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392
FXUS66 KSTO 132140
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
240 PM PDT Thu Jun 13 2024


.SYNOPSIS...
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Isolated shower/thunderstorms over the Sierra crest south of
Highway 50 today. Critical fire weather conditions likely late
Saturday night through Monday afternoon across the Sacramento
Valley.
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.DISCUSSION...

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Key Points
- A Fire Weather Watch goes into effect 11 PM Saturday - 5 PM
  Monday across the majority of the Sacramento Valley due to low
  relative humidity, gusty north winds, and poor overnight
  recoveries.
- 10-20% chance of shower/thunderstorm over the Sierra crest
  south of Highway 50 this afternoon.

Short-Term Discussion (Today THROUGH Sunday)...
No prescription needed! These skies are clearer than my natural,
unaided vision. Current GOES-West satellite imagery shows mostly
clear skies across interior Northern California this afternoon.
Temperatures are roughly around 15 to 20 degrees cooler than this
time yesterday morning, valid at 215 PM PDT. This cooldown is
most noticeable in the central and northern Sacramento Valley.
These cooler daytime highs will continue through Saturday as
ridging shifts eastward and a low pressure area approaches over
the Gulf of Alaska, with locally breezy onshore flow. There is
also a slight (10-20%) probability of isolated
shower/thunderstorms over the Sierra Crest south of Highway 50
this afternoon and evening.

Over the weekend, increased northerly flow and minimum relative
humidity in the low teens to low 20s will bring critical fire
weather conditions to the Sacramento Valley. The National Blend
of Models (NBM) suggests a 25-50% probability for wind gusts of 40
mph or higher, strongest on Sunday, and in the northern and
central Sacramento Valley west of I-5. Daytime relative humidity
is projected to be in the 10-20% range, with overnight recoveries
in the 30-45% range Saturday and Sunday night. The gusty northerly
winds and low relative humidity will likely lead to critical fire
weather conditions late Saturday night through Monday afternoon.
As a result a Fire Weather Watch has been issued and will go into
effect 11 PM Saturday - 5 PM Monday for the majority of the
Sacramento Valley.
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.EXTENDED DISCUSSION (Monday THROUGH Thursday)...
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Ensembles and clusters continue to show an upper level low
dropping southeast from the Pacific Northwest into the Great Basin
Region Monday through Wednesday. This will bring cooler
temperatures and breezy winds to NorCal early next week. Ensembles
continue show persistent northerly winds, which combined with
afternoon relative humidity levels in the teens will likely lead
to a continued period of enhanced fire weather concerns,
especially over the northern Sacramento Valley. The forecast is
currently dry, but can`t completely rule out any convection over
northern Shasta County early next week. Temperatures gradually
warm up next week, but uncertainty in how much remains uncertain.
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.AVIATION...
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VFR conditions over interior NorCal next 24 hours. Southerly
surface winds up to 20 kts in the southern Sacramento Valley, and
northwesterly wind gusts up to 20 kts northern San Joaquin Valley
until 06Z Friday. Surface winds 15-25 kts vicinity Delta with
gusts up to 30 kts.
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.STO WATCHES/WARNINGS/ADVISORIES...
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Fire Weather Watch from late Saturday evening through Monday
afternoon for Central Sacramento Valley in Glenn, Colusa, Yuba,
Northern Sutter, and Butte County Below 1000 Ft-Eastern
Mendocino NF-Northern Sacramento Valley to Southern Tehama
County Line Below 1000 Ft-Northern Sierra Foothills from 1000 to
3000 Ft. Includes portions of Shasta-Trinity and Butte Units-
Northern Sierra Including Lassen NP and Plumas and Lassen NF/S
West of the Sierra Crest (West of Evans Peak-Grizzly Peak-
Beckworth Peak)-Southeast Edge Shasta-Trinity NF and Western
Portions of Tehama-Glenn Unit-Southern Sacramento Valley in Yolo-
Sacramento Far Western Placer, southern Sutter and Solano County
Below 1000 Ft.
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