PORT WASHINGTON, NY

Tuesday, February 13, 2007

Forecast for Valentine's Day Snowstorm

Here's my forecast for today and tomorrow. The first feature of this system that I would like to point out is the strong nature of the primary low, currently situated over the Tennessee River Valley. The upper level convection and gulf moisture that this system is pulling in tells me that this will be a wet event across much of the northeast, even after the secondary low forms around the Delmarva pennissula Wednesday morning. I agree with the conventional media meteorlogists that when the secondary low "blows up" off the southern Long Island coast the system will probably be too close and too wet to keep enough cold air in the atmosphere and bring significant snowfall to NYC. That being said, most are underestimating the initial snow shield that will move into the area during the day late today (especially western NY, mountains of PA, and some areas in NJ). This initial snow band that will set up this afternoon and move east during the evening will probably be good for 2-4 inches of snow in some locations by midnight.


Then, things get interesting. Based on this map from NOAA's HPC, the coastal low pretty far south (off the Delaware coast) around tomorrow 7am. This would imply that at 7am the system is still well south of the NY area and we are on the cold northern side of the low. If surface temperatures remain below 30 (which they will north of 287), this sets up nicely for at least 2-3 hours of heavy snow, which will be an additional 3-6 inches during the morning hours.


As the storm moves north, the track of the low will bring it too far west for an all snow event, especially along the coast where temperatures will reach 35-40 by afternoon. Coastal locations will receive a couple of slushy inches in the early morning hours followed by rain which will limit accumulations. As you move north and west from the city, accumulations will get heavier. This will be a big event for the Capital district and points north (I'm going skiing this weekend!)


I put an 80% probability on this coastal track and therefore in the most populated areas around NYC and New Jersey, I wouldn't expect much snow from this storm tomorrow. My forecast for CPS is 2 inches. There is a 20% chance of an eastern track that would deliver a significant snowfall to NYC (12 inches+). Travel will be difficult due to the wintry mix as the system moves from snow to rain.
If you are really into tracking these types of storms, sign up for Eastern US WX forums, its a great site that has discussion forums where professional meteorologist give their opinions.

No comments: