Boulevard, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

642
FXUS66 KSGX 042158
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
158 PM PST Sat Jan 4 2025

.SYNOPSIS...
Weak Santa Ana winds expected this afternoon through Monday morning.
A moderate to locally strong Santa Ana wind event is expected late
Tuesday afternoon through Wednesday. Additional rounds of Santa Ana
winds are possible on Friday. Warmer conditions are expected for
Sunday. A cooling trend is expected for Monday and Tuesday, with the
potential for gradually warming conditions Wednesday into the end of
the week.

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...

An upper level low pressure system will continue to move east
through the Great Basin today, with weak ridging over the West Coast
bu Sunday. A weak surface high will set up over the Great Basin this
evening which will create an offshore pressure gradient for Southern
California. Weak north to northeast Santa Ana winds are expected to
develop on Sunday. Peak gusts of 30 to 35 mph are expected, but a
few gusts to 40 mph may occur below the Cajon Pass and through the
wind prone canyons in the Santa Ana mountains. Highs on Sunday will
warm to around 5 to 10 degrees above normal for inland areas due to
the weak ridging aloft and offshore flow at the surface. Weak
onshore flow will return by early Monday afternoon ahead of a weak
short wave trough which will dig into the Great Basin Tuesday. This
will bring some cooling for the coastal areas, but a few degrees of
warming or no change in high temperatures for inland areas.

Uncertainty remains regarding the evolution of the short wave as it
progresses south or southeasterly through midweek. Subtle
differences in the track of this wave will have large implications
on the wind speeds and to a lesser but still important extent the
moisture and precipitation potential. The shortwave is expected to
dig south into Southern California (55 percent of ensemble
solutions) or further east along the California/Arizona border (45
percent of solutions) Tuesday before digging south of the border and
potentially evolving into a cut off low Wednesday. A few members
of both the GEFS and ECMWF continue to show measurable
precipitation, mainly in the mountains for the evening into early
Wednesday. NBM chances for precipitation have increased in the
mountains from previous forecast for Tuesday night. For Wednesday,
about 60 percent of ensemble solutions show the low closing off,
with differences in the placement of that closed low somewhere
near the border of California and Mexico. 20 percent of ensemble
solutions keep the low directly to our south with 60 percent of
the solutions showing the low further east closer to Arizona.
While there is a range of solutions when it comes to the placement
of the low, there is high confidence in moderate to locally
strong Santa Ana winds developing Tuesday night into Wednesday
morning for the valleys and mountains. There is lesser confidence
in impactful winds reaching coastal areas. The main question in
determining how severe our fire weather threat will be surrounds
the timing of when the relative humidity values will drop and if
that will coincide with the stronger winds. More information on
that can be found in the Fire Weather discussion below.

As we head into Thursday, there is good agreement in ensemble
members that winds will weaken as offshore gradients begin to relax
and the low more likely (80 percent chance) begins to shift
eastward. There is some indication that another uptick of winds will
occur Thursday night into Friday as a shortwave from western Canada
digs south into the Intermountain West. This would have bigger
implications for locations that are more prone to easterly winds.

As far as temperatures go, they will be near to slightly below
normal Tuesday and Wednesday with the low in our vicinity and cold
air advection from the north. Warmer weather will follow for
Thursday through Saturday, though the degree of warming will depend
on the position of the low.


&&

.AVIATION...
042100Z...Coasts/Valleys...Most locations have cleared of the low
stratus and FG, and high clouds with bases around 25,000ft MSL
prevail through Sunday. Generally VFR conditions expected overnight
with only a 10% chance of low clouds tonight into Sunday morning
along the coast, but localized areas of VIS reductions possible
after 02z Sunday down to 2-3SM. A 15-20% chance of VIS below 5SM for
KSAN between 05-14z Sunday.

Mountains/Deserts...VFR conditions with FEW-SCT clouds at/above
20,000ft MSL prevail through Sunday. Periods of gusty east/northeast
winds 20-30kts near mountain peaks and on coastal slopes possible
Sunday morning.

&&

.MARINE...
No hazardous marine conditions are expected through at least early
Tuesday. Offshore winds strengthen late Tuesday through Wednesday
and could lead to choppy seas and hazardous conditions.

&&

.FIRE WEATHER...

Weak offshore flow will develop this afternoon and continue through
Monday morning. For most locations wind gusts will remain 35 mph or
less with afternoon relative humidity of 12 to 17 percent. Below the
Cajon Pass and in the Santa Ana mountain foothills wind gusts to 40
mph possible Sunday morning. Onshore flow will return Monday
afternoon.

A push of breezy southwest to west winds are expected overnight
Monday into Tuesday. Wind will quickly turn northeasterly from north
to south late Tuesday afternoon. Moderate to locally strong Santa
Ana winds are expected Tuesday night into Wednesday morning. There
is a 70 percent chance of wind gusts 50 mph or greater below the
passes and canyons and adjacent foothills, and into portions of
the valleys overnight Tuesday into Wednesday morning. Wind prone
locations have the potential to see gusts exceed 75 mph during the
peak of the winds. Winds are expected to decrease through the day
Wednesday, with low confidence in how quickly the winds will
diminish. Most ensemble guidance currently indicates a drop off in
the winds is likely for Thursday.

Minimum Relative Humidity will likely remain above 20 percent on
Tuesday as moisture is drawn into the region as an upper level low
digs south. Humidity forecasts for Wednesday are generally in the
upper teens in the valleys and low to mid 20s in the mountains
resulting in near critical fire weather conditions. There is still
the potential for this to trend drier, resulting in critical
conditions for Wednesday. The chances of relative humidity falling
to less than 15 percent increases by Thursday afternoon.

Drier air is expected continue into Friday. There is a potential for
another uptick in winds on Friday, especially for areas prone to
easterly winds. Critical fire weather conditions are possible for
the mountains, foothills, and portions of the valleys Friday if the
winds increase again with the dry air in place.

&&

.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...High Wind Watch from Tuesday afternoon through late Wednesday
     night for Orange County Inland Areas-San Bernardino County
     Mountains-San Bernardino and Riverside County Valleys-The
     Inland Empire-Santa Ana Mountains and Foothills.

     High Wind Watch from Tuesday evening through late Wednesday
     night for Riverside County Mountains-San Diego County
     Mountains-San Diego County Valleys-San Gorgonio Pass Near
     Banning.

PZ...None.

&&

$$

PUBLIC/FIRE WEATHER...CO
AVIATION/MARINE...Zuber