Dry and mild weather expected early this week before a transition toward cooler and more unsettled weather from Wednesday onward. Unsettled weather pattern expected to continue through the end of the week and into the weekend, with best chances for light to occasionally moderate precipitation favoring the northern Sacramento Valley and Sierra/southern Cascades north of I-80. Gusty southerly winds anticipated Wednesday and Thursday as well.
Discussion
As of early this morning, mostly clear skies are evident across the region as ridging aloft and surface high pressure build in. With largely stagnant surface flow outside of terrain driven winds, mild overnight temperatures in the 40s to 50s are expected for low temperatures the next several mornings.
While some potential for Valley fog development will be possible, current probabilities of visibility down to 1 mile sit around 20 to 30 percent at this time. Seasonably warm high temperatures are expected to provide the primary impacts today and Tuesday, with widespread high temperatures in the mid 70s to 80s throughout the Delta, Valley, and foothills and 60s to 70s still at higher elevations.
While some occasional scattered high clouds may inhibit the overall magnitude of warming, high temperatures the next couple of days will at least be nearing record values for late March in some locations.
Moving toward the middle of the week, a trough digging from the Gulf of Alaska is expected to advance toward the Pacific Northwest/NorCal coast. Ensemble guidance is largely in agreement regarding the progression of this trough, with some appreciable moisture advection expected toward the region ahead of it. While comparably cooler temperatures to earlier in the week are expected by Wednesday, the combination of moisture advection and still seasonably warm temperatures will likely result in a broad area of available instability during the afternoon and evening hours. Despite this, forcing will be limited and warm temperatures aloft are expected to inhibit much of the convective potential. Still, some isolated thunderstorm chances around 15 to 25 percent do exist, primarily through the northern Sacramento Valley and adjacent foothills/higher terrain, where the approaching trough may provide ample forcing for convective development.
While higher totals can be expected with any thunderstorms that develop, highest probabilities for exceeding 0.25 inches of precipitation through Friday evening sit around 30 to 60 percent along the northern Sierra/southern Cascades and into the northern Sacramento Valley. Additionally, breezy to gusty south winds are anticipated, Wednesday and Thursday, with strongest gusts 25 to 35 mph expected through the Sacramento Valley, with some gusts up to 45 mph possible along the Sierra/southern Cascades. Regardless of precipitation uncertainty, temperatures are expected to cool back to near normal through the end of the week.
Extended Discussion (Friday through Monday)
Ensemble guidance differs on the exact progression of additional waves through the upper level flow pattern, but broad west-northwesterly flow aloft is expected to keep unsettled weather around through the end of the week and into the weekend.
Despite the active look to the weather pattern through the extended, precipitation impacts are expected to remain periodic at the moment, with brief lulls between generally light to occasionally moderate precipitation impacts into the weekend.
The northern Sacramento Valley/southern Cascades/northern Sierra north of Interstate 80 remain favored for much of this precipitation, with mostly dry and seasonable weather elsewhere.
While the overall magnitude of precipitation impacts remains a bit uncertain, particularly through the weekend, ensemble guidance does continue to indicate potential for more widespread precipitation chances moving into early April.