As San Francisco residents enjoy the current streak of clear skies, the National Weather Service (NWS) San Francisco has indicated that this weather pattern is set to persist through the upcoming weekend and into the early part of next week. In a report updated early Wednesday morning, NWS forecasters expect temperatures to "hover near normal through the extended forecast" as the city experiences what could be described as a welcome stretch of "quiet weather."
The clear conditions are a surprise, considering the presence of a strong marine layer anticipated to spur overnight cloud formation. However, a decrease in northwest surface winds over coastal waters, which "led to a small but consequential increase in water temperature," has disrupted typical stratus cloud development, according to the NWS advisory. The forecast suggests another such clear overnight is not likely, with the cooling process after sunset poised to restore the balance for stratus formation near the coastline eventually.
Although San Francisco can generally expect a mild warm-up as the weekend approaches, temperatures will remain within five degrees of what's typical for this time of year. The departure of monsoonal moisture to the east is ushering in a drier air mass. This shift will mean "slightly cooler overnights" than recent evenings and "lower minRH values each afternoon," the NWS report stated.
In terms of aviation weather, while coastal regions are beginning to see some redevelopment of stratus clouds, which could temporarily affect visibility conditions with "MVFR-IFR-LIFR," the interior parts of the Bay Area remain predominantly clear with "VFR" (Visual Flight Rules) conditions. The prediction is for the stratus to "mix out by late morning," but there's an anticipation for the clouds to return overnight and into Thursday morning. Local airports, including SFO, will likely experience a usual pattern of brief IFR conditions during early mornings, with west winds expected to pick up periodically to "15 to 25 knots this afternoon and early evening," the advisory reported.
The forecast should be relatively good news for those setting sail or participating in marine activities. The earlier portions of the week are predicted to maintain "light to moderate breezes and moderate seas," but mariners should be prepared for an uptick in wind strength and sea conditions over the weekend, per the NWS. This could present fresher challenges for those on the water, so caution is advised as these changes develop.
