We have some pretty wild temperature swings this week with some days near 60 and some in the 30s and 40s. Lows will also swing quite a bit, ranging from the 20s to the upper 40s! Most days will contain a mix of sun and clouds with the exception of Wednesday and Thursday (see next paragraph)

There will be a storm system that produces a wintry mix mainly in the form of sleet and freezing rain, although some light snow is also possible mainly in northern MD. We will have many more details on this event around noon today with our first call on ice accumulations. But just know that travel disruptions are likely, and power outages are possible depending on how much ice we get. 

Confidence continues to increase in an accumulating and possibly impactful snow event on Sunday, with most models now agreeing in a few to possibly several inches of snow accumulation for most of the area. With that being said, there remains some discrepancies and complications that lead to some uncertainties and lower confidence in the forecast.

One of the complicating factors is temperatures, particularly on Saturday. We expect high temps in the low 40s on Saturday. This will warm the ground enough so that the first flakes that fall on Sunday will probably melt and not stick. In addition, rain is likely at times on Saturday. And while we don't expect a lot of rain, it will be enough to wet the ground, which also helps with melting. 

There is also uncertainty in the storm track, with all 3 longer range models showing slightly differnet scenarios, which in turn, will impact how much snow we get. The EURO model has the low pressure off shore far enough to where we only get 1-2" of snow, with no mixing. The GFS is slightly further inland, with a general 3-6" of snow and a little mixing SE of I-95. And the GEM is way inland, with 5-10" of snow in our northern areas, with plain rain elsewhere. 

We think the GEM is way too far inland, and that scenario doesn't really make too much sense. The EURO is plausible, but the GFS is a nice middle ground. Even so, we think those numbers are a little too high due to the melting we discussed earlier. There is another outcome, shown by the NAM, which takes the low so far off the coast that it leaves us with flurries at most. This is possible, but like the GEM, we think its unlikely and that it is too far offshore. However, this would be a bust scenario to keep an eye on if this were to occur. 

For now, we will forecast a widespread 2-4" of snow across most of the area north and west of a line from Bowie to Annapolis, with a coating to 2" further south and east where there could be some mixing as well as warmer temps. Within the 2-4" zone, an isolated amount up to 5" cannot be ruled out. 

In future updates, its likely that there will be some changes to this forecast, which could include either an increase or decrease in the expected accumulations. We encourage you to use caution when you see other snowfall maps this early on calling for much larger totals, as they do not take into account the aforementioned uncertainties and complexities that will impact how much snow actually accumulates. 

As far as timing goes, snow will overspread the area from southwest to northeast during the early and mid morning hours on Sunday, and continue throughout most if not the entire day. Snow may become moderate to heavy at times. Snow should taper off during the evening hours. The most widespread and "heaviest" snow should be from late morning through early and mid afternoon. 

This will likely result in hazardous travel due to slick and in some cases snow covered roadways. Visibility may be reduced at times due to snowfall rates of up to 1" per hour, especially from mid morning through mid afternoon. No alerts from NWS are currently in effect, although a winter weather advisory is likely to be issued tonight or Saturday morning in advance of this system, and if the storm trends stronger, winter storm watches cannot be ruled out.

A fairly calm week weather wise is expected with no significant or impactful weather in the forecast for this week. 

The biggest thing to note will be the wind chills, particularly Tuesday, Wednesday, and Thursday mornings. Wind chills could be near or even below 0 in some areas, with area wide single digits expected. This level of cold is dangerous if precautions are not taken. 

It will also be windy on Tuesday and Wednesday, with gusts up to 40mph possible on Tuesday, and up to 30mph on Wednesday. 

We will watch the end of the week for potential winter weather, but confidence is very low this far out.

9:21AM 1/4/25 - WINTER STORM UPDATE:
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As of early this morning, the NWS has issued a winter storm watch for the entire state. For our area, the watch is in effect from 7pm Sunday until 1am Tuesday for Montgomery, Prince Georges, and Anne Arundel. The watch is in effect from 10pm Sunday until 1am Tuesday for Washington, Frederick, Carroll, Baltimore, Harford, Howard, and Baltimore city.

