Expect cool, frosty, and foggy mornings through Saturday. Dry and mainly sunny skies persist into next week. Coldest morning on Saturday, with best potential for low temperatures at and below freezing.
Discussion
Mostly sunny skies are being observed across interior Northern California on this Thanksgiving Day Eve via GOES-West visible imagery. Latest observations show northerly winds gusting 15 to 25 mph along the I-5 corridor in the central and northern Sacramento Valley this afternoon [as of 2 pm]. Light to breezy north to northeast winds will gradually weaken later this afternoon, before slightly redeveloping overnight and becoming more localized to the Delta and far western portions of the Sacramento Valley. This will lead to the potential for fog development across portions of the central/southern Sacramento Valley and northern San Joaquin Valley east of the Interstate 5 corridor. Several hi-res models show reduced visibilities down to 1/4 mile or less from Stanislaus County to as far north as Yuba City, CA tomorrow morning, where north winds were weaker today. As a result a Dense Fog Advisory is in effect from 1 AM to 9 AM Thursday morning. The potential for fog continues Friday and Saturday mornings, as northerly flow aloft continues to weaken and ridging amplifies. This will result in even more favorable conditions for radiation fog development.
Additionally, this will allow for colder morning temperatures tomorrow and into the weekend. The National Blend of Models (NBM) has a 40-95% chance of temperatures below 36 degrees, with Friday and Saturday being highlighted as the two coldest morning of the week. The NBM shows a 20-40% chance of low temperatures less than 32 degrees across more rural areas of the Sacramento and northern San Joaquin valleys. These temperatures may impact pets, plants, and those without adequate heating, in addition to causing widespread frost.
For those who may be outdoors on Thanksgiving morning, be sure to dress appropriately for the colder weather. Sunday morning looks to be a few degrees warmer, but temperatures will still be in the mid to upper 30s. Otherwise, expect dry and calm weather heading into the work week.
Extended Discussion (Sunday through Wednesday)
Clusters and ensembles are in good agreement bringing high confidence in an extended period of dry weather as an upper level ridging pattern predominates into next week. Generally dry conditions with light to breezy winds, mostly clear skies and near normal to above normal high temperatures are expected through the middle of next week. Sunday morning lows are expected to be a little less cold than Saturday, with Valley lows forecast by the NBM to be mid 30s to near 40. For Monday through Wednesday lows trend slightly higher, generally near normal, which for the Valley is upper 30s to lower 40s. Patchy morning fog is possible in sheltered portions of the Valley and in mountain basins in this pattern of mostly clear nights and light winds.