fxus66 kmtr 221749 

Area forecast discussion 
National Weather Service San Francisco Bay area 
1049 am PDT Thu Mar 22 2018 

Synopsis...periods of moderate to locally heavy rainfall will 
continue through this afternoon as an atmospheric river takes aim 
at the California coast. Breezy to locally gusty southerly winds 
will also be possible ahead of a cold front that will sweep 
through the region this morning. After a brief break in rainfall 
later today, additional showers and cooler temperatures will be 
possible from Friday into the weekend before dry conditions return 
next week. 


Discussion...as of 09:00 am PDT Thursday...very active morning 
across the Bay area as moderate to locally heavy rain impacts the 
region with localized flooding. Latest radar imagery shows the 
bulk of the rain is now occurring south and east of sf Bay. This 
rain is ahead of the main cold front. The cold front is just 
entering the North Bay at this time. Buoy 13 just switched to the 
northwest as the front passed through. The cold front is also 
visible on satellite and as a few echoes on radar near Point 

For the rest of today - moderate to locally heavy rain will be 
possible ahead of the front, but then transition to scattered 
showers with and behind the front. Latest near term hi-res models 
continue to indicate there is a chance for afternoon 
thunderstorms. The greatest chance for afternoon thunderstorms 
will be most likely S and east of sf Bay. Storm Prediction Center day 1 outlook has this 
region in general mention of thunderstorms as well. The Sacramento 
Valley has an even greater chance for thunderstorms, similar to 

Given the dynamic situation will do some forecast updates this 
morning to better reflect reality. 


Previous discussion...as of 2:48 am PDT Thursday... 

The actual cold front is progged to move through the area this 
morning. As it does, periods of heavy rain are possible, along 
with a slight chance of thunderstorms. The winds will also switch 
from gusty southerly to northwest. 

Showers will diminish overnight tonight as the system pushes to 
the east and south. Another weaker system is forecast to spread 
rain across the North Bay Friday night, and south through the 
remainder of the County Warning Area by Saturday morning. Then another system 
then moves through quickly later Saturday and early Sunday. 
Neither of these systems are expected to be as wet as the one 
currently moving through. A warming and drying trend is then 
forecast beginning early next week. 


Aviation...as of 10:49 am PDT Thursday...for 18z tafs. Mainly 
MVFR conditions over the next couple of hours. The main front just 
moved through sfo in the past few minutes shifting the winds to 
west-northwest. The heaviest rainfall has already moved through and scattered 
showers are expected through the period with a break in 
precipitation late tonight into early tomorrow morning. MVFR cigs 
are expected to lift to VFR over the next few hours at most sites 
with occasional MVFR cigs possible with passing showers. Some 
brief clearing of cigs is expected this evening before the return 
of MVFR cigs tonight. Scattered thunderstorms remain a possibility 
this afternoon, but confidence is still low so thunderstorms in the vicinity will be left 
out of the tafs for now. 

As the front continues to make its way southward, winds will 
shift to the northwest. Gusts of around 25-30 kt possible out of the west 
to northwest through late tonight. 

Vicinity of ksfo...the front just moved through sfo and winds are 
now out of the west-northwest at around 15-20 kt gusting to 25-30 kt. Gusty 
winds will continue into tonight before dropping to around 10 kt 
into tomorrow morning. Cigs are expected to bounce between 
MVFR/VFR through the evening when some clearing is possible until 
the return of low cigs some time tonight. Scattered showers will 
remain in the area before a break tonight. Scattered 
thunderstorms remain possible this afternoon and evening. 

Sfo bridge approach...similar to ksfo. 

Monterey Bay terminals...rain, heavy at times, will continue this 
morning at both ksns and kmry. Cold front will arrive over the 
next couple of hours shifting winds to the west to northwest with gusts to 
20-25 kt. Showers are expected to end this evening and VFR 
conditions should then prevail through the period. 


Marine...as of 08:24 am PDT Thursday...winds over have begun to 
shift to the northwest over the northern waters. As the front 
continues to push through, winds over the rest of the waters will 
turn to the northwest. Unsettled weather will continue over the 
waters with rain and scattered thunderstorms possible through the 


Mtr watches/warnings/advisories... 
... Bay 
Small Craft Advisory...mry Bay 
Small Craft Advisory...pt Arena to pt Reyes 0-10 nm 
Small Craft Advisory...pt Reyes to Pigeon pt 0-10 nm 
Small Craft Advisory...Pigeon pt to pt pinos 0-10 nm 
Small Craft Advisory...pt Arena to Pigeon pt 10-60 nm 
Small Craft Advisory...Pigeon pt to pt Piedras Blancas 10-60 nm 
Small Craft Advisory...pt pinos to pt Piedras Blancas 0-10 nm 



Public forecast: mm/Sims 
aviation: as 
marine: as 

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