San Francisco Bay Area SKYWARN®

From Tropical Tidbits:

From MTR AFD:

.UPDATE...
Issued at 915 AM PST Wed Feb 5 2025

Highlights for the morning update: N Bay Valley Frost Adv allowed
to expire, ongoing Flood Warnings in Sonoma continue, drier today.

A chilly start to the day as temperatures plummeted into the lower
30s across some of the interior valleys, especially N and E Bay.
In addition to chilly temps, patchy dense fog also impacted the N
Bay valleys. Makes sense really, ample low level moisture from
yesterday`s rains, weaker winds, and some clearing overnight.
Temperatures fortunately are on the upswing so the Frost Adv was
allowed to expire. Fog is also beginning to dissipate.

Today will be much drier than yesterday. However, KMUX still
remains in precip mode. Colder air with marginal instability
today will lead to some widely scattered showers, especially the
N Bay. Despite the drier conditions and low chance for precip
flooding issues will remain as streams/creeks/rivers water levels
remain elevated.

Morning update will be issues shortly to address potential
Frost/Freeze products for tonight as temperatures will plummet to
critical levels.

&&

.SHORT TERM...
(Today and tonight)
Issued at 1209 AM PST Wed Feb 5 2025

Colder and drier air has settled in following yesterday`s cold
front. The satellite shows some cumulus clouds over the water, but
any showers are expected to be brief. The drier air mass has
precipitable water values of 50-75% of normal. Overall today will
be a reprieve between 2 systems. The colder air mass will be
noticeable, however. The current temperatures are roughly 10
degrees colder than 24 hours ago and a frost advisory is in effect
for the North Bay Valleys this morning. More frost advisories may
be needed tonight, but the increasing cloud cover ahead of
Thursday`s system will suppress radiational cooling and will
likely keep the region a degree or two warmer than this morning.

&&

.LONG TERM...
(Thursday through Tuesday)
Issued at 1209 AM PST Wed Feb 5 2025

By Thursday morning another plume of moisture will reach the
coast as a surface low pressure system develops offshore. There is
an outside chance for thunderstorms off the coast Thursday
afternoon. Compared to the atmospheric river on Tuesday, this
system will be much weaker in terms of both wind and rain.
Rainfall amounts are generally expected to be 0.25-1.25". The wind
will still be noticeable, with SW winds 10-20 mph and gusts up to
35 mph Thursday evening. This system will also bring a
reinforcing shot of colder air as it departs. The 1000-500 mb
thickness will fall to around 5,400 m by Friday. In fact, the snow
levels will drop to around 3,000 ft and there`s a chance some of
the higher mountains will get a few flakes. Otherwise Friday will
be a transition day as the skies gradually clear and the drier
ridging pattern stabilizes.

By the weekend, the only real hazard becomes cold morning
temperatures. Saturday morning will start roughly 10 degrees
colder than Friday morning. Many inland areas will drop into the
low 30s, and widespread frost advisories are expected. Afternoon
highs will only climb into the mid to upper 50s, so it will feel
chilly all day, although there will be ample sunshine. The ridging
pattern stabilizes through mid week, and the weather will be
pretty consistent. The next round of rain looks to arrive around
Wednesday.

&&

Severe Weather Statement
National Weather Service San Francisco CA
433 PM PST Tue Feb 4 2025

CAC081-085-050045-
/O.CON.KMTR.SV.W.0006.000000T0000Z-250205T0045Z/
San Mateo CA-Santa Clara CA-
433 PM PST Tue Feb 4 2025

...SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 445 PM PST 
FOR EAST CENTRAL SAN MATEO AND NORTHWESTERN SANTA CLARA COUNTIES...

At 433 PM PST, a severe thunderstorm was located over Stanford, or 
over Palo Alto, moving northeast at 65 mph.

HAZARD...60 mph wind gusts.

SOURCE...Radar indicated.

IMPACT...Expect damage to roofs, siding, and trees.

Locations impacted include...
  San Jose, Fremont, Sunnyvale, Redwood City, Mountain View, Palo 
  Alto, Newark, Menlo Park, Los Altos, San Carlos, East Palo Alto, 
  Los Altos Hills, Atherton, Woodside, Stanford, North Fair Oaks, 
  Portola Valley, West Menlo Park and Emerald Lake Hills.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Seek shelter inside a well-built structure and stay away from 
windows. This storm is capable of producing damaging winds.

