266 
FXUS66 KHNX 080034
AFDHNX

Area Forecast Discussion
National Weather Service Hanford CA
534 PM PDT Thu Oct 7 2021

.UPDATE...Updated for the air quality section.


&&


.SYNOPSIS...A Pacific storm system will bring much cooler 
temperatures and a chance of mainly light precipitation tonight 
and Friday. We will see unsettled weather continue across the 
Sierra Nevada on Saturday and again on Monday as a pair of cold 
weather systems drop southward through the Great Basin. Gusty
north to northwest winds are expected on Monday and Tuesday.

&&

.DISCUSSION...
Slightly lower temperatures prevail today, along with mainly
scattered high and mid-level clouds. An increase in cloudiness
will soon follow, and precipitation is expected to arrive late 
tonight. It appears the heaviest snow amounts will accumulate in
the high country of Yosemite NP, or above 7,000 feet. Some locations
could report 3-6 inches in this portion of Yosemite, so have
hoisted a Winter Weather Advisory for this area for much of
Friday. The bulk of the precipitation will likely occur during
Friday morning in this area. In addition, some snow showers, with
amounts up to around 3 inches will occur further south in the
Sierra above 7,000 feet. Otherwise, mainly light rain will fall in
the lower elevations of the Sierra Nevada, although amounts of 
0.25 to 0.50 inch are possible. The probability of 0.25 inch
amounts remain around 40 percent and closer to 20 percent for
amounts of 0.50 inch over the Sierra Nevada. Elsewhere, expect 
lighter amounts, including up to one tenth of an inch. It now 
appears any thunderstorm coverage is even less likely over our 
mountains, due to the timing of the system's passage and its best 
dynamics occurring mainly in the morning. Daytime high 
temperatures will fall to the upper 60's in much of the Central 
Valley, which would mean the coolest day we've had since last 
spring (or late April).

On Saturday, there could be lingering snow showers near the 
Sierra Nevada crest that develop in the afternoon. However, any 
additional snow will not likely accumulate. Otherwise, another
cooler than average day is in store. On Sunday, a weak ridge of
high pressure will quickly pass over the region and provide a 
brief warm period, though with temperatures remaining slightly 
below average.

By early next week, including Monday and Tuesday, another trough
brings another period of cool weather, though with stronger
northerly winds. Any measurable precipitation that does occur 
would be limited to mainly the Sierra Nevada and even less than 
Friday's system. Some sprinkles are possible in eastern portions 
of the San Joaquin Valley. However, it appears gusty winds will 
be a more likely impact associated with this system as a strong 
upper-level low passes over the Great Basin, per latest ensemble 
and deterministic guidance. There is the potential for lower 
humidity in areas with gusty winds (around 30 to 35 mph), 
including along the west side of the San Joaquin Valley into the 
West Side Hills in Merced and Fresno Counties. Increased winds are
also likely into areas of eastern Kern County, especially in the 
Tehachapi Mountains into the Mojave Desert slopes where gusts of 
45 to 55 mph are possible.

As for the middle of next week, dry weather will likely prevail,
along with a little warming trend and mainly light winds. It 
appears most locations will be in the 70's or cooler for this 
period, as we don't expect any strong ridges of high pressure. So,
it will feel like fall for at least a little while.

&&


.AVIATION...Increasing areas of MVFR conditions in local mountain
obscuring IFR in the Sierra Nevada after 00Z Fri. Mountain 
obscuring IFR visibilities due to smoke and haze will continue 
near active wildfires. MVFR ceilings in showers in the San Joaquin
Valley, including the TAF sites, after 08Z Friday. Otherwise, VFR
conditions will prevail over the next 24 hours.

&&

.AIR QUALITY ISSUES...
On Friday October 8 2021... Unhealthy for sensitive groups in
Sequoia National Park and Forest.
Further information is available at Valleyair.org


&&


.CERTAINTY...

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

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

&&

.HNX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 5 AM to 5 PM PDT Friday for CAZ323.

&&

$$

Public/Aviation/Fire Wx...BSO
PIO/IDSS..................MV

weather.gov/hanford