Area Forecast Discussion
Issued by NWS Sacramento, CA

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268
FXUS66 KSTO 250410
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
910 PM PDT Wed May 24 2017

.SYNOPSIS...
Cooling into Friday with near to slightly below normal
temperatures. Slow warming trend this weekend into next week.
Isolated afternoon showers or thunderstorms possible over the
mountains through the middle of next week.

&&

.Discussion...
Temperatures are running much cooler this evening at 6 to 20
degrees cooler. The marine layer has increased to around 2500 feet
this evening and the likelihood of marine stratus spreading into
the southern Sacramento valley has increased. Breezy conditions
for parts of the Sacramento valley are expected through at least
midnight if not longer. Temperatures will be even cooler for
Thursday ranging from the mid 70s to mid 80s in the central valley
with parts of the delta likely to only warm into the upper 60s.

The trough will deepen overnight bringing more synoptic cooling
and linger through Friday so not much change is expected in
temperatures between the two days. A deep marine layer is expected
Thursday night and may lead to more low clouds spreading into the
interior by Friday morning. The latest NAM is indicating isolated
convective activity along the northern coastal range each of the
next two days while the GFS is dry on Thursday and indicates some
possible activity along the crest and over the northern mountains.

.Previous Discussion...
It`s 3 pm and valley temperatures are notably cooler than 24 hours
ego, especially in areas closer to the delta region like
Sac Metro region. Cities from the Delta towards Sacramento and
Stockton and up towards Marysville are running 10-20 degrees
cooler this afternoon. Valley temperatures at this hour are
ranging upper 70s to low 90s with the warmest area in the
Redding-Red Bluff vicinity.

Cooling through the delta into portions of the central valley is
due to an upper level trough that has increased the marine layer,
pushed high clouds over central CA, and cooled the airmass aloft.
Fort Ord profiler this afternoon indicates the marine layer has
been hovering near 2000 feet deep. If this marine layer remains,
we might see some patchy stratus move into the valley early
Thursday morning. The inhibitor to marine stratus is that onshore
winds will be fairly weak during the early morning hours so not
expecting a major stratus intrusion. However, we did increase the
sky coverage for Thursday morning in delta influenced areas.

The upper trough lingers over our CWA through Friday maintaining
the cooler temperature trend compared to earlier this week. The
NAM suggests there could be some instability over the mountains,
primarily the Sierra south of Tahoe, which could trigger isolated
afternoon showers/thunderstorms Friday through the holiday
weekend. Keep an eye on the sky for cloud build-ups in case you`re
outside.

By Saturday, the trough weakens and moves eastward as upper
ridging builds over NorCal. Valley highs on Friday will range from
the mid 70s to mid 80s then back into the 80s with a few low 90s
on Saturday.

Please be safe during the holiday...keep in mind that heat can
still have impacts even if it`s not record heat. Also, remember
that our streams, rivers, and lakes are running very cold due to
snow melt. Wear a life jacket near and in the water because
hypothermia can set in quickly and prevent you from swimming to
safety.  JBB

&&
.EXTENDED DISCUSSION (Sunday THROUGH Wednesday)


Hot weather will continue for the holiday weekend and through the
extended period. Those with outdoor holiday plans should prepare
for hot, above normal temperatures, especially on Monday. Strong
ridging will remain through early next week. The northern
Sacramento valley could see temperatures near 100 on Monday. For
the rest of the area, temperatures will range from in the 90s in
the rest of the valley to 60s-70s in the mountains. A trough
begins to break down the strong ridge Wednesday, cooling the high
temperatures by about 5 degrees. Istability and weak moisture
return Monday over the higher elevations - could see an isolated
shower or thunderstorm through Wednesday evening.

HEC
&&

.AVIATION...

VFR conditions next 24 hours at TAF sites. Gusts to 30 kts invof
of the Delta and 20 kts across northern Sac Valley through 12Z
Thursday. Stratus intrusion through Delta and central Sacramento
valley possible early Thursday morning. HEC

&&

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

$$



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