The low pressure system that has been held over us by a blocking pattern will move away, allowing high pressure to bring better conditions to our area.
On Saturday, an upper air disturbance still associated with that low may rotate through, bringing mid-level cloudiness (altocumulus) in the late morning and early afternoon. Some clearing late afternoon. High on Saturday still cold at 39.
On Sunday, high pressure will build in for mostly sunny skies. Temperatures finally moderating with a high of 48.
This afternoon’s models have greatly diminished the chances of any accumulating snow Tuesday night. In fact, they have backed away from the high rain amounts, with the heaviest rain now tapering in the afternoon.
This is a very dynamic system and I expect further changes in the forecast.
Latest NAM cranks out several inches of snow by Wednesday morning (4 inches) as the heavy rain Tuesday transitions to snow Tuesday night. This is for PHL airport. More north and west.
The predicted thermal profile of this storm continues to become colder as it moves slowly past us Tuesday night. Stay tuned.
The models are coming together in predicting the development of a coastal storm that will be a slow mover, affecting us directly from Monday night into Wednesday morning, then indirectly into Thursday.
The models have become somewhat consistent in predicting very heavy rain for our area on Tuesday. The NAM has almost 2.5 inches of rain falling! Temperatures appear too warm for snow to form during much of the storm, but it looks like a possibility that wrap around cold air and moisture will bring us some wet snow, especially in the NW suburbs Tuesday night into early Wednesday morning.
Temperatures at the surface will be just about or above freezing, so accumulations will be limited. But this wrap-around moisture will be occurring at nightime Tuesday, perhaps allowing 2, maybe 3, wet inches to accumulate on grassy surfaces by Wednesday morning.
So, no accumulations on Tuesday, just heavy rain and windy, then possibly 2 inches or so wet accumulation later Tuesday evening into Wednesday morning.
Not much cold air around after this storm and a significant warm up may occur next week.