Warmer weather through Saturday with low clouds and patchy fog closer to the coast each morning. Tropical mid and high level moisture brings more clouds and cooler temperature, along with a slight chance of light showers for our southeastern regions by Sunday and Monday. Weak high pressure moves into the area by next Tuesday, returning to warmer and drier.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
, UPDATED AVIATION/MARINE/BEACHES DISCUSSION,
Nighttime satellite shows patchy low clouds struggling to develop at the coast with some high clouds above streaming in from the weak subtropical jet. At the moment, there is nothing else remarkable on satellite over our region.
A few hundred miles southwest of the coast, two visible weather features give us important context into the weather pattern this weekend into early next week. The stratocumulus deck is moving southwestward, as it does with northeasterly flow circulating around the North Pacific surface high pressure. Meanwhile, high clouds are moving the opposite direction - carried by the southwest winds of the jet stream. The flow reveals a fairly stationary trough as the clouds flow through a stationary path. What cannot be seen on satellite is the cyclonic flow at 850 and 700mb off the Baja coast which is beginning to advect an elevated but deep and moist airmass above 850 mbs associated with Hurricane Polo and Hurricane Odalys. Pwat's will generally increase to 1-1.5" tonight into Sunday, blanketing the region in mid and upper level clouds through Monday afternoon until the upper level trough moves through and brings much drier air moves in and replaces the entire airmass.
Despite the moisture, rain chances remain rather low across the region. While the highest PWAT's will likely be Sunday, a noticeably drier layer between the surface and around 800 mbs will significantly limit how much rain falls over the lowlands, with the most likely outcomes ranging from virga overhead to some spotty light rain accumulations. Higher chances for rain and higher precip totals will occur over mountain terrain above the dry layer, though convection will likely be very limited from extensive cloud cover.
While the trough will help provide lift for showers in the deserts (and areas east) on Monday, models shows the troughs drier air moving in just ahead of the lift from the cyclonic vorticity over the rest of the region. The mountains and deserts will have the greatest chances for rain Sunday (15-25%) and Monday (15-35%). Chances stay around 10-25% both days elsewhere, generally higher moving south and east across Socal.
In terms of temperatures, highs will be around 5-10 degrees above average today as the ridge to the east maintains its presence for one more day. Highs in the mid-to-upper-70s in higher mountain communities and beaches, 80s for coastal areas and lower mountain areas, 90s for inland valleys and Inland Empire, and around 100-105 in the Coachella Valley. Highs Sunday drop several degrees inland due to the extensive cloud cover, then drop more significantly Monday, another 6-12 degrees regionwide, as the upper level trough moves through. Highs slowly rebound through the rest of the week back to average for late September as another ridge develops and expands off of the coast. As a result, coastal temperatures will be a wild card in the late week forecast, depending on where the thermal through sets up.
261130z, Coast/Valleys, A bit more of struggle for low clouds to fill in to the coastal TAF sites this morning with clouds based around 600-900 feet MSL with elevated coastal terrain 1-5SM in in BR/FG. Low clouds expected to scatter to the coast between 15-17Z. VFR conditions through late this afternoon with SCT-BKN clouds AOA 20k ft. Patchy low cloud coverage expected once again tonight into Sunday morning. Cigs may be more intermittent due to shield of high clouds overhead during this time period.
Mountains/Deserts, SCT-BKN clouds AOA 20 kft through the period.
Increasing confidence in northwest winds occasionally gusting over 20 knots in the outer waters Monday afternoon and evening. Otherwise, no hazardous marine conditions are expected through Wednesday.
Southwesterly swell (3-4 ft at 13 seconds from ~200 degrees) from Hurricane Odalys persists through this weekend, bringing surf of 3-5 feet with sets up to 6 feet, highest along south and southwest facing beaches. Tides are already observed over 6 feet and are expected to gradually increase into this weekend, therefore a Beach Hazard Statement is in effect through next Wednesday afternoon. Minor tidal overflow and minor coastal erosion are the primary impacts.
The swell from Hurricane Polo (3 ft at 14 seconds from ~170 degrees) increases on Monday. Given this direction, most of San Diego County beaches will be largely sheltered from this swell, but Orange County beaches (especially in north OC) should be impacted. Meanwhile, a northwesterly swell (3-4 ft at 7 seconds from ~290 degrees) arrives late Sunday and Monday. Between these two swells, surf of 3-5 feet with sets to 6 feet looks probable along south/southwest facing beaches with surf 2-4 feet along west-facing beaches through Tuesday. Tides peak Monday-Wednesday mornings near 7.0 ft. Higher tides and elevated surf will combine to generate a risk for minor to moderate coastal flooding during the late morning/early afternoon high tides, especially along south/southwest facing beaches.
Please note - listed tide predictions have been adjusted to reflect actual measured tide observations.
Ca, Beach Hazards Statement through Wednesday afternoon for Orange County Coastal Areas-San Diego County Coastal Areas.
PZ, None.
