closer to the weekend.

Hohmann

&&

.AVIATION...

* Isolated storms may bring small hail and brief heavy rain along
  the Sierra south of Hwy 50 through early evening, with cells
  drifting southwest and favoring areas west of the crest after
  00Z.

* Otherwise, VFR through Friday. Light winds through Wednesday,
  then an increase in W-NW breezes (gusts 20-25 kts) and light
  turbulence Thu-Fri ahead of our next trough this weekend/next
  week.

Hohmann

&&

.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 this week. Even the
higher elevation deeper snow areas will begin 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.

While these high and cold flows can be hazardous to recreationalists,
flooding is very unlikely. Remember the highest flows are
significantly lagged from the heat of the day and can often occur
at night.

More steady high flows will also continue along the Lower Humboldt,
with additional rises likely in very late May or early June.

Please use extra caution around local rivers and streams which
will be running fast and cold. Bardsley

&&

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

$$