NWS San Francisco Bay Area, CA wrote its last area forecast discussion before the first event at Sep 1, 12:45 PM PST, 15 minutes earlier.
Area forecast discussion, Sep 1, 12:45 PM PST, 15 minutes before
Area Forecast Discussion
National Weather Service San Francisco Bay Area
145 PM PDT Fri Sep 1 2017
.SYNOPSIS...Oppressive heat is forecast across the interior and
higher elevations today through Saturday as strong high pressure
builds over the region. In addition, very warm temperatures will
spread to the coast as onshore flow weakens. A region-wide cool
down is forecast to begin on Sunday, especially near the coast,
but very warm to hot conditions will continue over inland areas
through early next week.
&&
.DISCUSSION...as of 1:43 PM PDT Friday...Temperatures continue to
climb across the San Francisco Bay Area and central coast this
afternoon. Compared to this time 24 hours ago, many locations are
running an incredible 10 and 20 degrees warmer. Triple digits
popped up as early as 11 am in the Santa Cruz Mountains and some
interior areas of Monterey County. At 11:20 am, Salinas Airport
(KSNS) broke their daily record high which was previously 96
degrees set in 1952. As of 12:20, the temperature continued to
rise to 104 degrees. For reference, the all-time record high at
Salinas Airport is 105 degrees set in October 5, 1971 with a
period of record dating back to 1959. Downtown San Francisco
reported 98 degrees at 1:43 pm PDT, already breaking the September
1 record of 90 degrees set back in 1950. For additional
information on record high temperatures for various locations in
the region, please refer to the climate section. Record Event
Reports will be issued in the evening as they are compiled.
More records will be broken as the afternoon continues as a large
upper level ridge builds over northern California. Expect
temperatures to surpass the 80s along the coast, reach the
mid/upper 90s for much of Downtown San Francisco, and rocket past
the 100 degree mark for inland areas. The hottest temperatures are
currently forecast to be near Livermore where guidance is
suggesting extraordinarily oppressive conditions. European MOS
guidance is suggesting a high temperature of 115 degrees in
Livermore which -- if verifies -- would tie the city's all-time
record high set back on September 3, 1950. Widespread high to very
high heat risks are anticipated throughout the region for the
next few days as temperatures remain well above normal. The entire
County Warning Area from Sonoma County south through Monterey
County has been upgraded to an Excessive Heat Warning through at
least 9 pm Saturday for the coast, and through Monday afternoon
for interior areas. Even the typical cool coastal beaches will be
subjected to much warmer than normal temperatures as the usual
onshore flow saving grace has ceased. Take the necessary
precautions to beat the heat: drink plenty of fluids and refrain
from alcohol and caffeine, limit outdoor activities during the
hottest time of the day, wear light-colored clothing, and wear a
hat. If you don't have air conditioning, consider going to a
community cooling center, a shopping center/mall, a library, or
movie theater. Never ever leave pets, children, or adults alone in
a parked vehicle. Heat -- on average -- has killed more people
than any other weather-related hazard in the United States. Do
not underestimate the heat.
Expect onshore flow to resume by Sunday with relief returning for
areas near the coast. Inland areas will remain hot, but not as
hot as today and Saturday. Additionally, moisture associated with
Tropical Storm Lidia will approach parts of the central California
coast late Sunday and overnight into Monday. Confidence still
isn't high on the exact track of the cyclone and its associated
moisture, but nonetheless have increased POPs as well as
introduced the slight chance of thunder to southern Monterey
County. Further cooling is anticpated by the middle of next week,
but the forecast calls for temperatures to remain above seasonal
normals.
Again, we cannot emphasize enough the hazards that millions across
the area (and tens of millions across the State of California)
will be subjected to. Please stay safe, stay hydrated, and beat
the heat.
&&
.AVIATION...As of 10:18 AM PDT Friday...VFR will continue through
the forecast period, with strong upper-level high pressure aloft.
This will inhibit marine layer and low clouds from developing.
Only concern will be reduced visibilities due to smoke from fires
in Northern California and the Sierra Mountains. Smoke has been
drifting over all terminals and dropping VIS below 6SM at some
Bay Area terminals at times. Taf reflects reduced VIS at terminals
that are currently being affected. This will continued to be
monitored as the day progresses. Generally light onshore winds
this afternoon, below 15 kt, except at KSFO. High forecast
confidence.
