textproduct: San Diego

SYNOPSIS

The ridge of high pressure over the region will weaken some over the weekend, where slight cooling will take place with a deeper marine layer near the coast. The ridge of high pressure will reamplify by next week, leading to a prolonged heat wave. This event will encompass temperatures of 20 to potentially up to 30 degrees above normal for this time of year, leading to moderate to high heat risk.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

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

Update: At nearly 8 pm this evening, many portions of the inland areas are still experiencing temperatures above 80 degrees. This is only a segue into what is going to happen next week in terms of a unprecedented heat wave for this time of year here in SoCal. With only some relief from the heat for tomorrow as we begin to see a better push of onshore flow, with many locations (especially within the IE) being notably cooler tomorrow. With tomorrow being the coolest day of the week, it will still be generally 10 to 15 degrees above the seasonal average, but will feel relatively cooler in comparison to how temperatures were for today. From then on, the ridge is going to continue to build in strong next week, with high pressure heights aloft approaching 600 dm just south of the region. This will translate into very hot temperatures, and likely not only shattering daily records, but possibly monthly records towards the end of next week. There could even be a few localities flirting with all-time records, as temperatures look to soar into the mid 100s for the IE, and over 110 within the deserts, by next Thursday. Even higher elevations will experience record warmth as well. The latest forecast for next Thursday calls for Palomar Mountain to have a high of 89 next Thursday, which would crush their previous daily record by 10 degrees, as an example. It is especially important during this very warm period to ensure that you are staying properly hydrated, especially if outdoors, and to also check up on elderly/pets/children, and anyone else sensitive to extreme heat. It is not only the strength of the high that makes this a rare and unprecedented event, but the duration of this remaining in place as well. Please continue to monitor, and stay advised of any heat advisories/warnings for your area.

Previous discussion submitted at 1229 pm:

A 588 dm high is maintaining its strength over the eastern Pacific. This hot air mass will give another very warm day out there with temperatures 15-20 degrees above normal. The places that will see some better relief from the hottest temperatures will be at the coast and higher elevations over 5,000 feet. The ridge will weaken some by this weekend, along for greater onshore flow and the marine layer to deepen slightly. This will give the chance for low clouds and fog to form near the coast by early Saturday morning (around a 20% chance at San Diego). Saturday will be the coolest day over the next week, though highs will still be near 10 to 15 degrees above normal. As onshore flow takes hold, there is near a 50-50 chance to see wind gusts over 30 MPH across mountain desert passes into the high desert by Saturday afternoon. The marine layer will be its deepest by Sunday morning with low clouds and patchy fog moving in from the coast to about ten miles inland.

The high off the coast will begin reamplify on Sunday, where higher pressure heights near 585mb move into the area. This will kickoff a major heat wave for the region as we move into the upcoming week. Sunday temperatures will warm another 5 to 10 degrees across inland valleys west of the mountains, about the same from Saturday everywhere else. Chances are low to moderate to see areas of the northern Inland Empire go over 95 degrees on Sunday.

The center of the high slowly moves toward the region by Monday through Wednesday, then moves slowly eastward into Arizona by later in the week. This is a very hot air mass with temperatures at 850 mb nearing 25C, which is about 15C above normal for this time of year, very hot! Due to this prolonged heat event, an Extreme Heat Watch has been issued for all areas west of the mountains Monday through Friday. The greatest warming will begin in these areas by Monday and Tuesday, with highs nearing 100 degrees by Tuesday for the valleys of San Diego/Orange County into the Inland Empire. The coastal areas will see a tougher forecast as cool westerly winds off the ocean will have a large effect on the temperatures within a mile or so from the coast, where some areas may stay much cooler than inland regions. Please use this time to prepare for the incoming heat by making sure you have enough water and products to keep cool.

The area of high pressure will continue to strengthen for the latter half of next week. This will bring even hotter temperatures to the area, where many of our climate sites will not only break daily temperature records but also monthly record temperatures. Please see the climate information section below for more details. The temperature forecast for later next week is somewhat lower confidence on the exact temperature details, but whatever you way you slice it, it will be very hot for the middle of March. 850 mb temperatures will peak near 25C during this period as the high amplifies near 593-595 dm. Thursday and Friday look to be the hottest days over all, with low to moderate chances of seeing highs reach 105 degrees across the Inland Empire, as well as reaching 100 degrees and inland valleys east of the 5 and the 15 in Orange and San Diego Counties. The most extreme heat will be across the Coachella Valley during this time. NBM probabilities show a a moderate to high chance of going over 110 degrees by late next week as well. To put this in perspective, the highest temperature recorded in March at Palm Springs and Indio is 104 degrees (both sites of which have a period of record over 100 years old). Low temperatures will cool off some into the 60s for many areas below 5,000 feet with lows staying in the 70s across the lower deserts. Please make sure to check on family, friends, and neighbors this coming week! Outdoor activities should be limited as the duration of this early season heat wave will lead to increased risk of heat illness. This includes the mountains, where highs will reach into the 80s and 90s by the latter half of the upcoming week. The ridge looks to slowly weaken by the following weekend, which will aid in a cooling trend.

LONG TERM

AVIATION

140000Z...VFR conditions with increasing high clouds through Saturday morning. Patchy low clouds and fog 300-500 ft MSL with vis 2-4 SM over the waters and isolated coastal areas 12-16Z Saturday. Cigs and reduced vis not likely at most coastal airports (15% chance at KCRQ/KSNA), but there is a better chance (40%) for intermittent cigs at KSAN. Greater coverage of coastal clouds 500-900 ft MSL Sat evening after 15/02Z.

MARINE

No hazardous marine conditions are expected through Wednesday.

SKYWARN

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

SGX WATCHES/WARNINGS/ADVISORIES

CA...Extreme Heat Watch from Monday morning through Friday evening for Orange County Coastal Areas-Orange County Inland Areas- San Bernardino and Riverside County Valleys-The Inland Empire-San Diego County Coastal Areas-San Diego County Valleys-Santa Ana Mountains and Foothills.

PZ...None.