Tornadoes can develop quickly from severe thunderstorms. Seek 
shelter immediately in an interior room on the lowest floor of a 
well-built structure.

Wind damage with this storm will occur before any rain or lightning. 
Do not wait for the sound of thunder before taking cover. Seek 
shelter immediately inside a sturdy structure and stay away from 
windows.

Torrential rainfall is also occurring with this storm and may lead 
to flash flooding. Do not drive your vehicle through flooded 
roadways.

&&

LAT...LON 3755 12220 3753 12217 3752 12216 3752 12214
      3748 12211 3749 12206 3748 12202 3748 12203
      3747 12205 3747 12196 3746 12200 3746 12197
      3734 12218 3741 12231
TIME...MOT...LOC 0024Z 221DEG 60KT 3732 12227

TORNADO...POSSIBLE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...0.00 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service San Francisco CA
359 PM PST Tue Feb 4 2025

The National Weather Service in San Francisco has issued a

* Severe Thunderstorm Warning for...
 San Francisco County in northern California...
 Northwestern San Mateo County in northern California...

* Until 415 PM PST.

* At 359 PM PST, severe thunderstorms were located along a line from 
 near San Francisco to near El Granada, moving northeast at 45 mph.

 HAZARD...60 mph wind gusts.

 SOURCE...Radar indicated.

 IMPACT...Expect damage to roofs, siding, and trees.

* Locations impacted include...
 San Francisco, Daly City, South San Francisco, San Bruno, 
 Pacifica, Brisbane, Colma, Broadmoor and Montara.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Seek shelter inside a well-built structure and stay away from 
windows. These storms are capable of producing damaging winds.

Torrential rainfall is also occurring with these storms and may lead 
to flash flooding. Do not drive your vehicle through flooded 
roadways.

&&

LAT...LON 3759 12252 3771 12251 3776 12252 3777 12253
 3779 12253 3783 12241 3782 12241 3780 12238
 3781 12238 3779 12237 3775 12238 3772 12235
 3771 12235 3770 12236 3769 12235 3767 12236
 3754 12252
TIME...MOT...LOC 2358Z 219DEG 37KT 3779 12243 3766 12249 3753 12254

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...0.00 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

WUUS56 KMTR 042215
SVRMTR
CAC041-042300-
/O.NEW.KMTR.SV.W.0002.250204T2215Z-250204T2300Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service San Francisco CA
215 PM PST Tue Feb 4 2025

The National Weather Service in San Francisco has issued a

* Severe Thunderstorm Warning for...
  Marin County in northern California...

* Until 300 PM PST.

* At 215 PM PST, severe thunderstorms were located along a line from 
  6 miles southwest of Petaluma to near Point Reyes Station, moving 
  east at 25 mph.

  HAZARD...70 mph wind gusts.

  SOURCE...Radar indicated.

  IMPACT...Expect considerable tree damage. Damage is likely to
           mobile homes, roofs, and outbuildings.

* Locations impacted include...
  San Rafael, Novato, Mill Valley, San Anselmo, Larkspur, Corte 
  Madera, Tiburon, Fairfax, Sausalito, San Geronimo, Lucas 
  Valley-Marinwood, Stinson Beach, Kentfield, Black Point-Green 
  Point, Muir Beach, Tamalpais-Homestead, Point Reyes Station, 
  Tamalpais-Homestead Valley, Strawberry and Ross.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Anyone outdoors should move to shelter inside a well-built structure 
and stay away from windows. These storms are capable of producing 
widespread damaging winds.

Torrential rainfall is also occurring with these storms and may lead 
to flash flooding. Do not drive your vehicle through flooded 
roadways.

Report severe weather to your nearest law enforcement agency or the 
National Weather Service office in San Francisco CA.

&&

LAT...LON 3803 12290 3822 12276 3817 12257 3810 12249
      3806 12247 3802 12249 3798 12244 3796 12248
      3794 12247 3793 12249 3788 12242 3785 12241
      3784 12243 3786 12245 3785 12247 3782 12247
      3781 12256 3790 12268 3789 12274 3798 12282
TIME...MOT...LOC 2214Z 230DEG 21KT 3817 12270 3796 12278 3770 12292

THUNDERSTORM DAMAGE THREAT...CONSIDERABLE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...0.00 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...70 MPH

$$

.SYNOPSIS...
Issued at 1202 AM PST Tue Feb 4 2025

An atmospheric river will continue to bring heavy rain, urban and
river flooding, and strong winds to the Bay Area and Central
Coast through Tuesday. There is also an increasing chance for
thunderstorms in the afternoon. While less impactful in the
second half of the week, rain chances continue through Friday.

