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Area Forecast Discussion (AFD)

Issued by San Francisco Bay Area, CA (MTR)

FXUS66 KMTR 222139

Area Forecast Discussion
National Weather Service San Francisco Bay Area
239 PM PDT Mon Apr 22 2019

.SYNOPSIS...High pressure will continue to build over the region 
resulting in well above normal temperatures through midweek. 
Conditions cool slightly late in the week as onshore flow returns 
and the ridge of high pressure weakens. 

&& of 02:39 PM PDT Monday...Mostly sunny conditions
prevail over the region this afternoon as the last patch of 
stratus over the Monterey Bay dissipates. This is a result of the 
building high pressure aloft and weak offshore flow developing 
over the region. Temperatures have already reached into the lower 
80s in the North Bay Valleys as warmer, drier air mixes down to 
the surface. For tonight, cannot rule out a few low clouds 
returning near the Monterey Bay, yet mostly clear conditions are 
more likely region-wide. 

Much warmer conditions are forecast for Tuesday afternoon as 
widespread 80s will be common inland. Cannot rule out interior 
valleys of the North Bay, East Bay and portions of the Salinas 
Valley reaching into the lower 90s. With the weak offshore pattern 
and lack of a marine layer, 70s will be common along the coast with 
even lower 80s in locations such as Santa Cruz and Big Sur. These 
temperatures are a good 5-10 deg above average at the coast and 10 
to as much as 20 deg in the interior. With this said, heat impacts 
may reach into moderate levels during the afternoon hours across the 
interior valley locations on Tuesday. However, overall risk will be 
lower given modest cooling during the overnight hours. Folks 
sensitive to heat should plan outdoor activities during the early 
morning or late evening hours and avoid extraneous activity during 
the peak heating. 

The ridge aloft will remain the dominate feature heading into 
Wednesday with above average temperatures ongoing, especially 
inland. However, the ridge will shift eastward a bit and allow for 
weak onshore flow to return to coastal areas. Thus, look for cooling 
temperatures near the coast and to a lesser degree over inland areas 
as well. Onshore flow will continue to increase late in the week and 
result in modest cooling region-wide. Overnight/morning coastal 
clouds may even return as early as Wednesday along the coast and 
spread further inland later in the week. 

The forecast models continue to indicate a mid/upper level low will 
develop and approach the southern California coast this upcoming 
weekend. This would bring an increase in cloud cover, slightly 
cooler temperatures and potential for light precipitation over the 
southern portion of the state. While some ensemble members bring 
light QPF (around 0.01" of an inch or so) to portions of the Central 
Coast, will maintain a dry forecast at this time as widespread 
rainfall appears unlikely. Something worth watching nonetheless.


.AVIATION...As of 10:54 AM PDT Monday...for 18Z TAFs. With the 
exception of some localized low clouds along the immediate coast 
from San Mateo County southward, VFR conditions are forecast to 
prevail throughout the region today as high pressure builds over 
the region. Light winds this morning will become onshore by the 
afternoon hours. Think that the San Francisco Bay Area terminals 
should remain VFR for Tuesday morning as the ridge axis is 
overhead, but the Monterey Bay terminals could see some MVFR/IFR 

Vicinity of KSFO...VFR conditions are forecast to prevail through
today and the evening hours. Light easterly winds this morning 
will become onshore by mid-day around 15-20 kt.

SFO Bridge Approach...Same as KSFO.

Monterey Bay Terminals...VFR conditions forecast through the day
with some localized low clouds along the immediate coast. Think
there will be some areas of lower ceilings around MRY and SNS 
overnight and into Tuesday morning. Models are hinting at a drier 
boundary layer compared today, so it's quite possible MRY and SNS
could even remain VFR. We'll continue to monitor the latest 
incoming guidance and adjust the TAFs accordingly.

&& of 08:57 AM PDT Monday...Moderate to locally strong 
northwest winds will prevail through the day as high pressure 
remains over the eastern Pacific. As the high shifts north on 
Tuesday the winds will remain strong over the northern waters but 
will decrease over the central and southern waters.


     .Tngt...SCA...Pigeon Pt to Pt Pinos 0-10 nm until 9 PM
             SCA...Pt Arena to Pt Reyes 0-10 nm
             SCA...Pt Arena to Pigeon Pt 10-60 nm
             SCA...Pt Reyes to Pigeon Pt 0-10 nm until 3 AM
             SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm until 3 AM
             SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm until 3 AM
             SCA...Mry Bay until 9 PM




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