Snow is expected to overspread the area from SW-NE late Sunday night or early Monday morning depending on location. Snow will become moderate to heavy at times and may mix with sleet to the south of Route 50. Elsewhere, it should remain all snow. Snow will end sometime late Monday night or very early Tuesday morning. ​

There remains uncertainty in the exact track, which ultimately will determine how much snow we see. There are basically 2 different scenarios with the models. One group tracks the low a little closer to DC, which brings a band of major snow to central and northern MD. The other group of models tracks the low further south, hammering the DC metro and southern MD/ northern VA.

Right now, we are going for the middle ground, with the heaviest band of snow along and south of I70. This is where 8-10" of snow is expected, and an isolated amount of 1 foot is possible. Elsewhere south of the PA state line, 5-8" of snow is expected, with isolated higher amounts possible. And for our southern PA counties, 2-5" is expected. ​

Even if this was a total bust, and we wound up with 1-3" (that is very unlikely), the roads would still be extremely hazardous as the temperatues will be well below freezing so everything will stick. We anticipate widespread closures on Monday as well as Tuesday. This will be a high impact winter storm, and the biggest one we have seen since 2022.

Our final call will be out Sunday afternoon around 12pm.
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Senior Forecaster Jack.

12:13PM 1/3/25 - Here’s what you have all been waiting for. Our first call on Mondays snow storm.
First off, this will be a high impact event regardless of just how much we get. Roads will be snow covered and very dangerous to travel on. We expect widespread closures not just on Monday, but potentially into Tuesday as well.

Precipitation type is still a little uncertain south of I-70. North of I-70, we should stay all snow. Between I-70 and Route 50, it should be mainly snow, but a mix is likely at times. South of Route 50, a mix is likely and some freezing rain is possible as well.
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The exact track of the storm is also still a little uncertain which is to be expected 3 days out. A track further north would lead to more snow in northern MD, while a track further south would lead to more snow in central MD. Either way, significant snow is likely in our area.

In total, we expect a widespread 3-6” for areas along and south of a line from Sterling to Laurel to Annapolis, as well as north of a line from Gettysburg to Shrewsbury. In between, across much of central and northern MD, 4-8” is expected. This may be a bit conservative, and an increase is possible. If there were to be any changes to this forecast, it would likely be the placement of the 4-8+” zone. It could shift either north or south. ​

On Friday, a clipper system will bring an area of snow showers and snow squalls to our area. These will be narrow and short lived, but could be impactful. In some areas NW of I-95, a coating to as much as 2" of snow is possible under the snow squalls (This wont happen everywhere). Most, if not all of this accumulation would be on elevated or grassy surfaces, but we cant rule out a few roads having some slick conditions due to a slushy coating. 

The timing is what is the problem, as its most likely to occur from 1pm-7pm, impacting the evening commute. Snow squalls can also produce brief whiteout conditions in heavy snow, so visibility may be reduced for a short period of time. If the snow squalls are particularly intense, then snow squall warnings may be required. 

For Monday, there is high confidence (>80% chance area wide) of accumulating snow. Snow will begin late Sunday evening/overnight and last until at least Monday afternoon. During this time, temperatures at the surface will be at or below freezing, so snow will stick to any untreated surface. For areas along and north of US.50, precipitation as of now looks to stay all snow. Areas south of there will probably mix with sleet or freezing rain. A shift in the track north or south could still occur, and will change the precipitation types so we will monitor for shifts. 

It is still too early to go into specific amounts (we will release a first call midday on Friday), but we can start looking at where the heaviest accumulation may be. Right now, that looks to be across central and northern MD, between DC and the MD/PA state line. This is where we are most likely to see winter storm warning level snow, which is 5 or more inches in 48 hours. Outside of that dark blue zone, light to moderate accumulations are still likely. 

This likely will be impactful, and it seems more probable that schools will be impacted on Monday. If you have travel plans on Monday, I would consider changing them. Whatever does fall probably will stick around for a while as we enter a very cold pattern after this system passes. 

