fxus66 kmtr 191010 

Area forecast discussion 
National Weather Service San Francisco Bay area 
310 am PDT Fri Oct 19 2018 

Synopsis...sunny and warm today with a only a few degrees of 
cooling through the weekend. More noted cooling returns early 
next week as fronts pass to our north with increasing onshore flow 
and a cooling airmass. Any light rain will likely stay north of 
Sonoma County next week while high pressure builds over southern 
and central California by the second half of next week. 


Discussion...as of 3:10 am PDT Friday...night time satellite 
shows most of the low clouds and fog confined to the ocean as well 
as down the Salinas valley with a shallow 800 foot marine layer 
in place. This is producing some 1/4 mild fog at Salinas 
currently. Gradients are light and the marine layer is shallow so 
only expect some patchy inland fog formation through sunrise with 
the latest scans showing fog starting to form in the North Bay 

The synoptic pattern features a building 500 mb ridge over Oregon 
while a weak cyclonic circulation exists over the Southern 
California bight. This puts the Bay area and central coast firmly 
in-between the two circulations with some light offshore flow and 
a warm airmass. This should translate into another day of above 
normal temperatures in what should be the warmest day of the next 
several. Expect widespread 80s once again for inland areas with 
comfy 70s around the bays with 60s confined to the immediate 
beaches. Pleasant October weather to finish out the work week. 

Weekend weather looks ideal for any outdoor activities. The ridge 
will push east and the low over Southern California will eject 
northward. This will allow for more stratus formation over the 
ocean with a few degrees of cooling this weekend. However, were 
splitting hairs and still expect lots of 70s and 80s with even 
lower 90s still possible for the hottest interior valleys. 

We've been tracking some possible frontal passages across norcal 
next week and not surprisingly the trends are showing decreasing 
rain chances. Latest European model (ecmwf) weakens the first front Tuesday 
afternoon with perhaps some North Bay sprinkles while the rest of 
the district will maintain dry and seasonable weather. A second 
front may approach Cape Mendocino by about next Thursday but any 
precip stays well north of the Bay area. In fact the latest GFS 
and European model (ecmwf) trends now showing a strong 590 dm plus ridge building 
over Southern California with a surface thermal trough across the 
Bay area suggesting likelihood of another round of above normal 
temps which often occurs as we approach Halloween. 


Aviation...as of 10:30 PM PDT Thursday...marine layer has 
compressed down to around 1000 feet this evening. Northerly 
gradient has increased which will delay the stratus from 
spreading inland and may keep it out completely if the latest 
model guidance verifies. For now will delay the timing of cigs and 
see how much the stratus spreads inland. 

Vicinity of ksfo...VFR is expected through 13z. Becoming MVFR from 
13z-17z but confidence is low as latest model guidance has backed 
off on the amount of stratus. 

Sfo bridge approach...similar to ksfo. 

Monterey Bay terminals...stratus over southern mry Bay extends 
into sns. Stratus has stopped just north of kmry but should be in 
after 08z. IFR cigs clearing after 17z. 


Marine...as of 10:34 PM PDT Thursday...a 1024 mb high centered 
350 miles west of Point Arena will slowly weaken over the weekend. 
This will keep light northwest winds over the coastal waters. 


Mtr watches/warnings/advisories... 


Public forecast: rww 
aviation: drp 
marine: drp 

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