textproduct: San Diego

SYNOPSIS

Showers will continue to taper off throughout the day and give way to a drying pattern developing over the weekend and continuing into early next week, with periods of weak to moderate strength gusty Santa Ana winds for Sunday through Tuesday. Slight warming will accompany the offshore flow for Monday and Tuesday. A low pressure system from the southwest could bring a return of precipitation for Wednesday through Friday.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

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

Today through tomorrow...

The area of low pressure that has been providing the inclement weather for us since Christmas Eve is finally beginning to exit the region, with more intermittent showers continuing to dissipate through the morning as it does. Further clearing will continue throughout the day with all precip eventually coming to an end. Temperatures for today will still be on the chilly side, with highs generally in the upper 50s to low 60s for the coastal and inland areas, to the 30s and 40s for the mountains, 50s for the high deserts, and mid to upper 60s for the lower deserts. As high pressure continues to build in over the region with offshore winds becoming predominant going into Sunday, temperatures will gradually continue to warm, with highs on Sunday getting up into the mid to upper 60s for the coastal and inland areas. The offshore winds will also help to keep the marine layer confined over the SoCal bight, with only patchy areas of low clouds and fog being possible overnight for some of the wind-sheltered valleys. Under clear skies, temperatures overnight will also be on the colder side, with lows dropping into the 40s for most of the coastal areas, and 30s for the inland areas for tonight.

The positively-tilted major shortwave trough will deepen as it progresses eastward and allow for an upper level low to become cut off and positioned well to the southwest of the region, over the Pacific waters. This will ultimately influence our weather here going into the middle to end of next week, right around New Years Day, as it transitions back up towards California.

Monday through Friday...

As the well-pronounced ridge over the entire West Coast continues to expand eastward, the area of high pressure will move in over the Great Basin and allow for weak Santa Ana conditions to build in across the region early in the week, with gusty offshore winds out of the northeast, especially across the higher terrain. These winds at this time look to remain below Wind Advisory criteria, although this will continue to be monitored in the upcoming days. RH values will drop into the teens for a few locations on Monday afternoon, although given recent rainfalls with an abundance in antecedent soil moisture, fire weather conditions are not anticipated to be of any concern. These strong and gusty winds will continue into Tuesday and then begin to subside thereafter as the ridge begins to break down and the aforementioned upper level low will begin to propagate back up towards the northeast as a longwave trough upstream advancing towards the region absorbs the energy of this U/L low and brings it back towards SoCal. This will lead to increasing clouds and the chance of rain, along with the gradual warmup occurring earlier in the week switching back to a gradual cooldown going into the later half of the week. The moisture from this feature, in combination with the 500 mb shortwave trough moving in as the "kicker" may allow for some more decent rainfalls again, depending on how this sets up and where the U/L ends up tracking. That being said, there is still quite a bit of uncertainty at this time between the deterministic models with respect to how this will evolve and where exactly the U/L low will move, however, ensemble members reflect a general consensus which shows an increasing chance of precipitation for SoCal right around the turn of the new year.

AVIATION

270930Z...Clouds based 4000-7000ft MSL and -RA are moving southeast and have already cleared Orange and San Bernardino counties. Further clearing through 12z for San Diego and Riverside counties, with patchy ground FG and low level clouds with bases around 500-900ft MSL developing in the wake of the higher clouds and moisture. Highest chances for FG/low clouds being in the valleys, Inland Empire, and foothills. VIS down to 2-6SM in BR and HZ, locally down to 0SM, clearing by 18-20z. Elsewhere, VFR with some lingering 3000- 5000ft MSL clouds across San Diego County into tonight. Offshore winds pick up after 15z Sunday, with gusty winds up to 25-30kts for coastal slopes of the mountains and into the valleys. Higher gusts through mountain passes with mod up/downdrafts near mountain peaks. Strong winds prevail into Monday.

MARINE

Northwest winds gusting near 20 kts will gradually decrease this afternoon. Otherwise, no hazardous marine weather expected through Thursday.

BEACHES

Westerly swell (250-270 degrees) producing surf heights 5 to 8 feet this morning and a High Surf Advisory remains in effect. Surf will begin to subside this evening and into Sunday.

SKYWARN

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

SGX WATCHES/WARNINGS/ADVISORIES

CA...High Surf Advisory until 11 AM PST this morning for Orange County Coastal Areas-San Diego County Coastal Areas.

PZ...None.