Friday, January 29th, 2:30 PM

I had hoped that today’s midday model runs would come to an agreement on how this weekend’s storm will play out, but unfortunately, we are still not that much clearer. Yesterday’s update pretty much still sums up my current thinking.

Confidence is still high that an area of low pressure west of the Appalachians will force relatively warm air aloft causing snow on Sunday. Some of the higher resolution short range models are suggesting that some light snow may arrive a bit earlier than I had thought yesterday, around sunrise, but I don’t think that will amount to much. Any accumulating snow looks to arrive around noon continuing through the afternoon, possibly moderate at times, with about 3 to 6″ of accumulation by evening that will make for some great sledding. Then it looks like we go into a lull during the overnight hours of light snizzle or frizzle as we wait to see where the coastal low develops. That is where the models continue to diverge. All models do indicate that there will be some redevelopment of precipitation (predominantly snow) around sunrise Monday morning, but without knowing where the coastal low forms and whether it stalls makes Monday’s accumulations more difficult to pin down.

For now, I think an additional 2 to 4″ call is reasonable with the caveat that it’s liable to change. If the storm forms closer to the coast, then we get some of the cold, wind-driven powder on the backside of the system, and could see 4 or more additional inches. But if the storm center slips to the east, then we see some light snow of 1 – 2″ that ends around noon. Regardless, this could be the first warning level event the area has seen in a long time, so, as I said yesterday, I will enjoy whatever falls on Sunday and cross my fingers for a lingering snow bomb on Monday.

I will update early Saturday morning with how the overnight runs looked.

Thursday, January 28th, 1:30 PM

There still isn’t any reason to parse the details, so here’s the summary as of this afternoon. Sunday morning snow will arrive across the area from west to east. Best guess is anywhere from 9AM to noon. Like the December storm, this first batch of precipitation will be from warm air arriving aloft ahead of the center of circulation. By Sunday evening, just guessing, but anywhere from 3 – 6″ of accumulation, and then we should go into a lull and some areas might even change over to light rain or drizzle as the dry slot of the storm crosses the area. This part of the system right now has the highest confidence of occurring. The storm is in the western US and traversing the country. All models agree on some kind of snow thump on Sunday.

Now for the less confident part. As the low approaches from the west, it will transfer energy to a developing system along the Atlantic seaboard. All major models now give us more snow from that developing low pressure. However, what is still uncertain is where that low develops, how fast it develops, and whether or not it stalls. Right now, most models seem to be converging on the idea of another 2 – 6″ beginning early Monday morning and dragging out into Monday night. It could be less if the storm develops too far east (or north, or south…), and it could be more if it decides to visit the boardwalk of Ocean City. Most forecasts are putting more stock in the European model which has the transfer and redevelopment just off the coast which would be a huge win for central MD. I don’t have to put my neck out so I can continue to say, “I’ll believe it when I see it.”

For now, I am going to focus on what looks like a likely event on Sunday that will have periods of moderate to heavy snow at times ranging from 3 – 6″. Obviously, this is a first guess and I’ll update as we get closer. But, assuming the Euro is the most right solution, then Monday morning a second round of moderate to very heavy snow will be possible and last through the day. You can look at a pretty snow map and see that the Euro HIRES suggests totals from both parts of the storm of about 10″ around DC, and upwards from there to about 18″ in northeast MD around Bel Air (northeasterly areas generally do better in this type of system, called a Miller B, as they tend to remain in the secondary development the longest). As I’ve said before, the snow maps are fun to look at, but they should be used as a tool and not verbatim. Nevertheless, IF the Euro is on to a win, then there will likely be a lot of snow around here by Monday night.

Again, this is all preliminary and I’ll update again tomorrow.

