Chino Hills, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

205
FXUS66 KSGX 302046
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
100 PM PST Mon Dec 30 2024

.SYNOPSIS...
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, along with cooler weather 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...

Patchy low clouds continued along the parts of the San Diego County
coast and parts of Orange County, with sunny skies elsewhere.
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 locally 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 70 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...
302030Z...Coast/Valleys...Low clouds have generally moved offshore
with fog lifting/cleared in the valleys. Patchy low clouds with
bases near 1500ft MSL continue for a few coastal sites, but should
clear by 22z. This will be short lived as low clouds again push
onshore tonight, generally after 01-02z, spreading up to 10 miles
inland. Bases will be lower than this morning, around 500-800ft MSL,
with locally lower to 300ft MSL. Confidence is high for impacts at
coastal sites (above 50%) with lesser confidence in inland extent
being more than 10 miles. VIS down to 1-3SM for coastal sites, and
locally lower for where clouds intersect terrain. Confidence is
highest for IFR (>60%) to LIFR (35-40%) CIGs at KSAN after 07z,
continuing through 14z. The stratus will be late to clear again
Tuesday 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.

Mountains/Deserts...Mostly clear skies and unrestricted VIS will
prevail through Tuesday. East to northeast winds return Tuesday
afternoon with periods of gusts up to 20kts near the mountains
possible through Tuesday evening.

&&

.MARINE...
Dense fog possible tonight into Tuesday morning, with visibility
under 1 NM, especially in the nearshore waters, clearing/lifting by
11AM. 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...
Above around 5000 feet, relative humidity below 10 percent was
occuring in some locations 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