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July 22, 2019 – Gradual warming this week with widespread triple digits expected. Any thunderstorm activity is expected to remain to the north and east of the area this week.
Satellite imagery shows clear skies across interior NorCal except for a band of mid and high clouds moving up from the south into northeast California and western Nevada. Current temperatures are mainly in the 50s and 60s in the mountains with mid 60s to mid 70s across the Central Valley.
South-southwest flow in the mid and upper levels will persist the next 24 hours as the region remains between strong high pressure over the Desert Southwest and low pressure off the PacNW.
Weak short-waves moving up from the south will likely help to initiate more thunderstorms east of the Sierra crest along an axis of deeper moisture and instability over western Nevada. Temperatures will edge up a bit as the marine layer becomes a bit more shallow despite continuing onshore flow.
Slight further warming is expected Wednesday and Thursday as the ridge over the southwest is forecast to extend westward into NorCal.
Extended Discussion (Friday through Monday)
Upper ridge of high pressure centered over the four corners area will keep the start of the extended period warm and dry.
With main subsidence under the ridge well east of the forecast area, daytime high temperatures are expected to come in just a few degrees above climate normals. Southwest flow aloft should keep any monsoon moisture east of the forecast area.
Although models differ a bit going into early next week and the GEFS ensemble spread grows, the forecast remains dry under upper southwest to west flow with daily highs cooling slightly.