Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
Issued by NWS San Francisco Bay Area, CA
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
545 FXUS66 KMTR 251725 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 1025 AM PDT Wed Sep 25 2024 ...New AVIATION, MARINE... .SYNOPSIS... Issued at 249 AM PDT Wed Sep 25 2024 An upper level trough off of the West Coast will bring cooler temperatures on Wednesday with a gradual warming trend into Friday has high pressure builds over the Desert Southwest. Temperatures return to near seasonal averages for the upcoming weekend. && .SHORT TERM... (Today and tonight) Issued at 249 AM PDT Wed Sep 25 2024 Widespread cloud cover with bases at between 300-1,300 feet continue to spread inland at this hour into the coastal adjacent valleys. As such, temperatures are expected to bottom out in the 50`s for most locations with lower 60`s in the East Bay Valleys and Santa Clara Valley. Cannot rule out mist or drizzle in the favored locations across the region as an upper level low off of the coast deepens the marine layer. Today will mark the much anticipated cool down with temperatures across the interior cooling between 10-20 degrees from yesterday`s maximum temperatures and 1-10 degrees closer to the coast. This is in response to the aforementioned upper level low which has developed over the eastern Pacific. Breezy onshore winds are expected this afternoon and will continue into the evening. Tonight, expecting a 1-5 degree cool-down as temperatures cool aloft. Look for a return of low clouds once again tonight into the coastal adjacent valleys and much better humidity recoveries as well. Winds diminish becoming light and variable overnight. && .LONG TERM... (Thursday through Tuesday) Issued at 249 AM PDT Wed Sep 25 2024 More of a zonal pattern develops to our north on Thursday, while an upper level high develops over the Desert Southwest. This will bring temperatures back up to near seasonal averages on Thursday and above average by Friday. Temperatures trend back to near seasonal norms for the weekend as an upper level low to the to our southwest approaches and an upper level trough impacts the Pacific Northwest. From the previous forecaster: "Model output is beginning to show the potential for light offshore flow during the night and morning hours this weekend. However, confidence in any specific impacts are too low to note in fire weather products at this time. CPC outlooks continue to show a lean towards temperatures above, and precipitation below, seasonal averages through the first week of October." && .AVIATION... (18Z TAFS) Issued at 1024 AM PDT Wed Sep 25 2024 Thanks to an extensive marine layer already 2000-2500 feet deep and deepening, extensive IFR-MVFR stratus covers the inland valleys, beginning to mix out along the edges. Most terminals should clear to VFR by 18-19Z with ceilings persisting through the TAF period at the immediate coast. Breezy onshore flow will develop this afternoon and evening, with stratus returning to the inland valleys tonight, starting to mix out by the end of the 24-hour TAF period. Vicinity of SFO... Terminal has cleared out and should remain VFR for the rest of the day. West-northwest winds develop this afternoon gusting to 15-20 knots, before winds diminish in the late evening hours. MVFR stratus will return this evening and mix out late Thursday morning, followed by afternoon winds gusting to around the same speed as today. SFO Bridge Approach... Some lingering stratus could impact the approach path for the next hour. Otherwise similar to SFO. Monterey Bay Terminals... IFR-MVFR stratus continues to around 19Z at SNS, closer to 20-21Z at MRY. Breezy onshore flow develops in the afternoon and diminishes in the evening, as MVFR stratus returns to the region. Model output is showing potential for reduced visibilities, but a deep marine layer should keep fog concerns at bay. && .MARINE... (Today through Monday) Issued at 1024 AM PDT Wed Sep 25 2024 Light to gentle northwesterly breezes continue today. Northwesterly breezes strengthen to become moderate to fresh and seas rebuild to become rough in the outer waters by Thursday through the weekend. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...None. && $$ SHORT TERM...RGass LONG TERM....RGass AVIATION...DialH MARINE...DialH 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