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April 22, 2020 – Some light precipitation possible today across the northern mountains, otherwise dry weather with a gradual warming trend into early next week.

Discussion

Other than a few high clouds moving into far northern California, skies are clear across the region early this morning. Current temperatures range from the lower to mid 30s in the colder mountain valleys, to the 50s to lower 60s across the Central Valley.

Axis of upper ridge slowly moves from the eastern Pacific to over NorCal through the remainder of the week. The result will be gradually warmer temperatures across interior NorCal. By Friday and Saturday, high temperatures are forecast to warm to around 10-15 degrees above average.

Prior to that, a weakening weather system will move over the ridge into NorCal today bringing an increase in cloud cover to the area and will generate some light warm-advection precipitation across far northern California. Satellite imagery indicates a nice plume of 1.25 to 1.50 inch TPW poised to move onshore near the OR/CA border, but very weak lift will limit QPF to mostly less than a tenth of an inch across the northern mountains this afternoon into this evening.

Extended Discussion (Sunday through Wednesday)

From the conclusion of the weekend into next week, the pattern will be dominated by very warm conditions while remaining dry. While brief flattening of the synoptic flow occurs on Sunday, a northward expanding ridge takes shape by the early/middle part of next week. In terms of widespread warmth, most locations will begin to approach the 90 degree mark which may be their first of the year unless reached this week. Forecast 850-mb temperatures are in the 20-22C range on Tuesday and Wednesday which would support mid 90s given a well mixed boundary layer. The current forecast highs over the Valley and Delta are between 89 and 94 degrees but these could budge a couple degrees upward. Relative to seasonal averages, these highs are around 10 to 20 degrees above climatology. By late next week, global ensembles show the ridge moving toward the Rockies which would favor a gradual cool down as weak longwave troughing enters off the Pacific.