Area Forecast Discussion
Issued by NWS San Diego, CA

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701 FXUS66 KSGX 080507 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 906 PM PST Wed Dec 7 2016 .SYNOPSIS... Fair and seasonally cool weather will continue through Friday, followed by an increase in clouds this weekend as onshore flow builds the marine layer. Over the weekend...a string of weak waves passing to the north, will drag a deeper moist layer across the state, which could result in some spotty, light precipitation. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Skies were mostly clear this evening, and winds light. Surface pressure gradients were around 3 MBS offshore from NV, and 1-2 MBS onshore to the lower deserts. The 00Z miramar sounding had a weak 2.5 degree inversion based near 4100 FT. Moisture returned to the dewpoint trace at about 10K FT, and continued up through 30K FT, which will support the higher cloud decks we can expect to see through the end of the week. Temperatures were falling through the 50s at 7 PM PST. Satellite imagery shows high clouds advancing from the northwest, but little in the way of low clouds early this evening. Given the weak inversion at the top of the marine layer and hi res model trends, expect only patchy marine clouds overnight. The higher clouds may make for a nice sunrise, otherwise look for more sun and slight warming on Thursday as a weak shortwave ridge passes overhead. Not expecting much change through Friday and perhaps through the weekend as weak systems move by to the north guiding increasing moisture across much of the state. Several models have been indicating light precip across SoCal west of the mts this weekend. It appears this is the result of deeper moisture working south along the coast and increasing onshore flow. Some low pops have been added to the forecast based on MOS guidance and spotty model generated rainfall. So we may get a bit damp in spots this weekend, but none of the precip is expected to amount to much with the storm track well to the north for the foreseeable future. Daytime temps will remain a few degrees below average, and clouds will be abundant at times into the weekend, then warmer early next week as ridging develops over the West Coast. && .AVIATION... 080415Z...Coast/Valleys...FEW-SCT clouds 1500-3000 ft MSL clearing overnight and variable clouds AOA 10000 ft MSL through Thursday. Stratus with bases near 1000-1500 ft MSL and areas of vis 3-5 SM over higher coastal terrain developing after 09/03Z and moving into the coastal airports and up to 20 mi inland Thu night. Mountains/deserts...Variable high clouds AOA 10000 ft MSL through Thursday evening. && .MARINE... No hazardous marine weather is expected through Monday. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...None. && $$ PUBLIC...JAD AVIATION/MARINE...SS is the U.S. government's official web portal to all federal, state and local government web resources and services.