A weak clipper system will bring a chance for snow showers and possibly some snow squalls during the afternoon and evening on Friday. Temperatues look to be above freezing, so there should be little to no travel impacts. However, it may snow heavily enough in narrow areas to produce a light coating to perhaps as much as 1" in a few isolated areas. In any snow squall, brief reductions in visibility and gusty winds could also occur. It wont accumulate in all areas outlined in white, but some areas could see a coating to 1".

Our first chance for widespread accumulating snow will arrive on Monday of next week (January 6th). There is very good model agreement that there will be a storm, but the exact track is still uncertain. The exact track will be the determining factor of who gets significant accumulations and who gets a dusting.

Right now, it appears the storm will take a more southerly track. This means that as of now, the highest chance for any significant accumulation would be in central and southern MD, generally along and south of I-70. That being said, we are still 5 days out, and its entirely possible that 2 things could happen. Either 1, it shifts a bit further north, putting everyone at risk of significant snow, or 2, it trends further south, leaving the greatest chance from DC south.

Its way too early to talk about accumulations, but there certainly is potential for plowable snow somewhere in the mid Atlantic, and travel disruptions are increasingly likely wherever the area of snow sets up as anything that falls will stick to any untreated roadways with temps below freezing. It will all depend on where the storm tracks, as temperatures will be cold enough to support snow. We should know much more on Friday, so be sure to stay tuned!

We have been closely monitoring model data over he last few days and its pretty clear that there is a "threat" of some winter weather on Monday of next week (about 6 days out). Obviously, it is way too early to give specific details, and anyone who is already posting snowfall maps is simply irresponsible. There is no skill in snowfall forecasts more than 3 days out, so its way too early for details. 

What we can talk about is potential. Models have been consistent about the POTENTIAL for accumulating snow Monday of next week. As of now, this does not look like a major snow storm (that could change). But there does seem to be a decent chance for the first legitimate, meaning more than a dusting, accumulation of snow of the season. That said, there is still disagreement within the models, which is to be expected this far out, and will continue for a few more days.

While there is a chance for snow area wide, the best chance will be across north central, northern, and western MD, northern VA, and the panhandle of WV. Temperatures in these areas look to be at or below freezing, so that is favorable for snow if this system does materialize. As of now, there is about a 50% chance for accumulating snow in these aforementioned areas, and about a 30% chance for the rest of the area. This is a very early look at the situation, and its very likely to change. There is a chance that the system doesn't even materialize, a chance that it does materialize but passes well to our south or out to sea, or it materializes and takes a track just south of us allowing potential for winter weather. We simply cannot provide any other information than this, this early in the game. We will know much more later this week, and you should expect an update late on Thursday, as that will put us within 4 days of this threat. 

3:57PM 12/30/24 - A storm system will bring thunderstorms and strong winds to the area on Tuesday and also Wednesday.
A low pressure system will bring a strong low level wind field to the area on Tuesday. The wind profiles are favorable for the development of thunderstorms. Instability is weak, but steep lapse rates will lead to the potential for strong wind gusts in any heavy shower or storms. A few lightning strikes and even some hail is possible given the steep lapse rates and strong wind fields. We don't think there will be much severe weather, but some of the hail or wind gusts could be near severe caliber (58mph or 1" in diameter). The most likely timing for any thunderstorm will be from 5pm until 10pm.

On Wednesday, the strong wind field will remain, and there will be a tightening pressure gradient. These 2 parameters are favorable for strong wind gusts across much of the area. 850mb winds will run between 45 and 50kts, with decent mixing of the boundary layer. This means that some of that wind will transfer to the surface. The current forecast calls for peak gusts of 35-45mph across most of the area, with gusts near 50mph in the higher elevations. Some model data suggests that winds could reach advisory level of >45mph across much of the area, and a wind advisory may be required if confidence increases. This could result in minor tree and power line damage and a few power outages.

This week, we will discuss the upcoming pattern change as well as increasing chances for snow and very cold temperatures.
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Senior Forecaster Jack