Significant Warm Up by Mid-to-Late This Week

May 4, 2020 – Dry and warm through this week. High temperatures warm to upwards of 15 to 20 degrees above normal beyond midweek with some locally gusty north to east wind late in the week.

Discussion

Fairly flat ridging will bring slightly warmer temperatures across the area today. Clear skies are expected this morning, with high clouds increasing in the afternoon as a upper level shortwave passes to the north over the ridge.

Temperatures will be slightly above seasonal normals the next couple of days, rising a few more degrees on Tuesday. A low pressure area in the Gulf of Alaska will help to prevent any further warming Wednesday as it passes through the Pacific Northwest on Wednesday. Northerly flow begins to increase later Wednesday behind the front as high pressure rebuilds inland.

A significant warmup trend begins on Thursday as Pacific ridging moves eastward. High temperatures are expected to be 10 to 15 degrees above normal, with low 90s in the Valley. Heat risk levels will generally be low, but should trend higher to moderate levels on Friday with highs rising to the mid to low 90s. Record highs of 96 are forecast for Redding and Red Bluff (set in 2001). Locations further south are forecast a few degrees less, and could fall short of record levels. Morning lows late in the week will also be quite warm with the northerly flow continuing, mid to upper 50s in the Valley to lower 60s in the foothills.

Extended Discussion (Friday through Monday)

Upper ridge axis moves over Interior NorCal Friday bringing the warmest temperatures of the week. Highs will be in the 90s in the Central Valley with the potential for specific locations in the Northern Sacramento Valley to tie or set new records. High temperatures Saturday forecast to be similar to Friday as ridge axis shifts into the Great Basin. Pacific frontal system progresses towards the West Coast Sunday bringing cooling and increasing onshore flow. Models suggest some potential for precipitation Monday, although differences in timing exist and being at the end of the forecast period, confidence is low attm.