Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
343 PM PST Sat Nov 28 2015
Synopsis...dry and cool weather will continue through the
weekend with areas of nighttime freezing temperatures forecast
across inland areas. Temperatures will begin to moderate early
next week. There is also a chance of rain developing by the middle
portion of next week.
Discussion...as of 3:00 PM PST Saturday... little change over
the western Continental U.S. Include central California as Rex block remains in
play. Currently... a weak upper disturbance to our southwest is
rotating counterclockwise beneath The Block per latest visible
satellite. However... this feature is resulting in only minimal
changes versus yesterday as the quasistationary upper low over
Great Basin remains the dominant synoptic feature. Our area
continues to reside in the dry north to northeast flow on the
backside of the aforementioned upper low positioned over the
Great Basin. As a result... clear skies and light winds are
dominating the region once again. Onshore winds have strengthened
slightly along the coast but offshore winds are prevailing for
most inland areas. Winds are expected to weaken moreso tonight
than last night... so despite 1-3 degree celsius cooling aloft...
still expecting another round of near to sub freezing temperatures
tonight for inland communities.
The synoptic pattern will break out of the Rex block and
transition into a more progressive flow by Sunday afternoon.
Models show a approaching weak trough offshore of the pacnw by
Sunday night... however this feature becomes split and elongated
as it slams into the backside of the remnant Rex block downstream.
This weakens the feature as it moves over California... reducing
the likelihood of tangible impacts at the surface. A ridge
develops in the wake of this feature... leading to a slight
warming trend from Monday through Wednesday. Temperatures will
climb to near normal by Wednesday... the warmest day next week.
Medium term models show a deeper more potent trough approaching
the Pacific coastline no later than Thursday morning.This looks
to be the next best chance of precipitation for the region. The
Euro is much wetter and progressive when compared to the GFS... so
there is a bit of model inconsistency at this point. Will need to
watch how these models evolve over the next few runs to hammer out
any specific timing/amounts for this upcoming storm system. Rain
could come to the North Bay as early as Wednesday evening or as
late as Thursday morning... before spreading southward. Long term
models show a poorly organized trough approaching the coastline
late next weekend.
Aviation...as of 3:40 PM PST Saturday...VFR clear. Winds
primarily light offshore.
Vicinity of ksfo...VFR clear through Sunday. Light offshore
winds. Confidence high.
Ksfo bridge approach...same as ksfo.
Monterey Bay area terminals...VFR clear through Sunday.
Marine...as of 02:14 PM PST Saturday...light winds and seas will
continue through the weekend. Winds and seas will gradually
increase beginning early next week as a weak cold frontal system
moves in from the west.
... Advisory...all coastal zones except San
freeze warning...all inland zones
Public forecast: drp
Visit US at www.Weather.Gov/sanfrancisco
Follow US on facebook and twitter at: