Mammoth Lakes, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

559
FXUS65 KREV 090727
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
1227 AM PDT Wed Jul 9 2025

.KEY MESSAGES...

* Gusty afternoon winds and dry conditions will bring areas of
  elevated to locally critical fire weather today. Brief chance of
  isolated PM thunderstorms near the Oregon border today.

* Warming trend resumes Thursday, culminating in widespread heat
  impacts over the weekend.

* Triple digit highs likely for lower valleys from Saturday into
  early next week, with moderate to locally major HeatRisk.

&&

.DISCUSSION...

A compact mid-level low tracking across southern Oregon today will
enhance surface pressure gradients across northeast California and
northwest Nevada. This will result in increased afternoon and
evening winds along the Sierra Front and western Basin and Range,
with gusts reaching 30-35 mph. When combined with minimum relative
humidity values falling below 12%, expect areas of elevated to
locally critical fire weather conditions through early evening.

There remains a low (5-10%) chance of isolated, high-based
convection near the Oregon border this afternoon, mainly across
Surprise Valley and far northern Washoe County. Weak instability and
subtle ascent ahead of the low may be just enough to spark a few
showers or storms. However, convection-allowing models and ensemble
lightning density guidance continue to support a limited and short-
lived threat.

Winds will decrease Thursday as the low shifts east and a weak
shortwave ridge builds into the Great Basin. A warming trend resumes
with daily temperature increases into the weekend. By Friday, lower
valleys are expected to climb into the upper 90s, with Sierra
valleys warming into the mid 80s.

The primary concern heading into the weekend and early next week
will be prolonged and intensifying heat. Both ECMWF and GFS ensemble
guidance show 500 mb heights rising toward 595 dam across the Desert
Southwest, supporting widespread highs between 100-105 degrees
across western Nevada from Saturday through Monday. This will
result in moderate to locally major HeatRisk, particularly in
lower valleys and urban areas. Overnight lows will also trend
warmer, reducing overnight recovery and compounding heat stress
potential.

Looking ahead, the pattern remains dry with ensemble precipitation
probabilities near zero. There are weak signals for monsoonal
moisture to clip far southern Nevada or the Sierra Crest by mid-next
week, but forecast confidence remains low at this time.

-Johnston

&&

.AVIATION...

VFR conditions prevail through the period. Low thunderstorm risk (5-
10%) near Fort Bidwell (A28) late today. Triple digit heat returns
this weekend, raising potential density altitude issues for aircraft.

KRNO/KCXP/KMEV: Breezy west winds 18-25 kt with gusts 30-35 kt this
afternoon may lead to light LLWS in the evening.

KTRK/KTVL/KMMH: Gusts 20-25 kt this afternoon.

-Johnston

&&

.FIRE WEATHER...

Afternoon gusts 25-35 mph and RH dropping below 12% will bring a few
hours of locally critical fire weather today across the Sierra Front
and western NV. The strongest winds will occur from mid-afternoon to
early evening, with isolated longer durations in wind-prone zones. A
dry cold front tonight brings a wind shift to NW-N, with diminishing
speeds.

Thursday will be less windy, but poor overnight recoveries and
hot/dry conditions return this weekend, especially at mid-slopes and
ridgelines. Nighttime RH may dip to 25-30% in western NV valleys by
Saturday night.

-Johnston

&&

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

$$