A storm centered in extreme southwestern Virginia at midmorning will be southeast of Cape Cod at sunrise tomorrow. With the storm adding moisture and a steady stream of ice cold air feeding in from eastern Canada, a substantial accumulation of dry, powdery snow will cover the I-95 corridor from northeastern Maryland to eastern Massachusetts with 6- to 12-inch blanket. Along the eastern New England coast, gale-force gusts will combine with the snow to create blizzard conditions. This map shows the pressure pattern across the Northeast at 10 a.m. ET.
This early-morning video shows how things should unfold during the next few days.
One tool I like to use in snow amount predicting sounds ridiculous. You look at a 200 mb map. At that high level, troughs are warm and ridges are cold, the opposite of the arrangement at 500 mb. I look for the warmest reading in a trough and the coldest temperature in the downstream ridge, then draw a line connecting them. I take the difference in readings and divide by two to get an accumulation estimate in inches. You can see why that seems ridiculous: how can a Celsius temperature calculation miles overhead give an estimate of snow accumulations in inches? I have found it helpful over the years. I won't use it for a specific accumulation forecast, but it is a guideline. Also, if we are thinking that a storm will bring a lot of snow, but the temperature spread from trough to ridge is small, it is a red flag suggesting we could go overboard on accumulations. Here is a map showing the arrangement this morning. Since we are making a forecast, I look at the downstream end of the line as being the area where this method may work best.
In this case, 7 inches is the predicted amount. Realize, of course, a tool like this cannot help with fine scale details within a storm, cannot handle changes in the flow pattern with time, cannot anticipate the effects of mountains and oceans, cannot help with the snow/rain line, etc., etc.
In response to heating at ground level and a weak cold front approaching from the west, showers and locally strong thunderstorms should develop across northern Ohio this afternoon.
... much greater interest is being generated on threats and rumors about tropical storms. It is worthwhile to read Dan Kottlowski's authoritative reports on this. Here is a copy of his map from this morning:
The tropical Atlantic shows signs of life in the storm development department. Dan Kottlowski's expert discussion suggests the third storm (which could be Hermine) of current concern is one that could head to the Bahamas, Florida, the Gulf or ???
A large high pressure area centered just south of Chicago will furnish a northwesterly of pleasantly cool and dry air to the eastern Great Lakes and all of the Northeast today into Tuesday.
As the trough moves through each locality, warm humid weather will be followed by showers and thunderstorms, then cooler an drier air will arrive
D actually makes up the largest part of this map and represents the large area that is sunny for the most part