May 21, 2020 – A few showers possible this evening over the far northern Sierra Nevada and near Mt Lassen as a quick moving weather system brushes northeast California, otherwise dry weather with temperatures rising to above average by Saturday. Hot next week with moderate heat risk.
Discussion
Skies are clear across the region early this morning other than some lingering low clouds across portions of northeast California east of the Cascade crest. Winds are generally light. Current temperatures are running a little warmer across most of the area compared to 24 hours ago and range from the lower 30s in the colder mountain valleys, to the mid 50s to lower 60s across the Central Valley.
Around 4-8 degrees of warming is expected today compared to Wednesday as the airmass continues to recover from the trough earlier this week. Highs today will be close to average for mid to late May.
The last piece of energy from the big western US trough will approach today, then brush across northeast California late tonight and early Friday. A few showers will be possible across the far northern Sierra Nevada and near Mt Lassen this evening ahead of the short-wave, but the remainder of region is expected to remain dry as overall moisture will be much more limited.
In the wake of this system, breezy northerly winds will occur on Friday and Saturday as ridging (surface and aloft) builds over NorCal. Highs Friday will be a bit cooler than today, but then significant warming will develop over the weekend which will be the beginning of a stretch of hot weather that will continue next week.
Extended Discussion (Monday through Thursday)
Dry weather and well above normal temperatures are forecast throughout next week for interior NorCal. Ensemble models continue to indicate upper level ridging continuing to build over the West Coast Monday through late next week which will bring hot temperatures to the area. Overall, daytime temperatures are expected to be 10 to 20 degrees above daily normals which are normally in the low to mid 80s in the Valley for late May. Daytime temperatures on Monday are expected to rise to the upper 90s for the Valley and 60s to low 80s for the mountains. Latest NBM guidance suggests Valley temperatures will hover near the century mark Tuesday and Wednesday, with mountain temperatures in the 70s to 80s. Some locations will be close to reaching records Tuesday and Wednesday if the forecast holds.
Overnight temperatures will be warmer as well, only falling to the mid to upper 60s in the Valley. Widespread moderate heat risk with some patches of high heat risk are likely Monday into late next week. This will impact those who have outdoor plans for the Memorial Day holiday as well as those who work outdoors. Precautions should be taken to stay safe in this heat.