Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
Issued by NWS San Francisco Bay Area, CA
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659 FXUS66 KMTR 100545 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 1045 PM PDT Thu May 9 2024 ...New AVIATION, MARINE... .SYNOPSIS... Issued at 108 PM PDT Thu May 9 2024 Temperatures peak today along the coast with a incoming southerly surge cooling the coastal regions on Friday. Interior regions see temperatures peak on Friday, before a slight cooldown begins over the weekend. Coastal regions cool to around the seasonal average temperatures by early next week. && .UPDATE... Issued at 812 PM PDT Thu May 9 2024 Onshore winds have returned in dramatic fashion. The temperature dropped 16F in an hour at the Half Moon Bay Airport. In fact, that site looked like it would challenged its daily record of 80 early, reaching 77 degrees at 12:15 PM, however the cool down came shortly after and the area is now back to dealing with a cool fog, per usual. This sharp cool down was limited to coastal areas and portions of the adjacent valleys. With strong high pressure aloft, the marine layer is still quite shallow. The Ft. Ord profiler is measuring it below 300 ft. This means that inland areas will still be dealing with heat tomorrow, but coastal areas will get some relief. Synoptic winds will gradually shift onshore tomorrow afternoon, bringing a slight cool down to the rest of the area over the weekend. The humidity will also increase as the winds return to an onshore breeze. && .SHORT TERM... (This evening through Friday) Issued at 108 PM PDT Thu May 9 2024 The peak of the heat event has started with highs today ranging from the low to mid 70s at the coastal regions, to the low to mid 80s at the Bayshore and near Santa Cruz, to the upper 80s across the interior valleys. The interaction between a strong ridge building into British Columbia and the Pacific Northwest with a weak cut-off low in the Great Basin is creating offshore flow across the region, but this pattern is also one that will tend to create a "southerly surge" of coastally trapped winds. Indeed, the high resolution HRRR is showing a southerly surge coming up the Central Coast today, abating overnight before a second surge travels farther north across the California coast, beyond the Golden Gate and Point Arena. Those two southerly surges will bring some relief to the coastal Central Coast later today, and to the coastal regions tomorrow, with Friday`s coastal highs expected to hover around the upper 60s to lower 70s. The surges will also provide the only substantial chances for cloud cover near the coastal areas impacted. That is little comfort to those inland, where high temperatures will continue to rise on Friday with the warmest spots bumping into the lower 90s. Even the City, which does see some relief from the approaching southerly surge, is expected to top out in the upper 70s tomorrow. The region will generally see a Minor HeatRisk today and Friday, with a Moderate HeatRisk for the interior regions of the North Bay, East Bay, and South Bay. This corresponds to a low to moderate risk of heat-related illnesses for vulnerable populations (children, the elderly, pregnant women, people without adequate cooling, and people with certain medical conditions). Here`s a reminder of some heat safety tips: * Stay hydrated and drink plenty of fluids. * Wear lightweight, light-colored clothing. * Reduce time spent outdoors or stay in the shade. * Never leave people or pets unattended in vehicles. * Use sunscreen if going to the coast or the pool. && .LONG TERM... (Friday night through next Wednesday) Issued at 108 PM PDT Thu May 9 2024 As the upper level ridge weakens as it moves through the Pacific Northwest over the weekend, onshore flow will begin to reassert itself. Coastal regions will continue to cool down and reach seasonal average highs of around the upper 50s to lower 60s by the early part of next week. The interior will continue to remain warmer than seasonal averages, but not as warm as the forecast for Friday, with highs generally in the low to mid 80s by the early part of next week. Ensemble model clusters are in agreement over a new ridge expected to approach the Pacific Northwest by Tuesday, but its evolution after that point remains unclear. && .AVIATION... (06Z TAFS) Issued at 1044 PM PDT Thu May 9 2024 Currently VFR at all terminals. VFR through the TAF period. As the upper-level ridge weakens as it moves through the Pacific Northwest, winds will slowly be allowed to increase and return to onshore flow by tomorrow afternoon. Vicinity of SFO...Currently VFR with breezy northwesterly flow. VFR through the TAF period. Winds will become offshore by mid-morning before slowly increasing and returning to westerly flow by tomorrow afternoon. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...Currently VFR and calm at MRY and VFR with westerly flow at SNS. Confidence remains low that MVFR conditions will return to the terminals during the TAF period. MRY will see a transition from drainage flow to northwesterly flow overnight before westerly winds prevail tomorrow afternoon. Northwesterly winds will prevail through the TAF period at SNS. && .MARINE... (Tonight through next Wednesday) Issued at 1044 PM PDT Thu May 9 2024 High pressure system brings light to moderate winds over the waters. Winds will become more southerly along the Big Sur and Monterey Bay region into Friday. Otherwise, gentle breezes out of the north and northwest continue through the weekend first portion of the weekend creating relatively calm conditions over the waters. Dry weather continues through the forecast period as high pressure dominates. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...None. && $$ SHORT TERM...DialH LONG TERM....DialH AVIATION...Sarment/SO MARINE...SO 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