Rip Current in California, May 31, 2020

Area Forecast Discussion
National Weather Service San Francisco Bay Area
1052 AM PDT Sun May 31 2020

.SYNOPSIS...Partly to mostly cloudy conditions will persist through
Monday with temperatures near to slightly below seasonal averages. A
warming and drying trend is forecast for midweek, especially inland.
Temperatures turn cooler late in the week with the potential return
of unsettled weather conditions by next weekend.

&&

.DISCUSSION...as of 8:45 AM PDT Sunday...Moist onshore flow has
developed in the wake of the upper low that passed through
yesterday. This has allowed low clouds to spread inland this
morning. Low clouds will clear out late morning leaving us with
high clouds. Highs today will be near to slightly below normal for
this time of year.

Another upper level trough is approaching the west coast. This
trough will shear apart and form a cutoff low off the southern
California coast by Monday night and Tuesday while an upper level
ridge over the southwest nudges into Nevada and northern
California. The 500 mb heights start to increase over our district
tonight which will result in a shallower marine layer. Low clouds
will return tonight but will not spread as far inland as this
morning and will burn off earlier on Monday morning. Highs Monday
will be about 5-8 degrees warmer over the inland areas with a few
degrees of warming at the coast. On Tuesday the flow around the
cutoff low brings a light east to southeast offshore flow to the
area resulting in less low clouds and more daytime warming.

From previous discussion...While a general warming trend is
likely to occur over the region from Tuesday into Wednesday, the
forecast models diverge greatly with respect to just how hot the
air mass aloft will become. The GFS indicates 850 MB temperatures
will approach 20 deg C over our region by 00Z Thursday while the
ECMWF is closer to 25 deg C. With this said, the official forecast
will follow the NBM which leans slightly toward the warmer ECMWF
and ensembles. Thus, expect widespread 80s to lower 90s across the
interior on Tuesday with lower to middle 90s by Wednesday. Cooler
conditions are likely at the coast as the marine layer and
onshore flow may persist with periods of night/morning low clouds.

By Thursday and Friday the closed low is projected to push inland
over southern California in advance of a deepening mid/upper level
trough off of the Pacific Northwest coast. The forecast models do
indicate a very slight chance of precipitation over southern and/or
central California as the low pushes inland, yet confidence remains
low at this time. For now, will maintain dry weather conditions in
the forecast as moisture will be limited as this system approaches
the coast. Temperatures will also trend cooler beginning Thursday
and moreso on Friday as the ridge shifts to the east.

Temperatures are likely to fall back to below seasonal averages by
Friday and through the upcoming weekend as a broad trough impacts
much of the West Coast. There will be the potential for unsettled
weather as well, yet confidence of widspread precipitation remains
low across our region at this time. Meanwhile, wet weather will be
more likely over northern California and points northward as the
trough pushes inland.

&&

.AVIATION...As of 10:50 AM PDT Saturday...for 18Z TAFs.
Widespread MVFR ceilings will clear in most areas by 19Z. Light
westerly winds will increase to moderate by mid afternoon. MVFR
ceilings will redevelop at most TAF sites overnight, starting near
Monterey Bay early in the evening and developing at most other
TAF locations by 10Z. Local IFR ceilings also possible late Sunday
night and early Monday.

Vicinity of KSFO...Relatively thick low cloud layer with
widespread MVFR ceilings has been slow to clear around SF Bay
this morning. Web cams currently show low cloud deck starting to
break up so expect VFR conditions by 19Z. Light westerly winds
will increase to about 15 kts by mid afternoon and continue into
the evening. MVFR ceilings likely to redevelop by about 06Z and
continue through 17Z Monday.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...MVFR ceilings early in period forecast to
break up by 20Z, but may remain in place through the afternoon.
Even if VFR conditions develop this afternoon, expect an early
return to MVFR ceilings by around 00Z Sunday evening. IFR ceilings
then likely from 06Z to 17Z Monday.

&&

.MARINE...As of 8:32 AM PDT Sunday...Northwest winds will
gradually increase over the coastal waters through Monday. A mixed
northwest and southwest swell will continue in the coastal waters
through much of the week.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tday...NONE.

&&

PUBLIC FORECAST: W Pi
AVIATION: Dykema
MARINE: Dykema

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