Point Arena to Point Reyes CA out 10 NM Marine Forecast
|Tonight...Nw Winds Up To 10 Kt. Wind Waves 1 To 2 Ft. Mixed Swell W 2 To 4 Ft At 8 Seconds And S 2 To 3 Ft At 11 Seconds. Patchy Fog After Midnight.|
|Fri...W Winds Up To 10 Kt. Wind Waves 1 Ft. Mixed Swell W 2 To 4 Ft At 9 Seconds And S 2 To 3 Ft At 11 Seconds. Patchy Fog. A Slight Chance Of Rain.|
|Fri Night...Nw Winds 5 To 15 Kt. Wind Waves 1 To 2 Ft. W Swell 3 To 5 Ft At 10 Seconds And S Around 2 Ft At 10 Seconds.|
|Sat...Nw Winds 10 To 20 Kt With Gusts Up To 25 Kt. Wind Waves 3 To 4 Ft. Nw Swell 4 To 6 Ft At 8 Seconds And S Up To 2 Ft At 10 Seconds.|
|Sat Night...Nw Winds 10 To 20 Kt With Gusts Up To 25 Kt. Wind Waves 3 To 4 Ft. W Swell 5 To 7 Ft At 8 Seconds.|
|Sun...Nw Winds 5 To 15 Kt. Wind Waves 1 To 2 Ft. Nw Swell 3 To 5 Ft At 7 Seconds.|
|Sun Night...Nw Winds 5 To 15 Kt. Wind Waves 1 To 2 Ft. Nw Swell 3 To 5 Ft At 7 Seconds.|
|Mon...Nw Winds 5 To 15 Kt. Wind Waves 1 To 2 Ft. Nw Swell 3 To 5 Ft And Sw Up To 2 Ft.|
|Tue...Nw Winds 5 To 15 Kt. Wind Waves 1 To 2 Ft. Nw Swell 3 To 5 Ft And Sw Around 2 Ft.|
| 823 PM PDT Thu Sep 17 2020 |
Synopsis for the Central California Coast and Bays Including the Monterey Bay, Greater Farallones and Cordell Bank National Marine Sanctuaries - PZZ500
Low pressure off the Pacific Northwest will bring light winds through Saturday except for stronger winds south of Point Sur. Seas remain mixed with a shorter period northwest swell and a moderate period south to southwest swell.
| Area Forecast Discussion|
National Weather Service San Francisco Bay Area
1052pm PDT Thu September 17 2020
A weak front will clip the North Bay on Friday Morning while mid level moisture streams across Monterey and San Benito Counties tonight. A few sprinkles are possible in these areas tonight and early Friday. Otherwise, near normal temperatures and dry conditions are expected through the weekend and into next week.
As of 9:05pm PDT Thursday...Mid level moisture continues to stream from southwest to northeast across Monterey and San Benito Counties this evening. Radar has been showing isolated returns close to 40 dBZ across far southern Monterey County. But these returns are around 14K feet above the surface, so it's unlikely that more than a few sprinkles are reaching the ground, and almost certainly no measurable rain. Primary concern is whether there will be enough mid-level instability overnight to generate isolated high-based thunderstorms with dry lightning within this band of moisture. 00Z NAM indicates highest mid-level instability between about 06Z and 09Z (11pm to 2 AM) across the southern third of Monterey County and extreme southern San Benito County. The upshot is that isolated thunderstorms with dry lightning can't be ruled out for the far southern end of our forecast area overnight, but chances are too low to add thunderstorms to our forecast. Mid level moisture and instability are forecast to quickly exit our area early Friday morning as the incoming upper trough pushes the moisture band off to the southeast.
Evening water vapor satellite imagery shows the incoming trough is currently centered along 130W. Numerous lightning strikes are currently being detected in western Oregon, along the associated surface cold front. That cold front is forecast to clip the North Bay on Friday morning and may generate some sprinkles in northwest Sonoma County. Also, patchy drizzle is possible in coastal areas late tonight and early Friday. Most areas should clear by late morning tomorrow. A difficult part of Friday's forecast is the amount of coastal clearing to expect. Cooler air arriving behind the cold front is forecast to drop 850 mb temps down to about 13 deg C which will weaken the marine inversion. However, winds are not expected to be all that strong and so there may not be enough low level mixing to produce widespread coastal clearing. Cooler temperatures are forecast in most areas tomorrow, with inland areas expected to cool a few degrees below normal.
The upper trough will exit to our east by Friday night and we can expect a warming trend over the weekend as heigheights increase and low level flow turns more northerly. Temperatures are forecast to climb anywhere from 3 to 8 degrees above normal by Sunday.
Air quality is quite good across most of our region this evening thanks to a few days of deep west-southwest flow clearing out much of the wildfire smoke. The HRRR (High-Resolution Rapid Refresh) smoke model indicates continued low concentrations of near surface smoke through tomorrow (except in southwest Monterey County in the vicinity of the Dolan Fire). As the flow turns more northerly over the weekend, look for smoke concentrations to increase, especially across the North Bay.
A shortwave trough moving inland to our north early next week will result in modest cooling on Monday and Tuesday. This will be followed by a warm-up Wednesday and Thursday as a ridge redevelops. However, throughout next week temperatures are expected to remain relatively close to seasonal averages.
Longer range models have been hinting at a possible offshore wind event around the final weekend of September. However, the 12Z ECMWF (European Centre for Medium-Range Weather Forecasts) completely backed off on this possibility by maintaining a nearly zonal flow into that time frame. Also, the 12Z ensemble mean from both the GFS and ECMWF suggests little evidence of an offshore event, at least not a strong event. This certainly doesn't mean we are out of the woods for any strong offshore winds for the remainder of the month, since model accuracy falls off considerably beyond 5 to 7 days. Also, it should be noted that this is the time of year when the incidence of strong offshore wind events is at its highest.
as of 10:39pm PDT Thursday...Low pressure off the Pacific Northwest will bring light winds through Saturday except for stronger winds south of Point Sur. Seas remain mixed with a shorter period northwest swell and a moderate period south to southwest swell.
.MTR WATCHES/WARNINGS/ADVISORIES... .Tngt...SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm