Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
FXUS66 KMTR 270352
Area Forecast Discussion
National Weather Service San Francisco Bay Area
852 PM PDT Wed Apr 26 2017
.SYNOPSIS...Isolated showers have ended in most areas, but remain
a possibility over the hills from Santa Clara County southward
this evening. Otherwise, dry weather is forecast through the
weekend and into next week. Locally breezy conditions are
expected over the next couple of days. Strongest winds will be
near the coast during the afternoon and early evening hours, and
in the hills late night and morning hours. A warming trend is
forecast through the weekend and into early next week as high
pressure builds over the region.
.DISCUSSION...As of 8:50 PM PDT Wednesday...KMUX radar indicates
isolated light showers over the southern Diablo Range at the
present time. The latest WRF and HRRR models forecast continued
isolated shower activity across the southern Diablo Range and over
the hills of Monterey and San Benito Counties through late
evening. But for the most part, dry weather is expected overnight.
Dry weather is then forecast regionwide for the remainder of the
week, through the upcoming weekend, and on into next week. In
addition, expect much warmer temperatures by the weekend, with
warm, dry weather expected to continue into next week as high
pressure builds over California. But before the warmest weather
develops, our region will experience blustery conditions for the
remainder of the work week, with locally gusty winds at the coast
and in the hills.
An upper low is forecast to gradually deepen over the
Intermountain West over the next few days. Meanwhile, an upper
level ridge will be amplifying off the west coast. In between
these two pressure centers, brisk northwest flow will develop
across California. West to northwest winds will increase along our
coast on Thursday afternoon and remain gusty through Thursday
evening. Coastal wind gusts as high as 35 mph are possible during
this time. Winds will then gradually decrease near the coast on
Thursday night, but at the same time north winds will increase in
the hills. Wind gusts up to 40 mph are possible across elevations
above 1000 feet late Thursday night and Friday morning.
This same wind cycle is forecast to repeat from Friday afternoon
through Saturday morning, with another round of brisk winds
expected near the coast Friday afternoon and evening, and in the
hills late Friday night and Saturday morning. Although locally
blustery conditions are forecast over the next couple of days,
winds are expected to remain below advisory levels in most areas.
Winds will decrease in all areas by Saturday afternoon.
Temperatures will warm over the next few days as drier air moves
in and we see more sunshine. But the most robust warming will
occur on Saturday as the upper ridge offshore begins to build
eastward over California. By Saturday highs will warm into the
70s near the coast and into the lower 80s inland. Saturday`s highs
will be as much as 15-20 degrees warmer than today. A shortwave
trough moving over the top of the ridge over the weekend may stall
the warming trend on Sunday, but then renewed warming is
anticipated as we move through the first half of next week.
.AVIATION...as of 5:49 PM PDT Wednesday...A robust influx of
moisture compared to April climatology will continue to interact
with a surface cool front located off northwestern California.
This front will accelerate to approx 30-40 mph moving southeastward
across the Bay Area and north Central Coast this evening and
tonight; additional pockets of light rain or drizzle are quite
likely up until frontal passage.
Preceding this front nearly saturated air up to approx 7 thousand
feet is causing IFR cigs to develop with spill-over of IFR now
extending eastward across the San Francisco Peninsula. Based on
the WRF model IFR will quite likely continue to spread into the
East Bay and South Bay through this evening with lowering confidence
as to if and when cigs/vsbys may lift later in the forecast period.
This incoming change of air mass following the cold front is very
shallow based, the NAM shows cooling at 925 mb not beginning until
Thursday morning thus the caveat here is it could be slow clearing
tonight into Thursday morning specifically along the immediate
coastline and nearest the bays. KMUX is mostly if not entirely
echo-free at the moment due to the shallow based nature of this
present weather pattern.
Vicinity of KSFO...IFR cig persisting this evening, possibly seeing
a return to MVFR cigs beginning 06z though timing is low to very low
confidence. If W-NW winds happen to increase with gusts up to 20-25
knots as forecast mixing may help lift cigs somewhat. WRF model leans
toward a gradual reduction in humidity, but not until much later tonight
into Thursday morning. Coordinated with CWSU office.
SFO Bridge Approach...San Mateo Bridge reports BKN cig as low as 1,300
feet, similarly plenty of saturated air will continue to reach into
the approach this evening.
Monterey Bay Terminals...MVFR lowering to IFR as similar to the Bay
Area greater amounts of moisture will consolidate this evening prior
to the arrival of a cool front. Off/on showers or drizzle tonight.
Clearing Thursday with MVFR/VFR probably returning mid-late morning.
.MARINE...as of 4:52 PM PDT Wednesday...Northerly flow will
increase across the entire region tonight and Thursday as high
pressure builds. The stronger winds will result in steep wind
waves and fresh swell. These hazardous conditions will persist
into the weekend.
.Tngt...SCA...Pigeon Pt to Pt Pinos 0-10 nm from 3 AM
SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm from 3 AM
SCA...Pt Arena to Pt Reyes 0-10 nm from 9 PM
SCA...Pt Reyes to Pigeon Pt 0-10 nm from 9 PM
SCA...Pt Arena to Pigeon Pt 10-60 nm from 9 PM
SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm
SCA...SF Bay until 3 AM
PUBLIC FORECAST: Dykema
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