President's Day Potential Nor'easter

The new American GFS model is predicting a massive Nor'easter to develop off the coast of New England around President's Day.

The energy for this storm is projected to drop south from the Pacific Northwest and strengthen as it enters the southern Plains. From there, it swings east and develops a negative tilt as it pushes northeast into the East Coast. The development of a negative tilt means the highest vorticity values at the 500 millibar level are positioned to the southeast. This is observed in the upper left hand panel of the above forecast image, which is valid for the night just before President's Day.  Typically, negatively-tilted storm systems are watched in the spring, when cold air can run aloft and provoke stronger thunderstorms than positively-tilted storm systems. As you might guess, positively-tilted storm systems have their highest vorticity values tilted towards the Southwest. The presence of a negatively-tilted winter storm would likely increase precipitation totals as cold air runs aloft and convective snow bands are enhanced. Thundersnow would naturally be more widespread in the presence of cold air aloft.

Snow totals from this system in a 24 hour period would approach the one foot mark, especially in western Pennsylvania. West Virginia and eastern Kentucky could surpass 6 inches, as well as western parts of the state of Virginia (not the state WV). New York, eastern Tennessee and portions of Maine could see shovelable snow, while other states get more of a quick, light accumulation. This forecast is certainly going to change, but this potential must be closely monitored. High latitude blocking will be increasing, leading to higher chances for these Nor'easters.

Andrew

Valentine's Day Potential Nor'easter

There is potential for another coastal storm in the Northeast on Valentine's Day.

Above is a 4-panel graphic forecast for the morning of February 12th. We see our storm system as a deep low pressure center in the eastern Rockies, about to eject into the Plains. The strength of the system is reflected in 500 millibar vorticity values in the top left panel. Reds indicate low pressure systems, purples show high pressure. Downstream from this storm, we are seeing some building of higher pressure in the Southeast, something that typically can drive storm systems further north than south. To me, the system wants to press south based on the mid atmospheric flow, but that can't happen unless dissipation of these higher pressures occurs in the Southeast. Considering how negative frictional torque values have also shifted north in response to the subtropical jet stream's northward movement, it would seem to me this system may be a bit too far south in this model's forecast.

Regardless, by Valentine's Day, the storm system has moved across the Plains, Midwest and Ohio Valley to arrive offshore the Northeast as a coastal storm. If this were to occur, another layer of accumulating snow would be put down on the same areas that are waking up today to nearly 40 inches of snow in some spots. The lack of high-latitude blocking over Greenland puts a concern out of how close to shore this system will be. If there is little blocking over that region, it is possible the models may slowly shift the storm more eastward with time. However, if that actually happens remains to be seen; my confidence is low on such a potential.

The same model forecast results in upwards of 6 inches of snow for many in the Mid-Atlantic and Northeast into New England. We are still a while away from this event, but it should be watched very closely. Valentine's Day has a reputation for having a major winter storm for some part of the nation.

Andrew

February 9-10 Blizzard Event

Blizzard watches have been issued for areas in the light green, and many others in winter storm watches (dark blue), as a potential blizzard bears down on the region.

A storm system will be ejecting from the Rockies in the next 24-36 hours, as pictured above. As it does so, lower level winds will be on the increase as the system strengthens. The resulting pressure drop will influence fairly strong lower level winds, with the highest values in south central North Dakota and north central South Dakota. With the system being as strong as it is, Gulf moisture should be pulled north far enough for the northwestern side of this storm system to experience the highest snow accumulations and hourly snowfall accumulation rates.

Total snowfall will exceed one foot in many areas, with the highest totals concentrated in much of South Dakota and even into southeast North Dakota. Totals are still rising in Minnesota, however this model does not have the entire snow event in its timeframe yet for Minnesota. I anticipate widespread reports of over half a foot in much of Minnesota, with isolated areas flirting with 1 foot, especially in northwest Minnesota.

Andrew

February 8-9 Historic Blizzard

Prognosis... Historic blizzard event evolving as expected. Main piece of energy has shifted northeast since this morning as it moves up the coastline. Infrared imagery (pictured above) and hourly surface analysis shows that the Alberta Clipper (seen as ragged green to the west of main storm system) continues to be dragged into the system. Further inspection of infrared imagery and radar reflectivity reveals a paralyzing snow event continues to unfold in New England, especially in Massachusetts and surrounding states. I anticipate the heaviest snow to move onshore in the next 3 hours, impacting Mass. the most at this point. High resolution model forecasts confirm these suspicions, with slightly lessened but still intense snowfall continuing across the Northeast until at least midnight, possibly later. Saturday morning will be an incredible sight to see; transportation will have to be made by dogsled.

High resolution forecasts for this historic event continue to print over 30 inches for many areas, with Massachusetts bearing the brunt. Lake effect snowfall in the eastern Great Lakes will enhance totals in their respective coastline areas, likely adding at least a couple inches as the storm moves out.

Andrew

Hisotric Northeast Coastal Storm -- 7:00 AM Update, 2/8

The latest NAM high resolution forecast has upped the ante on snowfall totals from this storm. Earlier yesterday, it was showing amounts that were beginning to hit that 30-35 inch mark. Now, multiple states in the Northeast are at risk for over 25 inches of snow, with just under 50 inches of snow aiming at east Massachusetts.

Surface analysis shows Albera Clipper in central and eastern Great Lakes, progressing eastward, while the main part of this system is immediately offshore the Mid-Atlantic. As the main storm system continues to move north up the coast, the clipper system will get sucked into its force and the two will collide. When this collision happens, the combined storm system will have lower level wind speeds nearing 100 knots. Thats over hurricane force!

Power outages and coastal flooding is expected. Preparations must be in place for this historic and potentially life-threatening storm system.

Andrew