Critical fire weather conditions today into Tuesday

May 10, 2021 – Dry weather with gusty north winds and critical fire weather conditions through the early part of this week. Warming trend develops through mid-week, with temperatures decreasing for the weekend.

Discussion

Satellite imagery shows ridging to our west and troughing to our east. The pressure gradient from Medford to Sacramento is around +10-11 mb, with wind gusts across the Sacramento Valley ranging from 15 to 30 mph. Model guidance holds the pressure gradient between +9-12mb through today, thus gusty winds will continue.

Peak gusts for the Valley should range from roughly 20 to 35 mph, locally up to 40 mph. With dry fuels in place and poor humidity values a Red Flag Warning remains in effect through Tuesday. Winds will start to ease late Monday night into Tuesday; however, fire weather conditions will still remain critical.

In addition to fire weather concerns, increasing temperatures will be observed for the first half of the week. Widespread upper 80s to low 90s are forecast for the Valley today while the mountains and foothills soar into the 70s and 80s.

Even warmer temperatures are forecast for Tuesday through Thursday as widespread low to mid 90s are expected for the Valley. In terms of Heat Risk, there are areas of orange/moderate heat risk forecast for portions of the Valle and foothills, especially by mid week. Be sure to practice heat safety.

We should see a Delta breeze develop on Wednesday and that will bring some relief to the Delta and eventually the Sacramento area from the hot temperatures during the late afternoon and evening.

Extended discussion (Friday through Monday)

EPAC upper ridge remains dominant synoptic feature over interior NorCal into Friday continuing above normal temperatures. Highs forecast around 10 to 15 degrees above average.

Short-wave trough approaches over the weekend with forecast uncertainties due to varying model solutions on depth and progression.

Ensembles still trend towards a deeper trough, with onshore flow and cooler temps. The NBM POP forecast continues to look mostly dry.