Afternoon update

After looking at Wednesday's model guidance, it appears more likely southern New England will miss the brunt of the upcoming storm. Much of what I wrote this morning is still valid, but with increasing confidence we won't have a major event here. This storm is large and three days away, there will be changes to the forecast, but for now it looks like we aren't going to see a big hit.

The map below from the GFS brings some snow to Cape Cod and the Islands and even a bit in Boston, but other models are even further south. If we do see snow it would be Saturday afternoon and end by sunrise Sunday. More details on Twitter @growingwisdom and tomorrow.

Earlier:

Another morning, another forecast and more model information. There is still going to be a large coastal storm developing this weekend, but how it will impact southern New England isn't fully known. However, the picture is becoming a bit clearer, especially from New York City south to Richmond, Virginia.





The storm is almost a certainty for the mid-Atlantic region. If you have travel plans to Washington, D.C. or Baltimore for Friday, I would cancel them unless you are staying there for a few days. The airports will likely have major delays and could close, depending on the severity of the storm. The same is true for the New York/New Jersey Airports Friday night and Saturday. Issues at those airports will ripple through the entire system, meaning areas thousands of miles from the storm could feel its effects.





The image below gives snowfall totals according to one set of models through Saturday evening. Note the bulls-eye over the Maryland/Virginia area. Also notice the sharp northern edge to the storm. The two take home points are the storm could bring a lot of snow here from a direct hit, but the northern edge of the storm will likely move through parts of southern or central New England.

Coastal concerns

Even if the full fury of this noreaster ends up off the coast, a strong northeasterly to easterly flow of air off the ocean will create beach erosion and coastal flooding concerns Saturday and Sunday. The tides are astronomically high this weekend, although the Saturday evening high tide around 11 p.m. is a foot lower than the one Sunday morning just after 11 a.m. Both of these could bring trouble.

Strong winds

Another possible effect of the storm would be strong winds along the coast, especially from Boston south to Cape Cod. These winds could cause some power outages. If the storm tracks further out to sea, we miss the winds; a closer pass would bring those winds further inland.

Snowfall potential

This storm has garnered so much attention for the past three or four days because of its snowfall potential. The image below is a forecast for the amount of moisture with this noreaster. The numbers are the amount of melted precipitation; some of this would be snow. If you multiply those numbers by 10, you get the approximate potential for snow. So one inch of water usually equals about 10 inches of snow. Boston south to Providence has the best chance of getting six or more inches of snow.





Areas to our south could see up to two feet of snow from this storm.

Model tracks and updates

Up until now, the wave of energy that will form the weekend storm has been over the Pacific Ocean.The computer models that forecast how this energy will evolve havent gotten great information about this system because the best way to learn about the atmosphere is to send up a weather balloon with a radiosonde to collect data. The map below shows where the balloons are launched twice each day.





This morning, the storm will finally cross onto land, where we can collect much more accurate data. This data is then fed into the GFS and European models, which means the forecasts should start to become more reliable. Im confident there will be fewer uncertainties about the track and impact of this storm by this evening, and certainly by tomorrow morning.

I'll have updates on this storm via Twitter @growingwisdom.