&&

.UPDATE...
Issued at 918 AM PST Tue Feb 4 2025

Will keep the morning update a little shorter than normal as
operations is rather active this morning a variety of impacts:
flooding, damaging winds, storm force over the coastal waters,
rock slides, and thunderstorm potential this morning.

Latest surface analysis still shows the lingering stationary
boundary to the north, which extends to the SW and connects to a
deepening low pressure. As a result, a moisture rich plume
continues to stream across the Bay Area and Central Coast. KMUX
radar imagery shows widespread rain showers across the region.
Given the rainfall rates, already primed streams/creeks, and
urban runoff issues, flood advisories and flood warnings have been
issued.

The main focus of the near term forecast will be this afternoon.
The aforementioned low pressure will ride along the boundary to
the northeast. As this happens, an upstream jet max will move
eastward an increase to 150kt+. This max will be parked right over
the coastal waters with the surface low on the northern fringe.
Expect rapid increase in surface winds (some CAMS are now showing
80-90mph over the waters) and low level shear. As noted below,
it`s a low CAPE high shear scenario, which may lead to spinning
cells.

If there`s a period over the next 24 hours to be weather aware it
will be this afternoon. A re-newed push of rain, winds, and
possible thunderstorms.

MM

&&

.SHORT TERM...
(Today and tonight)
Issued at 1202 AM PST Tue Feb 4 2025

Synoptic Overview: A stationary boundary is draped across
northern California with low pressure off the coast. The Bay Area
is now in the cross-hairs of the atmospheric river. Over the next
24 hours, a 150+ kt jet max will move over the Bay Area/Central
Coast, causing divergence aloft, and cyclogenesis along the
boundary (Patterson`s Law). This will encourage an active cold
front to move through the region, lifting the warm, moist air mass
on Tuesday.

Rain: Prefrontal rain has been ongoing for several hours in the North
Bay, and has recently spread south across the Bay Area to the
Santa Cruz Mountains. Observed rainfall rates have been as high
as 0.64"/hr in San Francisco. This pre-frontal rain will continue
through the early morning. While mostly stratiform in the warm
airmass, there are some embedded showers bringing stronger down
pours. As the cold front moves through during the day Tuesday, the
rain rates will increase significantly as the cold, dense air
mass lifts the warm, moist air mass, wringing out the atmospheric
sponge. This effect will be enhanced along the windward side of
the coastal mountains.

Flooding: Several area flood advisories are in effect for urban
and small stream flooding across the North Bay, San Francisco and
the northern East Bay. The Green Valley Creek at Martinelli Road
has reached moderate flood stage and continues to rise, verifying
a flood warning in central Sonoma county. In a significant change
to the forecast, The Russian River at Guerneville is now expected
to reach minor flood stage Wednesday morning as more water than
expected has entered the upper Russian. In additions to streams
and rivers, several reports have been coming in of urban and
roadway flooding as heavier bands of rain push through. Expect
this to continue through the day.

Wind: The strong jet max and heavy rain will allow good momentum
transfer down to the surface, especially in gusts. The winds look
strongest in the Monterey Bay region and higher elevations
through the afternoon, although strong winds will be pretty
widespread after the sun comes up and as the front moves through.

Thunderstorms: This is the most meteorologically interesting
aspect of the short forecast. Will we get thunderstorms tomorrow?
Is there a chance these storms will rotate? Overall the
approaching air mass is not that cold. Originating from a maritime
environment, the 1000-500 mb thickness is only around 546 dam
behind the front. That means the instability will be a limiting
factor. Even with good timing of fropa around the maximum day-
time surface heating, the most unstable CAPE values are only
expected to reach around 50 J/kg. On the other side of the
ingredient list, the low level shear looks quite impressive. 0-1
km shear of 35+ kts with nice, curved hodographs and low LCL
heights suggest that if thunderstorms are able to tap into the
moderate instability, they could start rotating. The best window
for this is from 3 PM to 6 PM somewhere south of San Jose where
The HRRR shows the 0-1 km helicity spiking above 300 as the front
moves through. The marine environment will also favor some
rumbles of thunder with a small chance of water spouts.

