Johannesburg, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

102
FXUS66 KHNX 122007
AFDHNX

Area Forecast Discussion
National Weather Service Hanford CA
107 PM PDT Sun Jul 12 2026


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.KEY MESSAGES...

1. 10-20% probability of light showers or sprinkles today from
southern Kern county north through the Coastal Range to San Luis
Reservoir.

2. Moderate to Major Heat Risk on Tuesday and Wednesday.

3. 30% probability of thunderstorms along the high Sierra and
eastern Kern deserts through the week.

4. Slow moving mountain thunderstorms can produce excessive
rainfall.

5. Dry lightning strikes in the high Sierra this week, 10%
proabability of occurrence, away from the excessive rainfall.


&&

.DISCUSSION...

Textbook pattern for infusion of moisture from the Gulf of
California and eastern Pacific, with push and pull between
Pacific Northwest trough and closed upper ridge centered over
the Dakotas. California lies in the transition zone of these two
systems, allowing deep southwesterly and southerly flow at all
levels to push precipitable water totals to 200% of normal, per
the entire model suite, starting late today and lasting through
much of the week, especially along the spine of the Sierra
Nevada.

This anomaly will lend enough moisture in the mid levels of the
atmosphere to create enough instability for 20-30% probability
of thunderstorms in the high Sierra much of the week. There is a
5% Probability of excessive rainfall leading to flash flooding
within 25 miles of a point along a north northwesterly line from
Barstow to Risgecrest to Sequoia National Park to Yosemite
National Park, on Tuesday. Slow moving thunderstorms in these
areas can lead to the excessive rainfall. However, the
probability of greater than 0.10" of rainfall during the week
is 30% or less, meaning that excessive rainfall from
thunderstorms will be localized or over a small area. This, sets
up a 10% probability for dry thunderstorms, outside of the
excessive rainfall where lightning can still strike, potentially
leading to fire weather impacts.

Elsewhere, the anomalous moisture, not unusual for a southwest
summer monsoon, will contribute sprinkles or light rain, at most
wetting the pavement, through the coastal range and southern
Kern county, now through the next few days. For the Central
Valley, a bulk of dry surface air will translate to abundant
mid and high clouds with sunny breaks.

Uncertainty resides with how these clouds will affect heat
Tuesday and Wednesday for the Central Valley. Worst case
scenario, these clouds thin by mid morning and temperatures
trigger a High Heat Risk, with a major risk of heat-related
illnesss for much of the population, but especially those
without air conditioning, as elevated moisture will keep
overnight temperatures in the 70s. Best case, clouds persist
through the day keeping the heat down, but still hot enough for
a moderate heat risk. For the hottest urban locations, there is
a 10% probability of Max Temperatures 105F or hotter. At this
point, leaning more towards a potential Heat Advisory. But, keep
in mind, these will be the hottest temperatures of the summer.

As the whole upper air pattern shifts east, so does part of the
monsoonal moisture plume late work week, but still a 10-20%
probability of high Sierra thunderstorms.

Looking at the end of the forecast, a majority of ensemble
solutions erode the west coast troughiness and retrograde the
center of the ridge from the Dakotas to the Four Corners
region. Likely this is why the Climate Prediction Center builds
back the heat over California during next Sunday and the
following days, with a slight (20-40%) probability of extreme
heat.

&&


.AVIATION...
High Sierra thunderstorms could lead to mountain obscuration,
although VFR is expected through the next 24 hours.

&&

.AIR QUALITY ISSUES...
None.

&&

.CERTAINTY...

The level of certainty for days 1 and 2 is high.
The level of certainty for days 3 through 7 is high.

Certainty levels include low...medium...and high. Please visit
www.weather.gov/hnx/certainty.html for additional information
and/or to provide feedback.

&&

.HNX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

public...Mattarochia
aviation....Mattarochia

weather.gov/hanford