Let’s preface this by stating the obvious, but no one should be expecting a foot of snow Sunday/Monday. The overnight model runs were good in that a storm looks likely beginning Sunday and lingering into Monday (or Tuesday. Seriously.). However, it isn’t a classic storm out of the Gulf of Mexico and hitting the outer banks of NC and then hugging the coast up to Maine, which all but guarantees us a whopper. But, instead, this is the deadly low traversing the country, then transferring to the coast, aka, the Gordon Barnes “double-barrel low” or the “rob Peter to pay Paul” low. Transfers are tricky and can end in miserable failure. When and where that transfer occurs is key for the mid-Atlantic and since we are still 4 days out, it would be wise to keep our expectations in check. Every model run this afternoon gave central MD some snow but the range is from about 2″ to upwards of 18″, and since we have been snow starved for what seems like forever, we shouldn’t be disappointed if we end up with 4″ of front end snow and then dry-slot to drizzle.

But man, the Euro is still pretty. The National Weather Service discussion this afternoon summarizes things way better than I ever could, so I’ve pasted it below and changed a little of the jargon to make it more readable. Anything in parenthesis are my words, but you can read the actual discussion here. I’ll update tomorrow.

Beyond (Saturday), attention turns to a system currently located just off of the West Coast. This system will move onshore tomorrow, and track across the (continental US) Friday into Saturday. By Saturday night the system will move into the Ohio River Valley. As it does so, warm air advection precipitation (ahead) of the (storm) will start to overspread the area either late Saturday night or early Sunday. Confidence is increasing that much, if not all of the forecast area will see at least some accumulating snow on Sunday in association with this round of warm air advection precipitation. Confidence in the details of the forecast decreases thereafter. The low is expected to progress very slowly toward the east Sunday night through Monday as a system over the Atlantic Ocean blocks its forward progress. Meanwhile, an additional disturbance descending down from the Upper Great Lakes in northwesterly flow will act to reinforce the backside of the trough as the first piece slowly progresses to the east. As the first piece progresses eastward, the primary surface low over the Ohio River Valley should eventually transfer to a developing coastal low off the Eastern Seaboard. Additional snow may be possible with this coastal low, but a lot of uncertainty remains with respect to the eventual strength and placement of this low pressure and its associated precipitation shield. Either way, at least some snow shower activity will remain possible on Monday, but the potential is also there for a more substantial snowfall with this round as shown in the deterministic 12z Euro. Ensembles continue to signal significant spread during this time period, which illustrates the high level of uncertainty in the forecast for Sunday night through Monday. Depending on how the downstream block evolves, snow showers may even linger into the day on Tuesday. We`ll continue to assess trends and adjust our forecast as confidence gradually increases moving closer to the event.

It’s going to be difficult to not get sucked in to believing snow is on the way as every major global model run this afternoon had an indication of a storm Sunday and/or Monday. Most of them are a moderate event from 3 to as much as 8 inches, but the European model, the same model with the best verification scores for years, dropped a snow bomb on the mid-Atlantic. I’m not going to bother going into any details for today’s run but there is a remarkable amount of agreement in the European ensembles that makes it hard to ignore.

For those that don’t know, when we look at the European weather model, we are looking at one of many simulations called the HRES (high resolution). Unfortunately, if there is any error in the initialization, and there always is, then the further out in time the model runs, the greater the error becomes. Obviously, the result is that a projected forecast is less and less reliable as time increases. One way to overcome this is to make a very slight adjustment to the initialization data and run a different simulation. Do that 50 times and blend them, and you get a mean or ensemble forecast.

The European HRES is considered the best model out there and is extremely accurate out to 72 hours. However, once you get past three or four days, especially in an active pattern such as what we are in now, it is better to look at the 50 member ensemble blend to see if maybe there are any outliers. If the HRES and the ensembles look anything alike, it gives confidence in the forecast. With that all said, the HRES model and the EPS (Euro ensembles) are in strong agreement that something is up. It’s just one run so I’m trying my best to not get too excited, but of all years, this is the year we need some snow.

Now, there is a ton of useful information on weather models, and admittedly, much of it is over my head, but one thing for sure is that snow maps are folly. They are never accurate and all they do is get the hopes up of snow lovers only to end up disappointing. With all that said, this snow map has to be shared. This is the Euro HIRES snow map for Sunday through Tuesday (courtesy of https://www.pivotalweather.com/model.php?m=ecmwf_full&p=sn10_acc&rh=2021012612&fh=loop&r=us_ma&dpdt=&mc=). And yes, that is a 39″ total in central VA.

