Area Forecast Discussion (AFD)
Issued by San Francisco Bay Area, CA (MTR)
000 FXUS66 KMTR 200010 AFDMTR Area Forecast Discussion National Weather Service San Francisco Bay Area 410 PM PST Tue Feb 19 2019 .SYNOPSIS...After a few days of dry weather, isolated to scattered rain/snow showers are forecast to return to the region Wednesday and persist into early Thursday morning. Snowfall will be likely in the region's highest elevations, especially across the Diablo Range, Sierra de Salinas and Santa Lucia Mountains. Dry conditions return late Thursday and continue into at least Friday before chances for rain return to northern California over the weekend. && .DISCUSSION...as of 02:03 PM PST Tuesday...Weather conditions today are very similar to those yesterday with temperatures generally in the 50s. While sky conditions are mainly clear over our region, an increase in cloud cover can be seen offshore and to our north ahead of our next approaching storm system. Temperatures will be cold once again tonight, yet should be a few degrees warmer that previous days given the increase in cloud cover and moisture. The latest thinking is that light rain showers will develop during the overnight hours near the coast and locally inland over East Bay Hills and Central Coast. The main mid/upper level system forecast to drop southward out of the Pacific Northwest and into California/Nevada will result in an increase in shower activity on Wednesday during the day. Snow levels are forecast to lower to between 2,500-3,000 feet a reinforcing shot of colder aid advects southward across the region. This will likely result in additional snowfall in the region's highest peaks, especially over the Diablo Range, Sierra de Salinas and Santa Lucia Mountains through early Thursday morning. Meanwhile, convective showers will impact lower elevations with the potential for brief moderate rainfall and small hail given the cold air mass aloft. Overall, rainfall amounts will be on the order of a few hundredths to a few tenths of an inch across the San Francisco Bay Area with locally higher amounts within heavier showers over the Central Coast. Showers will tapper off by Thursday morning as drier northwest flow returns in wake of the exiting system. Dry weather conditions will then develop region-wide by Thursday night and persist into Friday as a weak shortwave ridge develops aloft. The upcoming weekend looks to start off dry before another mid/upper level trough develops over the Pacific Northwest. This will bring increased chances for precipitation over Northern California and potentially down into the northern portions of our region. The storm door appears to remain open with a cool pattern in place, yet confidence in the details remain low at this time given model-to-model and run-to-run inconsistencies. With all this said, a widespread heavy rainfall event does not appear likely within the next 7-10 days. && .AVIATION...As of 4:10 PM PST Tuesday...Satellite image shows low clouds offshore that are moving south for the moment. Dry northerly flow will keep VFR conditions through the night but as an upper level system drops down from the Pacific Northwest clouds will increase on Tuesday. Moisture is limited so there is only a slight chance of showers. We expect cigs to remain in the VFR range but cannot rule out brief periods of MVFR associated with a heavy shower or from the clouds offshore. This system is an upper-level system with no surface feature so winds will remain west to northwest. Vicinity of KSFO...VFR through tonight. Increasing clouds Tuesday after 15Z with cigs down to 3500-4500 ft. West winds increasing to 15 kt gusting to 20 kt after 09Z. Winds increasing to 20 kt with gusts 25-30 kt after 16Z. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals....VFR conditions through this evening. Increasing clouds around the bay after 10Z with cigs down to 3500-4500 ft. Scattered showers arond southern MRY Bay after 16Z with winds increasing to 15 kt gusting 20-25 kt. && .MARINE...as of 03:50 PM PST Tuesday...Northerly winds will steadily increase over the waters through the night as a system drops south from the Pacific Northwest. A series of northwest swells will impact the region through the rest of the week. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tngt...SCA...Pt Arena to Pt Reyes 0-10 nm SCA...Pt Reyes to Pigeon Pt 0-10 nm SCA...Pigeon Pt to Pt Pinos 0-10 nm SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm SCA...Pt Arena to Pigeon Pt 10-60 nm SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm SCA...SF Bay from 3 AM SCA...Mry Bay from 3 AM && $$ PUBLIC FORECAST: RGass AVIATION: W Pi MARINE: Rowe Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/nwsbayarea www.twitter.com/nwsbayarea www.youtube.com/nwsbayarea