Marine Weather and Tide Forecast for National City, CA

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

Sunny and dry this afternoon with temperatures in the coastal areas a few degrees warmer than at this time yesterday but a few degrees cooler in the inland valleys, mountains and deserts. Santa Ana conditions producing northeast winds gusting 25-40 mph in the favored locations. Winds will continue to weaken this afternoon and evening.

From previous discussion...
Sfc pressure gradients will remain offshore through Wednesday and humidity will remain low. The dry airmass and lack of cloud cover will enable efficient radiation cooling overnight so that low temps in the wind-sheltered valley locations will fall into the 30s for the next few days. Lows in the 20s can be expected in the High Desert and in the teens and in higher elevation mountain locations. Highs today for inland areas will be 5 to 10 degrees below average, with slightly above average temperatures expected near the coast. That trend will continue through mid-week before cooler conditions develop for later in the week and next weekend.

For Monday through Wednesday...Most ensemble solutions indicate the development of a closed upper low retrograding from WA/OR to a position about 850 miles southwest of San Diego by Tuesday night, forming a Rex Block with a high north of the low. Meanwhile, sfc high pressure in the Great Basin will maintain offshore pressure gradients and Santa Ana conditions for SoCal. See the Fire Weather section below for more information on the dry, windy conditions.

The majority of solutions show the closed low to the southwest beginning to move northeast over SoCal by late Thursday, becoming an open wave over AZ on Friday afternoon as it becomes absorbed in the mean westerly flow. Most ensemble solutions show slight chances for mostly light precipitation in SoCal on Sat and Sun.
Since most of the available moisture will likely be concentrated in the boundary layer, any precipitation will be light and restricted to the mountain slopes and areas west to the coast.
Numerical model guidance tends to struggle with resolving the evolution of closed low-latitude lows in this part of the world so there is significant spread in the model solutions and consequently much uncertainty in the forecast beyond Thursday.

AVIATION
122145Z...Mostly clear skies continue through Monday afternoon.
Gusty north to northeast winds of 20-30 kts remain possible this afternoon/evening for the mountains and potions of the Inland Empire. Winds gradually decrease this evening/overnight with gusts 20-25 kts more localized to the mountains. Winds ramp back up late Monday morning into Monday afternoon, spreading back into the Inland Empire and the Orange County coasts with gusts of 25-35 kts.

MARINE
Breezy offshore flow increases Monday afternoon, continuing through Wednesday, with gusts near 15 kts. Otherwise, no hazardous marine conditions are expected through Friday.

BEACHES
Astronomically high tides of 6-7 feet may produce minor tidal overflow at susceptible low-lying beach parking lots and boardwalks Monday morning.

FIRE WEATHER
Santa Ana conditions with northeast winds, gusting 25 to 40 mph in wind-prone areas, will weaken through this evening. Winds are strongest on the coastal slopes of the San Bernardino mountains into the Inland Empire and on the Santa Ana mountains into portions of inland Orange County. Breezy conditions persist into Sunday afternoon with northeast winds gusting around 25 to 40 mph and humidity falling back to 10 to 15 percent, maintaining areas of critical fire weather conditions. Winds gusts briefly fall below 35 mph Sunday evening.

Another round of Santa Ana winds is expected for Monday through Wednesday. Guidance continues to indicate a more easterly component to the winds, with elevated easterly winds reaching San Diego County mountains and adjacent valleys by Monday evening.
Winds are currently forecast to peak Tuesday and Wednesday, with gusts of 45 to 55 mph expected. Relative humidity will remain around 10 to 15 percent each afternoon inland with poor overnight recovery in the wind prone areas and thermal belts. Critical fire weather conditions are expected for all mountain locations, the Inland Empire, San Diego valleys, and Inland Orange County.

Offshore winds will weaken significantly on Thursday and sea breezes could develop Thursday afternoon, but humidities will see no significant increase until Friday. Onshore flow will return in earnest on Friday, bringing cooler weather and increased humidity. By the end of next week, there is a potential for a pattern change to take place, bringing a slight (15 to 35 percent) chance of light precipitation west of the mountains. Some model solutions indicate a return of dry offshore winds early next week but uncertainty is high at this time.

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



SGX WATCHES/WARNINGS/ADVISORIES
CA...Red Flag Warning until 6 PM PST Wednesday for Orange County Inland Areas-San Bernardino County Mountains-Including The Mountain Top And Front Country Ranger Districts Of The San Bernardino National Forest-San Bernardino and Riverside County Valleys -The Inland Empire-San Gorgonio Pass Near Banning-Santa Ana Mountains-Including The Trabuco Ranger District of the Cleveland National Forest.

Red Flag Warning from 4 PM Monday to 6 PM PST Wednesday for Riverside County Mountains-Including The San Jacinto Ranger District Of The San Bernardino National Forest-San Diego County Inland Valleys-San Diego County Mountains-Including The Palomar And Descanso Ranger Districts of the Cleveland National Forest.

PZ...None.