College Heights, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

145
FXUS66 KSGX 301743
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
930 AM PST Mon Dec 30 2024

.SYNOPSIS...
Low clouds and fog will very slowly clear back to near the coast
today with sunny conditions inland and above normal temperatures in
the mountains and deserts. Weak Santa Ana winds will bring low
humidity and warmer weather west of the mountains Tuesday through
Thursday. Low clouds and fog will redevelop tonight but decrease
somewhat Wednesday and Thursday before returning late in the week.
More Santa Ana winds could occur early next week.

&&

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

Low clouds and locally dense fog made it well into the valleys last
night with only a few locations having cleared by 9 AM. The
foothills, mountains and deserts were sunny. There is a similar
marine inversion around 8-9 deg C, so that will combine with the low
sun angle to make the clearing of the stratus/fog be delayed, and
some coastal areas might not clear at all this afternoon. Northerly
winds were very local this morning with only a few gusts over 20 MPH.

High pressure will continue to our south with generally a zonal flow
pattern over California and a jet stream from west to east over
northern California ESE through Rockies. Surface high pressure was
building from southern Oregon to central Idaho, and this will spread
through the West the next few days, but with the high center staying
in Idaho/Wyoming. This will result in offshore MSLP gradients to San
Diego, but the long distance will keep the MSLP gradients moderate,
generally 6 MB or less from Las Vegas to San Diego. Winds at 850 MB
will be too light to bring much cold air advection, and winds at 700
MB will mostly be west-northwest, so mountain wave activity will be
limited with most of the winds coming through/below gaps, like the
Cajon Pass. Some gusts to 25-35 MPH will occur Tuesday and 20-30 MPH
Wednesday when the trend is more towards an easterly vs.
north/northeasterly wind. Warmer weather should occur west of the
mountains with some 80 degree highs by Thursday in the valleys.
The winds generally will not reach the coast, so some fog could
linger at the immediate coast even Wednesday and Thursday, and given
the pattern, it could be dense.

A trough of low pressure will move through the West Coast Friday-
Saturday, which like recent troughs will bring mostly dry weather to
SoCal. Less than 20% of the ensemble runs have any precipitation
over our forecast area, so will keep the forecast dry then. This
will be accompanied by cooler days and a brief resurgence of the
marine layer stratus/fog. With a large ridge likely building off the
coast early next week along with a surface high over the interior
west, we have around a 80 percent chance of more Santa Ana winds
developing then, but with no confidence yet on how strong the winds
will be. Humidity will almost certainly be quite low.

&&

.AVIATION...
301600Z...Coast/Valleys...Low stratus clouds present, bases around
800-1300ft MSL, across most of the coastal areas and western
valleys, including the northwestern Inland Empire. Visibilities
under these clouds are generally 2-4 SM, with locally lower VIS down
to 1/4SM where clouds intersect higher terrain. The stratus will be
late to clear again this morning, likely around 18-20z for San Diego
County, while Orange County could be closer to 19-21z. Clouds may
linger at the beaches beyond this period.

Low clouds look to fill back in and push ashore this evening around
02-04z Tuesday. Bases may initially be around 500-800ft MSL, but
should fall to 200-600ft by 09-12z. This could bring visibilities
down below 1SM to coastal areas. KSAN has a 35-45% chance of
visibilities below 1/2SM from 09-15z Tuesday morning.

Mountains/Deserts...Mostly clear skies and unrestricted VIS will
prevail through Tuesday.

&&

.MARINE...
Patchy fog over the waters possible through 11 AM, with visibility
dropping to near 2 NM at times. More dense fog possible tonight into
Tuesday morning, with visibility under 1 SM. Otherwise, no hazardous
marine conditions expected through Friday.

&&

.BEACHES...
Minor coastal flooding will possible in vulnerable areas including
beach parking lots during morning high tides over the next few days
with tides peaking Tuesday/Wednesday near 7 feet.


&&

.FIRE WEATHER...
Local north winds with gusts to 25 MPH will occur today, weakening
tonight in and just below the San Bernardino County foothills with
minimum relative humidity around 20-25 percent. Above around 5000
feet, some relative humidity will be below 10 percent but with
relatively little wind. Overall, the offshore flow looks rather weak
Tuesday and Wednesday with gusts 25-35 mph Tuesday mainly in the
Inland Empire and surrounding foothills and locally in the San
Diego County mountains and 20-30 mph Wednesday. Relative humidity
will drop to 15-20 percent Tuesday and 10-15 percent Wednesday
across the mountains, foothills, and Inland Empire. Fire
weather conditions will be elevated Tuesday and Wednesday, but not
critical. Low humidity will continue Thursday with local east wind
gusts 15-25 mph, but humidity will increase Friday through Sunday.
There is around a 70 percent chance of Santa Ana winds developing
early next week, and while low humidity is highly likely, the wind
speeds are still quite uncertain.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.

&&

$$

PUBLIC/FIRE WEATHER...Maxwell
AVIATION/MARINE/BEACHES...Zuber