Weekend Update: 50 degrees tomorrow, then potential storm March 12

Plenty of clouds have been the rule for today, which have helped to keep temperatures in the 30s. A storm system to our south is slowly moving northward, but will not interact with the jet stream to the north. This will keep the storm system out to sea. The lower pressures from the jet stream to the north, as well as the lower pressures out to sea, will help to create a relative wedge of higher pressures between them, which is another reason why the storm will ultimately miss us, as higher pressures create sinking air, thus a lack of lift. There is the outside chance of a few very light sleet pellets or drizzle in coastal sections, but we’re definitely leaning against that, and even if that were to occur, it would not disrupt any travel.

As the storm pulls away throughout the night, clouds will gradually diminish, as winds turn to the north. The initial cloud cover will prevent temperatures from dropping much below freezing, however.

Moving to tomorrow, a cold front will be developing in the Great Lakes via the northern jet stream, and moving eastward throughout tomorrow. This will help to the winds to turn more westerly as opposed to due northerly. This, combined with the previous subsidence left from the departing storm system will lead to sunny skies for tomorrow and a potentially warm day.

Today’s high-resolution NAM run shows 850mb temperatures around +3C at 1:00pm tomorrow afternoon, which support high temperatures in the 50s, given enough sunshine and mixing. (PSU E-Wall)

Temperatures aloft have slowly warmed due to more ridging building in between the low pressure offshore, and the low pressure in the northern stream. As sunshine comes out in full-force tomorrow, the relatively strong sun angle, combined with the fact that winds will be turning more to the west should lead to temperatures warmer than forecast by most other outlets. 850mb temperatures will be around +3C at 1:00pm and the flow will be pretty strong out of the west, as shown in the map above. This leads to downsloping off the Appalachian Mountains, which warms and compresses the air. The only thing that would prevent temperatures from exceeding 50 degrees is if the atmosphere takes a bit too long to become truly mixed, because of the previous higher pressures preventing much atmospheric turbulence. However, due to the winds and strong sun angles, we believe the atmosphere will become mixed by around noon or 1:00pm. This would help to translate the warm temperatures aloft to the surface. With a strong sun angle, you can often add 10 to 12C to the 850mb temperatures to the surface.

Interestingly enough, BUFKIT soundings show the atmosphere becoming fully mixed at 3:00pm, but temperatures aloft have cooled a bit by then, due to the approaching cold front — when a cold front approaches, the temperatures aloft fall faster than they do at the surface, due to stronger winds aloft. This is why most high temperature forecasts are only in the 40s for tomorrow. But just move the mixing up a couple of hours, and we are easily in the 50s for tomorrow, which seems to make sense given the strong sunshine. Thus, we feel that temperatures should reach the low 50s tomorrow, which will feel quite pleasant due to how cold it had been previously. Average temperatures this time of year are actually in the mid to upper 40s, so tomorrow’s warmth will not be unseasonable.

The cold front moves through on Saturday night, which will lead to Sunday having trouble getting out of the 30s, as well as some scattered snow showers on late Saturday night/early Sunday morning. Then, attention shifts towards Wednesday, as another potential storm begins to form.

Temperatures will moderate a bit again on Monday and Tuesday, when temperatures may hit 50 degrees again. However, cold air will be filtering back in from Canada with another northern stream disturbance, and may combine with a strong disturbance from the West, via a PNA ridge spike.

It’s too far out to really overanalyze the details, but we will compare today’s 12z GFS, which showed a weak storm, to today’s 18z GFS, which showed a stronger storm, for Wednesday.

Today’s 12z GFS showed some energy hanging back to the west, which prevented a strong storm from forming. (PSU E-Wall)

Above is today’s 12z GFS, valid for Wednesday morning. The top left panel is the 500mb pattern, which is right around the middle of the atmosphere, and the colors are vorticity, or spin in the atmosphere — generally an indicator of potential storminess and energy. Notice how we have a potent area of energy diving down from the northern stream near Manitoba, yet the energy out to the west gets held back, and there is little interaction. The small amount of interaction leads to only a weak storm system, with light to moderate snowfall for the East Coast.

Today’s 18z GFS shows much more interaction between the northern stream, and energy to the west, which yields a strong storm system on Wednesday. (PSU E-Wall)

Above is today’s 18z GFS, also valid for Wednesday morning. Notice how much less energy is hanging back to the west, and more has phased into the trough and has interacted with the northern stream energy diving down from Manitoba. This helps to further strengthen the trough, which leads to a strong storm system. We do see an area of high pressure in SE Canada, as well as part of the Polar Vortex extending southward — this helps to supply some cold air, and may try to keep the storm a bit to the south. That being said, the Polar Vortex is not in nearly as suppressive of a position and orientation as it was for this past Monday’s storm, which leads us to believe that if the pieces of energy were to phase, we’d get a powerful storm system that may bring a lot of snow to a large chunk of the Northeast.

In fact, the Polar Vortex might be far north enough so that areas closer to the coast would have to deal with precipitation-type issues, such as rain or sleet, instead of snow, and only areas northwest of NYC would get major snowfall. Regardless, however, the potential is there for a major storm system, given that we have a strong ridge out west, and lots of energy diving down from Manitoba, and a cold air source to the north — the ingredients are there.

But if more energy to the west hangs back like what was shown in today’s 12z GFS, the storm would ultimately be much weaker, and could miss the area. It is still too far out in time to say which scenario holds more merit, but we can say that the ingredients are there for a major storm system of some kind — whether it actually happens as advertised is a different story, however.

For all of you model watchers out there, if you want a storm, look to see how much energy from the West with the PNA ridge ejects eastward with the storm system — if we trend towards more energy ejecting eastward, then storm-lovers will be happy. If we trend the opposite way, then people who don’t want a storm will be happy.

The wild card is the area of vorticity in the southeast states. If that were to also phase into our storm system, we could truly have a bomb of a storm, and some people would be measuring snow with a yard stick. But if that trends stronger and runs out ahead of the storm, it could also act to suppress the storm and make it weaker, since they would be competing for energy.

There are lots of variables and parts on the table. We will be sure to keep everyone updated over the next few days. Until then, enjoy your weekend!