Warmer and drier Sunday through Tuesday with periods of moderate gusty Santa Ana winds. A low pressure system from the southwest will likely bring a return of precipitation for Wednesday through next weekend, though exact timing and precipitation amounts are still uncertain.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Today through tomorrow,
Currently this morning, there are a few of the inland areas sheltered by wind which are experiencing some patchy fog, such as Ramona. This is generally very isolated in nature, although the visibilities have dropped down to a quarter of a mile, so take caution of this if commuting within these areas. Under high pressure conditions and clear skies, radiational cooling has allowed for temperatures to cool off quite substantially throughout the night, with some of the coastal areas falling into the 40s, and 30s within the inland valleys. This will give way to a notably warmer day as weak offshore and downsloping winds help to adiabatically warm up the lower elevations, with widespread upper 60s and low 70s for the coastal and inland areas. The higher elevations will still be a little on the chilly side, especially for the high deserts with the colder air advection blowing in from the north.
A well-pronounced ridge over the entire West Coast will continue to expand eastward, with an area of high pressure moving in over the Great Basin to establish marginal Santa Ana conditions to build in across the region. Gusty offshore winds out of the northeast, especially across the higher terrain, will begin to strengthen later tonight through tomorrow. These winds at this time look to remain below High Wind criteria for most of the wind-prone locations and marginal at best across the San Bernardino Mountains, however Wind Advisory criteria looks to be more likely, especially for the passes, with Cajon Pass in particular. For these locations, wind gusts may occasionally approach 60 mph, as well as other higher terrain prone to strong winds. Strongest wind gusts will peak later tonight and going into Monday morning, and then the stronger gusts will filter in further southward by later in the day, and then gradually weaken going into Tuesday. 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. The main concern with these winds and the recent rainfalls will be the possibility of trees being easily uprooted for the San Bernardino Mountains. There will be a lesser threat of this going into the mountains of Riverside and San Diego counties, since less rain was received across these areas.
Tuesday through Saturday,
These strong and gusty winds will continue into Tuesday and then begin to subside thereafter as the ridge begins to break down, and allows for an upper level low (which will become cut off well to the southwest of the region over the Pacific waters) to 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 return of 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 low ends up tracking. Some of the models are also showing a weak signal of an atmospheric river associated with this, which may help to nudge up rainfall amounts. The deterministic models are beginning to tighten up in terms of agreement with the progression of this U/L low as it moves up from the south and nears SoCal, which places the center of the low roughly around 500 miles west of San Diego over the E Pac waters from Wednesday night going into Thursday morning. The first initial wave with bands of precipitation should reach the CWA sometime during the afternoon on Wednesday, with the more persistent and heavier precip not moving in until later in the evening into Thursday morning. Models are still struggling thereafter with the track, with the ECMWF having the low center nearing Pt Conception, while the GFS still keeps the low centered further offshore, and the Canadian having it evolve into an open wave. This will continue to be evaluated in the upcoming days, but there is growing confidence that inclement weather will impact the region right around the turn of the new year. As the major shortwave trough acting as the kicker continues to propagate towards California, it will help to increase precip chances going into Saturday, and likely through next weekend.
280930z, VFR condition are expected through the TAF period with FEW- SCT high cirrus AOA 25,000ft and localized areas of ground FG with VIS below 1SM through sunrise, generally in the valleys. North- northeasterly offshore winds pick up after 12z, gradually strengthening this afternoon/evening. Wind gusts of 25-30kts expected for the coastal slopes of the mountains and mountain passes from 12-18z, spreading below mountain passes and into the inland valleys after 18z. While gusts may not surface at terminals like KONT or KSBD until late tonight or Monday morning, gusty northerly winds below Cajon pass could produce crosswinds on approach/takeoff within the Inland Empire Sunday afternoon. LLWS may be possible, especially late tonight, for Inland Empire airports. Gusts strengthen to 35-45 kts for the coastal mountain slopes and passes after 00z Monday with mod up/downdrafts expected. Strong offshore winds prevail into Monday evening.
No hazardous marine weather conditions expected through Friday.
Ca, High Wind Watch from this evening through Tuesday afternoon for San Bernardino County Mountains-San Bernardino and Riverside County Valleys-The Inland Empire-San Gorgonio Pass near Banning-Santa Ana Mountains and Foothills.
High Wind Watch from late tonight through Tuesday afternoon for San Diego County Mountains-San Diego County Valleys.
PZ, None.