&&

.LONG TERM...
(Wednesday through Monday)
Issued at 1202 AM PST Tue Feb 4 2025

We will get a break on Wednesday, but it won`t last long. A ridge
will briefly build allowing the new air mass to dry out a bit.
Another moisture plume and surface low pressure will arrive at
the coast and push inland on Thursday. This system looks a good
deal weaker than the current atmospheric river, with less rain and
lighter winds. Outside of the coastal mountains, most areas will
receive a more manageable amount of rain between 1/2" to 1". This
system will dive a little farther south however, bringing a
reinforcing shot of cold air. The 1000-500 mb thickness will drop
below 540 dam. As things dry out Friday and the clouds start to
clear over the weekend, overnight lows will drop back into the
30s. Some places will be more than 10 degrees colder on Saturday
morning, compared to Friday. Once the dry, cold weather sets in
the pattern will stabilize with more of the same through early
next week.

&&

SF Bay Area Skywarn weather spotters should self-activate today through 9pm PST.

• Flood Watch until February 5, 04:00 AM PST
• Wind Advisory in effect from February 4, 07:00 AM PST until February 4, 11:00 PM PST

Flood Watch in effect from February 3, 04:00 PM PST until February 5, 04:00 AM PST

From MTR AFD:

.SHORT TERM...
Issued at 1247 PM PST Mon Feb 3 2025
(This evening through Tuesday)

Key Points:
* Flood Advisory continues for portions of Sonoma County
* Flood Watch goes into effect 4 PM Monday through 4 AM Wednesday
  across the Bay Area and Central Coast
* Mon PM-Tue AR ontrack late Monday with moderate to at times
  heavy rain
* Mon PM-Tue will also bring gusty winds and thunderstorms
* Thur-Fri AR is expected to be weaker and aimed farther south
* Cold morning temperatures return mid-week but temperatures
  will drop more significantly over the weekend

Being upfront - lengthy AFD as lots of interesting and impactful
weather headed our way.

Near term - KMUX is showing an increase in shower activity off the
North Bay coast and northern Sonoma county. The increase is a
result of better forcing tied to a low pressure off the coast
moving eastward. The approaching low has also allowed for gusty
southerly winds across the region this afternoon. This is only a
preview of things to come over the next 36 hrs.

This evening through Tuesday:
The broader meteorological picture still shows a quasi-stationary
boundary to the north. This front extends west to a surface low
near a triple point 37N 128W and farther west of that is an
occluded low pressure 32N 140W also tracking eastward. Aloft is a
little more interesting as split flow with a high amplified polar
jet (digging SW thru BC and then recurving into NorCal) is showing
some phasing with the sub-tropical jet arriving from the SW. These
upper level jet features/phasing will aid in overall large scale
ascent. On top of this features, PWAT satellite imagery shows a
Pineapple Express (AR) plume just SE of Hawaii extending north
along the surface boundaries to NorCal.

So what does this mean and how will it impact the Bay Area and
Central Coast? The upstream "triple point" low will move east and
help to lift the stationary boundary slightly, but also allow for
a more defined surface front. This surface enhancement will be
aided by an upper level jet exit region over NorCal this evening.
Large scale forcing, orographic enhanced, and PWAT transport will
lead to heavier rain spreading over the North Bay this evening.
Could see some decent rainfall rates of 0.5" per hr. Rainfall
coverage and intensity will gradually move S and E over the rest
of the forecast area by Tuesday morning. Not only will rain
increase this evening through early Tuesday, but the winds will
too. The winds will increase rapidly over the northern coastal
waters this evening and then spread to the coastal areas Monterey
Bay northward. A Wind Adv was issued to account for this increase
in winds.

Early Tuesday will feature a brief "lull" in activity as the
"triple point low" fades with an exiting jet region aloft. The
lull will be short lived as even better jet dynamics aloft take
aim at the Bay Area and Central Coast Tuesday mid morning through
Tuesday evening. Expect another rapid increase in winds and precip
on Tuesday as a cold front pushes through the region. This will
bring the most widespread and intense rainfall.

