textproduct: San Diego

SYNOPSIS

Minor to moderate HeatRisk continues through Monday with cooler weather Tuesday and beyond. Thunderstorm chances each day in the mountains through Wednesday, with best chances and highest rain rates Monday and Tuesday. Patchy coastal fog Monday morning with a deepening marine layer through the end of the week.

..UPDATED AVIATION DISCUSSION

Satellite shows high clouds streaming into Riverside and San Bernardino counties from the southeast after a collapsed MCS this morning, although any precipitation died off before reaching our borders. Much of the high clouds should move out by the afternoon, and high pressure situated over the Four Corners will keep temperatures well above normal and allow for monsoonal thunderstorms to develop over the higher terrain this afternoon. PW values above 1" indicate that brief, heavy rainfall will be possible with any storm, but realistic maximum rain rates are likely closer to 0.60"/hr or less for Riverside and San Diego mountains and 0.40"/hr or less for San Bernardino this afternoon.

Soundings are a bit more optimistic for storm potential on Monday/Tuesday as the high becomes more compressed by upper level troughing over the PacNW, allowing for a more unstable environment and monsoonal moisture to surge up into the mountains of SoCal. Temperatures will also begin to cool on Monday as we shed the last of our heat products. While HeatRisk will be lower on Monday, highs will still be above 100 in the High Deserts and above 105 in the low deserts, so continue best practices when spending time outdoors - frequent water/AC breaks and avoid strenuous activity during the hottest parts of the day. If attempting to escape to the mountains to avoid the heat, be prepared for more widespread thunderstorms Monday afternoon with heavy rain, frequent lightning, and localized flooding possible as instability peaks on this day. With easterly flow and ample mid and low level moisture, PWs will be increasing closer to 1.5-1.6, and rain rates may potentially exceed 1-1.25"/hr at times with any anchored storm. The majority of the storms are expected to remain in the mountains, but a few stronger cells may make it off and migrate into the deserts.

Temperatures will cool further Tuesday back down to near normal as heights continue to fall and the marine layer deepens into the end of the week. One final day of scattered monsoonal thunderstorms in the higher terrain as PWs remain at or above 1.5" and instability lingers across southeastern CA. After Tuesday, more robust upper level troughing and the high sliding further eastward will usher in slightly below normal temperatures into the end of the week, along with lower storm chances (10-15% chance for a storm or two off the higher terrain will exist each afternoon Wed-Fri). This cooler weather will be a welcome change after temperatures have remained at or above normal since early July.

AVIATION

100600Z....Coast...Patchy low clouds to gradually develop overnight, slowly increasing in coverage, with best chances of cigs at coastal TAF sites between 11-15Z Tuesday. Bases around 700-1100 feet MSL. Scatter out of any cigs Tuesday by 16Z. VFR conditions expected Monday afternoon and evening.

Valleys/Mountains/Deserts...SCT-BKN clouds mostly above 15000 feet through 18Z Monday. Scattered TSRA over mtns with an isold TSRA or two in the High Desert 19Z Monday to 02z Tuesday with bases around 9000 feet MSL with tops to 50000 feet. Any TSRA could produce lightning, strong up/downdrafts and associated vis reductions.

MARINE

No hazardous marine conditions are expected through Friday.

BEACHES

High tides will exceed 7 feet during evenings Monday through Wednesday between 800-930 PM, resulting in minor tidal overflow of low-lying areas along the beach. Surf will be low and is not expected to add much to the flooding potential. Check the Coastal Flood Advisory for details.

SKYWARN

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

SGX WATCHES/WARNINGS/ADVISORIES

CA...Coastal Flood Advisory from 6 PM Monday to 11 PM PDT Wednesday for Orange County Coastal Areas-San Diego County Coastal Areas.

PZ...None.