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FXUS66 KMTR 260400

Area Forecast Discussion
National Weather Service San Francisco Bay Area
900 PM PDT Thu May 25 2017

.SYNOPSIS...Seasonably cool temperatures will continue into 
Friday with a deep marine layer near the coast. Seasonable 
temperatures on Saturday should trend warmer inland by Sunday and 
Memorial Day Monday. Aside from the isolated coastal drizzle, dry 
weather forecast through the next 7 to 10 days.


.DISCUSSION...As of 9:00 PM PDT Thursday...Cool temperatures were
observed across the region today with most locations topping out 
in the mid 50s to mid 60s. Warmest inland locations reached into 
the low 70s. It was a mixed bag of trends with some locations 
warming a few degrees with others cooling as much as 22 degrees 
over yesterdays temperatures. The deep marine layer allowed for 
significant inland intrusion of the cool marine air and cloudy 
conditions limited the amount of, if any, sunlight to reach the 
ground. Low pressure over the region will maintain the deep and 
undefined marine layer across the region through Friday and hence 
similar temperatures to those that were seen today. Coastal 
drizzle will once again be possible Friday morning. 

The upper level trough that currently dominates the western United
States is forecast to begin moving eastward on Friday. This will
allow a shortwave ridge to build over California beginning
Saturday, and result in a modest warming trend for inland areas
over the Memorial Day Weekend. However, coastal areas are not
expected to warm much over the weekend since onshore flow will 
continue, along with a persistent marine layer. 

Longer range models indicate the arrival of a trough along the 
West Coast around the middle of next week which should result in 
at least slight cooling for inland areas during the second half of
the week. 


.AVIATION...As of 5:30 PM PDT Thursday...A deep marine layer along
with southwesterly winds has resulted in a challenging forecast 
for this evening. Although most terminals developed VFR conditions
by late afternoon, the boundary layer remains moist and it's 
likely that MVFR ceilings will develop in most areas by late 
evening. A complicating factor is southerly flow which may delay 
onset of ceilings at KSFO and KMRY. 

Vicinity of KSFO...VFR conditions forecast to persist through 04Z
with MVFR ceilings thereafter. However, southerly flow may delay
onset of ceilings. Clearing expected to occur by 17Z on Friday.
Moderate and gusty southwest winds this evening and again on
Friday afternoon. Low confidence on onset of low clouds this 
evening. Otherwise moderate confidence.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...VFR early in period as southerly winds
downslope off the Santa Lucias. However, MVFR ceilings will likely
develop by 03Z as cooling occurs in the boundary layer. MVFR
ceilings then likely through midday Friday before low clouds
scatter out. Moderate and gusty southwest winds through early this
evening then light winds thereafter. Moderate confidence.

&& of 07:48 PM PDT Thursday...Gusty south to southwest
winds along the coast and over the bays will diminish through the
late evening. generally light winds are then expected overnight
and into friday. high pressure will  redevelop over the eastern
pacific late week and into the  memorial day weekend bringing a
return to more typical afternoon  and evening onshore winds to the
coastal waters and bays.


     .Tngt...SCA...SF Bay until 9 PM
             SCA...Mry Bay until 9 PM
             SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm until 9 PM
             SCA...Pt Arena to Pigeon Pt 10-60 nm until 9 PM




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