Ross, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

807
FXUS66 KMTR 090447
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
947 PM PDT Tue Apr 8 2025

...New AVIATION...

.SYNOPSIS...
Issued at 750 PM PDT Tue Apr 8 2025

Warm and dry conditions persist through the week with minor heat
impacts for those extremely sensitive to heat.

&&

.UPDATE...
Issued at 750 PM PDT Tue Apr 8 2025

The inherited short term forecast is in good shape with no
real changes needed. Mostly clear skies are anticipated across
the Bay Area and Central Coast tonight. Our 00Z evening weather
balloon from Oakland has revealed that the column is beginning to
dry as a more subsident airmass starts to build across the region.
The drier air should mean that pockets of fog are confined to
valleys and areas along the coast and the evening NWP appears to
capture this well. The fog could be dense in spots, largely across
river valleys and across coastal areas. While coverage is
expected to be less tonight compared to Tuesday morning, motorists
commuting early Wednesday morning should be cognizant of sudden
changes in visibility

Otherwise, our warming trend will be in full swing tomorrow with
"minor" heat risk expanding across the area. For more details, see
the discussion below.

&&

.SHORT TERM...
(This evening through Wednesday)
Issued at 111 PM PDT Tue Apr 8 2025

Longwave ridging begins to build today resulting in near normal
temperatures and minor HeatRisk. Let`s say that your favorite team
is playing a (re)match in San Jose this evening around sunset and
you are concerned about the heat. Fortunately, after the maximum
temperature is reached this afternoon and sun angle lowers,
conditions will cool off quickly. In fact, clear and calm conditions
will result in radiational cooling overnight.

NWS Minor HeatRisk:

- Heat of this type is tolerated by most; however there is a minor risk
  for extremely heat-sensitive groups to experience negative
  heat- related health effects.

- The risk is primarily for those who are extremely sensitive to heat,
  especially when outdoors without effective cooling and/or
  adequate hydration.

- Very common heat.

- For those at risk, actions that can be taken: increase
  hydration, reduce time spent outdoors or stay in the shade when
  the sun is strongest, and open windows at night and use fans to
  bring cooler air inside buildings.

&&

.LONG TERM...
(Wednesday night through next Monday)
Issued at 111 PM PDT Tue Apr 8 2025

Let`s take a deep dive into the maximum temperature forecast for
Wednesday and Thursday. The forecast may seem straightforward, but
it`s actually a lot more nuanced than one might think. For those of
you that don`t know, the National Weather Service (NWS) uses the
National Blend of Models (NBM) as a starting point for building the
forecast. There were multiple sites along the coast where the
deterministic forecast fell below the whisker (10th percentile) of
the box and whisker plot. Because of this, maximum temperatures for
Wednesday and Thursday for areas that would be impacted by a 500
foot marine layer are a 50/50 blend of NBM/NBM 50th percentile. The
marine layer will add even more complexity. As of now, HREF guidance
does not show high probabilities of low clouds returning tonight,
but if they do, expect them to primarily remain confined to the
coast. If low clouds do form and end up sticking around for a
prolonged amount of time, that`ll certainly impact maximum
temperatures. Think of a place like San Francisco. The maximum
temperature of 2025 (80 degrees) occurred on March 25th, but more
importantly for this scenario is that it occurred at 1:43 PM (before
onshore flow kicked in). So hopefully I have painted the picture in
your mind that if clouds linger in a coastal area for too long,
the surface will not be able to warm as much as it would have
without the clouds, thus a very boom or bust forecast at the
immediate coast. Nonetheless, Wednesday will have the warmest
conditions across the board thanks to the longwave ridge axis
being overhead. The gradual cooldown begins Thursday as heights
begin to ever so slightly fall as an upper-level shortwave trough
in the Pacific Northwest nudges the ridge to the east. A surface
low and its attendant weak, dry cold front will sweep through the
region on Friday bringing with it an increase in northerly winds.
Global ensemble cluster agreement begins to diverge Saturday,
particularly in the amplitude and location of the upper-level
shortwave trough. This lack in confidence gets compounded in the
following days as the progression of the longwave pattern gets
called into question. There`s a very real possibility that an
upper-level shortwave ridge will be undercut by an upper-level
shortwave trough right across our region. All in all no
widespread impacts aside from minor HeatRisk are expected through
the forecast period with no rain in sight.

&&

.AVIATION...
(06Z TAFS)
Issued at 946 PM PDT Tue Apr 8 2025

WHile the rest of the TAF sites stay VFR, HAF and STS will see CIGS
in the late night and early morning, with some fog as well at STS.
Winds become weak into the night with most sites becoming variable
due to more localized effects.  CIGs and fog erodes into the mid
morning on Wednesday, leading to widespread VFR. Moderate west winds
will be slow to build into Wednesday, arriving in the late morning
and afternoon. Winds reduce again that evening and into the night.
CIGs build along the coast into the early night, affecting HAF, and
look to slowly move inland early Thursday morning.

Vicinity of SFO...VFR lasts through early Thursday. winds have
reduced and look to stay moderate through much of the night. These
winds become light and variable for early Wednesday morning. Expect
west winds to build again into Wednesday afternoon before reducing
again into that night. IFR CIGs arrive into early Thursday morning
along with a slight increase in westerly winds.


SFO Bridge Approach...IFR CIGs build slightly later than SFO into
Thursday morning.

Monterey Bay Terminals...VFR through the TAF Period. Light winds
look to last through the night and into Wednesday afternoon. Low-
level cloud cover fills over the Monterey Bay itself in the late
night but fails to make it over the terminals. Expect cloud cover to
thin by the mid morning, with moderate westerly winds building that
afternoon. These winds last into the mid to late evening before
becoming light again.

&&

.MARINE...
(Tonight through next Monday)
Issued at 611 PM PDT Tue Apr 8 2025

Northerly flow will prevail over the coastal waters through the
week. Winds will be locally stronger Tuesday afternoon into
Wednesday south of Point Sur. Expect a gradual improvement of the
sea state as swell heights subside through midweek. A larger swell
will rebuild heading into the weekend.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 3 AM PDT Wednesday for Pt Pinos to Pt
     Piedras Blancas 0-10 nm.

&&

$$

SHORT TERM...Sarment
LONG TERM....Sarment
AVIATION...Murdock
MARINE...MM

Visit us at www.weather.gov/sanfrancisco

Follow us on Facebook, X, and YouTube at:
www.facebook.com/nwsbayarea
x.com/nwsbayarea
www.youtube.com/nwsbayarea