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Area Forecast Discussion (AFD)

Issued by San Francisco Bay Area, CA (MTR)

                            
000
FXUS66 KMTR 161755
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
1055 AM PDT Tue Apr 16 2019

.SYNOPSIS...Isolated showers across southern zones will end this
morning with dry conditions in all areas this afternoon. A 
warming trend is forecast for Wednesday and Thursday, with 
temperatures expected to climb well above normal by Thursday with 
widespread 80s for inland locations. A cooling trend is forecast 
to begin on Friday and continue into the weekend. Generally dry 
conditions are expected over the weekend and early next week.

&&

.DISCUSSION...as of 08:30 AM PDT Tuesday...Upper level trough is 
moving to the east, and a ridge of high pressure is advancing 
towards the area from the eastern Pacific. Rainfall totals through
this morning varied across the area, with the SF Bay shoreline 
receiving a few hundredths to around a tenth of an inch, the North
Bay Valleys and Central Valleys 0.1 to 0.2 inches, and higher 
terrain 0.25 to 0.75 inches. KMUX reflectivity is showing just a 
few isolated showers which are exiting our southern regions. 
Conditions in all areas will dry out later this morning, with 
partly cloudy skies across the area this afternoon. A 
strengthening surface pressure gradient will bring breezy 
northwest winds this afternoon, especially to coastal locations 
where gusts of 25-30 mph are possible. Breezy winds combined with 
below normal highs in the upper 50s to mid 60s will make for a 
cool, blustery day in some locations. A strong warming trend will 
then develop later this week in response to high pressure and 
warming temperatures aloft. For additional details, see the 
previous discussion. 

&&

.PREV DISCUSSION...As of 3:22 AM PDT Tuesday...KMUX reflectivity 
imagery reveals some remnant scattered showers this early morning 
in the wake of yesterday's quick-moving system. Overall, rain 
accumulations were on the light side with most populated locations
not even exceeding a few tenths of an inch. Rural locations 
receiving the most rainfall in this event include places such as 
Mt Tam (0.54") and Venado (0.52") in the North Bay, and White Rock
Ridge (0.36") in Monterey County. High resolution forecast models
such as the HRRR and 3 km NAM decrease the shower activity by the
early or middle morning hours with dry conditions expected along 
with the return of some sunshine this afternoon. Winds will become
brisk at times this afternoon with sustained winds around 20 mph 
and gusts to 30 mph along the immediate coast. High temperatures 
are forecast to reach the 60s region-wide, equating to about 2-7 
degrees below middle April climatological normals.

A very robust warming trend will commence throughout the Golden 
State from the middle of the week through Thursday as an upper 
level ridge builds over the eastern Pacific. By Thursday 
afternoon models boost 500 mb heights to around 584 dm, which 
ranks above the 90th percentile for this date at OAK (per the 
Storm Prediction's Center's sounding climatology page). Along 
with warming temperatures at 500 mb and 850 mb, surface 
temperatures will warm significantly over the next several 
days...going from the 60s on Tuesday to the 70s along the coast 
and 80s inland on Thursday, or about 7-15 degrees above normal. 
Can't rule out the opportunity for some locations in the southern 
Salinas Valley or around Pinnacles National Park to rise to the 
upper 80s, or even approach 90 degrees on Thursday. 

Onshore flow will then return to the region on Friday as the 
ridge axis shifts eastward, allowing for temperatures along the 
coast to drop to the 60s. Inland communities will likely see 
cooling as well, though the degree of cooling is not expected to 
be as notable as the coast. By the weekend both the ECMWF and GFS
advertise the arrival of a short wave and light precipitation 
chances on Saturday for the higher elevations of northern 
California. Think at this point we should remain mostly dry for 
our part of the state with the National Blend of Models keeping 
rain chances less than 10 percent for most Bay Area 
locations...the best chances would be in the North Bay where PoPs 
peak around 15 percent.

Heading into next week, models rebuild the eastern Pacific ridge 
with warming temperatures expected. This aligns well with the 
latest 6-10 and 8-14 day outlook from the Climate Prediction 
Center, which gives California increasing odds of experiencing 
warmer than normal temperatures.

&&

.AVIATION...as of 10:50 AM PDT Tuesday...VFR. Low clouds continue
to lift and dissipate this morning with FEW/SCT clouds between
500-3,500 ft lingering. Otherwise, look for onshore winds to
increase and become locally gusty (up to 25 kt through coastal
gaps such as near KSFO) this afternoon and evening. Winds diminish
overnight with low confidence of lowering ceilings toward 
Wednesday morning.

Vicinity of KSFO...Breezy west winds through this evening, with 
sustained winds 15-20 kt and gusts 20-25 kt possible. 
Redevelopment of MVFR ceilings possible early Wednesday morning, 
low confidence.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...Breezy onshore winds 10-15 kt with gusts
up to around 20 kt through the afternoon. Redevelopment of MVFR 
ceilings possible early Wednesday morning, low confidence.

&&

.MARINE...as of 08:22 AM PDT Tuesday...Northwest winds are 
forecast to increase and become gusty by the afternoon in wake of 
an overnight frontal passage. These gusty winds will prevail 
through early Wednesday morning, primarily along the coast and 
just offshore. Moderate northwest swell will continue through the 
forecast period.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tday...SCA...Pigeon Pt to Pt Pinos 0-10 nm from 2 PM
             SCA...Pt Arena to Pt Reyes 0-10 nm from 11 AM
             SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm from 11 AM
             SCA...Pt Reyes to Pigeon Pt 0-10 nm from 2 PM
             SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm from 2 PM
             SCA...Mry Bay from 2 PM

&&

$$

PUBLIC FORECAST: ST
AVIATION: RGass
MARINE: RGass

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