I can’t share the ensemble maps that I have seen because of copyright concerns, but for a mean forecast of 50 members, it is a remarkable correlation. Yes, the mean is about half the snowfall of this graphic, but a 10-20″ snow on the ensembles is tough to ignore. Even better, the mean has the heaviest snow about 40 miles north, and most importantly, the placement of 45 of 50 low pressure systems for this event depicted on the mean are in a workable location for snow just off the coast.

Obviously, this far out it isn’t worth getting too invested in, but I’m feeling hopeful. I’ll update as things progress.

It’s not going to be a major storm but some form of precipitation will develop across the area this evening from about 6 or 7PM and continue into the early morning hours. Surface temperatures are in the mid 30’s this morning, but dew points are in the teens so most areas will start as either snow or sleet and then eventually change over to freezing drizzle or light rain around midnight. As a result, untreated surfaces, especially elevated bridges and overpasses, could be icy during the overnight hours. Accumulations could range from a trace around the DC beltway to as much as 3″ along the MD/PA line. Interestingly, some of the short range models are insistent that this evening between 7 and midnight could be pretty snowy for most of central MD. I’m not sold on that as I think there will be more of a mix than snow for most of us, but keep your fingers crossed. Regardless, it’s not going to be a big event, but it’s something. To put it in perspective, I think that this would probably be a delay-event for most areas along and west of 95 in normal times.

Thursday’s system looks suppressed and weak to the south for now.

This winter was never expected to be great as a result of the La Nina conditions in the Pacific, but what wasn’t expected has been the persistent -NAO. In the negative phase, the North Atlantic Oscillation can bring a blocking high pressure area over Greenland which allows cold Canadian air to settle over the eastern US while the storm track is forced south and (hopefully) up the eastern seaboard. Most of our major snowstorms have happened during times of the negative phase of the NAO. Of course, in the mid-Atlantic snow is rarely easy, so the -NAO is not the only thing we need, but it helps. Unfortunately, in spite of the -NAO, there hasn’t been any true arctic air intrusions on our side of the globe this year, so even with a good index, snow has been scarce. Many winter forecasts that I read back in October and November spoke of the possibility of the second half of winter being better around these parts as the long range models were already showing the blocking pattern emerging, and there was some hope that the Pacific would be more cooperative by February. I’m not sure if that is what is happening, but regardless, we do have a couple of systems to track, with one of them potentially being a major event.

First on tap is late Monday and Monday night. A system will approach the area from the west and it looks like the boundary between frozen and not-frozen precipitation will be setting up across central MD. Depending on where you live, you can probably find a model du jour showing what you want at your location. If you want snow, the Euro is showing most areas north of about route 50 getting 1-3″, while the GFS shows mostly sleet and freezing rain for most of us with snow being limited to the Mason Dixon line. The NAM brothers start as a mix, then snow when the column cools, and then back to light blah. Then there is the Canadian and UK models…

Making a total guess right now, I think most of us will see some snow as the precipitation starts Monday evening, and then it will change to something else much like the December storm, but without the really heavy snow to start. Maybe a couple of inches in the favored areas before the changeover, and hopefully it won’t bring much freezing rain. I’ll certainly update as things become more clear.

The second system for Thursday is worth keeping an eye on. The GFS and Canadian (CMC) both favor a decent storm just off the coast, but there are some issues with cold air with the GFS (well, at least the current GFS. There is a new version of the GFS that is scheduled to replace the current one in February. That the new one is available for public viewing and it likes snow for Thursday. Like I said, if you look at enough weather models, you’ll almost certainly find the weather that you want). The Euro hadn’t been showing much for Thursday, but today’s midday run took a decent step in the right direction, so I think this one could be the best chance we have had in a few years for an area-wide warning event. Hopefully I’m not jinxing it.

