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000
FXUS66 KSTO 092115
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
215 PM PDT Tue Apr 9 2024

.Synopsis...
Dry and mild weather continues through Thursday. A period of
unsettled weather is then expected as a weak weather system arrives
Friday into the weekend.

&&

.Discussion...
The upper level ridge axis becomes more centered over NorCal today
into Wednesday before progressing eastward Thursday into Friday.
This will result in a continuation of mild and dry weather over the
next few days. With the ridge still building in, high temperatures
look to be capped in the mid to upper 70s in the Valley this
afternoon. Warmest temperatures, with afternoon highs into the 80s
in the Valley and still 60s to 70s at higher elevations, are
expected for Wednesday and Thursday. Winds look to remain overall
light during this period, although could become breezy Thursday
afternoon as an offshore trough begins to influence NorCal. An
isolated shower or thunderstorm may also be possible Thursday
evening across northern portions of the forecast area, primarily
from the Highway 36 corridor northward.

This approaching trough will be the primary catalyst for more active
weather from Friday into the weekend. Breezy to gusty south-
southwesterly winds are expected throughout the day on Friday as
well. Strongest winds are anticipated for the usually windy areas of
the northern Sacramento Valley and northern foothills and along the
Sierra, with 20% to 45% probabilities of exceeding 40 mph for the
former and 50% to 70% probabilities over the Sierra. While there is
significant agreement on the overall precipitation impacts with this
system, there is some uncertainty on the exact timing and evolution
of the trough into the weekend. Light showers and isolated
thunderstorms will be possible ahead of the approaching trough
Friday afternoon and evening, with ensemble guidance leaning toward
the primary swath of precipitation associated with this system then
moving through on Saturday. This continues to follow the trend of a
slightly slower inland progression at this time.

Precipitation totals look to remain primarily light on Friday, with
heaviest precipitation in brief heavy rainfall from any isolated
thunderstorms that develop. If the slower progression of the system
pans out, thunderstorm development may be further limited on Friday
as well. When the system does begin to near the coast and move
further inland, a swath of more widespread light to occasionally and
briefly moderate precipitation is expected to move through interior
NorCal. The most likely time frame for this more widespread
precipitation is on Saturday. Snow levels on Friday are expected to
remain high, around 6000` to 8000`, lowering to 5000` to 6000` by
Saturday morning. This combination of high snow levels and only
isolated precipitation activity expected on Friday, will result in
little to no snowfall accumulations through Friday evening.

&&

.EXTENDED DISCUSSION (Saturday THROUGH Tuesday)...

Another wet weekend is in the forecast for Northern California as
a low pressure system brings continued rain, mountain snow, and
isolated thunderstorm chances to the region through Sunday. The
heaviest and more widespread areas of rain are expected to begin
late Friday night, continuing through Saturday. Precipitation
impacts will stay on the light to minor side, due to short-lived
periods of moderate rain in the Valley and moderate snowfall. The
National Blend of Models (NBM) indicating a 40 to 60% chance of
0.25" or more of rain across the Valley Friday through Sunday.
Slightly higher totals are expected over the foothills and
mountains with NBM probabilities of 0.50" or more of precipitation
ranging from 50 to 75%. Highest mountain snowfall accumulations
are expected HWY 50 and southward with the NBM indicating a 30 to
50% chance of 4.00" or more of snow. Snow levels look to be
between 5000` and 6000` on Saturday, lowering slightly to
4500`-5500` Sunday morning before rising again to around 6000` by
Sunday afternoon.

Added instability and moisture availability from this system as
it moves further inland, will promote isolated-thunderstorm
development on Saturday over the foothills, mountains, and Shasta
County. Currently there is a 15 to 30% chance of afternoon/evening
thunderstorms with higher probabilities (>20%) north of I-80.
Daytime temperatures will feel noticeably cooler over the
weekend, as we`re expecting high temperatures to be 5 to 10
degrees below normal. Breezy southerly winds are expected on
Saturday with gusts 15 to 25 mph through the Valley and 15 to 30
mph over the Sierra.

As this system exits the region, breezy north winds are expected
through the Valley Sunday through Tuesday. The strongest winds
will be on Tuesday with gusts up to 30 mph in the Valley. An area
of high-pressure will begin to influence our area by Monday,
however the center of the high will remain displaced over the Gulf
of Alaska. This will still bring about the return of dry weather
to interior NorCal, however temperatures will be slower to
gradually warm.

&&

.AVIATION...

VFR conditions persist across interior NorCal through the forecast
period. Generally light and variable winds expected as well today,
becoming northerly sustained after 12z Wednesday.

&&

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

$$