Scientific Forecaster Discussion
fxus66 kmtr 260206
Area forecast discussion
National Weather Service San Francisco Bay area
704 PM PDT Sat Mar 25 2017
Synopsis...partly cloudy and dry through midday Sunday. The next
weak cold front moves into the North Bay Sunday afternoon with
showers spreading southward through the Bay area and central coast
Sunday night before ending by sunrise Monday morning. Cool and
breezy Monday afternoon, then high pressure builds with a warming
and drying trend next week.
Discussion...as of 2:50 PM PDT Saturday...skies are partly
cloudy this afternoon with afternoon readings from the upper 50s
at the coast to mid 60s inland. Clouds will dissipate as the sun
GOES down but before sunrise high clouds will start to increase
across the North Bay and keep overnight lows in the 40s.
Looks like Sunday morning will start with increasing high clouds
that will make for a chilly Sunday morning as a weak cold front
associated with pretty cold air aloft will approach the region.
Model trends have been drier with the next system and it now looks
like some light rain or showers will break out in the North Bay
Sunday afternoon and then spread southward through the Bay area
and central coast Sunday night. Rain totals look light, about 0.10
to 0.25 on average with lower amounts for the rain shadowed inland
All showers end before 12z Monday morning but a cool airmass will
be in place with sub 540 dm thickness values in place over the
Bay area Monday morning. Skies will turn partly cloudy by Monday
afternoon but there could be some blustery winds off the ocean
Monday afternoon as a strong surface pressure gradient sets up
across the state. Its getting to be our windy time of year near
the coast as Cool Spring time storms blow in.
A warming and drying trend is forecast Tuesday through much of
next week. Although the 12z ECMWF did throw a wrinkle in things by
taking an inside slider for next Thursday and pulling it farther
west. The main impacts under this scenario would be for the Sierra
and Central Valley but would also bring cooler weather back to the
Bay area. Will monitor the trends with that system over the coming
days but as the calendar approaches April it'll be harder to get
sustained storm cycles again.
Aviation...as of 7:04 PM PDT Saturday...marked drying noted in 24
hours trends as dewpoint temperatures lower indicating less surface
based water vapor in the atmosphere. Winds will remain onshore
through tonight the pressure gradient then tending to become more
neutral sfo-SAC on Sunday. Moderate to high confidence VFR
forecast except local MVFR cigs possible Sunday morning. Light
rain with next weather system reaches the North Bay beginning late
Vicinity of ksfo...VFR. Tempo MVFR cig 11z-15z Sunday.
Sfo bridge approach...same as ksfo.
Monterey Bay terminals...VFR. Onshore winds becoming light and variable
late tonight then southerly on Sunday.
Marine...as of 02:31 PM PDT Saturday...generally light winds and
moderate seas across the waters through tonight. Winds south of
pt sur and over northern Monterey Bay are expected to strengthen
throughout the day. On Sunday, winds over the northern waters will
increase and turn southerly as a weak cold front approaches.
... Bay until 8 PM
Small Craft Advisory...pt pinos to pt Piedras Blancas 0-10 nm until 2 am
Public forecast: rww
Visit US at www.Weather.Gov/sanfrancisco