SFOAFDMTR (09/26/16 1110)

FXUS66 KMTR 261809
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
1109 AM PDT MON SEP 26 2016

.SYNOPSIS...Strong high pressure over the region and offshore
flow will once again result in extremely warm temperatures over
the San Francisco Bay Area and Monterey Bay Region this afternoon.
Modest cooling is forecast by Tuesday with a more significant
cooling trend expected for the second half of the week as an upper
level trough deepens along the West Coast.

&&

.DISCUSSION...as of 08:56 AM PDT Monday...A warm start to the day
already underway as strong high pressure remains over the region
and absent onshore flow. The forecast for today is very similar to
yesterday, maybe a degree or two warmer in many locations given
the warm start to the day and very warm, dry conditions aloft.
Expecting 80s to lower 90s even at the coast today with widespread
90s inland with a few of the warmest spots peaking in the 100-105
degree range. Have made only minor adjustments to the maximum
temperature forecast for today to reflect current trends and
latest model data. Overall, the ongoing forecast remains on track.
Please see the previous discussion for additional details.

&&

.PREV DISCUSSION...as of 4:28 AM PDT Monday...Heat advisory
remains in effect today with another round of hot temperatures and
a good chance of tying or breaking some more records...or at least
making a good run at them. Not surprisingly most of the trends at
this hour show temperatures running several degrees of where they
were this time yesterday. The sfo-wmc gradient has eased from 14
mb to 9 mb with the northerly gradient down the coast flat so we
will lose some of the ideal adiabatic warming. Either way its
splitting hairs as all signs point to another very warm to hot
day. 4 am readings of 68 in the city and 71 at downtown Oakland
portend another hot day.

So the next forecast challenge becomes when will the cooling trend
begin. We should see at least an inkling of a seabreeze by late
this afternoon and evening as winds briefly turn westerly. We will
lose the offshore winds but not seeing signs of a southerly surge
or significant cooling for Tuesday. Nonetheless expect to see a
few degrees of cooling inland on Tuesday but more noted cooling
only near the coast Tuesday afternoon. 

The beaches should get a decent marine push later Tuesday night
into Weds morning. Inland locations will then see much more
dramatic cooling for Weds afternoon. Most places will be 15 to 25
degrees cooler by Weds compared to this afternoon.

ECMWF solution then brings a fairly cool trough down the west
coast the second half of the week...sending temperatures below
normal Thursday through Saturday. However, no precipitation is
forecast with the trough with all long range guidance still
keeping things dry into October.

&&

.AVIATION...As of 11:00 AM PDT Monday...Guidance continues to
suggest that onshore flow will not be strong enough over the next
24 hours to bring back clouds to our area. Therefore, will keep
VFR going at all terminals. High confidence.

Vicinity of KSFO...VFR conditions through the period. Winds of 290
to 310 increase to around 12KT after 22z to 04Z. High confidence.

SFO Bridge Approach...Similar conditions to KSFO.

Monterey Bay Terminals...One more clear day and night forecast
with VFR expected. Winds of 280 to 300 to around 10 KT after 20Z
to 04Z. High confidence.

&&

.FIRE WEATHER...As of 4:28 AM PDT Monday...For Sawmill fire
expect another hot and dry day but the offshore breezes are
easing. Winds will be like a turnstile turning light southerly
this afternoon...then light offshore/northeast again tonight. Very
warm temps well into the 90s with humidity in the teens. Only
subtle cooling Tuesday with any significant cooling holding off
until Weds.

Soberanes Fire...not expecting any of the strong southerly winds
that were observed Sunday. Current trends show temps starting out
today much warmer and drier with single digit humidity already in
place. Expect over 100 degrees for Tassajara and Arroyo Seco and
mid to upper 90s even for portions of the West ops. Really no
changes of note on Tuesday with perhaps a few degrees of cooling
but still dry. Will need to wait until Weds for any appreciable
inland cooling but even that will be moderated for the interior
portions of the fire/forest.

&&

.CLIMATE...Here are the record highs for September 26.
 
                   September 26            
                   Record/Year             
Bay Area

Kentfield.............99/1921 
San Rafael............99/1963
Napa.................105/1963 
San Francisco.........94/1992
SFO...................95/1958 
Oakland Museum........93/1973 
Oakland Airport.......97/1958
Richmond..............95/1963
Livermore............103/1952
Mountain View.........95/1999 
San Jose..............98/1963
Gilroy...............104/1963

Monterey Bay Area

Monterey...............98/1970
Santa Cruz............101/1970
Salinas...............100/1970
Salinas Airport........99/1970
King City.............105/1963

&&

.MARINE...as of 10:50 AM PDT Monday...High pressure covers the
eastern pacific and the great basin while a thermal trough lies
along the california coast. the trough will move into the
california interior tomorrow which will cause them to increase
from the northwest tuesday and wednesday.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
 .Tday...Heat Advisory...All locations.

&&


PUBLIC FORECAST: RGass AVIATION: Bell MARINE: Bell CLIMATE: BAM/DRP FIRE WEATHER: RWW Visit us at www.weather.gov/sanfrancisco Follow us on Facebook and twitter at: www.Facebook.com/nwsbayarea www.twitter.com/nwsbayarea