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May 22, 2020 – A few showers may be possible along the crest of the northern Sierra this afternoon, otherwise dry weather persists. Below average temperatures today, then a warming trend is expected into next week with moderate to high heat risk possible beginning Memorial Day.

Discussion

Some mid and high clouds are slowly drifting south through NorCal early this morning ahead of a mostly dry cold front. A few showers occurred Thursday evening across the far northern portion of the forecast area, but these have now moved east into Nevada. Northerly breezes are picking up across the northern Sacramento Valley and surrounding terrain (a few spots gusting 20-30 mph) as the north-south surface pressure gradient tightens behind the front (MFR-RDD now over 8 mbs).

A potent vort will swing through NorCal today as the upper trough shifts east. While moisture is rather limited, it may provide enough lift for a few showers this afternoon along the crest between Mt Lassen and Lake Tahoe. Otherwise, the remainder of the region will continue dry weather with slightly cooler temperatures today. Northerly breezes are expected to spread down the Central Valley with gusts of 20-30 mph.

Temperatures will steadily warm across the region this weekend as ridging from eastern Pacific builds across NorCal. Another episode of early-season heat is expected next week as valley and foothill temperatures climb into the upper 80s to upper 90s by Memorial Day. Waterways continue to run cold and fast and precautions should be taken if heading to the water.

Extended Discussion (Tuesday through Friday)

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An extended period of anomalously hot weather is in store for interior Northern California next week as upper level ridging remains dominant. Models continue to indicate that daytime temperatures are expected to be around 15 to 20 degrees above the daily normal through Thursday. Current forecast now has daytime Valley temperatures ranging from 99 to 103 degrees Tuesday through Thursday with the mountains in the 70s to near 90. Minimum temperature forecast has increased too, so morning lows will only fall to the mid 60s to low 70s, which may not provide much relief from the heat. Moderate to high heat risk is expected in the Valley and foothills through Thursday. Prolonged heat like this could impact not only those who are sensitive to the heat, such as the elderly or outdoor workers, but also those who do not have access to proper hydration or adequate cooling.

Some slight cooling may be in store Friday as ensembles indicate an approaching trough could finally push the ridge to the east. However, temperatures would still be well above normal with Valley temperatures in the 90s.