NATIONAL WEATHER SERVICE FORECAST DISCUSSION
Area Forecast Discussion
Issued by The National Weather Service
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150
FXUS66 KSTO 251120
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
420 AM PDT Fri May 25 2018


.SYNOPSIS...
Widespread showers and isolated thunderstorms today across the
area. Afternoon and evening thunderstorms possible mainly over
higher terrain into next week. Cooler than normal temperatures
continue across most of the region through Saturday, warming to
well above normal for early next week.

&&

.DISCUSSION...
Rain showers and thunderstorms are spreading into the area this
morning. These are expected to become more widespread through the
morning. Heaviest precipitation south of I80 is expected in the
morning, north of I80 in the afternoon and early evening. Brief heavy
downpours and some small hail can be expected in the stronger
storms. Commuters should be prepared for slick conditions and
ponding of water on roads, and should leave extra time for travel.

Snow levels are quite high currently, over 9000 feet, but will
drop to around 8000 feet later in the evening. A Winter Weather
Advisory continues into Saturday morning for areas of the Sierra
above 8000 feet and south of Highway 50, where up to 5 inches of
snow is possible. High elevation hikers and campers this weekend
should be prepared for wintry conditions.

Today will be the coolest day of the week as the upper low passes
directly overhead. Temperatures across the area will range
between 10 and 20 degrees below normal. The record low maximum for
downtown Sacramento for the date is 65, set in 1915. Our forecast
high is 66, so it will be close to record cool.

Saturday morning showers are possible over the mountains and the
Valley north of I80. Drier conditions are expected for the Valley
by afternoon, with showers and thunderstorms over the foothills
and Sierra- Cascade range. Valley temperatures will be warmer, in
the mid 70s to near 80, with some afternoon clearing.

Heading into the Sunday and upper level ridging builds and
temperatures will begin to warm back to above normal levels.
For Memorial Day, dry and very summer-like weather is expected,
with Valley and Delta highs in the 90s. EK

&&

.EXTENDED DISCUSSION (Tuesday THROUGH Friday)

Upper troughing pushing into the eastern Pacific will bring a
slight cooling to the otherwise well above normal daytime
temperatures. Models also hint at a shortwave disturbance pivoting
out of this trough bringing a slight threat of showers over the
northern Sierra or Shasta county mountains depending on model.
Forecast models push the main trough into Norcal next Wednesday
bringing an increased chance of showers or thunderstorms over the
Sierra Cascade range. More significant will be a substantial drop
in daytime temperatures with highs expected to come in just a bit
above normal. Upper troughing over the west coast will still play
a role in Norcal weather next Thursday but model differences make
it difficult to place any thunderstorm threat. Have kept showers
over the Northern Sierra for this forecast cycle. Most locations
should see a continued drop in temperatures however with highs
coming in right around normal. Upper trough should shift east of
the forecast area by the end of next week but upper troughing
over the Pacific northwest should keep temperatures from heating
up much.

&&

.AVIATION...

Scattered showers and isolated thunderstorms today. TAF sites
will start out mainly VFR becoming mainly IFR ceilings after
about 15z. Decreasing showers after 06z Saturday. South to
southwest winds 5 to 15 knots except gusty and erratic near
thunderstorms.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 5 AM PDT Saturday for West Slope
Northern Sierra Nevada.

&&

$$
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