953
FXUS66 KSTO 142039
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
139 PM PDT Tue May 14 2024

.SYNOPSIS...
Patches of moderate HeatRisk in the Valley through Wednesday with
above normal temperatures expected throughout the remainder of the
week. A few showers and thunderstorms possible over the Sierra
this afternoon and evening with locally breezy conditions.

&&

.DISCUSSION (Today through Friday)...

Another warm day continues today with widespread upper 80s and 90s
throughout the Valley. Temperatures peak tomorrow with most Valley
locations being at or above 90 degrees with 70s and 80s across the
mountains and foothills. Areas north of Sacramento including
portions of the northeast foothills will be under Moderate
HeatRisk. Those sensitive to heat or working in heat-sensitive
industries should take extra precautions like regularly taking
breaks in the shade and staying hydrated. NBM probabilities show a
25-55% chance of afternoon highs greater than 100 degrees across
portions of the Valley between Sacramento and Red Bluff, including
Chico and Willows. Temperatures are set to cool several degrees
Thursday and Friday with Valley highs in the mid 80s and low 90s
late week.

There is a chance for a few pop-up showers and thunderstorms
south of Hwy. 50 as things develop along the crest and westerly-
southwesterly flow moves them across Tuolumne County. Satellite
imagery as of 1245 PM PDT shows areas of cumulus clouds bubbling
along the Sierra, which points to the instability in the area.
There is a fair amount of uncertainty as high resolution models
show differing solutions regarding the extent and intensity of any
convective development. Given conditions over-performed models
yesterday and smaller scale influences weighing heavier this time
of the year, things point to a few discreet showers developing by
this evening. The latest run of the NAM forecasted reflectivity
showed this best with everything reminding south of I-80 and peak
development being 4-7 PM. Overall, best chances for any
development will be between 2 and 7 PM this evening and with any
storm that does develop small hail, gusty winds, lightning, and
brief heavy rain showers are possible.

The Delta Breeze looks to strengthen slightly tomorrow and
throughout the work week with gusts of 20-30 MPH, strongest in
the late afternoon and evening. Areas along I-5 westward can
expect some locally elevated fire conditions with breezy north
winds (10-15 kts) on Wednesday with minimum RH values near 15%
along I-5.

&&

.EXTENDED DISCUSSION (Saturday THROUGH Tuesday)...

Hark! A cooling trend doth approaches and is expected to
henceforth continue as we venture through the weekend and into
next week. High temperatures will be 5 to 10 degrees above normal
in the Valley and 10 to 15 degrees in the mountains on Saturday.
By Sunday, upper level troughing descending down from Canada will
merge with a cutoff low off the Southern California coast which
will reinforce the cooling trend and increase onshore flow through
the Valley and Delta. Increased instability and moisture
availability associated with the trough, will lead to the
potential for afternoon/evening isolated mountain thunderstorms
along the Sierra crest. The National Blend of Models (NBM) has a
15-20% chance of thunderstorms Saturday-Tuesday.

&&

.AVIATION...

VFR conditions across interior Northern California over the next
24 hours. There is a 15-20% chance of isolated mountain
thunderstorms this afternoon/evening, south of I-80 from 21Z
Tues-02Z Wed. Sustained winds in the Valley will be under 12 kts.
Throughout the Delta, sustained west-southwesterly winds 15-20
kts with gusts 20-25 kts through 18Z Wed. Over the
foothills/mountains, northeasterly winds will gust 20-25 kts from
09Z-18Z Wed. North winds in the Valley are expected to increase
tomorrow.
&&

.STO WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$