Technical NOAA Weather Discussion

FXUS66 KMTR 191626

Area Forecast Discussion
National Weather Service San Francisco Bay Area
826 AM PST Tue Feb 19 2019

.SYNOPSIS...Cool, dry weather conditions are forecast to persist
along with cold overnight temperatures through Wednesday morning.
Another cold weather system is forecast to bring light rain
showers to the region Wednesday into Thursday morning with snow
likely in the higher elevations. Dry conditions return late
Thursday and persist into at least Friday.

&& of 08:25 AM PST Tuesday...Clear sky conditions
prevail over the region this morning with only very localized fog
showing up along some of the region's rivers, especially along the
Russian River around Guerneville. This is likely occuring as air
temperatures are in the 30s for much of the region while 20s are
being reported in the higher terrain. Meanwhile, current
temperatures around San Francisco are in the low/middle 40s.
Overall, expect today to be a near repeat of yesterday with mostly
sunny conditions and temperatures warming into the 50s for most
urban areas. The ongoing forecast remains on track at this time
and no updates are needed. Please see the previous forecast
discussion below for additional details.


.PREV of 3:00 AM PST Tuesday...Overnight satellite
imagery reveals mostly clear skies across the entire state of
California thanks to high pressure. A quick look at many automated
sensors around the Bay Area also indicated rather light winds
overnight. The exception are the hills where some gusts of 25-35
mph remain. The combination of light winds and clear skies set the
stage for excellent radiational cooling. Temperatures early this
morning will be rather cold with lows in the 20s (interior
valleys) to 30s and 40s (urban areas and coast). The cold
temperatures will likely lead to frost and some window scraping
for morning commuters. It should also be noted that if any
continued water runoff from the recent rains occurs on some roads
black ice would be possible in the hills/coldest valleys.

After a cold start, today will feature another sunny day with
highs in the 50s for most locations and colder in the hills/mts

The next weather item of note is currently dropping south along
the British Columbia Coast. High pressure currently over the
region will weaken as this disturbance moves in from the north
Wednesday and Wednesday. Latest forecast models indicate it will
be another cold system with 1000-500mb thickness levels/700mb
temps puts snow levels back to 2500-3000 feet. Unlike some of the
previous systems from the past few weeks this system appears to be
more moisture starved leading to scattered showers. Nonetheless,
forecast will bring scattered showers down the coast early Wednesday
and spreading more inland Wednesday afternoon. Rainfall amounts
will be on the order of a few hundredths to a few tenths at best
or a dusting in the hills.

Drier northwest flow returns Thursday as any lingering precip ends
from N-S. Dry weather returns completely Thursday night and Friday
as shortwave ridging develops overhead. Next weekend looks to
start off dry then another round of precip will be possible by
Sunday. A very broad upper level trough sweeps through the region
Sunday into Monday with scattered showers. Additional rain chances
will be possible next week, but details vary from model to model.

Simply put, the storm door remains open.


.AVIATION...As of 03:45 AM PST Tuesday...For 12Z TAFs. Widespread
except chance of very localized patchy fog around STS thru
sunrise hours. Otherwise, increasing high clouds with generally
light offshore winds through the morning, becoming onshore by the
afternoon and evening. Approaching system will bring gusty winds
overnight with VCSH by sunrise Wednesday.

Vicinity of KSFO...VFR. Increasing high clouds through the day.
Generally light offshore am winds becoming 8-12kt onshore by the
mid afternoon through evening. Winds increase to become gusty
onshore overnight. VCSH around Wednesday morning.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals....VFR. Light offshore winds in morning
become light onshore winds in the afternoon and evening. Onshore
breezy to gusty winds overnight with VCSH later tomorrow.

&& of 03:47 AM PST Tuesday...Northerly winds steadily
increase through the day today and will persist across the waters
through midweek. A series of northwest swells will impact the
region through the rest of the week.


     .Tday...SCA...Pt Arena to Pt Reyes 0-10 nm
             SCA...Pigeon Pt to Pt Pinos 0-10 nm
             SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm
             SCA...Pt Arena to Pigeon Pt 10-60 nm
             SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm
             SCA...Pt Reyes to Pigeon Pt 0-10 nm from 3 PM




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Prepared by Weather at: Tue Feb 19 08:30:02 PST 2019
From the National Weather Service