June 18, 2019 – A little more warming today with warmest temperatures over the northern and central Sacramento valley. A slow cooling trend through the end of the week dropping to near normal by Friday. Warmer temperatures again next weekend. A slight chance of afternoon mountain thunderstorms early next week.
A little warming expected today as high pressure pushes in over the north state. Daytime highs could reach 106 degrees in the northern and central Sacramento valley so will leave up heat advisory currently in place.
Subsidence under the ridge should bring an end to afternoon showers over the Sierra Cascade range. Increased northwest surface gradients will bring breezy north winds down the Sacramento valley and breezy west winds through the delta.
An upper level low pressure system dropping in to the Pacific northwest will bring the start of a cooling trend on Wednesday. As this system drops to the southeast the cooling trend will continue with temperatures dropping to near normal by Friday.
A moderate delta breeze may bring some coastal stratus into the delta region especially Wednesday and Thursday mornings but a significant intrusion is not expected. At this time, models indicate any shower activity associated with the low should remain well north and east of the forecast area.
Extended Discussion (Saturday through Tuesday)
Model ensembles continue to be in good agreement in showing a cooling trend for the weekend into early next week. This is due to eastern Pacific ridging flattening as a shortwave drops southward into the region from the Gulf of Alaska. Forecast temperatures start at about 5 degrees above normal levels on Saturday then drop to around normal levels by Monday. GEFS and EPS 500 mb heights show low anomalies continuing through the week.
The Delta breeze is expected to strengthen as the flow becomes more onshore bringing cooler temperatures to Delta influenced areas. Highs across much of the Valley are only expected to reach into the mid to upper 80s Monday, with mountain highs in the 60s to 70s. GEFS mean temperatures drop below normal by Tuesday, with forecast highs dropping an additional 5 degrees. Generally dry weather is expected, though the GEFS is hinting at some precipitation potential late Tuesday over the northeastern portion of the state. For now have limited forecast to some afternoon/evening showers and thunderstorms over the Lassen National Park.