Vicinity of KSFO...VFR through the forecast period. Periods of
smoke may reduce VIS below 6SM at times. Winds becoming westerly
to around 15-18 KT after 22Z. High confidence.
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...VFR through the period. Light winds
becoming west to northwest after 19Z. High confidence.
&&
.FIRE WEATHER...As of 9:40 PM PDT Thursday...Strong high pressure
will continue to build over the district through Friday,
producing very hot and dry conditions inland through the weekend.
The hottest days are expected to be Friday and Saturday when
widespread highs of over 100 are expected inland and even coastal
areas will warm into the 80s to mid 90s. Daytime relatively
humidity values will be as low as the single digits and teens
during this heat event. Also, nighttime humidity recoveries in the
hills during this period of time will be very poor with relative
humidity values not expected to rise above 30 percent for most
elevations above 1000 feet. In addition, temperatures in the hills
will remain warm overnight, with lows expected in the 70s and
80s. Finally, moderate northeast winds are expected in the hills
tonight and then become moderate and gusty northwesterly winds by
Friday afternoon. These weather factors will result in the
potential for rapid fire spread, especially in the hills. A Red
Flag Warning is in effect from this evening through early Saturday
morning for elevations above 1000 feet in the North and East Bay
Hills, the Santa Cruz Mountains, the Diablo Range, the Santa Lucia
Range and the interior mountains of Monterey and San Benito
Counties.
Although temperatures are expected to moderate Sunday and Monday,
a prolonged period of very warm to hot weather will likely last
well into next week, especially for inland areas.
Also, will need to be cognizant of the possibility of showers and
thunderstorms starting late in the weekend and continuing into
next week as subtropical moisture increases across the district
from the southeast.
&&
.CLIMATE...The following is a list of daily record high
temperatures for the next 3 days at the selected cities.
San Francisco Bay Area....Fri Sep 1...Sat Sep 2...Sun Sep 3
..........................Temp/Year...Temp/Year...Temp/Year
...............Kentfield 103/1955 104/1955 104/1950
..............San Rafael 103/1955 101/1955 104/1950
....................Napa 107/1955 109/1955 105/1950
......San Francisco Dtwn 90/1952 94/1991 92/1961
...San Francisco Airport 94/1955 93/1950 93/1961
.........Oakland Airport 99/1952 97/1950 95/1961
................Richmond 93/1955 89/2008 89/2004
...............Livermore 109/1952 111/1952 115/1950
...........Moffett Field 93/2002 93/2002 93/1961
................San Jose 101/1950 102/1950 99/1950
..................Gilroy 102/1976 104/2002 104/2002
Monterey Bay Area.......
.................Salinas 91/2010 90/2008 94/1961
.........Salinas Airport 96/1952 90/2008 94/1961
...............King City 108/1955 113/1955 103/1955
The following is a list of All-time record high temperatures for
the selected cities. Note the period of record for each individual
site will vary from one to the other.
San Francisco Bay Area....All-Time Record High
..........................Temp Date
...............Kentfield 112 Jul 11 1913
..............San Rafael 110 Jun 15 1961
....................Napa 113 Jun 14 1961
......San Francisco Dtwn 103 Jun 14 2000
...San Francisco Airport 103 Sep 14 1971
.........Oakland Airport 104 Jun 14 1961
................Richmond 107 Sep 15 1971
...............Livermore 115 Sep 03 1950
...........Moffett Field 106 Jun 14 2000
................San Jose 109 Jun 14 2000
..................Gilroy 115 Jun 15 1972
Monterey Bay Area.......
.................Salinas 106 Sep 14 1971
.........Salinas Airport 105 Oct 05 1987
...............King City 113 Sep 02 1955
&&
.MARINE...as of 01:18 PM PDT Friday...Look for light to moderate
northerly winds through the day, occasionally breezy along the
immediate coast. Light seas are forecast to persist through the
period.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
.Tngt...Excessive Heat Warning...CAZ506>508-510>513-516>518-528
Excessive Heat Warning...CAZ006-505-509-529-530
&&
PUBLIC FORECAST: Rowe
AVIATION: BAM
MARINE: BAM
CLIMATE: Rowe/Dykema/BAM
FIRE WEATHER: Dykema
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