Today and Tonight

Sunday, February 22, 9AM

Light rain has commenced across the area with snow already mixing in along the MD/PA border. Regardless of whether your area changes to snow later this morning or afternoon, temperatures should remain above freezing in the metro areas, so travel today shouldn’t be a problem. The exception is northern MD and areas with elevation where temps will be slightly lower.

My expectations for this storm have been somewhat muted for our area as I felt that things would end up east of us, but the recent model runs, particularly the short-range models, have me pretty excited for tonight into early Monday morning. If central MD is going to get any decent accumulations, it won’t happen until late this afternoon and into the overnight hours when colder air is pulled into the system and we lose the sun. Along the 95 corridor, I think snow becomes an issue around 4PM north of Baltimore to 6PM down by DC. Total snow accumulations from around 3″ down towards DC, and increasing to up to 8″ just northeast of Baltimore are possible, with that 8″ amount spreading west along the northern tier. There’s also going to be a narrow band somewhere, oriented on a line from northwest to southeast, that is going to get dumped on and has the potential for up to 12″. That will be a now-casting issue as it’s impossible to know where it happens. If anyone is interested in what causes this phenomenon in these types of systems, google norlun trough. So, for central MD, let’s just with a general 4 – 8″ by Monday morning.

I don’t have a lot of confidence in the accumulations that I stated, but I’ll be watching this all day and will probably annoy you with updates as the coastal storm develops. On that topic, if anyone wants to check in occasionally on the coastal development, this is a nice radar site for it. Click on the link, uncheck the Weather Stations box, check the Radar box, and then zoom out to get a nice view of our area and the coastal areas from NC to NY. Hit the play button and increase the speed to 5x. More later.

Saturday Morning Update

Saturday, February 21, 9AM

I don’t envy anyone that has to make a forecast for this event across the area as it has so many moving parts that it will be difficult to pin down snow totals for a specific area. There’s still a full day of model runs before anything begins, but I can’t recall a storm in the past 20 years that was within 24 hours and had this much uncertainty. The difficulty is that there are several pieces of energy that are phasing into a coastal storm and the timing and location of that phase will ultimately determine the outcome for central MD. If you want to be assured of a snowstorm, the best local’ish place to be is probably Delaware as they are further east and north enough to catch the full brunt of all the model’s placement of the developing coastal storm. Most areas on the eastern shore will start as rain on Sunday, but by Sunday evening, the rain changes to heavy snow with extremely high winds. Blizzard Warnings are up for the coastal areas of Delaware, extending north to New York, and will likely be expanded into New England later today. If you’re on the coast, Sunday night is going to be the real deal for a winter storm. Heavy snow, high winds, and huge drifts.

For central Maryland, we have several issues to overcome to get accumulating snow. Marginal temperatures through the day on Sunday are likely a problem. I am confident that it’s going to snow tomorrow, but with temperatures in the mid 30’s and a late winter sun angle, it’s going to be difficult to get accumulations on anything other than grassy surfaces. The only thing that could make tomorrow impactful is heavy snow rates, and for that to happen, we need the phase to happen early and the low to form and hover close to the coast. The gfs has that, but the euro does not. My initial guess, which could be really wrong, is that tomorrow will be a pretty day of falling snow but with minimal impact. By tomorrow evening, the coastal storm really starts cranking and it will pull cold air down so that temperatures around sunset will fall below freezing. That’s when things could get interesting but again will be determined by the placement of the coastal storm. Too far east and it’s just light snow, but if it’s closer to the coast, we could have several hours of moderate snow that would accumulate quickly. I do think tomorrow night has the potential to be impactful for the area. The NWS has issued, and recently expanded, Winter Storm Watches for at least 5″ of snow for the entire area. This is only a watch and it means the potential is there, but it is not a forecast. Just my thoughts, but the areas most likely to exceed the warning criteria from the coastal storm are along the fall line just west of I-95 and then points east. I think these areas could end in the 4 – 6″ range with more possible close to the Bay, especially to the north. Later today the watches will either be upgraded to a warning or just an advisory, so keep an eye on the NWS site to get an idea of what they expect. If your county goes pink, they think you’re going to see 5″ or more of snow. If it goes purplish, that’s an advisory for less than that.

