Technical NOAA Weather Discussion

FXUS66 KMTR 261131
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
331 AM PST Wed Jan 26 2022

.SYNOPSIS...Dry high pressure continues through Thursday with
periods of offshore winds. By Friday temperatures may cool a few
degrees as a weak low approaches the coast but dry and seasonal
weather continues into the weekend. Slight chance of light rain by
around Monday as a weak front passes through Northern California.

&&

.DISCUSSION...as of 03:23 AM PST Wednesday...Satellite imagery 
overnight has a summer-esc vibe to it with low stratus expending 
inside San Francisco Bay, the West Delta, and the North Bay 
Valleys. Automated sensor in the North Bay show visibility at less
than one mile for with fog being reported. Areas south of San 
Jose are clear with no clouds or fog being reported. Another 
summer- like aspect overnight is the current synoptic pattern 
leading to offshore flow just above the stratus deck. Inland high 
pressure and low pressure along the coast has kept the offshore 
gradient going. Observations in the hills continue to show 
northeasterly flow with gusts 30-40 mph. Additionally, the 
offshore flow is also leading to a rather dry and mild airmass 
with humidity 20-35% and temps in the 50s. The KOAK balloon 
sounding will be launched shortly and it will be interesting to 
see the very low level moisture and offshore flow just a few 
hundred feet up in elevation. Snapping out of the summer vibes are
the interior temperatures this morning. Inland valleys, 
especially clear skies and calm winds, have allowed temperatures 
to drop into the 30s. Lowered temperatures below the NBM this 
morning to better reflect reality.

Today and Thursday...Upper level high pressure and lingering
offshore flow will remain. The net result will be continued mild
and dry conditions over the Bay Area. Some night/morning patchy
clouds/fog will also be possible.  

Looking farther to the west, more precisely, 800 miles to the west
an upper level low pressure is slowly moving toward the CA Coast.
By Friday the upper ridge moves eastward as the upper low moves
closer. This low still appears to be dry with no precip, but it
will likely bring a slight dip in temperatures and more cloud 
cover. Ultimately, the upper low will pass harmlessly to the 
south on Saturday. 

Sometimes when looking at weather models you're looking for
trends. Well, the trend is not our friend if you're looking for
rain. We have been mentioning a pattern shift toward the end of
the month for a few weeks now with the possibility of precip
returning to the region. However, the latest guidance (
deterministic,ensembles, clusters) all show much less in the way 
of precip for the Bay Area. There is still a small chance for 
light rain Sunday night/Monday as a weak trough passes to the 
north, but it's no looking promising for widespread precip. In 
fact, the pattern trend has shifted the EPac ridge eastward and 
transitioned to a more inside slider-ish pattern. Meaning - 
storms stay farther north and sweep through NE CA/S OR with little
precip for the Bay Area. This pattern can also promote additional
bursts of offshore flow. Lastly, the latest CPC 8-14 day out look
keeps the region below normal for precip.

&&

.AVIATION...as of 3:31 AM PST Wednesday...For the 12Z TAFs. Fog,
fog locally dense and low clouds /VLIFR-IFR/ across the Bay Area 
otherwise it's VFR. East to southeast cold air drainage winds is 
keeping the north Central Coast clear /VFR/ this morning. Conditions
lifting to VFR at all terminals by late morning and afternoon. VFR
tonight and Thursday.

Vicinity of KSFO...Low clouds /IFR/ this morning, clearing to VFR
by late morning. VFR tonight and Thursday morning. Mainly light
wind.

KSFO Bridge Approach...Similar to SFO.

Monterey Bay...VFR. East to southeast cold air drainage winds
shifting to light onshore late this afternoon. East to southeast
cold air drainage winds redeveloping tonight and Thursday morning.

&&

.MARINE...as of 3:25 AM PST Wednesday...Northwest to west swell 
gradually decreasing through late week. Winds offshore today with 
stronger gusts possible through coastal gaps, particularly the 
Golden Gate, which may make for rougher seas for smaller vessels 
through early this afternoon.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tday...SCA...Pt Reyes to Pigeon Pt 0-10 nm until 9 AM

&&

$$

PUBLIC FORECAST: MM
AVIATION: Canepa
MARINE: Canepa

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Prepared by Boulder-Creek.com Weather at: Wed Jan 26 08:30:03 PST 2022
From the National Weather Service