Of particular concern is between 18 and 21 UTC Tuesday, flow
through the column increases. In fact, examining the wind field at
300mb reveals a phased or coupled jet type pattern with a wind
maxima approaching the CA/OR coastline with a broader field of
+120 knot mid level flow. In response, the lowest 1 km wind field
responds and 925mb flow ramping up to around 50 knots. This is
particularly true along and south of the trough/cold frontal
boundary for regions along the Central Coast and Big Sur
Coastline. While instability values will be on the lower end of
the spectrum with under 50 J/kg. Forecast hodographs indicate a
large amount of low level curvature with 0-1 km shear in excess of
30 knots. These types of high shear, low CAPE regimes do support
both the transfer of damaging 55+ mph winds aloft down to the
surface and in some instances brief tornadoes. We`ll continue to
monitor trends in high-resolution output, but as it stands right
now, the favored region for enhanced winds of 55+ mph and a
slightly higher tornado risk will be along the San Francisco
Peninsula Coast (Pacific Ocean side) down to the Big Sur Coastline
late Tuesday morning and through the evening hours. That being
said, have included thunderstorms to the forecast for Tuesday
with specific wording highlighting gusty convective winds.

Heavy rain will transition late Tuesday to more shower activity
from N to S behind the departing cold front. Rainfall amounts
tonight through Tuesday night will 4-6" North Bay and coastal mts
(jackpot up to 9" above Big Sur), 2-4" elsewhere, with lesser
amounts 0.75 to 1.5" Santa Clara Valley/Interior Central Coast.

It goes without saying, but these rounds of intense rainfall will
lead to flooding concerns, especially in areas where rain fell
over the weekend. Do expect Flood ADvisories to be issues for
urban and small stream flooding concerns. If you encounter
a flooded roadway or road closure barricades remember - turn around,
don`t drown!

&&

.LONG TERM...
Issued at 240 PM PST Mon Feb 3 2025
(Tuesday night through next Sunday)

Wednesday can be described as another lull in overall activity as
one storm/moisture plume exits and another approaches from the
west.

Thursday and Friday...a surface low will approach the Central
Coast. Unlike the Tuesday AR this system will have less support
aloft and track a little farther south. Additionally, the moisture
tap is less with IVT/IWV values solidly in the Weak AR realm.
Thankfully, this low also appears to be a fast mover with highest
rainfall totals North Bay and Coastal Mts around 1" with
0.25-0.75" elsewhere. Given the more southern track this system
will be cold with lowering snow levels. Snow level will lower N to
S, but by the time the lowest snow levels arrive the precip may be
tapering off Thursday into Friday. Regardless, some wet snow will
be possible over the higher peaks Thursday into Friday. Not
expecting much in the way of accumulation.

Speaking of colder, the precip threat will quickly transition to a
temperature threat next weekend. Cold advection aloft behind the
departing low combined with clearing skies will lead to some
chilly overnight lows. Both Sat/Sun mornings will feature temps
in the 30s (even toward the coast) with far interior in the 20s.
Will likely need a mix of frost/freeze products.

&&

Flood Watch in effect from February 3, 04:00 PM PST until February 5, 04:00 AM PST

Moderate to heavy rain now expected to cover Bay Area by about 10am Tuesday.

From MTR AFD:

.SHORT TERM...
(Today and tonight)
Issued at 304 AM PST Mon Feb 3 2025

Key Points:
* Flood Advisory continues for portions of Sonoma County into Monday
* Flood Watch goes into effect 4 PM Monday through 4 AM Wednesday
  across the Bay Area and Central Coast
* Second AR arrives late Monday bringing moderate to at times heavy
  rain
* Third AR arrives Thursday-Friday but is expected to be weaker and
  aimed farther south
* Cold morning temperatures return mid-week but temperatures
  will drop more significantly over the weekend

