Final Call for Messy Holiday Weekend Storm
Snow to Rain Near the Coast & Significant Ice Inland
Synoptic Overview:
The larger synoptic scale overview remains unchanged from Wednesday's First Call.
This weekend, a southern stream wave will begin to interact with a lobe of the polar vortex pinned to the south of a potent -NAO block.
The combination of antecedent elevated east coast heights attributable to the Maritime continent phases of the MJO and the -NAO block being positioned sufficiently north as to allow a partial midwest phase will maintain enough eastern ridging to allow for an inland track of the low.
This will delay the transfer of the mid level low to the coast until the system reaches a very high latitude, which will ensure that snowfall will be relatively limited across much of the region. However, once the system progresses far enough to the east, it will begin to be influenced initially at the surface by confluence due to the tandem of the -NAO block and the potent 50/50 low.
It now appears as though the surface low will redevelop on the coast quickly enough so that a portion of the area receives a significant, albeit manageable ice storm on Sunday.
Expected Storm Evolution:
Precipitation will overspread the region as snowfall from southwest to northeast on Saturday evening.
After a few inches of snowfall, precipitation will rapidly transition to some ice and rain to the south of the Mass turnpike after midnight early Sunday morning.
The changeover will slow somewhat as it works into northern areas by mid day due to increased resistance from confluence. However, the potent primary mid level low to the west will ultimately win the battle and snowfall will give way to ice.
And then eventually rain, outside of perhaps northern Worcester country during the afternoon.
However, towards evening the surface low will transfer to the coast, which will re-advect colder air from the northeast down the coast. This would reintroduce icing issues across especially interior northeastern Mass over through the eastern slopes of the Worcester hills.
In fact, precipitation may even change back to snowfall prior to ending entirely later Sunday evening.
FINAL CALL:
First Call issued Wednesday, February 12 @ 830pm: