Wave After Wave After Wave

Friday, February 7, 8AM

During the cold stretch in January, the jet stream looked like a roller coaster with a big northern arc (ridge) over the western US, and a big dip (trough) across the eastern US. This is important because the jet stream acts as a boundary between warm air and cold air. An oversimplified explanation is that if the jet stream is to your north, it’s generally warm, and if it’s positioned to your south, it’s cold. Since we were in a trough through most of January, and the jet stream was south of us, arctic air was plentiful. Since that pattern broke a couple of weeks ago, the jet stream has stretched out and is now more zonal (west to east) without a big ridge or trough. The chatter among weather enthusiasts was that this period would probably be a break from winter until around mid month when the pattern looks to change again with a more “buckled” jet stream (and the pattern does look really good for the second half of the month). What no one really expected was that this period of zonal flow would give us multiple waves of winter weather, but that’s exactly what is happening. Waves of low pressure are sliding along the boundary, and depending on what side of the boundary we are on for any specific wave, we could have rain, snow, or a mix. This looks to continue for the next week or so with precipitation possible every two or three days.

First up is the system for tomorrow. Like yesterday’s event, this will also be slopfest. Some form of precip develops across the area around 1 – 2PM and continues into the overnight hours. Temperatures look to be a little bit colder for most areas, so tomorrow afternoon could be sketchy if you’re planning to be out. The one thing going for us is that it will be during day light so that should mitigate a lot of icing on roads, but know that by about 5PM, if temperatures are still below freezing, things could deteriorate very quickly with the setting sun. Tomorrow is a good day to find something to do at home.

After tomorrow comes the system on Tuesday/Wednesday that already has everyone talking. Right now it looks like we will be on the cold side of the boundary, and cold enough for accumulating snow. Models are about the same with timing which is Tuesday afternoon into early Wednesday morning, but are not in agreement on the exact placement of the boundary or the amount of precipitation. For now, just know that winter weather is likely beginning after noon on Tuesday, and it could be in the form of moderate snow. Any accumulation numbers you’re reading or hearing now are just a guess, and I’d certainly be skeptical of the big numbers that the GFS is tossing out. Some GFS runs have produced pretty snow maps that are a lot of fun to look at, but it has not been consistent from run to run so don’t believe them. The Euro has been more consistent with a moderate event that frankly looks more convincing. I’ll update periodically over the weekend.

Winter Reset

Sunday, February 2, Noon

Now that our recent pattern has broken down, we can talk about how cold its been. This past January was 4.0 degrees below normal at BWI, which really isn’t that cold, but it was the coldest month since 2014. Unfortunately, precipitation was much below normal, so we are still below normal for snowfall. The only decent snow was on January 6, but because of the cold, we had snow cover for about three weeks, and some remnant snow piles are still around.

So, now that we are two-thirds through meteorological winter, what’s next? If you haven’t heard, the rodent Phil saw his shadow this morning so folklore says we have six weeks of winter to go. I wouldn’t read too much into that since over his 138 year history, an early spring has only been predicted 21 times. But, over the next couple of days, we will slide to the south side of a warm and cold air boundary with tomorrow and Tuesday being a prelude to spring. Enjoy it because the front looks to slip south Tuesday night as a wave of low pressure approaches, bringing much colder air and a chance of mixed precipitation on Wednesday. It’s too early to for details, but Wednesday afternoon and evening could be sloppy. I’ll update as things come into better focus.

Long term and the remainder of February, the next couple of weeks look seasonal with temperatures and precipitation averaging around normal as we oscillate back and forth on either side of the boundary. There will be several chances at some snow, but it will depend on what side of the boundary we are on. First chance is on Wednesday. By mid month, the early January pattern looks to reload and models are suggesting that winter ends on a cold and possibly snowy note. Way too early to get our hopes up, but with less than 4 weeks until March, let’s hope they’re right.

More on Wednesday’s potential tomorrow.

Unsettled Weekend and Then Frigid

Wednesday, January 15, 1PM

First, we officially have a winner in the Snow Contest! The first inch of snow was recorded at BWI airport at 4AM on January 6th, so Mack wins this year’s contest with a guess of 4:30AM. Congratulations, Mack, and if you’re reading this, please send contact info to me by emailing theweathermill@gmail.com.

As far as the weather is concerned, the snow from nearly 10 days ago is still on the ground which demonstrates how cold it has been since we started the new year. So far, January is running about 4 degrees below normal, and over the next week it’s going to only get colder, especially early next week.

Regarding snow potential, an Alberta clipper system to our north tomorrow will drag its associated cold front across the area so a few snow showers are not out of the question for tomorrow afternoon and evening, but it should not cause any issues. Behind the front is just more cold, dry, and blustery conditions, so right now there are no big snow events in our immediate future.

The good news is that if you are tired of the cold, by Friday afternoon and through Saturday, the temperatures should begin to moderate to where they might actually get to our normal high of the low 40’s. Precipitation potential for the weekend is still not clear, but maybe some rain Saturday evening and maybe some rain to snow Sunday depending on how quickly the cold air returns. The bad news is there is no question that the cold is returning. The MLK holiday will be very cold with temperatures not rising out of the 20’s during the day on Monday, and it gets worse. Lows Tuesday morning are expected to be in the single digits and the highs will likely not get out of the teens. It’s going to be so cold and windy that I am concerned that there may be schedule changes as a result of sub zero wind chill temperatures through much of the day Tuesday.

Precipitation is unsettled through the period, but there look to be several opportunities for snowfall over the next 7 – 10 days. Sunday/Monday is still not a done deal, and then depending on your model du jour, something may develop midweek and/or at the end of next week. Hopefully I’ll have cause to update.