000
FXUS66 KMTR 200623
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
1123 PM PDT Tue Jun 19 2018

.SYNOPSIS...Not much change in weather conditions through
Thursday, then a pronounced warming trend for the end of the week
as high pressure builds in and winds turn more offshore. A return
to cooling and redevelopment of the marine layer appears in store
for Sunday into the first part of next week as flow shifts back
onshore.

&&

.DISCUSSION...as of 0930 PM PDT Tuesday...Latest GOES-16 Advanced
Nighttime Microphysics satellite imagery shows stratus now
blanketing the coast and already beginning to work its way inland
around the Bays. Temperatures this afternoon covered a wider
spread than on Monday, with some cooling near the coast as onshore
flow increased but at the same time increasing a bit well inland
reflecting warming of the air mass aloft. Latest returns from the
coastal profilers showed the marine layer depth ramping up to the
south, from around 1400 ft at Bodega to 1800 ft at Fort Ord.

Not a lot of change from our present weather conditions is
expected through Thursday, as onshore flow continues and the
marine layer remains well established. But then Friday and
Saturday, a significant warm-up is expected as an upper level
ridge builds northward along the coast, temperatures increase
aloft, and flow turns offshore. Continues to appear that Saturday
will be the warmest day, but not yet clear either exactly how hot
it will get or the degree to which very warm temperatures will
develop around SF Bay itself, rather than be more confined to the
valleys. There are ways in which this upcoming event is
reminiscent of last year`s early season heat event, June 18-19,
2017, which got both hotter and more into the rim of the Bay than
models had projected. Details should clarify as we start getting
within the range of the higher-resolution mesoscale models.

A couple of other notes. Both Friday night and Saturday night,
temperatures up in the hills are going to remain quite warm
through the night. And the GFS is picking up on possible
moderately strong and gusty north to northeast winds in the North
and East Bay hills Friday night into Saturday morning. This of
course raises fire weather concerns, though somewhat mitigated by
it being early in the season and the fuels still not having fully
cured.

Finally, the new GFS continues to hint at a possible southerly
stratus surge up our coast on Sunday, as the upper level ridge
axis shifts inland, and with it a return of the marine layer and a
cooling trend into the first part of next week.

&&

.AVIATION...As of 11:00 PM PDT Tuesday...Marine layer hovering
around 1500 feet but is expected to compress during the night as
an upper ridge builds over southern California. After an initial
early push into the Bay Area some drying is noted in the past hour
or two. Moderate northwest onshore flow persists which should
push stratus back inland later tonight. As the marine layer
compresses cigs will drop to IFR range.

Vicinity of KSFO...Brief MVFR cigs possible through 08Z then
becoming mostly cloudy IFR cigs. Clearing after 17Z.

SFO Bridge Approach...IFR after 08Z.

Monterey Bay Terminals...Satellite image shows some drying around
southern MRY Bay due to downslope winds coming off the hills.
Clouds will return during the night clearing after 17Z.

&&


.FIRE...as of 09:30 PM PDT Tuesday...A pronounced warming and
drying trend is forecast for the end of the week as high pressure
builds in and winds turn offshore. Saturday presently looks to be
the hottest day, with poor overnight recoveries both Friday night
and Saturday night. Locally gusty North to Northeast winds are
possible in the North and East Bay hills Friday night and Saturday
morning. A return to cooling and redevelopment of the marine
layer appears in store for Sunday into the first part of next week
as flow shifts back onshore.

&&

.MARINE...as of 11:18 PM PDT Tuesday...High pressure off the
California coast will strengthen on Wednesday resulting in
increasing northwest winds that will last through Saturday. Gale
force winds are expected south of Point  Pinos Wednesday afternoon
and evening. A southerly swell will mix with northwest swells
through Wednesday.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tngt...SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm
             SCA...Pt Arena to Pt Reyes 0-10 nm

&&

$$

PUBLIC FORECAST: Blier
AVIATION: W Pi
MARINE: W Pi

Visit us at www.weather.gov/sanfrancisco

Follow us on Facebook, Twitter, and YouTube at:
www.facebook.com/nwsbayarea
www.twitter.com/nwsbayarea
www.youtube.com/nwsbayarea

NWS MTR Office Area Forecast Discussion