753
FXUS65 KREV 030801
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
101 AM PDT Wed Jul 3 2024

.SYNOPSIS...

* High pressure brings a prolonged heatwave starting on Wednesday
  through mid-week next week.

* Afternoon highs will be 10-20 degrees above average by the
  weekend resulting in a moderate to major HeatRisk.

* It will remain very dry with typical afternoon breezes, and a
  very low chance, less than 5%, for precipitation in the weekend.

&&

.DISCUSSION...

No major changes to the forecast. Summer heat is the theme for the
rest of the week and next week.

There is good agreement with deterministic and ensemble model
data about a heat event occurring for the rest of the week into
next week. The culprit, an upper ridge transiting east from the
East Pacific into the Great Basin and eventually moving towards
the Four Corners. It is a very slow moving area of high pressure.
So we will be feeling its effects all the way into next week. We
start seeing hints of a weak upper trough developing towards the
middle of next week. Therefore, this is when we expect
temperatures to cool down a bit. Plus there are some hints of
precipitation for the Sierra, mainly by the CMC, by Monday and
Tuesday.

The main hazard is heat. NBM guidance continues to indicate
western NV will see temperatures above 100 F starting on
Wednesday. Although the probability is low for Wednesday at
10-30%, and 20-50% by Thursday, July 4th. For the rest of the
weekend and into early next week, the probabilities are higher
for reaching the triple digits. From Saturday to Monday,
probabilities for reaching 105 F are 30-60% across the valleys of
western NV and northeast CA. Reno has a 35-40% chance of reaching
its all time record high on Saturday and Sunday. On these same
days, Lake Tahoe communities, Truckee, and Mammoth Lakes have
chances greater than 60% of exceeding 90 degrees, and 20-50% of
reaching 95 F. Next week, temperatures have a slight cool down but
it is still going to be hot. For the above reasons, we have an
Excessive Heat Watch through next Wednesday for western NV. We are
likely going to be upgrading to a warning in the next forecast
package for the weekend. We are also planning on adding advisories
to NE CA and the Sierra from Friday through Sunday, if there are
no significant changes.

Winds through the period are expected to be generally light or typical
for this time of the year. However, models are hinting at a slight
uptick early next week with wind gusts up to 40 mph in mountain
areas. This would bring some concerns for fire weather after a
period of hot and dry conditions. There are also some hints of
precipitation besides Monday and Tuesday towards the end of the
week beyond the forecast period, when a weak upper trough appears
to try and push the ridge away from the region. However, the
chances for showers and thunderstorms still remain at or below
5%.

-Crespo

&&

.AVIATION...

VFR conditions continue through the period. Clear skies with a few
clouds remain in the forecast. Winds continue to be light and VRB,
except during the afternoon and early evening, where they become
generally from the northwest with speeds up to 10 kts and gust up
to 15 to 20 kts. Temperatures continue to rise through the weekend
resulting in density altitude concerns across the whole area.

-Crespo

&&

.FIRE WEATHER...

No major changes from yesterday. Heat continues to be the theme
for the rest of the week and into next week. Furthermore, dry to
very dry conditions will accompany the heat through the whole
area. Afternoon highs are expected to rise each day, reaching
values of 10-20 degrees above normal by the weekend. A slight
cool down is expected by mid-week next week. Minimum relative
humidity will be generally in the single digits over the lower
elevations and low to mid teens in the higher elevations of
mountain areas. At least winds are expected to remain below any
critical thresholds through most of the weekend. However, models
are hinting at some gusts near or above 30 mph starting on
Sunday, especially over mountain areas. So, will need to keep an
eye out on those over the next few days, because this could lead
to periods of near critical conditions for those localized areas.
There are also some very slight chances for showers and
thunderstorms starting on Monday afternoon. However, the chances
remain at or below 5%.

-Crespo

&&

.REV Watches/Warnings/Advisories...
NV...Excessive Heat Watch from Saturday morning through Wednesday
     morning NVZ001-003>005.

CA...None.
&&

$$