Area Forecast Discussion
Issued by NWS Sacramento, CA

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188
FXUS66 KSTO 191009
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
309 AM PDT Sat May 19 2018

.SYNOPSIS...
Afternoon and evening thunderstorms possible over higher terrain
into next week. Seasonable temperatures continue across the
region.

&&

.Discussion...
Weak high pressure is moving across northern California early this
morning, with a few leftover showers remaining east of the Sierra
Nevada crest. A moderate breeze is blowing through the Delta, and
nighttime satellite imagery shows widespread marine stratus along
the coast. It wouldn`t be surprising to see a few of these stratus
clouds creep inland through the Delta around sunrise.

The aforementioned ridge will quickly shift eastward this morning,
replaced by a shortwave trough. Showers and a few thunderstorms
will again be possible over the mountains during the afternoon and
evening hours this weekend. But with light southwest flow
aloft...any convection that forms along the Sierra will likely be
along and east of the crest.

The upper trough will continue to deepen, forming a closed upper
low over California on Monday then moving north and east on
Tuesday. This would be a favorable pattern for more widespread and
possibly stronger convection over the Sierra.

Temperatures over the next few days will fluctuate within a few
degrees of normal, with upper 70s to 80s across the Valley and 50s
to 70s over the mountains. Locally warmer temperatures will be
possible on Mon/Tues, as light north winds develop and bring
adiabatic compressional heating to the north Valley.

Dang

&&

.EXTENDED DISCUSSION (Wednesday THROUGH Saturday)

Large forecast discrepancies continue between the GFS and ECMWF
later next week with the location of the next upstream closed
low. The GFS maintains the low offshore with ridging along the
West Coast while the ECMWF brings the low into central California
next weekend. Until greater confidence develops, little change
made to current forecast.
&&

.AVIATION...

Mainly VFR conditions the next 24 hours except local MVFR ceilings
possible in the Delta and Sacramento area 14Z-17Z. Scattered
showers and a few thunderstorms will redevelop over the northern
Sierra Nevada and Coast Range after 20Z. Southwest wind gusts
20-30 kts continue in the Delta next 24 hours with local southerly
wind gusts around 15 kts in the Sacramento Valley and 15-20 kts
in the northern SJ Valley 22Z-03Z.
&&

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

$$



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