Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
Issued by NWS San Francisco Bay Area, CA
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436 FXUS66 KMTR 301920 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 1220 PM PDT Tue Apr 30 2024 ...New AVIATION, MARINE... .SYNOPSIS... Issued at 133 AM PDT Tue Apr 30 2024 High pressure brings quiet weather and slowly warming temperatures this week. Breezy onshore winds will keep temperatures along the coast cooler however. Cooler and more unsettled conditions return this weekend into next week with light rain chances in the forecast. && .UPDATE... Issued at 854 AM PDT Tue Apr 30 2024 Low clouds continue to dissipate across the Santa Clara Valley and the Santa Cruz Mountains this morning while they are hanging around the Monterey Bay region. However, conditions will continue to improve throughout the morning with mostly sunny conditions this afternoon. Breezy northwest winds will also prevail and strengthen this afternoon with gale force gusts out over the ocean. No changes anticipated to the ongoing forecast. && .SHORT TERM... (Today and tonight) Issued at 203 AM PDT Tue Apr 30 2024 Dry conditions prevailing with high pressure from the offshore waters to far northern California and the Pacific Northwest. Gusty northwest winds continue over the coastal waters. Forecast highs today 60s near the coast and bays to the 70s inland. && .LONG TERM... (Wednesday through Monday) Issued at 203 AM PDT Tue Apr 30 2024 Dry conditions prevailing through mid-week. A slowly retrograding long wave trough along the West Coast varies in strength late week and early next week. There is a large difference between recent GFS (wet) and ECMWF (not nearly as wet as the GFS) in calculating the trajectory/progression of a low pressure system moving through the long wave trough, now well within 120 hours (5 days) forecast. QPF differences are showing up in the GEFS and EPS as well, though recent EPS have increased a little. As of current, it remains a low confidence forecast from a global model forecast perspective. Given the model forecast trajectory of the low pressure system is from near the Bering Sea/Aleutians southeastward across the Pacific (and surface high pressure over the Pacific retrogrades) where below normal sea surface temperatures exist including a negative phase Pacific Decadal Oscillation (PDO) i.e. the potential forward slowing due to local surface heating is reduced therefore the quicker arriving QPF in the GFS solution may not be that far off if development much closer to our forecast area verifies. The northern hemispheric pattern remains active with the current number of long wave troughs reflecting a winter-like circulation. Stay tuned to latest forecast updates, as currently advertised the official forecast shows potential for showery, cool weather this weekend. Planning travel to the mountains? This pattern has potential for snow accumulations, it`s a good idea to monitor the latest forecasts. Per 30 year climatology we are of course past peak cool season rainfall, however it can still rain in May in the Bay Area and north Central Coast. Recalling a Lead Forecaster here years ago mentioned it`s always a good idea to carry chains in case needed (for Sierra Nevada travel) through Memorial Day. July climatologically is our driest time of year since by then the jet stream has reliably weakened and returned northward and high pressure often sets up. && .AVIATION... (18Z TAFS) Issued at 1220 PM PDT Tue Apr 30 2024 VFR conditions prevail through the TAF period. However, strong and gusty winds will be the main concern through the late evening today. Winds increase out of the W/NW to become sustained generally around 15-20 knots into the afternoon today, with gusts in the 25-30 kt range. The one exception to prevailing gusty conditions this afternoon will likely be Monterey Bay terminals, though they will still see winds nearing 15 kts. One thing to keep an eye on will be whether winds at KSFO strengthen above the forecast 30 kt gusts. Will expand more on this in their discussion section. Into the late night tonight, winds slowly ease near the surface, but in the mid levels (1500+ feet), winds turn more northerly and increase to around 25-30 kts on average, with select terminals seeing stronger winds. This will introduce directional and speed shear for most terminals tonight, especially the North Bay. It is not until the mid to late morning of Wednesday that wind shear diminishes. Vicinity of SFO...VFR through the TAF period, with the terminal seeing strong and gusty winds out of the W/NW. Current thought is that wind gusts will stay contained to around 30 kt this afternoon and not exceed or reach AWW criteria (35 kt). As it currently stands, high resolution models have the mean (50th percentile) wind gusts this afternoon at KSFO at 25 kts, with the higher end (90th percentile) only reaching 28 kts around the time for strongest winds near 01Z. However, current SFO-ACV gradient is stronger now than at this same time yesterday. Therefore, moderate confidence in wind gusts not exceeding 30 kt at KSFO this afternoon. If the gradient continues to strengthen, gusts may increase beyond 30 knots. This will be something to watch closely over the next few hours. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...VFR through the TAF period. Winds out of the NW and moderate around 12-15 knots. Some higher gusts are possible, though do not look to be as prevailing compared to terminals to the north. Winds ease into the late night to below 10 knots. && .MARINE... (Tonight through next Sunday) Issued at 1220 PM PDT Tue Apr 30 2024 Strong winds persist through Friday, with gale force gusts of 40 to 45 knots are possible over the outer waters and portions of the immediate coast near Point Reyes and Point Sur through much of the week. The strong winds will result in hazardous seas and steep wind waves with significant wave heights reaching 10 to 14 feet in the outer waters. Conditions will gradually improve over the weekend and into next week as winds begin to ease. Chances of rain begin early Saturday as a trough descends over the region. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...Small Craft Advisory until 3 AM PDT Wednesday for SF Bay N of Bay Bridge. Small Craft Advisory until 3 AM PDT Wednesday for Mry Bay-Pigeon Pt to Pt Pinos 0-10 nm. Small Craft Advisory from 9 AM to 9 PM PDT Wednesday for Mry Bay. Gale Warning until 3 AM PDT Wednesday for Pt Arena to Pt Reyes 0- 10 nm-Pt Reyes to Pigeon Pt 0-10 nm. Small Craft Advisory from 3 PM to 9 PM PDT Wednesday for Pigeon Pt to Pt Pinos 0-10 nm. Gale Warning until 9 PM PDT Wednesday for Pt Pinos to Pt Piedras Blancas 0-10 nm. Gale Warning until 3 AM PDT Thursday for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 10-60 NM. && $$ SHORT TERM...Canepa LONG TERM....Canepa AVIATION...AC MARINE...AC 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