Sunday brought in light and isolated showers to the region. Moisture coming off the Pacific was in the form of puffy cumulus clouds. Orographic (mountain) uplift and weak instability caused most of the showers to occur in the foothills of the Cascades and in the high country. Snow levels started at 4,000′ and got to around 4,500′ by the afternoon. Snow levels will drop again overnight, however moisture will fizzle out so only very minimal amounts of precipitation will occur in the morning hours of Monday.
Monday morning will see a break in cloud coverage. Partly cloudy skies will be the story in the morning hours. This could lead to some frost situations. Some temperatures could get near 33-36 degrees in areas that are clear overnight. Any sensitive outdoor plants could suffer from the near freezing temperatures. If your area is prone to cooler than average temperatures and clouds seem to be thinning in the evening, covering plants is recommended. Fog will also be a concern in some areas as we have a saturated air mass overhead. Areas that see temperatures cooling off rapidly will see patchy fog form in the morning. Regions that could see fog on Monday morning include the coast, west side valleys, and parts of Northern California, especially near Happy Camp.
After the fog lifts clouds will begin increasing in the late morning hours ahead of a warm front that will move to the west of the region. Temperatures will warm after passage of the front allowing for warming anywhere from 5-10 degrees above the last few days (even with the cloud coverage). Models have come into better alignment as to whether or not we would see showers with this system. It’s looking like the coast and the mountain locations will see the most precipitation with the pre-frontal moisture in the afternoon hours. Because of the warmer air moving in, snow levels will rise to around 7,000′ causing the precipitation to be mostly rain. Rainfall totals will be very minimal though as the showers will only last a few hours. The rain shadow effect will cause the valleys to see only light precipitation, if any. Northern California and the Klamath Basin will only get cloud coverage from this system. Rain should end around the early morning hours of Tuesday. This will be the last bit of precipitation before the very strong high pressure ridge builds into the area.
High pressure will strengthen on Tuesday and clouds will become scarce in the area. Above average high temperatures will enter the region along a thermal trough that will enter the area. Temperatures will jump to 5-15 degrees above average by Tuesday afternoon. The Chetco effect will begin on Tuesday and strengthen by Wednesday. High pressure will allow for the offshore flow needed to achieve these higher temperatures. Temperatures along the coast will reach the lower 70s on both days. A weak embedded high pressure ridge will hit the coast Thursday causing winds to shift to the west, which will end the offshore flow and bring in cooler air. As this ridge moves inland, temperatures will once again warm for the inland locations. Thursday will be the warmest of the upcoming days. On Thursday, afternoon temperatures in Northern California will reach the upper 80s. The Basin will see highs in the upper 70s. Some mountain locations will see 70 on Thursday. And the valleys will get into the upper 80s as well. Some areas in the could even hit the 90s! This early season heat wave will make temperatures get very close to records. If conditions are right, record temperatures could be broken in some locations. After Thursday, clouds will move in with a weak system. Some showers could be seen overnight in the Cascades. Other areas will just get cloud coverage. because of this, temperatures will not be as high into the weekend.
Thanks for logging on and enjoy your week!
Meteorologist Seth Phillips