Light showers continue to the north of our CWA but are expected to
shift southwards again as a second, stronger, AR arrives later
today. Forecast IVT values are in excess of 600 to 700 kg/ms which
is supportive of a more moderate intensity AR arriving mid to late
Monday and continuing into Tuesday. The first round of moderate to
heavy rain will take place later in the day on Monday and a second
round of heavier rain will take place on Tuesday. While the bulk of
the moisture is still located to our north, there will be enough
lingering moisture for light showers across the region Monday
morning. By the late morning/early afternoon, showers will start to
pick up in intensity across the North Bay as troughing deepens over
the Pacific and a shortwave approaches the West Coast. This
shortwave, in combination with the sub-tropical jet lifting
northward, will push the main moisture plume southwards with shower
activity subsequently increasing throughout the day across the Bay
Area and Central Coast. At the same time, a stationary cold front
over northern CA will gradually give way to a more progressive cold
front as a surface low associated with this shortwave moves inland.
The initial rain (on Monday) will primarily be concentrated over the
North Bay through the late afternoon before we start to see more
moderate intensity rain shift south of the Bay Bridge over the
evening hours. Rainfall totals - for Monday - will be highest across
the North Bay Mountains which will see between 1.5"-2". Elsewhere,
initial rain totals of up to an 1" are possible on Monday with the
bulk of the rain from this AR to fall late Monday into Tuesday. As
this occurs, we will see a southwards shift in where the highest
rainfall totals are located with an emphasis on the Santa Cruz
Mountains and Santa Lucia Range (see the long term discussion for
more information). Gusty winds ramp up along the coast and across
elevated terrain Monday into Tuesday. While winds generally stay
below Wind Advisory criteria, coastal areas may flirt with Wind
Advisory criteria Monday afternoon/evening around the time of
frontal passage. For now, continuing to hold off on a Wind Advisory
due to the short duration and more isolated nature of higher gusts
but will continue to monitor and update if things change.

The WPC has issued a day one (Monday) slight risk (15%) of excessive
rainfall for the North Bay and a marginal risk (5%) for portions of
the Bay Area and Central Coast. A Flood Watch will go into effect at
4 PM PST on Monday for the Bay Area and Central Coast as rain starts
to ramp up in intensity and becomes more widespread across the
region. As has been talked about for the past few days, rainfall
across the North Bay and coastal areas has acted to saturate soils
and has essentially "primed" them for flooding to occur. For areas
that have not received as much rain, moderate to heavy rain is
expected to saturate soils fairly quickly Monday/Tuesday with
increased potential for urban nuisance flooding as heavier rain
rates occur. While the most recent CNRFC forecasts continue to limit
mainstream river flooding to the North Bay, smaller creeks and
streams across the rest of the Bay Area and Central Coast may see
sharp rises as the bulk of the rain passes through. If you encounter
a flooded roadway or road closure barricades remember - turn around,
don`t drown!

&&

.LONG TERM...
(Tuesday through Sunday)
Issued at 304 AM PST Mon Feb 3 2025

Heading into Tuesday, heavier showers will spread into the rest of
the Bay Area and Central Coast overnight with the highest
accumulations anticipated in the Santa Cruz Mountains and Santa
Lucia Range. Rain may briefly lighten mid to late morning but
widespread heavy rain will return Tuesday afternoon as a second
pulse of moisture (higher IVT values in exceedance of 700 kg/ms)
arrives. This second pulse will be associated with with the greatest
flood risk as any areas not previously saturated by the Friday to
Sunday rains will be at least partially saturated from the Monday to
early Tuesday morning rains. Moderate to heavy rains will then
persist through the evening hours before rains decrease in intensity
overnight Tuesday into Wednesday. When all is said and done from
Monday to Tuesday, the North Bay will (in total) see an additional
2"-4", an additional 1"-3" south of the Bay Bridge, 3"-5" in the
Santa Cruz Mountains, 1"-2" across the Central Coast, and 5"-8"+ in
the Santa Lucia Range. Given that the moisture plume is oriented
almost perpendicular to the coastline, areas where orographic uplift
is favored may see locally higher totals than previously mentioned.
An additional factor is that over the last few grid updates the
forecasted QPF totals have continued to increase for this event with
particular emphasis on the southern portions of our CWA (Santa Cruz,
Monterey, and San Benito counties). As such, it is important to stay
up to date on the most recent forecast and be aware that there is
elevated potential for flooding to occur. The WPC has issued a
widespread day two (Tuesday) slight risk (15%) of excessive rainfall
exceeding flash flood guidance across the Bay Area and coastal
Central Coast and a marginal risk (5%) of exceeding flash flood
guidance across interior Monterey/San Benito Counties. Gusty winds
will continue through the day on Tuesday before weakening Tuesday
night into Wednesday. Winds continue to look below Wind Advisory
criteria on Tuesday but we will continue to monitor in case frontal
passage slows down and the time period of stronger winds becomes
more prolonged.

