276 FXUS66 KSGX 020539 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 940 PM PST Mon Feb 1 2021 .SYNOPSIS... Mid level clouds in moisture-laden southwest flow aloft will drift east of the area tonight. Light rain and drizzle in San Diego County will end late. Tuesday will be a mild day with partly cloudy skies. An upper level trough will move southeastward through the Great Basin on Wednesday. Little if any showers are expected with this system. Dry weather will prevail through the weekend. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Deep layer moisture advection between 700-200 mb over the past 24 hours nearly doubled the PW on the NKX sounding. Yesterday evening the PW was 0.50". This evening it was 0.98". It was a warm airmass too with a freezing level above 8,000 feet. The 700 mb temperature (~10kft) was 2C with a dewpoint of 0C and an RH of 85%. At 850 mb (~5,000kft) the temperature was 14C and the dewpoint was also 0C, for an RH of only 30%. Rain accumulations were light and mostly confined to the mountains and foothills, but some of the coastal and valley sites picked up light rain or drizzle with amounts ranging from a Trace to 0.02". A precipitation summary is headlined on our webpage. weather.gov/sgx The conveyor belt of moisture will drift south and east of the area tonight with rain ending in San Diego County by daybreak. Tuesday will be a dry, mild day with fewer clouds. *From Previous Discussion* What looked like a chance of more widespread precipitation by Wednesday is no longer. The upper level trough moving into the Pacific Northwest is shown by both the GEFS and EPS to pass to the east with little if any shower activity over SoCal. Just a slight chance of insignificant showers over the mountains on Wednesday, but most likely staying dry with no real precipitation chances through the end of the week. Extensive mid-high cloudiness overhead currently will gradually clear overnight with more sun on Tuesday. Little change in temps, before conditions cool Wednesday-Thursday. West winds will increase over the mountains and deserts Wednesday afternoon- evening with localized gusts to about 40 mph then will switch to northeasterly as the trough axis passes and surface high pressure builds south into the Great Basin. The surface pressure gradient doesn't look too strong, but gusts of 30 mph or so will be possible below passes and canyons Thursday and slightly less on Friday. An upper level ridge will build over the western U.S. late this week, promising warmer conditions over Southern California. Global models show a cut off low moving towards our region by Sunday, but with little if any moisture, so we expect dry conditions to continue. Sunday will likely be the warmest day of the weekend with temps well into the 70s west of the mountains and pushing 80 over the lower deserts. The NAEFS suggests that next week will stay mostly dry while conditions cool as upper troughing digs southward over the Intermountain West. However, any displacement of the trough further west would open the door for Pacific storms to move in, but right now that scenario is not favored. && .AVIATION... 020430Z...BKN-OVC clouds with bases 10000-15000 feet MSL to continue through the night, with higher clouds in our northern areas. Period of MVFR ceilings possible at KSAN/KCRQ mainly 10-14Z with cigs 1000- 1500 feet. Very light precipitation possible at times tonight, especially across southern and eastern San Diego County. No impacts to visibility expected for the region through the morning hours. Winds will be very light, under 10 knots most areas. Onshore winds pick up slightly for tomorrow with SCT-BKN clouds AOA 15,000 FT MSL. && .MARINE... A brief period of stronger northwest winds is expected Wednesday afternoon and Wednesday night mainly over the outer waters, with gusts up to 20-25 knots. Seas will peak at 6-9 ft this period over the offshore waters. Otherwise, hazardous marine conditions are not expected for the next several days. && .SKYWARN... Skywarn activation will not be needed this week. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...NONE. && $$ PUBLIC...Moede PREVIOUS DISCUSSION...Gregoria AVIATION/MARINE...APR