Wednesday, December 24, Noon

It’s going to busy 24 hours across central MD as the entire area is under a Flash Flood Watch and a Wind Advisory. A strong cold front is poised to cross the area overnight, and ahead of the front are strong southerly winds and increasing chances for showers. As the front progresses east this evening, there will be heavy rain and even a chance for some severe weather. In addition, winds will also increase causing isolated tree damage and power outages. The front is expected to bring 1 – 3″ of rain and wind gusts of up to 40 mph.

Once the front crosses the region between midnight and 5AM, temperatures will fall very quickly and change any leftover rain to snow showers. In the normal far western and northern areas, there may be enough snow to whiten the ground, but no real accumulation is expected. However, for those doing any traveling early tomorrow morning, the models are showing some impressive temperature drops with the frontal passage, so assume that any surfaces that appear wet are actually frozen. Early travel tomorrow morning may be impacted, especially in areas well west and north. If anyone is traveling west through western MD, WV, or PA, WInter Storm Warnings are up for heavy snow beginning around midnight.

The weather settles down after early tomorrow and the rest of the long weekend looks sunny and cold. I’m still keeping an eye on late next week for the chance of winter storm. So far the models are not showing anything, though the pattern looks promising, so hopefully we have something to track soon.

Be safe and Happy Holidays!

Monday, December 21, 7AM

Last week’s storm gave BWI 1.6″ of snow, which although isn’t a whopping number, it was enough for Kristin Taylor to win the Snow Contest. She picked December 16, at noon, and the first inch fell between noon and 1PM easily giving her the best guess. Had this been The Price is Right, she would have won both showcases for making her guess within an hour. Congratulations, Kristin!

Here’s the entire list of entries for comparison.

Click to access snow-contest-20-21.pdf

As far as last week’s storm was concerned, it ended up playing out pretty much like the models suggested. Eastern areas started as snow and changed to all rain, while western areas eventually changed over to something other than snow. Most areas to the west and north also got some help late when the precipitation changed back to snow, and total accumulations varied from one to as much as eight inches from southeast to northwest, with northern Carroll county doing the best (Parr’s Ridge is always the winner in snow accumulations). Surprisingly, the areas that had snow on the ground as the storm ended, continue to have snow cover even today. Cloudy and cold days since the storm, combined with the sleet that fell made for a condensed, mini glacier in many areas making it feel and look like winter for the first time in December in a long time. As a matter of fact, even as winter is just officially starting today (thank you Carnival King for the reminder!), many of us have already exceeded last winter’s total accumulation, although that’s not saying much.

Looking ahead, there’s a small disturbance passing through the area tonight that will bring some showers, and then as a cold front approaches mid week, temperatures will rise ahead of the front in a southerly flow, but crash back to below normal for Christmas day and next weekend. Showers associated with that front are expected on Thursday, but snow showers are possible late Christmas Eve and early Christmas Day. We don’t usually do very well with getting snow from cold front passages, but some of the models have been showing it consistently, so maybe some areas get lucky and see enough snow to call it a White Christmas.

Beyond the weekend, there is growing model consensus for an advertised blocking pattern that has the potential to bring several opportunities for wintry precipitation across the area beginning next week. As far as I am concerned, it’s a little early to buy into some of the chatter I’m hearing, but if it comes to fruition, it may be a busy end of the year.

Wednesday, December 16, 8:30 AM

No big changes from last night’s update, though I think that many of us are in for a long duration sleet event. East of 95 still looks like it will warm enough to change to rain, but we have to see how far west the warm air makes it this afternoon. There is not model consensus on the placement of the storm which translates to lower confidence in the forecasts. I feel confident that warm air will nose in to the mid levels in the areas along and west of 95 causing snow to change to sleet, but I don’t feel confident that the surface temperatures will be scoured out. As a result, sleet could be the predominant precipitation for most of us from mid afternoon into the evening. And it could be heavy. Most models have the mid levels warming even in northern MD and as far west as Frederick, but we can only wait to see if they’re right. If so, those areas will also see sleet. Regardless, for most areas west of 95, although it won’t be a classic snow storm, this will be a high impact event so be careful.

