May 20, 2020 – Dry weather returns today except for a few lingering showers over the northern Sierra. Dry weather continues with temperatures rising above normal temperatures by Saturday, becoming hot next week.
Discussion
Upper level low continues to shift eastward is now centered over southern Idaho. Most of the area will see dry weather with high temperatures 2 to 4 degrees warmer than yesterday, generally upper 70s for the Valley and Delta.
A vorticity max on the western side of the low is dropping southward across the northern Sacramento Valley into the northern Sierra. This provided lift for a thunderstorm which tracked southeastward from around Red Bluff to Chico, becoming an area of showers by midnight. This area of showers is currently reaching the I-80 corridor in the Sierra. Snow levels have dropped to around 6500 feet, and a brief period of heavy snow showers is possible over the next couple hours, spreading to around Highway 50. This could bring some slippery conditions and poor visibility on both roads, though little snow accumulation is expected. The majority of the showers will diminish in the morning but a few showers could linger over the mountains into the afternoon as a weak wave pushes over the Sierra. Dry weather is expected across the area by sunset.
Short wave ridging will remain in place for Thursday. Highs will rise another 4 to 7 degrees. A trough will be digging to our northeast on Friday. No precip is expected with this trough but we will see enhanced northerly flow, bringing breezy north to east winds and drying conditions into Saturday. Temperatures cool slightly on Friday, with an upward trend resuming Saturday with above normal highs becoming the norm through the weekend into next week.
Extended Discussion (Sunday through Wednesday)
Hot and dry weather will dominate the extended forecast. Ensembles continue to indicate an upper level ridge will build over California this weekend into next week. Temperatures will be around 5 to 10 degrees above normal on Sunday, rising to around 15 to 20 degrees above normal for Tuesday and Wednesday. This equates to daily temperatures in the low 90s in the Valley and 60s to 70s in the mountains on Sunday, rising to mid to upper 90s in the Valley and 70s to 80s in the mountains by Tuesday. This will bring a moderate heat risk to much of interior NorCal Monday through midweek, especially for those who are sensitive to heat. Those with outdoor plans for Memorial Day weekend should be sure to take precautions to stay safe in the heat.