Today through Monday night, satellite and radar imagery are showing the beginnings of the next frontal system which is poised to move across the Pacific Northwest and northern California today into Wednesday.
Oddly enough, the radar returns have pushed a bit farther inland– already reaching the Cascades. This might suggest that the models, including the higher resolution models, may not have the best handle on this situation yet. That being said, observations have shown very little precipitation, if any, has actually been reaching the ground.
As of the time, only the Umpqua and Agency Lake in the Cascades have measured precipitation so far. The web cameras also appear clear. Thus, the returns are most likely virga which will work to moisten the atmosphere for when the front actually does move inland this evening.
Still, models are suggesting that the front will stall a little bit today as a ridge overhead will amplify and bring some warmer than normal temperatures to the area. In fact, there’s still over a 60 to 70 percent chance of Medford reaching 70 degrees today.
However, conditions will gradually become less conducive for outdoor activities from west to east as the ridge pushes eastward and the front finally begins to move ashore. Precipitation will move inland from west to east this afternoon. There is a 50-80% chance along the coast Sunday afternoon with a 30-50% chance of rain for areas inland to the Cascades, Umpqua Basin and the Illinois Valley.
Meanwhile the Rogue Valley will be downsloped leading to around a 15% chance for precipitation through the late afternoon.
The weather front will move slowly with around an inch to as much as an inch and a half of additional rainfall for the coast tonight, with amounts tapering off quickly east of the Coast Range. Meantime, downslope southerly winds will keep conditions mainly dry in the Rogue Valley.
By Monday afternoon, the coast will have an additional inch to inch and a half of rain and the front and associated precipitation will move to the Cascades.
The approach of the front will also result in gusty southerly winds to 35 mph from late Monday morning into Monday evening for the Shasta Valley and east of the Cascades. The front will continue across the area Monday night with widespread light precipitation and snow levels falling to 2500 to 3500 feet.