textproduct: San Diego

SYNOPSIS

Cooler weather persists through the weekend, with a deeper, more persistent marine layer and night and morning coastal low clouds extending well inland and onto the coastal slopes of the mountains. Southwest to west winds for the mountains and deserts will gust to 40 to 50 mph through Sunday, with isolated gusts to 65 mph. Gradually warmer, dry weather with generally weak winds will follow Monday through Thursday, followed by a slight cooldown from Thursday into Friday.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES...

Today through tomorrow night...

Currently, GOES night fog 10.3 reveals the formation of the marine layer taking shape in vicinity of San Clemente with a weak coastal eddy becoming established over the inner waters of the SoCal bight. This will help to allow the marine layer to thicken up a little bit more through the early hours, and there could even be a few areas of drizzle as a result, especially along some of the coastal slopes and inland foothills.

An "inside slider" type of major shortwave trough is continuing to deepen and propagate over the desert southwest this weekend, which is resulting in rather strong and gusty over the higher terrain out of the west to southwest, and especially through the mountain canyons, where winds will be sustained up around 40 to 50 mph by later this afternoon for wind-proned areas. There could also be some isolated gusts approaching 65 to 70 mph for the windiest areas, namely within the gaps and along desert slopes across the Apple and Lucerne Valleys. There could be some areas of blowing dust, and especially within the Coachella Valley. For the high deserts, as min RH values drop into the low teens by later this afternoon with the strong and gusty winds, conditions will be favorable for fire growth and spread, although fuels are not yet critical for these areas and recoveries overnight will be respectable. Onshore flow will also continue to be more enhanced, leading to a more persistent marine layer, which will likely remain rather prevalent for the coastal areas for today, along with cooler temperatures stretching inland. Highs will be as much as 10 degrees below average for some locations within the IE and inland areas. Given the track of this system, it should remain dry, with only perhaps a few areas of drizzle will be possible against the coastal slopes during the early morning hours tomorrow, otherwise just cooler and more breezy throughout for today, followed by weakening winds and slightly warmer temperatures for tomorrow.

Tuesday through Saturday...

After passage of the trough, high pressure is going to build back in behind it going into Tuesday, with diminishing winds switching to a weak offshore flow aloft returning through the middle of the week. This will result in gradual warming through Wednesday before the longwave pattern becomes more zonal with only weak ridging aloft going into the latter half of the week. This will give way to the appearance of the more common "May Grey" diurnal pattern becoming more predominant by later in the work week, with better coverage along the coastal areas throughout the day, and temperatures slowly cooling off from Thursday into Friday. Temperatures will then level off by Saturday, and be right around the seasonal average for this time of year for most locations. Dry conditions look to also persist going into the following weekend as ensembles reflect PWAT anomalies being nearly neutral, or on the drier side through then.

AVIATION

171000Z...Coast/Valleys...Multiple SCT-OVC decks with one layer closer to 2000-2500ft MSL and another 3000-4000ft MSL. More widespread MVFR CIGs this morning after 12z, filling in along the coastline. Localized VIS reductions to 3-6SM, primarily where clouds intersect terrain and in inland valleys. Clouds should begin to clear out by 18-20z, although some may linger in inland valleys through the afternoon. Low clouds based > 2500ft MSL will move inland again as early as 23z, and will fill in sufficiently to much of the Inland Empire and San Diego County by 06z. Bases may rise a bit after 12z Mon.

Mountains/Deserts...Gusty north to northwest winds this morning, intensifying after 18z with widespread 30-40 knot surface gusts expected in the deserts, locally up to 55-60 knots in vulnerable mountain passes such as the Banning Pass. MOD up/downdrafts and local LLWS in lee of mountains as well as localized VIS reductions to 4-6SM expected, especially during periods of strong gusts. Winds weaken after 06z Mon, but will remain elevated in wind prone spots.

MARINE

West-northwest gusts up to 20 knots remain possible for the outer coastal waters near San Clemente Island through 7AM this morning. In addition to the winds, seas of 7-10 feet with a 9-12 second period will generate choppy seas. Winds and seas will slowly diminish through the remainder of the day.

SKYWARN

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

SGX WATCHES/WARNINGS/ADVISORIES

CA...Beach Hazards Statement through Monday morning for Orange County Coastal Areas-San Diego County Coastal Areas.

Wind Advisory until 11 PM PDT this evening for Apple and Lucerne Valleys-Riverside County Mountains-San Bernardino County Mountains-San Diego County Deserts-San Diego County Mountains-San Gorgonio Pass near Banning.

PZ...Small Craft Advisory until 7 AM PDT this morning for Waters from San Mateo Point to the Mexican Border Extending 10 to 60 nm out including San Clemente Island.