Wednesday will be the lull between our Monday-Tuesday AR and our
Thursday-Friday AR. Lingering moisture may be enough to support
scattered, light showers but any totals from this will generally be
below a tenth of an inch. Notably, morning temperatures will begin
to drop Wednesday after cold frontal passage occurs Monday/Tuesday.
This may necessitate the issuance of frost/freeze products for
portions of the Bay Area and Central Coast.

Thursday to Friday will see a third, albeit weaker, AR impacting our
CWA with additional totals between 1"-2" likely across the region.
This system will be spurred by the arrival of another upper level
shortwave and a surface low pressure system with IVT guidance
showing a subtropical moisture tap. The main thing to note about
this system is that, so far, it looks fairly progressive and has
started to trend more southwards (Central Coast into Southern CA) on
recent model runs. This may result in additional fluctuations in
forecasted QPF amounts Thursday and Friday as we get closer to this
AR. Another cold front is expected to pass through the region on
Friday bringing with it locally gusty winds and a more significant
drop in morning temperatures on Saturday/Sunday. Current guidance
suggests temperatures may drop into the 30s to upper 20s. The
combination of prolonged wet conditions, gusty winds, and cooler
temperatures will create hazardous conditions for anyone without
access to adequate heating or shelter. The issuance of additional
Frost and Freeze products are likely Saturday and Sunday.

&&

The Mon/Tues storm forecast for the Greater Bay Area remains on track, with a slight shift to a later onset of heavy rain and gusty winds to later Mon night and lasting through Tuesday.

Keep track of current MTR-issued alerts: https://www.weather.gov/mtr/

This graphic shows the 6-hour precip forecast with increased rain intensity moving into the Greater Bay Area by approx 10pm Mon night.

From MTR AFD:

.LONG TERM...
(Monday through Saturday)
Issued at 248 AM PST Sun Feb 2 2025

Light showers continue Sunday into Monday with the next round of
higher intensity rain returning late Monday morning/Monday
afternoon. Taking a look at the synoptic pattern, an upper level
trough off of the PNW and an upper level ridge over southern CA have
in part kept our moisture plume tighter and pushed farther north
this weekend. By Monday, the upper level trough will deepen over the
PNW, pushing farther into northern CA, and ridging over southern CA
will start to shift eastward. This will allow for the moisture plume
to widen and shift southwards again late Monday morning/Monday
afternoon with precipitable water values generally increasing to
greater than 1" across the region. At the same time, the stationary
front over the North Bay will give way to a more progressive cold
front that will move through the Bay Area Monday into Tuesday. Rain
will start to pick up in intensity by mid to late Monday morning
with the initial heaviest rain located in the North Bay. High
resolution models are starting to show precipitation lingering over
the Bay Area (south of the North Bay) and Santa Cruz Mountains
overnight Monday through Tuesday morning. Totals have trended
upwards Monday into Tuesday with an additional 3"-4" possible across
the North Bay, 2"-3" across the rest of the Bay Area, and 1"-3"
across the Central Coast. Locally higher totals (4"+) are possible
in areas where upsloping is favored (North Bay and coastal
mountains). A slight chance (<10%) of thunderstorms continues to be
monitored for Tuesday morning but the probability has been trending
downwards recently.

Wet weather will then continue Wednesday through the end of the week
as troughing persists over the West Coast. Late week rain totals
will be lower, however, with most areas seeing less than 1" of
additional rain. The exception, again, will be where upsloping is
favored within the coastal mountains where totals will be between 1"-
2". This second system will be colder with morning lows expected to
drop into the mid 30s to low 40s across the region. The combination
of damp weather and cooler temperatures may create conditions that
are particularly hazardous for people without access to adequate heat
or shelter.

It is worth noting that the WPC maintains a slight to marginal risk
of excessive rainfall for the Bay Area and portions of the Central
Coast through Tuesday and again on Thursday. Flooding concerns will
remain elevated through the week as our initial rainfall from Friday
to Saturday have caused soils to saturate. This will lead to
increased surface runoff and is likely to lead to additional flood
related products as we move through our next two rounds of wet
weather. In addition, gusty winds are likely to persist for coastal
areas and elevated terrain Monday through Wednesday with the
strongest gusts likely to develop ahead of/around the time of cold
frontal passage Monday into Tuesday. This may result in a few trees
being knocked over and increased potential for power outages to
occur. Make sure to have multiple ways to receive warnings and stay
up to date on the forecast as we move through the upcoming week.