FXUS66 KMTR 191734
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
1034 AM PDT Thu Sep 19 2019

.SYNOPSIS...Seasonably cool conditions will persist on Thursday
followed by a warming trend forecast through the upcoming weekend.
A low pressure system moving southward to our east early next week
may create the potential for warming temperatures, dry offshore
flow and increased fire concerns. 

&&

.DISCUSSION...as of 08:37 AM PDT Thursday...Mostly clear skies 
overnight allowed temperatures to drop into the mid to upper 40s 
in the inland valleys, while lows along the coast were in the mid 
to upper 50s. An upper trough centered to our north will continue 
to track east, keeping us in a cool northwesterly flow pattern for
today. Temps at 850 mb were measured around 9C on the 12z Oakland
sounding, and are forecast to warm to about 11C this afternoon. 
Cool temperatures aloft will prevent a well-defined marine layer 
today and will keep high temperatures seasonably cool. Highs are 
expected to range from the upper 60s to lower 70s along the coast 
with mid 70s to around 80 in the inland valleys. A warming trend 
will begin on Friday and continue through the weekend as the 
upper trough shifts east and a ridge in the eastern Pacific 
expands towards the West Coast. Made a minor adjustment to sky 
cover this morning, otherwise forecast is on track. For additional
details, see the previous discussion.

&&

.PREV DISCUSSION...as of 03:00 AM PDT Thursday...Seasonably cool 
conditions are forecast over the region today as a mid/upper 
trough persists over the region. Afternoon temperatures will be 
cooler at the coast today compared to yesterday, generally ranging
from the upper 60s to lower 70s while inland areas warm into the 
middle 60s to upper 70s. In addition, mostly sunny conditions are 
likely region-wide. 

High pressure building over the eastern Pacific will then begin to 
build toward the West Coast through the upcoming weekend. This will 
result in a warming trend through the weekend with more widespread 
80s across the interior by Friday and even lower 90s by Saturday 
afternoon. With the lack of a marine layer and persistent onshore 
flow, coastal areas will also warm into the 70s to even lower 80s 
through Saturday. 

Conditions trend slightly cooler on Sunday and Monday as a mid/upper 
level trough drops southward into the Pacific Northwest and 
Intermountain West. Mainly dry weather conditions are likely as this 
system will lack sufficient moisture and the best mid/upper level 
support stays inland to the east of the region. With the upper level 
low lingering over the Desert Southwest into early next week and a 
ridge of high pressure building inland to our north, weak offshore 
flow will potentially develop over the region. As a result, warming 
temperatures and much drier conditions are likely to develop by 
Tuesday and Wednesday of next week. Thus, the forecast will need to 
be closely monitored in the coming days as this pattern will create 
the potential for increased fire concerns. 

&&

.AVIATION...As of 10:34 AM PDT Thursday...For 18Z TAFs. VFR 
conditions will likely prevail at most TAF sites through the 
forecast period. Satellite shows some cumulus clouds beginning to 
pop up in the hills surrounding the Bay Area that will continue 
through peak heating in the afternoon and early evening. Light 
winds this morning will become onshore and locally gusty this 
afternoon. Dry northwest flow will continue overnight, maintaining
VFR conditions at most terminals.

Vicinity of KSFO...VFR conditions are forecast to prevail through
the period with some daytime cumulus clouds at/above 3,000 ft AGL.
Light winds will increase out of the west around 15-20 kt with
gusts near 25 kt. Winds will diminish after sunset.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...VFR conditions are forecast to prevail
through the day. Could see some localized stratus try to develop
overnight along the Monterey Bay shoreline, but confidence of
occurrence is rather low.

&&

.MARINE...as of 08:20 AM PDT Thursday...Northwest winds will 
increase through the day over the waters, with the strongest winds
in the outer waters north of Point Reyes and locally south of 
Point Sur along the Big Sur coast. An 11 second northwest swell 
will be the predominate wave in the waters today, bringing the 
potential of hazardous conditions from squared seas to portion of 
the waters. A much lighter southerly swell will also be mixed in.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tday...SCA...Mry Bay from 3 PM
             SCA...Pt Arena to Pt Reyes 0-10 nm from 3 PM
             SCA...Pigeon Pt to Pt Pinos 0-10 nm from 3 PM
             SCA...Pt Arena to Pigeon Pt 10-60 nm
             SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm
             SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm from 3 PM

&&

$$

PUBLIC FORECAST: ST/RGass
AVIATION: Rowe
MARINE: Rowe

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