A closed low that has been off shore now for over a week is currently making its way northward toward the Central CA coast. A pattern shift with a fall like trof dropping out of BC, Canada is drawing it northward. This closed low will have plenty of upper divergence and surface deformation for showers and Thunderstorm’s anytime between Tuesday and Wednesday night. The showers that developed this afternoon was the first wave coming through. It has pretty much come and gone. However, there is some convection reforming to our south and so can not rule out some showers later this evening.

The closed low off to our south will be moving north the next 24 to 36 hours. Mono county will becoming under the influence of the NE quad with upper divergence and deformation at the surface. No doubt that there will be thunderstorms over the sierra and that some areas will get some pretty heavy rains within the deformation zone, but at the moment, it is unknown where that will set up for Tuesday afternoon and especially Wednesday.

This weather pattern appears to be part of a significant pattern change. A shift from Summer to Fall like weather. What the Dweebs are looking at on a larger scale is a pattern change that will switch the mean upper ridge currently over the Great Basin to Long Wave Troughing over the northern portion of that region. The Transition will not happen over night through but soon enough.

The first trough coming in this Thursday is part the process that is ejecting the cut off through California Wednesday. That trof will spread breezy conditions and cooler air over our region Friday into Saturday. That trof will be followed by an even stronger Trof the following week if the Euro model is correct. So far any showers directly associated with both systems will remain well to our north. However, the nights will really be cooling down this weekend with low 30s in some areas. Further cooling may occur by the middle of next week. Daytime highs in the low to mid 60s Friday.

Tuesday12:00 PM update shows GFS is coming in deeper and so confidence is increasing for the first dusting of snow next week with the “Equinox Storm”

The first blast of Fall Weather is always exciting here in Mammoth. However, it usually is followed by warmer weather into October.

Dr Howard and the Dweebs………………….:-)