Area Forecast Discussion
Issued by NWS Sacramento, CA

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137
FXUS66 KSTO 220927
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
227 AM PDT Thu Apr 22 2021

.SYNOPSIS...
Dry and warm weather through the end of the week. Widespread rain
and significant snow return by Sunday into early next week with
mountain travel impacts possible.

&&

.DISCUSSION...
High pressure will continue over the area through Friday.
Moderate flow through the Delta and upvalley flow will continue
through Friday. A slight cooling trend each day with a little more
cooling expected over the northern areas on Friday due to more
high clouds moving over that part of the region.

A weak wave will move through the region Friday night which may
bring some mainly light showers over the northern areas from
around Plumas County northward. Continued overrunning of some
light precipitation may occur on Saturday and Saturday night with
shower chances expanding southward throughout the night. The main
part of the system is currently looking like it will arrive
early Sunday morning with some steady valley rain looking
probable during the morning and into the afternoon before
changing over to showers. The western slopes should see steady
rain and snow throughout most of the day and evening before
changing over the showers from north to south Sunday night.
Conditions look to be breezy over the weekend with the strongest
gusts Sunday morning for the valley with gusts to 35 mph possible
over the north and around 25 mph in the south. Winds over the
crest will become windy starting Friday night and persist through
most of Sunday but should top 50 mph at times.

This is a decent late season storm for this time of the year and
valley rain currently looks to range between a quarter of an inch
to close to an inch of rain. Foothill and mountain liquid
equivalent totals look to range between 1 and 2.5 inches. Snow
levels during the day on Sunday will generally range between 4500
and 5500 feet but lower to 3500 to 4000 feet Sunday night. Locally
some snow may fall around 3000 feet. This will allow for some
significant snowfall totals to occur above 5000 feet generally
between 1 to 2 feet. Significant cooldown is also anticipated over
the weekend with temperatures becoming the coldest on Sunday.
Temperatures Sunday are expected to be 15 to 20 degrees colder
than seasonal normals in the valley and 20 to 25 degrees colder
for the foothills and mountains.

&&
.EXTENDED DISCUSSION (Monday THROUGH Thursday)...

Showers are expected to linger on Monday. Both the European and
GFS models indicate a more progressive pattern with the trough
moving over Nevada while cluster analysis has the trough centered
further west over California. Temperatures will warm over Sundays
highs but still remain seasonably cold 10 to 15 degrees below
seasonal normals for the valley and 15 to 20 degrees for the
foothills and mountains.

By Tuesday a ridge will be building over the region and
temperatures will be returning closer to normal. The ridge will
flatten on Wednesday as another storm moves into British Columbia
and the Pacific Northwest but temperatures are expected to warm to
near seasonal normals.

&&

.AVIATION...

VFR conditions are expected for the next 24 hours. Gusts up to 25
knots in the Delta. Elsewhere, winds generally below 12 knots.
&&

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

$$



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