, Issued at 900 PM PDT Thu Mar 26 2026 (Tonight through Friday Night)
Above normal warmth is anticipated to continue as we end the work-week. The current expectation is that we'll see a modest push of offshore breezes through the pre-dawn hours on Friday. 925mb flow of 20 to 30 knots is forecast to extend from the northern Sacramento Valley southward through the Bay Area and portions of the Central Coast. This could translate to wind gusts at the highest elevations of the North Bay exceeding 35-45 mph thanks to mountain wave activity through sunrise Friday. In addition to the compressional warming associated with offshore wind patterns, the marine layer will remain nearly non-existent. With a dry airmass in place, there should be a large diurnal temperature range with MinT values in the 40s (a few upper 30s cannot be discounted) with Friday afternoon MaxTs in the 70s and 80s, even across coastal regions.
..issued at 900 PM PDT Thu Mar 26 2026 (Saturday through next Thursday)
The weekend will be largely pleasant with the start of our cooling trend expected to commence early next week. Highs on Saturday and Sunday are expected to remain above normal, especially for areas away from the coast. That said, there are some signs that onshore flow may be a *slightly* stronger on Saturday which may equate to MaxTs a few degrees lower than Sunday. In fact, higher resolution NWP from PGE/SJSU WRF hint that a very shallow and compressed marine layer may try to invade coastal regions (Pacific Coast and SF/Monterey Bays) on Saturday with potentially some morning drizzle/patchy fog. We'll fine tune this in future forecasts. By Saturday afternoon, however, most of the shallow moisture should be scoured out with mostly sunny skies. Depending on the breadth/inland extent, this could modulate MaxTs by 2-5 degrees. Still, it'll be largely pleasant on Saturday. Offshore surface to 925mb flow appears more organized on Sunday, and while morning low clouds/fog cannot be discounted during this time,especially along the coast, Sunday for sure looks to be the warmest day this weekend.
After an extended time of above normal warmth, there will be a very noticeable change as unsettled conditions take shape. This will mean opportunities for rainfall and increased onshore winds. Our stubborn area of high pressure will be dislodged eastward by our longwave pattern that is well-advertised by a majority of deterministic and ensemble guidance. There are some differences with respect to the overall amplitude/depth of the upper trough. That said, the greatest spread in the NWP is due to differences in the progression of various upper troughs. What this translates to is high confidence that we'll see widespread cloud cover and rainfall with lower confidence in specific onset/end times.
A discernible plume of precipitable water (above 150% of normal for this time of year) will stretch from the Central Pacific eastward toward the West Coast by the time we get into Monday. Confidence is increasing that a bulk of the more widespread activity will be later Monday and into Tuesday as a ribbon of 50-70 knot mid-level flow develops ahead of a positively titled upper trough. This corridor of greater winds has shifted a bit farther south compared to what was forecast yesterday by NWP. Not surprisingly, the richest plume of moisture appears that it's aimed a bit more at the Central Coast compared to areas north of the Golden Gate. In fact, the latest QPF through Thursday evening has increased across the Santa Lucia Range/Big Sur Coastline while ticking down slightly across the Western Sonoma Hills. This aligns well with both GEFS and EPS probability of Integrated Vapor Transport above 250 kilogram/meter/second maximized south of the Golden Gate (and probably south of Monterey Bay), at least with this initial upper trough on Tuesday.
A second, more compact upper trough will swing through the region early Wednesday. This second opportunity for precipitation will be what allows totals to tick up a little higher across the North Bay. In total, rain amounts across the Coastal Ranges in Sonoma County still have the best chance of eclipsing 1" (around a 40% chance), with the probability of 1" lower farther south. Of course, areas such as the Santa Cruz Mountains and Santa Lucia Range are likely to be the spots where rain totals could rival regions farther north. Instability does build a little bit more with this second system. While the probability of thunder remains around 10%, the convective nature of activity does complicate rain amounts some due to the isolated to scattered nature of precip.
It does appear that ridging will return sometime Thursday and into Friday, but timing of when this trough will progress eastward is highly uncertain. Total rain amounts are forecast to average between one tenth of an inch across inland areas (including the population centers) to half an inch across coastal regions of the Central Coast and portions of the North Bay. As noted above, western Sonoma County will have the best chance for rain amounts at or above 1 inch. It should be restated that if this second system amplifies more than currently anticipated, then the window for rainfall could be extended into Friday which could drive totals upward. Still, rain amounts appear largely beneficial as even the 90th percentile QPF (reasonable-worst case scenario) are largely 1-2" across the region which shouldn't translate to a major flood risk given the recent dry spell.
This second system will have the potential to produce the stronger non-convective winds (largely across the higher terrain) as the breadth of higher momentum resides through the column. Probability of 40 mph winds are around 60-80% across the North Bay Mountains, East Bay Hills, Sonoma Coastal and Gabilan Range(s).
Ridging is expected to return toward the end of next week. At the surface a cold front will slide southward and dry out the low levels. As surface pressures rise across the Great Basin, we may find ourselves in another period with modest offshore winds. We'll examine this a little closer with time.
(12z TAFS) Issued at 517 AM PDT Fri Mar 27 2026
It'll continue VFR through today with surface pressure gradients supporting light winds in the valleys to offshore winds in the hills and mountains. The gradient pattern then quickly eases and reverses to onshore including possibly southerly winds developing along the north Central Coast later today, tonight and Saturday according to recent high resolution rapid refresh (hrrr) model output. If it does develop this may bring stratus /IFR/ northward along the coast to KSNS and KMRY and possibly as far north as KHAF if it develops and becomes stronger than currently forecast. At this time, satellite shows stratus gathering south of Point Conception. However, the SMX-SFO and SBA-SFO pressure gradients do not currently support southerly winds.
Vicinity of SFO, VFR. Light and variable wind becoming westerly 10 knots in the afternoon and evening. Wind light and variable tonight and Saturday morning.
SFO Bridge Approach, Similar to SFO.
Monterey Bay Terminals, VFR through today and early evening, then there is a low probability of a southerly wind reversal bringing stratus /IFR/ to KSNS and KMRY this evening to Saturday morning. Currently satellite imagery shows stratus gathering south of Point Conception. There is an upper level trough to our southwest and as it moves northeastward today it may help develop a southerly wind reversal. Recent high resolution model output show a weak 1 mb SMX- SFO gradient developing but not until early tonight; ideally for a robust southerly reversal the SMX-SFO gradient should reach at least 2 mb or greater.
(today through Wednesday) Issued at 441 AM PDT Fri Mar 27 2026
Winds and seas ease today. Light onshore winds and moderate seas over the weekend. Light rain returns by the middle of next week.
Ca, None. PZ, None.
