Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
Issued by NWS San Francisco Bay Area, CA
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560 FXUS66 KMTR 030459 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 959 PM PDT Thu May 2 2024 ...New AVIATION... .SYNOPSIS... Issued at 119 PM PDT Thu May 2 2024 Warm weather continues through the day today and tomorrow afternoon. Beneficial rain befalls the region late Friday and through the afternoon of Saturday. Cool overnight temperatures expected Sunday and Monday mornings. Dry conditions return Sunday and last through next week. && .UPDATE... Issued at 858 PM PDT Thu May 2 2024 Pleasantly warm day throughout the Bay Area with temperatures primarily in the 70`s and a few stations reaching the low 80`s. One more day of above average temperatures before cooler, below average temperatures return heading into the weekend. Breezy to gusty westerly to northwesterly winds continue through Friday in coastal regions and elevated terrain. Gustier winds will extend farther inland heading into the weekend as a low pressure system moves inland. Precipitation forecast looks to be on track with continuing good model consensus that beneficial rainfall returns Saturday. Overall forecast remains on track. && .SHORT TERM... (This evening through Friday) Issued at 119 PM PDT Thu May 2 2024 A look across the region at this hour shows many interior locations already reaching into the low to mid 70s. Meanwhile closer to the coast and bay shorelines, temperatures are in the upper 50s to low 60s. Temperatures will warm today into the high 70s away from the coastline, with a select few locations maybe seeing temperatures reach the 80 degree F mark. However, chances of reaching the 80 degree mark are fairly low even for the favored interior spots. Napa appears to be the most highly favored for the chance to reach 80 degrees, but even then, with only a whopping 30% chance. Elsewhere in locations such as Gilroy and Hollister, chances are only in the 20% range. Coastal locations will only see highs in the mid 60s at best. As upper level ridging builds and continues, temperatures are expected to be largely similar tomorrow. Breezy northwesterly winds in the afternoons will continue, but ease into the nighttime. Late Friday night, rain begins to approach the region, impacting the North Bay first, and then slowly making its way south. The previous forecaster`s long term discussion still largely holds, so will not reinvent the wheel. Will just mention that rain totals have increased ever so slightly from the previous forecast, but not by much. By a few hundredths generally. Descriptions in the long term discussion still hold largely. && .LONG TERM... (Friday night through next Wednesday) Issued at 119 PM PDT Thu May 2 2024 Seeing good global and mesoscale model agreement, one long wave trough is now stationary along the West Coast, part of an unsteady northern hemispheric long wave trough pattern. A low pressure system from the Aleutian Islands will move through the long wave trough and bring rain to our forecast area Friday night and Saturday. Rain developing first over the North Bay Friday night, rain quickly spreading southeastward across much of the rest of the forecast area Saturday. Expect noticeably cooler temperatures especially inland Saturday with daytime highs in the upper 50s to mid 60s, warmest southern interior; daytime temperatures 5F to 15F below early May normals. The low is still expected to brush by and tap higher levels of water vapor extending far north of Hawaii, while retaining a strong mid-latitude influence e.g. it`s an appreciably cold core system up through the 700 mb level by comparison on Oakland upper air climatology, the pool of cold air a little more compact by the 500 mb level. Unlikely there`ll be layer instability extending above 700 mb, forecast 700-500 mb lapse rates are low and much more stable. Recent precipitable water values on the GFS maintain between 1.00" and 1.10" Saturday, not far from the max moving average on Oakland upper air sounding climatology in early May. Seeing some recent increases in model forecast rainfall amounts. For example over 0.50" to 1" rain totals North Bay, near 0.50" low elevations and up to 0.75" to 1" East Bay hills/mountains and the Santa Cruz Mountains, 0.10" to 0.20" interior north Central Coast to around 0.50" Big Sur Coast. The Bay Area and northernmost north Central Coast may receive over half if not nearly May normal precipitation from this system if current QPF verifies. As mentioned expect wet and cooler weather Saturday, gusty northwest winds over the coast temporarily subsiding with the passage of a surface cold front/trough. Chilly to cold overnight low temperatures for the time of year (40s coastside and bayside / 30s inland) are forecast late Saturday night to Sunday morning and Sunday night to Monday morning. San Francisco and Oakland downtown possibly including a few other locations may be nearing record lows Sunday and Monday mornings. Stay tuned to updates, right now Sun-Mon mornings look to be the chilliest. Forecast temperature guidance could edge a little lower between now and late weekend. End of previous discussion. Overall, this weekend`s system will bring beneficial, although late-season rain. Late Saturday, rain begins to cease and a dry pattern returns to the region with temperatures gradually warming through the next week into the low to mid 70s for interior regions. Despite gradual warming, CPC 6-10 day outlooks place much of California in a below-normal temperature category, and below normal for precipitation. && .AVIATION... (06Z TAFS) Issued at 958 PM PDT Thu May 2 2024 IFR and MVFR CIGs have pushed slightly inland affecting the Monterey Bay terminals and SFO. Winds ease into the late night becoming light to moderate. Cloud cover thins in the mid to late morning Friday, leading to widespread VFR. Gusty westerly winds arrive Friday afternoon and last into the night. As winds reduce, low clouds move into the coast and bays Friday night, leading IFR CIGs spreading farther inland. Winds turn southwesterly as showers approach the region into early Saturday. Vicinity of SFO...Moments of IFR CIGs through the late night. Expect moderate westerly winds to reduce into early Friday morning. Scattered lower clouds linger into the mid morning. Gusty west winds build into Friday afternoon, peaking around 27 kts and gusting above 30 kts. Winds reduce into late Friday evening, but remain breezy until they shift and become southwesterly with the arriving showers. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...MVFR/IFR through the mid to late morning. Winds stay light to moderate through the morning before moderate to breezy winds arrive Friday afternoon. IFR CIGs return Friday evening as winds reduce. && .MARINE... (Tonight through next Wednesday) Issued at 858 PM PDT Thu May 2 2024 Gusty winds persist throughout Friday afternoon, with gale force gusts of 35 to 45 knots possible in the southern waters. Strong winds will result in hazardous seas and steep wind waves with significant wave heights reaching 10 to 13 feet in the outer waters. Conditions briefly improve over the weekend, but will increase into next week to more moderate levels. Rain chances begin late Friday night as a trough descends over the region into Saturday. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...Small Craft Advisory until 9 AM PDT Friday for Mry Bay-Pt Arena to Pt Reyes 10-60 NM. Small Craft Advisory until 9 PM PDT Friday for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm. Gale Warning until 3 AM PDT Friday for Pigeon Pt to Pt Pinos 0- 10 nm. Gale Warning until 3 AM PDT Saturday for Pt Pinos to Pt Piedras Blancas 0-10 nm. && $$ SHORT TERM...AC LONG TERM....Canepa AVIATION...Murdock MARINE...Murdock 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