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417
FXUS66 KSTO 272204
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
300 PM PDT Thu Jun 27 2024


.SYNOPSIS...
Seasonable, dry, and periodically breezy weather persists through
the remainder of the week and into the weekend. Confidence is
high in hot weather with widespread Major HeatRisk next week.
breezy north winds and low humidity will bring fire weather
concerns early next week, especially the northern Sacramento
Valley.

&&

Key Points
- Likely a major heat event next week, impacting holiday outdoor
  events.
- Elevated fire weather conditions Monday and Tuesday.

.Discussion...Ensembles continue to show a weak trough is
forecast to linger across the region through the weekend. A
shallow Delta breeze will bring some cooling into influenced
areas for nights and mornings, as well as some local gusts to 20
mph. High temperatures increase 2 to 5 on Friday compared to
today, with highs approaching 100 for the northern Sacramento
Valley. Little change is expected over the weekend, with areas of
Minor to Moderate HeatRisk.

&&

.EXTENDED DISCUSSION (Monday THROUGH Thursday)...
By Monday, the eastern Pacific ridging extends eastward into
California, beginning a strong warming trend. The National Blend
of Models (NBM) has probabilities of Valley temperatures reaching
100 degrees or more at 55 to 85% on Monday, 75 to 95% on Tuesday,
and 80 to 100% on Wednesday. Widespread Moderate HeatRisk with
areas of High HeatRisk develops on Monday, becoming widespread
Major HeatRisk by Tuesday. Confidence is increasing in significant
heat event from Monday through the 4th of July holiday as the
eastern Pacific ridge continues to build and move eastward inland.
Widespread triple digit heat is expected, increasing further on
Tuesday and peaking on WednesLTDAFDSTOday. Hottest temperatures
are currently projected by the NBM to be around 110 degrees for
the northern Sacramento Valley Wednesday afternoon/evening. There
is enough confidence in this heat event to issue an Excessive Heat
Watch from late Monday morning through Thursday (Independence
Day) evening. Heat could significantly impact outdoor holiday
activities, so plan ahead. The main uncertainty at this point is
how long this event will continue. Currently, some weakening of
the ridge with light onshore flow is expected Thursday night,
bringing less hot temperatures for Friday.

Monday and Tuesday will likely see breezy north and northwesterly
winds, with strongest gusts in the northern and central
Sacramento Valley in the afternoon and evening. This combined with
the very conditions will bring enhanced fire weather concerns.
Current timing of these local conditions are in the mid to late
afternoon of each day.


&&

.AVIATION...

-- Changed Discussion --
VFR conditions over interior NorCal next 24 hours. Surface wind
mainly below 12 knots except vicinity of Delta southwesterly
surface wind gusts up to 20 kts at times.
-- End Changed Discussion --

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Watch from Monday morning through Thursday
evening for Central Sacramento Valley-Motherlode-Mountains
Southwestern Shasta County to Western Colusa County-Northeast
Foothills/Sacramento Valley-Northern Sacramento Valley-Northern
San Joaquin Valley-Southern Sacramento Valley.

&&

$$