The final complicating piece to all of this is a trailing upper lever low that will cross the area Sunday night. Models have been pointing to a relatively narrow band of nearly stationary heavy snow developing somewhere west of I-95 that could dump a lot of snow in a very short time. That location is very difficult for anyone to pin down and will probably be a nowcasting situation. So, to reiterate the difficulty in making a forecast, it’s entirely possible that areas near the Bay end up with 8″ of snow from the coastal storm, and somewhere west of 95 ends up with 8″ of snow from the upper level low, and some areas in-between end up screaming at the sky. I’m going wait to see what the midday model runs say and then update.

Saturday Morning Update

Saturday, January 24, 10AM

The arctic airmass has obviously arrived, and global models have come to some agreement, but the mesoscale models, which should be in range at this point, are concerning. They drive the primary low into the arctic mass to the west of us which brings a relatively warm layer aloft. So, although at the surface it’s well below freezing, snow falls from high altitudes, passes through a warm layer, melts to rain (or least no longer snow), then after passing through the warm layer, hits cold air and refreezes. If the cold layer at the surface is deep, the rain refreezes before hitting the ground as sleet. If the surface layer is shallow, the rain hits surfaces as a liquid and refreezes (freezing rain). Freezing rain is the most dangerous because it coats everything, including trees and power lines, with a heavy coating of ice. Sleet is terrible for roads and walkways, but it doesn’t stick to surfaces. Think ball-bearing ice pellets. It still is going to snow, but if the short range models are right, then the snow totals will be on the lighter end of the totals I’ve said the past couple of days. I’d be only guessing as to which scenario is correct, but the end result will still be extremely impactful.

In summary, snow develops around midnight, becoming heavy by morning with significant accumulations. I’m sticking with the totals from the past couple of days, but it depends on when the changeover occurs. After the change, there will be significant accumulation of sleet. In some areas it is going be really impressive. Hopefully we don’t get any freezing rain or drizzle because that would just make the glacier worse. I’ll update this evening with more details.

Finally, a reader asked a couple of questions and wanted my thoughts. First, they wanted to my opinion on when to start clearing a messy system like this. It’s a great question. Just my opinion, but for a storm like this, I would say to wait for all precipitation to end to start shoveling and clearing vehicles. Yes, it’s going to be much heavier, but getting under the fluffy snow is much easier than trying to get under ice. If it was going to be an all snow event, then I would say try to keep up, but with possibility of freezing rain, I am waiting. Also, we always read stories about heart attacks from shoveling, so go slow, and take breaks. You’re in no hurry as we are likely not going anywhere tomorrow or Monday.

The second question was about phone weather apps and why they show ridiculous snow totals. I never look at my iPhone app, but I just did and even now it say’s 20″ for tomorrow. That’s comical. I don’t know the algorithm that they use, but I suspect it is AI and obviously has no human input. I googled “why my phone app says high snow totals” and ironically, the AI response is pretty good, though there are a lot of human articles too. But here’s what AI wrote (the highlighting is not mine):

“Your phone’s weather app is likely showing high snow totals because

it is pulling raw, automated data from a single computer model—often the American GFS model—without any human meteorologist to interpret or adjust the numbers. These models often over-calculate, particularly when they cannot accurately differentiate between heavy snow, rain, or a wintry mix.

Here is a breakdown of why your app is showing high, and potentially inaccurate, snow totals:

Raw Model Output (No Human Touch): Apps often take direct, unedited output from computer simulations. Human meteorologists analyze multiple models and local factors to filter out these “fluke” high numbers, but apps generally just display the automated result.
The “10:1 Ratio” Fallacy: Many apps calculate snow by assuming 1 inch of rain equals 10 inches of snow. However, if the atmosphere is warmer or the snow is lighter, the ratio changes, and the app will significantly overestimate the total.
Wintry Mix Miscalculations: If the storm includes sleet, freezing rain, or rain, the computer model may mistakenly interpret this as heavy snow, leading to massive, inaccurate, and “eye-popping” numbers.
Model “Flip-Flopping”: Computer models often produce wildly different totals with every update (every 6 hours). The app may be showing a maximum potential model run rather than a likely scenario.
Timing of the Forecast: If the high number is for a storm several days away, it is highly likely to change as the storm gets closer and forecasters get more precise data.

