Weather Service Report

FXUS66 KMTR 241729

Area Forecast Discussion
National Weather Service San Francisco Bay Area
929 AM PST Fri Feb 24 2017

.SYNOPSIS...Drier and cooler conditions are forecast through 
tonight with chilly overnight temperatures. Unsettled weather 
conditions return over the weekend with a storm system moving in
from the north. A longer stretch of dry weather is expected 
starting the middle of next week.


.DISCUSSION...As of 8:40 AM PST Friday...Chilly start with many
locations in the 30s and a few areas even dropping into the 20s.
Weak building ridge of high pressure will lead to sunny conditions
although highs will remain cooler than normal -- mostly lower to
mid 50s. 

Latest model guidance in (outside of the Canadian which continues
to look questionable) continues to downplay the system for the 
weekend. 12Z NAM is now keeping almost all of the rain from just 
at the coast to offshore. Agree with CNRFC that most locations
will see less than 2 tenths total by Monday morning.

No major updates planned.

.PREVIOUS DISCUSSION...Skies are generally clear over the 
district at this time, except for scattered strato- cumulus clouds
over the coastal waters. Latest observations show temperatures 
ranging from the mid 30s to the mid 40s, generally 2 to 6 degrees 
cooler than at yesterday at this time. Dew point temperatures are 
in the 30s, also cooler. Clear skies, light winds, and drier air 
will result in cooler morning lows this morning and Saturday 
morning. Overnight lows are forecast to be in the 30s in most 
locations away from the coast and some of the coldest inland 
valleys may see upper 20s. Patchy frost is likely in most valleys 
by sunrise.

Dry and cool conditions are expected to persist today into
Saturday before a couple of low pressure systems bring rain
chances back to the district. The first system, now over British
Columbia, will move south of the coast on Saturday, but latest
model runs hold off any rain until late in the afternoon, as the
main system remains offshore most of the day. A second system then
moves south into Northern California by late Sunday. Neither of 
these are expected to bring much in the way of rain to the area,
up to a half inch at the very most, per the latest GFS and ECMWF.  

After these systems move through, drying conditions are expected
as a blocking high forms off the coast. Even the most recent
outlooks from the Climate Prediction Center put California under a
"below normal" probability of precipitation into the first week of


.AVIATION...As of 9:25 AM PST Friday...For 18z Tafs. Currently VFR
across all taf sites. VFR conditions should prevail for all
terminals through at least this evening. Cigs are expected to
lower tonight to between VFR and MVFR. Light to moderate westerly
winds through the period, although southern taf sites will see a
shift to SE winds sometime tonight around 04-06z. Low confidence 
on timing and amount of lowering cigs.

Vicinity of KSFO...VFR this morning and afternoon. MVFR possible 
by 08z-10z as a low pressure system approaches. Lighter onshore 
winds today than previous couple of days, ranging from 9-12 kt by 
this afternoon.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR today, with a few low clouds possible.
Generally light onshore winds this afternoon becoming SE by 04z. 

&& of 08:10 AM PST Friday...Weakening high pressure 
over the waters today before a low pressure system drops southward
along the coast. winds will turn southerly on saturday and then 
return to a northwest flow by sunday as the low dissipates. 
generally mild winds and seas are expected through the forecast 
period. showers will move in saturday morning from the north and 
progress southward throughout the day lasting through monday.


     .Tday...Flood Watch...Salinas River




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