textproduct: San Diego

SYNOPSIS

Santa Ana winds expected today through Saturday, with the strongest and most widespread on Friday. Additionally, moderate to major HeatRisk is expected for coastal areas. Cooler conditions will spread inland Sunday, with greater cooling and chance of showers next Tuesday and Wednesday.

..UPDATED AVIATION DISCUSSION

Today through tomorrow night...

As an upper level low that has been cut off east of the region establishes itself to the southwest of San Diego, with a high positioned to the north over northwestern Nevada in a rex blocking pattern, the pressure gradient between the two are going to allow for offshore winds to strengthen, initally out of the north to northeasterly direction today, and then becoming more easterly tomorrow. These winds are expected to peak tomorrow, with gusts at around 35 to 55 mph for the inland valleys, and stronger gusts along the slopes, with local gusts approaching 70 mph within some of the higher terrain passes and canyons. As the low taps into some of the remnant tropical moisture from Simon, it will provide a slight increase in humidity tomorrow, and there will be slight chance of a shower or two developing over the mountains during the afternoon hours. RH values will diminish to 15-25 percent by later this afternoon, but then gradually increase to 20 to 30 percent minimum values from Friday, with the influx of moisture. (see fire weather section below). Temperatures will be warmest for the coastal locations, due to the offshore flow. This will also help to impede the marine layer from forming overnight. Highs will be the warmest tomorrow, and for the coastal regions, ranging from upper 80s to low 90s, hence the reason for the Heat Advisory.

This weekend through next Wednesday...

Santa Ana conditions will persist through Saturday, and then these offshore winds will begin to weaken. Temperatures will gradually cool throughout the weekend, and onshore flow will eventually return going into Sunday, whcih may bring about the onset of some dense fog for portions of the coastal areas during the early morning hours. There will also be an approaching major shortwave trough towards the middle part of next week, which will bring chances of precipitation back into the picture by late Tuesday into Wednesday, along with the return of much cooler temperatures.

FIRE WEATHER

Elevated fire weather conditions with near critical conditions in locations with abundant dry fuels where topography and wind direction are well aligned for today through Saturday.

Northeast to east Santa Ana winds are expected to increase later today and continue through Saturday, with the strongest and most widespread winds on Friday. Winds will be mostly out of the north and northeast today, becoming more northeast to east by Friday, and easterly on Saturday. Gusts for the valleys will mainly be 35 to 55 mph, with the strongest winds below passes and near mountain foothills. For the coastal slopes and through passes, local gusts have the potential to exceed 65 mph. Lowest daytime relative humidity for the valleys and inland coastal areas will fall to 15 to 25 percent by later this afternoon, then recover to 20 to 30 percent for Friday and Saturday. Winds will weaken from Friday's peak on Saturday but remain elevated. Much weaker offshore winds expected Sunday, with the pressure gradient returning to onshore by Monday. There will be a slight chance of a shower or two developing over the mountains and adjacent deserts during the afternoon on Friday, although very little probability of there being any significant wetting rain.

AVIATION

151130Z...SKC and VFR today and tonight. Areas of northeast winds in mountain foothills becoming stronger gusting 25-45 kts and spreading into valleys and inland coastal areas after 16Z. Areas of MOD-STG up/downdrafts in lee of (south and west of) mountains along with areas of LLWS where strong winds do not surface in valleys.

MARINE

Isolated northeast gusts could exceed 20 knots Friday into early Saturday. Otherwise, no hazardous marine conditions are expected through Monday.

BEACHES

A prevailing southerly swell will generate surf 3-5 feet with local sets to 6 feet today, and produce strong rip currents. Late morning high tide near 6.5 feet today, producing minor coastal flooding. Tides are expected to fall thereafter, diminishing the threat for coastal flooding. Check the Beach Hazards Statement for details.

SKYWARN

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

SGX WATCHES/WARNINGS/ADVISORIES

CA...Beach Hazards Statement until 2 PM PDT this afternoon for Orange County Coastal Areas-San Diego County Coastal Areas.

Heat Advisory from 10 AM this morning to 8 PM PDT Saturday for Orange County Coastal Areas-Orange County Inland Areas-San Diego County Coastal Areas.

High Wind Warning until 8 PM PDT Saturday for San Bernardino and Riverside County Valleys-The Inland Empire.

High Wind Warning from 8 PM this evening to 8 PM PDT Saturday for San Diego County Valleys.

High Wind Warning until 8 PM PDT Friday for San Bernardino County Mountains.

High Wind Warning until midnight PDT Saturday night for Riverside County Mountains-San Diego County Mountains-San Gorgonio Pass near Banning.

High Wind Warning until noon PDT Saturday for Santa Ana Mountains and Foothills.

Wind Advisory until noon PDT Saturday for Orange County Inland Areas.

PZ...None.