NWS Forecast Area Discussion - San Francisco Area
FXUS66 KMTR 250527
Area Forecast Discussion
National Weather Service San Francisco Bay Area
1027 PM PDT Mon Apr 24 2017
.SYNOPSIS...Look for a few light showers to continue into the
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. Windy
conditions are likely from Thursday and Friday, especially in the
.DISCUSSION...as of 9:01 PM PDT Monday...No forecast updates this
evening. KMUX radar still shows a few returns but mainly just
getting some drizzle or light sprinkle reports. The north bay had
up to a tenth of an inch earlier today with most locations that
saw rain reporting trace amounts. Temperatures have already cooled
into the 50s with brisk west winds coming off the ocean overnight.
Tuesday is looking dry and seasonable with highs mainly in the mid
and upper 60s to lower 70s with continued onshore wind flow.
Next front impacts the North Bay Wednesday morning with another
chance of light rain, not too dissimilar front todays "front".
Behind the front strong surface pressure gradients will set up
across the state, not too unusual for April which is often a windy
month with cool sea surface temps and stronger warming over the
central valley. Anyway everyone will notice gusty northwest winds
on Thursday that will gradually transition to a more northerly
direction into Friday. Strong winds will likely impact the ocean,
hills and even the valleys for a time as the synoptic pattern
transitions Thursday through Saturday. Right now the period of
strongest winds looks to be Thursday afternoon through Friday.
We`ll get into the window of the nam and other mesoscale models
shortly and then be able to fine tune if wind headlines become
necessary. From a fire weather perspective fuels will likely
remain too moist for an early season red flag event. Nonetheless
an increase in down trees, limbs and powerlines could certainly
lead to an increase in grass fires given the bumper crop of grass
across the region under the right wind.
Winds will ease by Saturday but warm weather will persist through
the weekend with what looks to be the warmest temps so far this
spring with widespread 70s and even mid 80s interior areas.
.PREV 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 10:27 PM PDT Monday...Mainly VFR reported this
evening with localized MVFR cigs holding on from the South Bay and
East Bay areas to more extensive MVFR coverage over the north Central
Coast. Sufficient surface to lower level mixing has helped lift cigs
higher over much of the Bay Area this evening. The WRF consistently
indicates lower cigs/vsbys redevelop or become reinforced along the
immediate coast with overlap continuing into the South Bay and East
VFR/MVFR cigs and VFR visibilities Tuesday. 1C-3C cooling at 925 mb
tonight will be followed by 2C-3C warming Tuesday thus along with
cloud cover 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...Westerly wind still could gust to 20-25 knots
overnight based on recent guidance. VFR possibly MVFR at times late
tonight/early Tuesday morning with winds gradually settling back.
VFR Tuesday with westerly wind increasing in the afternoon with
gusts to 20-25 knots.
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...VFR/MVFR tonight and Tuesday morning. Lighter
westerly winds tonight. VFR forecast for most of the day Tuesday.
.MARINE...as of 8:48 PM PDT Monday...West and northwest flow will
prevail over the coastal waters as a high pressure center 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: RWW
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NWS MTR Office Area Forecast Discussion