What to do instead:
For more accurate, localized, and context-driven forecasts, it is highly recommended to check with your local TV meteorologists or the National Weather Service. “

Friday Update

Friday, January 23, 12:30 PM

The global models have stopped the north bleeding since I last posted yesterday, and if anything, they are trending slightly south and with a colder profile. We are still too far out to rely heavily on the mesoscale (short range) models, and until the globals come to a consensus, I don’t see any reason to change much from yesterday’s post. In summary, the NWS has issued Winter Storm Warnings early this morning for all of MD west of the bay for Saturday night into Monday morning. Arctic air is arriving today and there are also Cold Weather Advisories for dangerous wind chills tonight through early next week. Regarding the storm, and this is still preliminary, but snow will develop from southwest to northeast across MD from 10PM to 1AM tomorrow night. The snow will initially be light but will pick up in intensity and be moderate to heavy by sunrise. Heavy snow will continue during the morning, but a warm layer will begin working in from the south and east, and snow will transition to a mix of snow and sleet, and even all sleet in many areas. It’s too early to know when that happens, but I still feel that 6-9″ of snow accumulation for areas along the bay to just west of I-95 respectively, before the changeover. For the normally colder western and northern counties west of Route 32 and north of I-70, 8 – 14″ of snow before any changeover, if at all. By Sunday evening, colder air will begin wrapping into the system’s higher levels and we will have to see if there is a changeover back to snow with additional accumulations. The accumulations that I stated are initial thoughts for what I think that accumulate before the changeover. We can save any talk about any possible additional snow accumulations Sunday night until tomorrow. Also, although the NWS defines sleet as snowfall, I am talking about just snow. Some areas are going to be measuring sleet in inches, so regardless of whether your area changes to sleet, this is going to be a very impactful storm well beyond Sunday. Sleet over snow with the frigid temperatures is going to make for a glacier. The good news is that right now freezing rain does not appear to be a major concern for most of central MD as the depth of the cold should be able to overcome a narrow warm layer. The exception is for readers in south and east areas including lower AA, Calvert, and especially St. Mary’s counties as icing could be substantial in some of those areas.

I’ll update later today if there are any substantial changes. If not, assume no changes, and I’ll send out something tomorrow morning. And finally, never trust snow accumulations on a phone’s weather app.

Weekend Update

Wednesday, January 21, 11AM

Yesterday at this time we were hoping that the storm wouldn’t be suppressed south, but model trends through yesterday afternoon and overnight has a lot of people wondering if this is going to end up too far north. I’m in the camp that we are going to see some big adjustments as the players come onto the playing field. The NWS stated in their discussion this morning that they will be sending recon flights over the Pacific where our southern energy is currently located, and that data from those missions will be ingested into tonight’s 0z model runs (midnight, our time). Additionally, the northern stream energy, specifically the arctic high that will be moving across the northern US during the event, is currently located in an area where data sampling is sparse. With that in mind, this will probably not be settled until late tomorrow or even Friday. But, we can still discuss what the models see at this point, but know that we are still early so expect changes.

Just about every model shows snow moving into the area Saturday night and continuing Sunday. The snow is moderate to heavy at times and they all show at least 8″ along the 95 corridor into early afternoon Sunday. They also show that surface temperatures stay well below freezing for all of central MD throughout the event. Where they differ is how much warm air is pulled in at the higher levels that could change the snow to sleet or possibly freezing rain. That is dependent upon how far north the primary low goes to our west as the storm transfers its energy to a coastal storm. The more north, the greater the chance of mixing. I am only guessing but the arctic high pressure to the north should be very strong so I don’t see it getting bullied as much as some models have shown. Not to mention, this is still a La Niña and the phasing and amplifying that we’re seeing right now on the models could be overdone. One other thing that is certain is that whatever falls, it won’t be going anywhere for awhile as temperatures next week look to be frigid for the duration.

I don’t like investing in any one model this far out, but I’m waiting for the midday GFS to run before posting, so for fun, here is what the morning AI EURO (6z) showed. Snow beginning around midnight Saturday/Sunday with a total of 10 – 12″ with temperatures never exceeding the mid 20’s. Some mixing in the afternoon on Sunday, but mainly south and east of 95. I only chose the AI Euro because it’s been fairly consistent from run to run so far.