One other thing that I mentioned in last evening’s update was the the low possibility of cashing in on some backside snow love. Just a quick and simple primer, as the storm approaches from the south, counterclockwise winds around the storm will be from the east or even southeast. That’s the kiss of death because relatively warmer air rotates in from off the ocean. We want north and northeast winds. East and southeast winds invade the mid levels causing snow to change to sleet, and eventually warms the surface so sleet goes to rain. But once the storm gains enough latitude, winds shift to northeast, north, and eventually northwest (that’s why it generally gets colder and drier after a storm). Anyway, a couple of days ago models were suggesting that when this storm got enough latitude to shift the winds back to the north and rapidly cool the mid levels back below freezing, there was remaining moisture that was modeled to fall as snow. Since then, the global models have backed away from that idea, but the possibility is still there, especially in the northern areas. If that situation develops, or if there are any surprises (fingers crossed), I’ll update again.

7:30 PM, Tuesday, December 15

The evening model runs are in and though I think we could still fare worse than what models are showing, here are how things stand now. Most areas will start as snow tomorrow morning (between 9 and noon from south to north) and what we get before the changeover is probably all we will see. In model runs before today, there was a chance of a changeover back to snow tomorrow night that had the potential to drop several inches in a hurry, but that’s not looking like it will happen. We need to start as snow, and hope we hold on to cold temperatures as long as possible before the storm brings in warmer air from the east because that’s probably where we will see most if not all of our accumulations. Regardless, there is going to be a tight gradient between those that get a decent event and those that throw a fist in the air and curse the snow gods. To illustrate this, parts of Montgomery and Howard counties are in a Winter Storm Warning for an excess of 5″ of snow and sleet, while a short drive to the east in Anne Arundel, Prince Georges, and counties south of there, you’ll find Flood Watches posted. So, unless there’s a late save, which I don’t expect, here’s the latest breakdown.

If you live in eastern Baltimore, Anne Arundel, or PG counties, and anywhere east or south of there, you’re probably in for a cold, rainy day. You will probably start as snow in the morning, but warm air will nose in quickly and switch the snow to sleet and rain fairly quickly. Maybe an inch or so before the changeover. After that, it’s just a cold rain. And lots of it.

For areas right along and just east of I 95, especially the more south you are, things are not a whole lot better. Precipitation will start as snow and transition to sleet and rain by mid afternoon and may change back to snow late tomorrow evening, but for the most part, it looks more wet than frozen. About 1 – 3″ from east to west right along 95.

Once you get west of 95, the initial thump of snow should hold on longer before the changeover, so anywhere from 3 – 6″ from 95 to about route 97. West of there, and north of 70 stands the best chance of seeing the most snow, but even in those areas, I would not be surprised to see a change over to a long period of sleet, or even rain. I think that by late tomorrow, most of central MD will change over to sleet and rain and the highest accumulations of maybe 6 – 10″ will be limited to extreme northern MD and out west past Frederick. For the rest of us, whatever falls tomorrow during the day will likely be waterlogged by late evening.

If you want to see big snows tomorrow, the best areas look to be along the I 81 corridor where they may stay all snow and exceed a foot. Obviously, the mountains in Garrett and Tucker counties will fare well too.

For us, if we weren’t changing over to sleet and rain, this would be a great December storm. And to be fair, any snow in early and mid December is really a bonus, so I’ll be happy with whatever we see tomorrow. But it is disappointing to see the promise of a great snow event just a couple of days ago being washed down the gutter. If there’s any good news it’s that the pattern looks to be just starting, so there may be a couple more opportunities for snow in the next couple of weeks. Something actually popped up in this evenings runs for right around Christmas, so maybe we will finally get that elusive White Christmas.

By the way, the evening European model just finished running and if it’s right, I’d have to cut back the totals I just posted. Either way, I’ll update in the morning.