Feb 7-11 Southern Rain Bomb and Miller B... potentially....

Well the groundhog says spring. But the models say nope, cold. Which one should I trust, an animal, or the collective work of thousands of people who have dedicated their lives to studying the weather. I'm inclined to trust the models, at least through mid month. That being said, the models could use some work. Many of you have heard about early next week as our next window as a storm and that is true. However, the setup will be very complicated, with multiple pieces of energy moving through the area in a couple of days.

Before we get into that, I do want to mention that there is a non-negligible chance at some snow even before that period. After the cold front pushes SE of us tonight, low pressure will develop, throwing moisture north. Although it looks like the bulk of the precipitation will be south and east of us, flurries and snow showers will be possible Friday. Little, if any, accumulation is expected and there should be no major impacts. 

NAM 4km Nest Forecast for Friday nudged the storm north. The edge of the precipitation shield is right over us. A little more north and we get more snow. More south and we will get nothing.

 After this storm clears out (the friday event forms off the front that just passed through tonight), we will hopefully be able to see more clearly what will go on next week.

Here's what we know now:

• There will be two shortwaves that will impact the area. First one comes through Sun-Mon and the second one comes through Tues-Weds.
• First shortwave will be a subtropical jet stream system
• Second shortwave will be a polar jet system
• It's more or less one storm hits us or the other. 
• Or nothing.

So in long words, the situation goes like this: There are two closely spaced waves that will move to the east coast, rounding the base of a large trough. The trough will bring cold air into the area since it is associated with a lobe of the polar vortex.

The first wave, originating from the subtropical jet, will be moisture laden, but warm. Since temperatures will not be exactly cold before the first storm, if it comes up the coast, there will likely be temperature problems, meaning snow to rain or just rain. 

The second wave will drop out of Canada along the polar jet stream. The primary low pressure will drop into eastern US before transferring to a coastal low. This transfer situation is referred to as a "Miller B" storm. Be forewarned, Miller Bs have a long history of screwing us over while the primary low dies to our west and the new low doesn't get going until it is north of us, leaving us with only snow showers. Miller Bs are notoriously hard to forecast for our region because there is no easy way to pin down the transfer location this far out. We do know that the farther the trough (and therefore the primary low) digs, the farther south the coastal forms. The farther south it forms, the better for us since the new coastal low would have more time to get going before it gets to us.

If I had to pick which shortwave to succeed, I would pick the second wave. There will be ample cold air and seems more promising for snow, than the first wave. Now the task is making sure the first wave doesn't mess up the second one. These storms don't like being close to each other. Close enough and the waves phase (merge) but these two are too far for that. But they are close enough to fore the first one to interfere with the second one's development. We already walk the line with Miller Bs so if the first storm hangs around  then the second storm can't get its act together fast enough and we're out of the game for accumulating snow. Since humans can't model atmospheric conditions in their heads, this is where models come in-to insert even more uncertainty.

00z Euro Feb 2 2016 for 7PM Wednesday shows a weaker low farther north and a stronger primary low

00z Euro Feb 3 2016 for 7PM Wednesday shows a strong low in an ideal position

The short intervals between each shortwave are wreaking havoc on the model projections.  The vary between each other and run to run a lot. For example, one run of the Euro bombed the second low off the coast of MD while the run a day before showed only a weak coastal low. Lately, they have been keying in on bombing the first low off the coast of SC (to different degrees) and running the storm out to sea (miss). However, the storm hangs around just long enough to delay the development of our second storm. At the moment, neither storm seems really promising. This can change though. What we are watching is for s trend for a weaker southern wave and a northern wave that digs farther south. Simple, right? Yeah no. It's one thing if a model shows something, it's another thing if the model is right. Likely the only thing the models will get right before this weekend is the fact that after the two waves comes a third one-the lobe of the PV itself. We're going to be cold next week.

First Week of Feburary and a little bit more

Well... It's February. Time for another pattern shift. Actually that happened at the end of the last snowstorm. That's when the blocking that set up our snowstorm broke down and ushered in a new pattern of warmth. It took a week and a half for 2 upwards of 3 feet of snow to be reduced to just mere inches. The next few days will remove what is left of the snowpack. By the end of the week, dirty snowpiles will be all that's left of Blizzard of 2016. It's sort of interesting to note that apart from the mountains out west, the upper Midwest and Northern New England (at Canada's latitude), we are the only place with decent snowcover. That's going to change soon.

A storm currently dropping snow in the Desert Southwest well strengthen and track NE through the great plains, dropping a wide swath of snow over the next few days. We remain cool-ish , in the upper 40s and low 50s tomorrow but SW flow ahead of the storm will bring temperatures into the 60s on Wednesday. Say goodbye to the snowpack if you haven't already. It will be missed dearly but it will live on in the history books. By Thursday,  the cold front should be clearing the area. Temperatures will drop to seasonable levels, with highs in the 40s and lows in the 20s.


I bet many of you don;t really care about the warm rainer, only about whether it's going to snow. Well, we are entering the prime period for snow. However, the overall pattern is not perfect. Unlike 2 weeks ago, when the pattern was very predictable (thanks to Atlantic blocking) the upcoming weeks will be very chaotic. A smattering of southern and northern stream disturbances will make its way over the Continental US towards us. The timing and how these disturbances interact will dictate whether it snows or not, or whether we even get a storm in the first place.

The upcoming pattern is reminiscent of Feb 2015, and to some extent, 2014. The Tropospheric polar vortex will split, with lobes of energy dropping out of Canada. There are indications that the Stratospheric PV will weaken and even split- something that is much rarer. The Pacific looks to be cooperative to some extent with a +PNA and a -EPO. However, the -NAO -associated blocking in the Atlantic that we so highly covet does not seem to be materializing. Since everything is a moving target, models will have a hard time figuring out how disturbances interact. During this period, there will be multiple chances for moderate precipitation events. Lead times will be short and confidence will be lower than usual. A repeat of the blizzard is unlikely unless blocking can develop, which has been indicated in the longer range (mid month) by some models.

The next time period to watch is February 8-10. A longwave trough will set up over the Eastern US and multiple shortwaves (like 3 or 4 of them) will ride up along this trough and we will be caught up in the middle of it. That's all I can say with confidence Oh, and that they will interact in some way. The bottom line is that there will be cold air, and there will be disturbances. We will need to thread the needle to get a snowstorm.  A mixed event is more likely and rain even more so. After all, we are classified as a humid subtropical climate. Analysis of the Feb 8-10 timeperiod will likely follow in the next few days.