Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
Issued by NWS San Francisco Bay Area, CA
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575 FXUS66 KMTR 221116 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 416 AM PDT Wed May 22 2024 ...New AVIATION, MARINE... .SYNOPSIS... Issued at 1237 PM PDT Tue May 21 2024 Summer-like pattern to persist through Thursday. Temperatures are forecast to dip below seasonal averages by the upcoming weekend as an upper level trough impacts the region. && .SHORT TERM... (Today and tonight) Issued at 212 AM PDT Wed May 22 2024 Stratus is slowly creeping its way up along the coast from Monterey Bay through Half Moon Bay. An otter eddy has developed over the Monterey Bay with stratus cycling cyclonically over the bay. Stratus coverage is expected to fill in and become more widespread over the Monterey Bay by the early morning hours. Morning lows will be slightly cooler than yesterday with more widespread low temperatures in the upper 40s to mid 50s. High temperatures today will be 3 to 5 degrees cooler than observed yesterday with inland highs in the upper 70s to low 80s and coastal highs in the upper 50s to low 60s. Increasingly onshore flow along the coast will help to bring in moister, cooler air and begin a weak cooling trend. Minor heat risk continues today and tomorrow for most of the interior Bay Area and interior portions of the Central Coast. For those who are extremely sensitive to heat, remember to take breaks while outdoors and to drink plenty of water. Broad upper level troughing continues through Thursday with weak upper level offshore flow contributing to drier conditions inland. Minimum relative humidity values on Wednesday will be slightly higher than yesterday as stronger onshore flow along the coast will bring in increased moisture. Inland daytime RH values will rise by at least 10% with values ranging from 30 to 45 percent expected. The driest conditions (daytime RH values around 30%) are collocated with decent upper level offshore flow over the North and East Bay Mountains. Along the coast, stronger onshore flow will keep daytime RH values ranging from the mid 60s to low 80s with moister conditions extending farther northward today. && .LONG TERM... (Thursday through Tuesday) Issued at 212 AM PDT Wed May 22 2024 A weak cooling trend continues through Thursday before a more significant temperature drop begins Friday as stronger upper level troughing dips southward and a weak surface low pressure system moves inland. High temperatures on Friday and Saturday will be 5 to 15 degrees below average. Inland areas will see highs extending from the low 60s to low 70s while coastal areas see highs in the mid 50s to low 60s. Ensemble guidance continues to indicate that light, non- impactful precipitation is possible with this system but values continue to be less than a tenth of an inch. Precipitation chances remain low overall but the most likely scenario suggests light drizzle along the coast and maybe a trace of rain inland. Stratus coverage is expected to become more widespread beginning over the weekend as this system moves through and increased onshore flow develops. This will follow a typical "May Gray" pattern where gloomier, overcast conditions are expected throughout the morning before overcast conditions clear out mid to late morning. While below average temperatures are expected to continue through the end of the month, a weak warming trend will begin Sunday as upper level ridging builds over the West Coast. Temperatures will be slightly below average to seasonal with inland regions warming back into the 70s and low 80s and coastal regions continuing to linger in the upper 50s to mid 60s. && .AVIATION... (12Z TAFS) Issued at 415 AM PDT Wed May 22 2024 Generally VFR for all but the Monterey Bay terminals, which will see overnight/morning IFR stratus. The other exception is at KAPC which has maintained a TEMPO ceiling over the past few hours. Otherwise look for breezy onshore winds this afternoon with mostly clear skies. LLWS potential tonight at KAPC due to decoupling light surface winds and gusty offshore flow aloft potentially reaching 30-35 kt at 2 kft AGL. Vicinity of SFO...VFR but with FEW-SCT010 this morning at the terminal. Breezy onshore winds this afternoon with gusts to around 25 kt. Winds gradually becoming lighter around/after 05Z. SFO Bridge Approach...Similar to SFO Monterey Bay Terminals...IFR stratus persists this morning before mixing out around 17-18Z. Modest onshore winds develop this afternoon with some periodic gustiness through the Salinas Valley. Low stratus returns later this evening and persists into Thursday morning. && .MARINE... (Today through Monday) Issued at 415 AM PDT Wed May 22 2024 Building high pressure over the Eastern Pacific will allow strong northwesterly winds to prevail through Thursday, with gale force gusts across the outer waters. Expect hazardous conditions and steeper wind waves during the week. Winds diminish heading into the weekend as surface high pressure over the Eastern Pacific Ocean weakens. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...Small Craft Advisory from 3 PM this afternoon to 9 PM PDT this evening for Mry Bay. Small Craft Advisory until 9 AM PDT this morning for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm. Gale Warning from 9 AM this morning to 3 AM PDT Thursday for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm. Small Craft Advisory until 3 AM PDT Thursday for Pt Reyes to Pigeon Pt 0-10 nm. Small Craft Advisory from 9 AM this morning to 3 AM PDT Thursday for Pigeon Pt to Pt Pinos 0-10 nm-Pt Pinos to Pt Piedras Blancas 0-10 nm. Gale Warning until 3 AM PDT Thursday for Pt Arena to Pt Reyes 10- 60 NM. && $$ SHORT TERM...Kennedy LONG TERM....Kennedy AVIATION...SPM MARINE...SPM 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