MINOR SNOW EVENT WED MORNING IN NORTHERN MID ATLANTIC .. and looking at Saturday March 12
After the cold front pushed through on Monday night, and Tuesday morning, a much colder air mass has moved into the Middle Atlantic and New England regions. However, the southern end of the cold front has stalled across the Southeastern states, and another area of LOW pressure is going to form on the front which will cause widespread rain to develop on Tuesday night across most of the southeast US. This Low is coming north and will bring rain and snow to the Middle Atlantic and New England.
Some of the models on Monday, midday, were showing that as the LOW pressure area comes North into the Carolinas, the low-level temperatures would be just cold enough for the rain to change over to snow in the Northwest third of Virginia, central and western Maryland, and the eastern portions of West Virginia into southern Pennsylvania and New Jersey. The high-resolution short-range models showed an interval where the rain would change to snow in these areas somewhere between 4 and 5 am on Wednesday until about 9 to 11 am. Of course, further north into Pennsylvania, New Jersey and southern New York, where temperatures will be colder, the snow risk would be more of an issue and the duration of the snow interval could be considerably longer. 2
As is the case with most possible snow events in the middle of March, there are several factors at play which will be critical in determining what if any snowfall occurs early Wednesday morning in these areas. A difference of one or two degrees will be quite critical in figuring out what if anything is going to happen on Wednesday morning. In addition, the ground and road temperatures after the last several days are quite warm throughout all of the Mid-Atlantic region and in southern New England. So any snow that does fall will only have a chance to accumulate on the normally colder surfaces. All the main roads should be snow-free throughout the northern Middle Atlantic and New England, or at best will see just a slushier accumulation. Any accumulation of snow will be on car tops, lawns, trees, bushes, the back porch etc. The snow ratio will not of course be 10 to 1. If the snow actually falls as forecasted, the snow ratio will be more like 5 to 1. This means that the snow accumulation maps have to be adjusted downward significantly.
Starting last night and continuing to midday today, the short range models are showing the temperatures will not be cold enough to support rain changing to snow on Wednesday morning in the northwest third of Virginia, western and central Maryland, or the eastern portion to West Virginia. The Min temperature readings early Wednesday morning will drop down into the mid-30s but no colder. It is possible that in far northwest Virginia, western third of Maryland, and the eastern portions of West Virginia there could be a couple of hours of wet snow at 33 or 34 degrees, but that’s about it.
The new data on Tuesday midday shows that rain-snow line is going to set up along the PA- MD Border across Southern New Jersey. The Philadelphia metro area will be right on the edge of the rain — snow line, while areas just to the west and north will see several hours of wet snow Wednesday morning to midday. This includes areas such as Harrisburg, Gettysburg, Lancaster, York, Reading, Allentown, Princeton and much of northern New Jersey. In these areas temperatures will be closer to 33 or 32 degrees during the height of the moderate precipitation, which might allow for some small accumulations on normally colder surfaces. The snow will moving into New York City during the midmorning hours as temperatures drop down to around 33 or 34 degrees. The snow will reach Connecticut, Massachusetts, and Rhode Island by 11 a.m., or noon on Wednesday, and continue until about 8 p.m. Wednesday evening
In most of Virginia, Maryland, and West Virginia this will be a rain event and the rain will be quite heavy at times with rainfall amounts of 1 to 2 inches likely across the southern half of Virginia, the southern Delmarva, western half of North Carolina, all of southwest Virginia, eastern Tennessee and up to 3 inch rains in the mountains of western North Carolina
MOST LIKELY OUTCOME
SATURDAY MARCH 12
Of more concern is the event for the end of the week. In some ways the event for this Friday into Saturday resembles the upper air pattern to the historic March 11–12, 1993, historic East Coast winter storm. But in this case, the mean Trough position of the jet stream is too far to the west and the upper air pattern in eastern Canada and Greenland is not favorable for an East Coast track.
As this huge trough develops across the Mississippi River Valley on Friday night and Saturday, it will develop a strong arctic cold front that will sweep across the Midwest and reach the Appalachian Mountains on Saturday morning. By 7 am. on Saturday morning the arctic cold front will run from Montreal to Binghamton to Martinsburg to Roanoke to Asheville, and then just to the northwest of Atlanta. All areas east of this front on Saturday morning will be seeing southerly winds that will force temperatures to rise as the warm air continues to flow from Georgia to New England. This means that Friday night into Saturday morning temperatures will be rising in these areas east of the cold front.
In the areas west of the cold front, LOW pressure will develop early Saturday morning in Northwest South Carolina that will move into Central Virginia by 7 am. on Saturday. With the cold HIGH pressure dropping into eastern Kansas, the interaction between the LOW pressure area in Virginia and this HIGH pressure area in Kansas will produce strong north winds which will change the rain to snow for several hours on Saturday morning in far northwest Georgia, the eastern half of Tennessee, eastern Kentucky, all of West Virginia, southwest Virginia, western Maryland, the western half of Pennsylvania, and New York.
During the day Saturday, the cold front will progress eastward while at the same time the LOW in central Virginia will track to New York City to Worcester Massachusetts by 1 pm. Heavy rain will continue in eastern New England but the rain will change to heavy snow from west to east across New England, during the day on Saturday. In the Middle Atlantic region, the rain will also change to snow in the following areas: much of New York State, northwest New Jersey, all of central and eastern Pennsylvania (including Philadelphia), northern and eastern Virginia, Washington DC, and Baltimore, Fredericksburg, Charlottesville, and the northern Shenandoah Valley. Winds on Saturday after the front passes will gust up to 40 mph
Surface temperatures will crash dramatically. In Richmond temperatures at 7 am. on Saturday will be 55 degrees, but by 1pm temperatures will be 34 degrees. We will see the same kind of dramatic temperature drop in Washington DC, Baltimore, Philadelphia, and New York City during the early afternoon hours.
Based upon the current data it does look like there will be a changeover to snow in the above mentioned areas in the big cities of the Middle Atlantic and New England on Saturday late morning into early afternoon. There could be several hours of hard snow but the ground temperatures will be again rather warm and wet, and it will be difficult to get the snow to accumulate.
If this event was a typical mid-winter storm, there could be a few inches of snow in northwest, all of West Virginia, western and central Maryland, and much of Pennsylvania into northwest New Jersey with even 1–2 inches in D.C Baltimore, Philadelphia, and New York. But, of course, this 12 is NOT a mid-winter storm. The ground temperatures, the Sun angle, and the heavy rains before the changeover, are all going to be contributing factors in reducing any snowfall. Indeed, if you look at the model data which shows snow depth on the ground as opposed to actual snow accumulation, you will see it shows very little accumulation in any of the areas of the Mid-Atlantic or New England, for locations below 1000 feet on Saturday.