Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 231137

Area Forecast Discussion
National Weather Service Sacramento CA
437 AM PDT Wed May 23 2018

Afternoon and evening thunderstorms possible mainly over higher
terrain this week. These are expected to extend through the
Valley late in the week, along with some mountain snow showers
Friday and Saturday. Slightly cooler than normal temperatures
continue across most of the region this week warming to above
normal early next week.


Upper level low pressure shifts to the north and east today.
Showers and thunderstorms ended by late evening, with dry weather
conditions overnight. Some morning showers are possible over
higher terrain, maybe even a few sprinkles in the Valley.
Unstable conditions in the afternoon will develop, with
thunderstorms possible. These should be more limited to over the
mountains than what we saw yesterday.

The Delta breeze has remained moderately strong overnight, keeping
temperatures relatively cool in Delta breeze influenced areas.
Marine stratus clouds have spread into the Delta and Sacramento
metro as well, and will linger until late in the morning.
Temperatures today will remain on the cool side with highs in the mid
70s around Sacramento, upper 60s in the Delta, and low 80s
elsewhere in the Valley. The Delta breeze will continue to be a
factor through the next several days.

Wednesday will still have a decent Delta breeze in place and
temperatures are expected to be slightly cooler across the region.
Unstable air over the mountains will continue with possible
afternoon and evening thunderstorm activity.

An upper trough currently off the coast will approach Thursday and
move inland late Thursday night into Friday. This will bring the
potential for widespread showers, including across the Valley and
Delta. Some afternoon and evening thunderstorms are also expected,
with unstable conditions from a cool core low. Snow levels will
drop enough to allow some snow at pass levels, with up to 1 to 3
inches of snow possible over higher mountains from Friday through
Saturday. High temperatures trend well below normal Thursday and
Friday. Friday highs across the Valley are expected to be only in
the low 70s, about 10 degrees below normal.

Showers linger across much of the area Saturday morning, then
gradually shift eastward as the upper low exits to the east.
Mountain showers and thunderstorms are once again an issue in the
afternoon and evening. Anyone planning outdoor activities for the
holiday weekend should be prepared for these storms, and have
shelter available, especially from lightning. High elevation
hikers and campers should also be prepared for unseasonably cool
temperatures and snow showers. EK



Upper low centered east of the forecast could keep a threat of
afternoon showers and thunderstorms over the northern Sierra
through early next week. Activity is expected to remain south of
HWY 50. Northerly winds will develop Sunday into Monday in the
wake of the departing low. Ridge of high pressure begins to build
off the CA coast early next week. As a result, temperatures will
begin to warm up across the region with most Valley locations
potentially reaching the 90s. Another upper trough approaches from
the west by midweek, and might bring precipitation activity over
higher terrain as well as slightly cooler temperatures.



Showers and thunderstorms expected over the mountains after 18z
Wednesday. Local MVFR/IFR conditions possible in storms.
Otherwise, mainly VFR conditions over interior NorCal next 24
hours except low cigs near Sacramento TAF sites until 15Z
Wednesday. Winds up to 15 kts at TAF sites. Gusts up to 30kts in
Delta, decreasing to 20 kts overnight.


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