Anyway the 12z GFS is done and it stopped the north bleeding and has snow starting late Saturday evening and going into Monday morning. Verbatim, there is no mixing issues for areas west of the bay, temperatures never get above about 20 degrees for duration and total accumulations are similar at 10 – 12″.

My takeaway from the runs this morning is that a major winter storm is likely across the mid-Atlantic on Sunday, but there are a lot of details to iron out. If the midday Euro and AIEuro show any drastic changes, I’ll do a brief update, otherwise I will probably wait until after the later evening model runs.

Sunday

Preface

If after reading the update, you feel like you haven’t learned anything, it’s deliberate because confidence is low on specifics. My official first forecast for tomorrow is that it’s a good day to get any errands or activities wrapped up by late morning and then hover around a fire for the remainder of the day.

Saturday, January 18, 9AM

Hopefully we all got a chance to enjoy the relatively milder temperatures because the bottom is about to fall out. During the day tomorrow arctic air will begin spilling into the area and for the MLK holiday and well into the shortened work week, temperatures will struggle to reach even 20 degrees for highs, and some areas will likely fall below zero for the first time in years. I’ve been a pretty quiet regarding tomorrow because the snow portion is a tricky forecast, but the coming cold air is guaranteed. The difficulty in the forecast for Sunday for the majority of the area is the timing of the arrival of the cold air, so I’m going to keep this short and worry about details in later updates as the models come in during the day today.

Precipitation will arrive tomorrow morning from southwest to northeast across the area from 7 – 9AM. If it starts as snow, you’re locked in to 4 – 6″. If it’s raining, obviously the amount of snow will be determined by when the colder air arrives. I think areas west of 95 changeover by noon and east of 95 to the bay between noon and 2PM. Regardless, by about noon until about 5PM, the precip could become moderate to heavy. It’s a quick moving system, but I think all areas west of the bay across central MD get 2 – 4″ by the time things wrap up, and areas that are currently under a Winter Storm Warning (Frederick, Carroll, and northern Baltimore counties) end up in the 4 – 6″ range.

I’ll send out an update this evening between the upset in Kansas City and the taming of the Lions.

Still on Track for Snow

Sunday, January 5, 11AM

I can’t recall the last time we had snow coming with a legitimate arctic air mass in place, but that’s what we have beginning tonight. The watches from yesterday have been upgraded to Winter Storm Warnings across the entire area, so decisions for school systems should be easy and quick. They will probably start announcing closings later this afternoon with an annoying scroll across Uncle Nam’s TV football games.

Models are still in some disagreement on how it all plays out for central MD, so my overall confidence in snow totals is not very high. For what it’s worth, my current thinking, and I am fairly confident on this point, is that snow will develop from southwest to northeast between midnight and 3AM. Snow will become moderate to heavy quickly and continue into the morning. Morning travel is not recommended as temperatures for the duration of the storm will be below freezing. By noon, I am expecting anywhere from 3 – 6″ to have accumulated. During the afternoon there will be a lull in precipitation with snizzle and maybe even freezing drizzle. During the evening, another steady area of snow should develop and add an additional 1 – 2″ to freshen up any crusty snowpack for a total of 4 – 8″.

Regarding the low confidence in snow totals, for central MD I think the chances of being under the 4″ threshold is less than being over the 8″ threshold. This storm will be packing a punch in the morning hours as warm air from the system collides with the arctic air. If we are going to get the higher amounts, it would most likely be during the morning hours. The afternoon lull and evening 1 – 2″ seems reasonable to me. It’s the morning that could, and hopefully will provide some surprises.

If I see anything different, I’ll send out shorter updates during the day.

Looking Ahead to Friday

Wednesday, Jan 17, 10AM

It’s been a good week if you like snow and winter weather. Obviously, I love falling snow, but I also enjoy when the snow sticks around for awhile. A fresh arctic air mass after a snow is what I would order every time because as far as I am concerned, if it’s going to be winter, it might as well winter.

Anyway, not much to say about the system on Friday because there isn’t a consensus on how it plays out. Right now it looks like snow begins around sunrise on Friday and continues into the afternoon with a general 1-3″ across the region, with the lesser amounts to the south and higher amounts north. Much of the forecast will focus on whether the system tracks to our south, right over us, or to the north. To maximize our snow potential, we need it to track to the south and right now most models have it too far north to bring much snow, so it’s too soon to say how it plays out.

I’ll keep an eye on it and update from to time.