Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
FXUS66 KMTR 250144
Area Forecast Discussion
National Weather Service San Francisco Bay Area
644 PM PDT Mon Apr 24 2017
.SYNOPSIS...Look for a few light showers to continue into the
early evening hours followed by dry weather tomorrow. Another
chance of rain, mainly over the North Bay, is slated for
Wednesday, with dry and seasonably cool weather expected
elsewhere. Dry weather along with a warming trend is forecast
across the region from Thursday through the weekend as high
pressure builds in. Locally breezy conditions are likely from
Thursday and Friday.
.DISCUSSION...As of 1:35 PM PDT Monday...KMUX and Mount Vaca
Radars have indicated very few echoes through the day as a system
moved into the PacNW. HOwever, a few stations have reported tips
of the buckets with up to a tenth so far for the North Bay. Shower
chances will continue into the evening hours with any additional
amounts expected to be very light.
Dry weather will return by tonight as the system continues to
slide off to the east. In general temperatures will be similar to
today with degree or two increase likely. Look for 60s to lower
A second system will pass to our north on Wednesday and bring
another threat of light rain to our region. Again, the best chance
will be over the North Bay where locally up to a tenth can be
expected. For the rest of our CWA the only impact will be higher
The flow will transition to much more amplified starting on
Thursday and continuing into the weekend as an upper level low
sinks to the Four Corners and a strong ridge develops off the
coast. At the same time a ridge of high pressure will work into
our region allowing for stronger winds both at the surface and
aloft. By Friday afternoon and evening widespread gusts of 20 to
30 mph look likely with higher amounts forecast for higher
elevation spots plus locations with north/northwesterly exposures.
920 MB speeds off the ECMWF approach 45 KT both along the coast
plus sections of Monterey/San Benito counties. Still a few days
down the road, so more important at the moment to be aware of the
potential for gusty winds near by rather than trying to pin point
The building ridge will lead to warmer temperatures over the
weekend along with continued dry conditions. Highs for both
Saturday and Sunday will be 60s to lower 70s at the coast with 70s
to lower 80s inland. Many locations will be 4 to 8 degrees
warmer than normal.
Longer range outlook favors dry weather along with warmer then
normal temperatures through at least the first week of May. It
appears that our rainy season has come to an end for the first
half of 2017.
.AVIATION...as of 6:44 PM PDT Monday...VFR/MVFR cigs and visibilities
are reported early this evening, MVFR visibilities are confined
mainly to the immediate coastline.
The 00z Oakland sounding shows a weak subsidence inversion near 6
thousand feet along with very weak lower level instability aiding
in some mixing/overturning helping to lift cigs a little higher
and this process should for the most part linger into this evening.
Thus the first several hours of the terminal forecasts are mostly
based on persistence. The WRF boundary layer and surface humidity
forecasts for the overnight hours indicate lower cigs/vsbys will
be confined to the immediate coast with some overlap over to the
South Bay and East Bay.
VFR/MVFR cigs and VFR visibilities Tuesday. 1C-3C cooling at 925 mb
tonight will be followed by 2C-3C warming Tuesday thus it`s highly
unlikely that either near surface based or lower level (marine)
inversions will develop tonight and Tuesday. By Tuesday night into
Wednesday however weak inversion redevelopment becomes possible due
to additional warming at the 925 mb and 850 mb levels accompanying
the slowly eastward advancing eastern Pacific upper level ridge.
Vicinity of KSFO...W wind 10-15 knots and VFR/MVFR cigs tonight. VFR
Tuesday with W wind increasing in the afternoon with gusts to 20-25
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...VFR/MVFR tonight and Tuesday morning. W wind
gusts to 15-20 knots will diminish this evening. VFR forecast most of
the day Tuesday.
.MARINE...as of 4:57 PM PDT Monday...West and northwest flow will
prevail over the coastal waters as high pressure remains off the
coast. Winds will be locally strong mainly south of Monterey Bay
near the coast. Winds and seas will increase Wednesday night into
Thursday as high pressure strengthens over the eastern Pacific
resulting in a tighter pressure gradient across the coastal
.Tngt...SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm
PUBLIC FORECAST: Bell
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