textproduct: San Diego

SYNOPSIS

Increasingly warm, and dry conditions are in store for next week with periods of weak to locally moderate Santa Ana winds. Patchy fog possible tonight and Sunday night.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

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

Clear skies and weak onshore flow prevails this afternoon. High temperatures are leveling off a few degrees above and below 70F inland. Lows tonight will be slightly more mild than this mornings lows, still seasonably typical. Very patchy fog may develop overnight tonight over the coastal waters (40-50% chance) and over coastal areas (15-25% chance, locally higher in Orange County). There is a similarly low potential for patchy fog for the same areas Sunday night into Monday morning.

Over the next few days, the broad upper high pressure area currently a few hundred miles west of San Diego will slowly expand east to cover California, then amplify northward, cutting off what is left of the onshore flow and warming temperatures up to 10-20 degrees above average by Tuesday. Highs likely above 80F just a few miles inland of the coast. From Tuesday through Friday, confidence is high that the ridge will keep its general positioning over the Western US. For each of these four days, around a 30% chance for high temperatures to exceed 85F in the inland valleys. Next Saturday and onward, most model guidance show either weakening of the ridge, or progression of the ridge into the interior US causing temperatures to cool down slightly but without a significant pattern change until at least the following week.

Meanwhile, a surface high pressure will develop over Colorado on Sunday behind the broader trough throughout the eastern US, driving a modest 10-15 mb pressure gradient between Southern California and the interior US. Offshore (E/NE) Santa Ana winds pick up Sunday afternoon through the passes, then expand to coastal slopes Monday, remaining elevated through at least Thursday as long as the surface gradient persists. During this period, wind gusts of 30-45 mph, locally up to 50 mph are possible each day for the passes and coastal slopes. The intensity of the winds will vary slightly day to day and will be generally strongest in the mornings. Daytime humidities inland will drop into the 10-20% range during the afternoons, only recovering into the 30-40% range at night. In the case that the ridge weakens or moves east by the end of the week, onshore winds may prevail again Saturday onward.

AVIATION

062030Z....Low clouds/fog have the potential to develop along the immediate coast after 03Z Sun. Chances are 10-20% in San Diego County through 12Z Sun and 20-30% in Orange County through 19Z. Areal coverage of any low clouds/fog will be patchy with bases less than 500 ft and visibility 1 mile or less. Confidence is not high enough in VIS restrictions to include fog in the TAFs at coastal sites at this time. VFR conditions will prevail for inland areas through the TAF period.

MARINE

There is a 10-20% chance of dense fog with visibility 1 nautical mile or less developing overnight tonight into Sunday morning.

SKYWARN

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

SGX WATCHES/WARNINGS/ADVISORIES

CA...None. PZ...None.