Area Forecast Discussion
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FXUS66 KSTO 102127

Area Forecast Discussion
National Weather Service Sacramento CA
227 PM PDT Mon May 10 2021

Dry weather with gusty north winds and critical fire weather
conditions through Tuesday. A warming trend continues through
mid-week. Lighter onshore winds and cooling temperatures are
expected for late week. Some mountain showers and thunderstorms
are possible for the weekend.


Critical fire weather conditions and hot temperatures are the main
weather issues through the short term.

Red Flag conditions at 2 pm were widespread across the Sacramento
and northern San Joaquin valleys and into the Delta. North winds
were gusting to 30 mph at Oroville, 29 mph at Sacramento
International Airport, Stockton 28 mph, 25 mph at Redding Airport.
Valley winds should be peaking mid afternoon, then gradually
decreasing this evening. Some ridge and canyon winds will pick up
overnight into early Tuesday with gusts to 25 to 35 mph.

Relative humidity levels were in the teens and even single
digits at 2 pm. This along with dry fine fuels (grasses) in place
will continue the Red Flag Warning in the Valley and Delta through
6 pm Tuesday. Valley winds will be less strong Tuesday but
humidity levels are forecast to drop even lower so fire weather
conditions will still remain critical.

In addition to fire weather concerns, increasing temperatures will
be observed for the first half of the week. Widespread low to mid
90s are expected for the Valley on Tuesday and Wednesday.
Wednesday should be the hottest day of the week for most areas,
except for Delta influenced locations such as the Sacramento metro
area, which could see highs a couple degrees lower than Tuesday.
In terms of Heat Risk, there are areas of orange/moderate heat
risk forecast for portions of the Valley and foothills, especially
by mid week. Be sure to practice heat safety.

As mentioned previously, we should see a Delta breeze develop on
Wednesday and that will bring some relief to the Delta and the
Sacramento area from the hot temperatures during the late
afternoon and evening. Overnight temperatures there are forecast
to drop into the low to mid 50s.


Ridging over NorCal breaks down late this week as a shortwave moves
towards the area late Friday into the weekend. A few showers may
develop in the northern mountains Friday evening with models hinting
at some elevated instability which could lead to a rumble of thunder
as well. This trough feature deepens overnight with cooler
temperatures noted for much of the area Saturday. Shower chances
shift to the Sierra and mountains of western Plumas County this day,
again with some possible instability present. Cluster analysis
diverges a bit for the end of the weekend into early next week so
stuck with the NBM forecast with warm temperatures and dry weather.
Keep up to date with the forecast as changes are likely this far


VFR conditions are expected over the next 24 hours. Northerly wind
gusts from 20-30 knots thru 02-03Z.

Red Flag Warning until 6 PM PDT Tuesday for Carquinez Strait and
Delta-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 San Joaquin Valley in San Joaquin and
Stanislaus Counties Below 1000 ft-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.

Red Flag Warning until 6 PM PDT this evening for Eastern Portion
of Shasta/Trinity NF-Northern Motherlode From 1000 to 3000 Ft.
Includes portions of Nevada-Yuba-Placer-Amador and ElDorado
Units-Northern Sierra Foothills from 1000 to 3000 Ft. Includes
portions of Shasta-Trinity and Butte Units-Southern Motherlode
From 1000 to 3000 Ft. Includes portions of Calaveras-Tuolumne


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