FXUS66 KMTR 211146
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco Bay Area
446 AM PDT Thu Jun 21 2018
.SYNOPSIS...A robust warming trend will begin over the next
several days as high pressure builds off the West Coast. This will
lead to hot conditions on Saturday with moderate to locally high
heat risks across parts of the region. Additionally, winds will
turn offshore, bringing heightened fire weather concerns to parts
of the area on Saturday. Cooling will commence on Sunday along
with the redevelopment of the marine layer for early next week.
&&
.DISCUSSION...As of 3:15 AM PDT Thursday...GOES-East fog product
reveals areas of stratus again impacting parts of the San
Francisco Bay Area and central California coast this early
Thursday morning. The Fort Ord profiler along the Monterey Bay
shoreline indicates the marine layer is running around 1,000 ft
deep, similar to what it was 24 hour ago. Despite the similar
marine layer depth, the stratus coverage doesn't appear to be
quite as widespread as it was yesterday morning.
Synoptically-speaking, an upper level high is presently centered
in southwestern Arizona. A quick shortwave trough is currently
pushing through the outer periphery of this high across northern
California, and will quickly exit the state within the next 6-12
hours. Some weak ridging is expected to occur behind this
shortwave during the day, which should allow for some warming
across interior locations this afternoon.
By Friday, an upper level ridge will begin to amplify off the
California coast, resulting in further warming across interior
locations. We'll likely see some locations in the interior North
Bay, interior East Bay, and southern reaches of Monterey and San
Benito Counties reach the triple digits for Friday afternoon. The
warming will continue on Saturday for what should be the hottest
day as the ridge continues to strengthen offshore. The hottest
areas of the county warning area -- far northern Sonoma and Napa
Counties, far interior East Bay, and far southern Monterey + San
Benito Counties -- may flirt with 105 degrees on Saturday. The
warm-to-hot conditions will likely creep toward the San Francisco
Bay shoreline as well -- 90s to low 100s seem quite probable
along the US 101 corridor from Gilroy north through San Jose and
continuing toward Redwood City. Temperatures farther north toward
SFO and San Francisco will likely be cooler with highs along the
bay shoreline in the 80s with cooler conditions along the
immediate Pacific coast. These temperatures are expected to
produce moderate to locally high heat risks across much of the
interior, and will likely see heat advisory headlines launched
later today for certain zones as a result of these forecasted hot
conditions.
Another concern for late Friday night/Saturday will be locally
breezy north to northeast winds over the North Bay Mountains.
High-resolution models are starting to capture this event, and are
showing wind speeds around 15 to 25 mph with local gusts around
35 mph across far Northern Napa and Sonoma Counties. Combined with
poor relative humidity recoveries, this will likely lead to
heightened fire weather concerns.
For Sunday, models have consistently been advertising appreciable
cooling across the region as the ridge axis pushes east into the
North American continent. Additionally, the GFS, NAM, and local
in-house WRF model have suggested the potential for a southerly
surge pushing north along the Monterey County coast and continuing
toward the Golden Gate during the day. Cooling will continue into
the first half of next week with highs gradually returning close
to late June climatological normals.
&&
.AVIATION...As of 4:46 AM PDT Thursday...For 12z TAFs. Marine
layer currently sits slightly below 1,000 feet, per the Ft. Ord
Profiler. GOES-16 fog product shows patchy stratus affecting the
Greater SF Bay terminals (BKN/OVC deck around 1,200 feet), as well
as Monterey Bay terminals (BKN/OVC deck around 500 feet). The
shallow stratus should erode by 16-17z for most terminals this
morning. Building ridge of high pressure will compress the marine
layer even more by this evening. Therefore, not expecting cigs to
form tonight. However, there could be some patchy dense fog that
may reduce vsby around the Monterey Bay region overnight tonight,
low confidence on exact timing. Light to moderate west/northwest
winds this afternoon, locally gusty at times.
Moderate-high forecast confidence.
Vicinity of KSFO...MVFR cigs becoming VFR by 16-17z. Onshore winds
15-20 kt, with higher gusts possible by this afternoon. A very
compressed marine layer should keep cigs from forming tonight.
SFO Bridge Approach...Approach remains clear for now (per SMB ob),
but intermittent MVFR cigs possible before 16z.
Monterey Bay Terminals...LIFR/IFR cigs through about 16-17z, then
VFR. Light to moderate west/northwest winds this afternoon, around
10-12 kt. Compressed marine layer may produce fog tonight,
reducing horizontal and vertical vsby by Friday morning.
&&
.FIRE WEATHER...as of 3:15 AM PDT Wednesday...A pronounced
warming and drying trend is forecast for the end of the week as
high pressure builds in and winds turn offshore. Saturday
presently looks to be the hottest day, with poor overnight
relative humidity recoveries for both Friday night and Saturday
night. Locally gusty north to northeast winds are possible in the
North Bay hills Friday night and Saturday morning. A return to
cooling and redevelopment of the marine layer appears in store for
Sunday into the first part of next week as flow shifts back
onshore.
&&
.MARINE...as of 2:40 AM PDT Thursday...High pressure over the
Eastern Pacific will continue to strengthen through the rest of
the week and into the weekend. In response, strong and gusty
northwest winds are expected to affect the majority of the coastal
waters zones through this period. Winds are expected to be
strongest over the northern outer most coastal waters,
strengthening to near gale force, with gale force gusts, by Friday
evening through Saturday morning. As a result of the strong
winds, steep and hazardous seas are likely for the majority of the
coastal waters through at least the first half of the weekend.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
.Tday...SCA...Pigeon Pt to Pt Pinos 0-10 nm
SCA...Pt Arena to Pt Reyes 0-10 nm
SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm
SCA...Pt Arena to Pigeon Pt 10-60 nm
SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm
SCA...Pt Reyes to Pigeon Pt 0-10 nm
SCA...Mry Bay from 12 PM
&&
$$
PUBLIC FORECAST: Rowe
AVIATION: BAM
MARINE: BAM
FIRE WEATHER: Rowe
Visit us at www.weather.gov/sanfrancisco
Follow us on Facebook, Twitter, and YouTube at:
www.facebook.com/nwsbayarea
www.twitter.com/nwsbayarea
www.youtube.com/nwsbayarea
Prepared by Boulder-Creek.com Weather at: Thu Jun 21 08:30:02 PDT 2018
From the National Weather Service
|