12z models say yes

Now entering the 5 day range, so I'll start discussing more in depth what appears to be a legitimate threat for Thursday 12/11 to Friday 12/12.

Progression of events through the end of the week

Sunday 12/7

A shortwave (associated with the clipper moving through tomorrow) will align with a negative tilt through central PA, with surface low reflection near Toronto and coastal low pressure running east of Cape Cod. See previous post for details on snow potential (update on the situation later tonight and through the event tomorrow morning). Out west, a strong short wave will be diving southeast, near the Washington / British Columbia coastline. Meanwhile, a piece of energy will move into southern California. Above (below) normal temperatures will be found in the west (east).

Monday 12/8

Northeast shortwave lifts north with surface low pressure beginning to retrograde west into northern Canada. Shortwave energy in the southwest moves into New Mexico with surface low developing in Colorado. Positive vorticity advection moves into the northern Rockies in association with a shortwave over the Pacific northwest. Precipitation will move into Montana, with new precip developing near the four corners region. Temperatures will be well below normal in the east with cold air advection developing in the northwest and warm air advection over the central states.

Tuesday 12/9

The two pieces of energy out west phase with a strengthening vorticity maximum crossing New Mexico. Surface low pressure strengthens as it moves through Missouri and Illinois. High pressure moves east of New England, allowing ridging and warm air advection to encompass the eastern third of the nation bringing 2m temps to near normal. Below normal temperatures pour south across the northern plains, west of the surface low. Precipitation will overspread a large area from the midwest to Great Lakes and New England. A moderate snowstorm is possible for portions of the midwest into the Great Lakes. Precipitation will begin as snow in New England, mixing with and changing to a wintry mix from south to north.

***12z models in decent agreement, although consistency between runs begins to decrease starting Wednesday.***

Wednesday 12/10

Frontal boundary aligns from Michigan to Texas with strong vertical vorticity. 500mb low begins to develop in Mississippi. Surface low pressure moves northeast through western NY and into southern Quebec. Strong warm air advection out in front of the storm will quickly change any wintry precipitation left into plain rain across SNE, with 2m temps ranging from the upper 30's to low 50's from north to south. Strong cold air advection will bring 850mb temps to -10 to -20C across the central states, with ridging reentering the western US. Weak short wave with surface low reflection will ride over the ridge into the Dakotas.

Thursday 12/11 to Friday 12/12

That shortwave will move into the Great Lakes and strengthen and act as a kicker for the next storm:

Front crosses the northeast with colder and drier air moving in with high pressure building to our north. Energy at the southern end of the front stays behind. With that energy, good agreement between ECMWF, operational GFS, and GFS ensembles for a 500mb low developing in the southeastern states on Thursday. Surface low pressure develops in the southeast and may move up the coast towards the region Thursday afternoon while strengthening and spreading snow across the eastern seaboard.

Being at a 5 day range, details are a long way away from being worked out. The 12z models suggest a significant to major winter storm for the Mid Atlantic and Northeast. The GFS has been flipping between storm and no storm for a while now, and this is the first run the Euro likes the storm. Once the shortwave in the Gulf of Alaska moves out of the data devoid Pacific and into the northwest (Monday), the models will become a bit more consistent. For now, counting down from about 20 model runs of the GFS, and 10 of the Euro to go before Friday.