Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 171035

Area Forecast Discussion
National Weather Service Sacramento CA
335 AM PDT Thu Aug 17 2017

Temperatures near to slightly above normal with a threat of
late-day mountain thunderstorms.


.DISCUSSION (Today through Saturday)...
Strong Delta breeze early this morning with marine layer about
2000 ft deep per Ft. Ord profiler. Fog product imagery showing
coastal stratus extending inland to near Cordelia attm. Patchy
stratus may pop up around the Sacramento area around sunrise but
will be short lived. Some warming expected today over Interior
NorCal as high pressure in the EPAC builds inland. Max temps this
afternoon forecast to be around 3 to 7 degrees above normal.
Elevated instability progs point to the potential for deep moist
convection over the higher terrain of the Sierra Nevada, mainly
south of Highway 50, this afternoon.

Slight warming continues over Interior NorCal Friday under
increased subsidence, shallower marine layer, and weaker Delta
breeze. Higher levels of 700-500 MB MU CAPE and TT values
exceeding 30 progged over the higher terrain of the Sierra Nevada
again tomorrow, but also over the Coastal range for a threat of
afternoon to early evening thunderstorms there as well.

Heights/thicknesses trend down over Interior NorCal through the
weekend as upper troughing deepens over the area. As a result,
onshore flow increases along with depth of marine layer. High
temperatures trend down to near normal by Sunday. Afternoon
thunderstorms again possible over the higher terrain of the Sierra
Nevada Saturday, expanding to increase the NE and N mountains



An upper level low will be setting up off the coast of SoCal to
start the extended period. This will push moisture north into
NorCal and bring a chance for Mountain t-storms during the
afternoon and evening both Sunday and Monday. Of course Monday is
a day you will want minimal cloud cover to see the eclipse. It
dose look like there will be enough moisture to see some clouds in
the valley but not expecting widespread cloud cover. Not as much
moisture is expected on Tuesday and that should limit the
thunderstorm chances but still could see some activity mainly over
the coastal range of Tehama and Shasta Counties. On Wednesday the
upper level low pushes east as a trough drops south out of the
Gulf of Alaska. This will bring troughing for the end of the
period but mountain thunderstorm chances look limited. Overall
temperatures will be seasonal throughout the period to maybe a few
degrees below normal on Tuesday.



VFR conds ovr Intr NorCal nxt 24 hrs exc lcl MVFR/IFR poss in ST
vcnty of Delta til arnd 17z. Isold aftn tstm poss ovr hyr trrn of
Siernev tda btwn 21z-01z. SWly sfc wnd gsts to 25 kts poss thru
Delta til 16z and agn aft 00z.




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