Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
Issued by NWS San Francisco Bay Area, CA
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806 FXUS66 KMTR 090258 AAB AFDMTR Area Forecast Discussion...UPDATED National Weather Service San Francisco CA 758 PM PDT Sat Jun 8 2024 ...New UPDATE... .SYNOPSIS... Issued at 1205 PM PDT Sat Jun 8 2024 Seasonal temperatures with breezy onshore winds will last through Sunday before another warm up begins Monday. && .UPDATE... Issued at 758 PM PDT Sat Jun 8 2024 The short term forecast remains in good shape, and the only alteration to the grids was to beef up winds across the East Bay Hills as well as the SF Peninsula as early evening mixing of 20-25 knot momentum continues. Winds across the bay side of the SF Peninsula should subside in a few hours as nocturnal cooling transpires. Locations along the ocean side of the peninsula as well as across the East Bay Hills will remain a bit breezier due to more channeling effects around the various terrain features. In fact, NBM probabilistic guidance suggests around a 60% chance for hourly wind gusts of at least 30 mph or greater across the East Bay Hills and winds have been adjusted upward across this area to reflect more of the 75th percentile output (which appears to have captured the overachieving winds this afternoon and early evening). Individuals across the area should anticipate wind gusts of 25 to near 40 mph---due to acceleration around some of the terrain---across the aforementioned areas (as well as some of the areas along the Pacific coast). The rest of the forecast remains largely unchanged and our attention will turn to our next warm spell Monday through Wednesday. Tuesday appears to be the hottest day with the potential for upper 80s to the triple digits across the interior portions of the area. Be sure to abide by your heat safety protocols. Another potential impact of the above normal warmth will be the additional drying of grasses which may result in an uptick in fire starts. Be sure to do your part and avoid activities that could spark a grass fire (e.g., tossing lit cigarette ends on the ground, dragging tow chains). && .SHORT TERM... (This evening through Sunday) Issued at 1205 PM PDT Sat Jun 8 2024 The stratus clouds have eroded everywhere except along the immediate coast. Despite the clearing, area profilers and the morning sounding confirm the marine layer is roughly 2,000 ft deep. This is allowing cool air to infiltrate into the valleys and keep the afternoon temperatures mild. A short wave trough at 500 mb is approaching the coast this afternoon. This wave will amplify and become a cut-off low SW of the Channel Islands by Sunday evening. This synoptic change will cause the mid-level winds to shift from southerly to northerly over the next 36 hours. This change won`t be as obvious at the surface. While the surface wind direction should veer a bit, the weather Sunday will continue to be dominated by a deep marine layer, morning stratus, and breezy onshore winds in the afternoon. Broadly speaking, the temperatures Sunday will be similar to Saturday and the seasonal averages. && .LONG TERM... (Sunday night through next Friday) Issued at 1205 PM PDT Sat Jun 8 2024 Abandoned by the jet stream, the Southern California cut-off low will continue to drift south Monday, allowing a ridge of high pressure to build across the Bay Area. This ridge will cause the marine layer to compress from 2,000 ft over the weekend to around 1,000 ft by Tuesday. While the cut-off low is part of the typical offshore wind equation, we are missing the other piece of the puzzle; strong high pressure over the intermountain West. While weak offshore winds are expected at 700 mb Mon-Tue, they likely won`t reach the surface. The combination of offshore winds aloft, and a shallow marine layer will cause inland areas to warm above seasonal averages from Monday through Wednesday. Tuesday currently looks like the warmest day of the week, with inland highs in the 90s. Coastal areas will stay in the 60s and 70s. By Thursday, an approaching trough will kick the cut-off low inland, where it will quickly weaken. This will bring the return of onshore flow and allow temperatures cool back to the seasonal average. && .AVIATION... (00Z TAFS) Issued at 505 PM PDT Sat Jun 8 2024 Moderate-high confidence in VFR through the TAF period at APC, LVK, OAK, SFO, SJC, and STS. While stratus is currently eroding in the Monterey Bay region, moderate confidence that IFR and MVFR ceilings will return to MRY and SNS respectively tonight and into tomorrow morning. Widespread VFR will prevail by tomorrow afternoon. Winds will remain onshore through the TAF period. Vicinity of SFO...Moderate confidence in VFR through the TAF period. Winds will remain elevated and prevail out of the west through the TAF period with gusts up to 25 knots to be expected through today as well as tomorrow afternoon and evening. MVFR stratus could impact the terminal early tonight and/or during the early-to-mid morning hours of Sunday, will continue to monitor trends in models/guidance and have the 03Z TAF amendment reflect. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...Confidence is moderate on IFR stratus returning to MRY and MVFR stratus returning to SNS tonight into tomorrow morning. Winds will prevail out of the west/southwest through the TAF period, becoming gusty tomorrow afternoon at SNS. VFR to prevail by tomorrow afternoon. && .MARINE... (Tonight through next Friday) Issued at 505 PM PDT Sat Jun 8 2024 Moderate to fresh northwesterly breezes continue to prevail due to the gradient between subtropical high pressure and lower pressure over the Southwestern United States. As high pressure slowly progresses towards the coast, the pressure gradient will tighten, causing the wind speed to increase through the weekend. A fresh to strong northwesterly breeze will persist through next week. Significant wave heights will mostly be dominated by wind driven waves, though there is a moderate northwesterly swell and a low southwesterly swell mixed in. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...Small Craft Advisory until 3 AM PDT Sunday for SF Bay N of Bay Bridge. Small Craft Advisory from 3 PM to 9 PM PDT Sunday for Mry Bay. Small Craft Advisory until 9 AM PDT Monday for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM-Pt Reyes to Pigeon Pt 0-10 nm. Small Craft Advisory from 3 PM Sunday to 9 AM PDT Monday for Pigeon Pt to Pt Pinos 0-10 nm. Small Craft Advisory from 9 AM Sunday to 9 AM PDT Monday for Pt Pinos to Pt Piedras Blancas 0-10 nm. && $$ UPDATE...Bain SHORT TERM...Flynn LONG TERM....Flynn AVIATION...Sarment MARINE...Sarment 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