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So here we go (plot along with me if you would like ---- and stormchaser, another map would be appreciated greatly. Thanks.)
4-8 Inches ---- on the northern side Cleveland OH east-southeast to Mount Pocono PA then sharply southeast to sandy hook NJ and out, on the southern side Accomack VA, west southwest to Lynchburg VA, then back northwest to Charleston WV and northwest again to Columbus OH and back to Cleveland.
8-10 Inches ---- Atlantic City NJ northwest to Reading PA, then west to Pittsburgh, the southwest to Parkersburg WV, on the northern and western side, then from Parkersburg WV southeast to Harrisonburg VA, east to Rehoboth beach DE and out.
Within this area local amounts up to 12 inches will be possible especially across portions of the Shenandoah Valley, Blue Ridge and Potomac highlands.
Now as far as the specifics of the system are concerned, this will initially be a very impressive STJ s/w with a strong corresponding vort max and negative tilted trough. Only problem here is that for one the system never closes off at H5 once it comes out, and dampens out on its way east.
Here is the afternoons (12z) ETA initialization:
We notice that the ETA initializes a closed low at h5 with the s/w across northwest Mexico. But as you will see the system dampens out substantially by 48hrs.
48hr ETA valid 12z 1/26:
By this time the vort max associated with the s/w is barely even discernable, and the trough has lost the amplitude it had while across the Midwest. The jet is lifting up across which is allowing slight ridging to develop in response across the eastern part of the country which is being aided by the digging s/w to the west. So as the STJ s/w energy encounters the ridging it weakens and proceeds to dampen out almost completely by 12z Monday.
The ETA brings strong rising air motions (UVM / Negative omega) over the mid-Atlantic region between 18z SUN and 12z MON:
30hr ETA valid 18z SUN:
36hr ETA valid 00z MON:
42hr ETA valid 06z MON:
48hr ETA valid 12z MON:
The ETA does manage to get some strong UVV all the way up to New York City by 06z Monday. However at this time the best overall negative omegas appear to occur from southern Pennsylvania into Maryland and the Washington DC area throughout the period.
1000-500mb Thicknesses of about 540 across the Mid-Atlantic region suggest about 10:1 ratios ---- however further north into southern and central PA thicknesses are lower (between 534 and 528) which could lead to higher ratios where the cold air is stronger.
42hr ETA (SLP, thicknesses and 6hr precip) valid 06z MON:
48hr ETA (SLP, thicknesses and 6hr precip) valid 12z MON:
Thus we will assume a 10:1 ratio south of the PA/MD border where thicknesses are around 540 throughout much the event and a 12:1 ratio further north where the colder air is stronger and 1000-500 thicknesses are around 534.
The one fascist of this system that we haven’t seen much this winter across the mid-Atlantic and northeast is a favorable environment for snowfall growth. The ETA (BUFKIT soundings) suggests a low dendrite layer (the -12 to -15C layer of the atmosphere ---- favorable for maximized crystal growth) across the region, with the best UVV coinciding with that layer. This we should have NO PROBLEM getting our moneys worth regard to ratios unlike previous events. The GFS had more of a CSI look to it with a dry adiabatic lapse rate (~7.00C/km ---- between 500 and 700mb) good negative EPV, and decreasing theta-e with height.
The ETA though it has baked off some on the 12z run, it still is the furthest north with the heaviest QPF and has been for several runs now. While the GFS and NGM are further south and drier. I think the GFS may be too dry (and the NGM obviously is given the fact that it’s normally too dry). If we recall, the ETA was the first model to see the precipitation making it further north with the event last weekend while most of the other models didn’t pick up on it until close to the start of the event. Plus the trend with most of the events this winter has been to bring systems (and the heaviest precip) further north than what the data implies at a longer range. So I’m in no way going to discount the ETA.
Last nights EC was basically the mean between the GFS and ETA solutions ---- so I would think that it is on the right track as well and may have the best handle on the placement of the surface low. But due to the low-resolution nature of the model and the 24hr time steps, I will not make any other judgments based on its output.
Attention then shifts to the potential for icing in places which see the heaviest snow accumulations on Monday and Tuesday. Soundings suggest that areas across northern PA may only mix with IP/FRZRA or FRZ drizzle for a short period of time. But with additional QPF in these areas, additional snow and ice accumulations are possible as well. But we will take this one step at a time.
