(possibly final) Monday-Tuesday Storm Update

 The models have actually trended colder for this storm, giving us a higher chance to see winter precipitation. And although we are close to the storm, not many maps have been made yet. So we will also be looking at some models, like the NAM 3KM and HRRR + plus the American and European model. But, this storm is going to be very messy. Since the temperatures and dew point are so close to freezing, it is going to be difficult to predict what precipitation we will be starting as until the precipitation is very close to us or is already falling. And I also expect precip types to switch and change rapidly during the course of the storm. This storm is going to be more impactful the more north and west you are. There are winter storm watches in western Maryland and NW Virginia, where significant and dangerous ice accumulation is expected. I think that the watches will turn into warnings. I feel like MoCo will probably get advisories, for both parts of the county too(more confident in upper MoCo though, southern MoCo 65% chance). But, we could also get warnings as well. The timeline of this storm is 2 PM Mon - 10 AM Tuesday. Surface temps, for pretty much the whole region will be cold enough to support any wintry precipitation, so that won't be an issue. Now, let's see some models.

Note: All models are either from tropicaltidbits.com or pivotalweather.com. They are very good websites to use when tracking any type of weather, and I would highly recommend using them on your own time.

NAM 3km:

The NAM 3KM shows a very messy storm. It shows it starting as rain/snow, then shows the precipitation types changing so quickly, from snow to a mix, from freezing rain to rain, its a mess. From 9PM Monday to 12 AM Tuesday, the NAM shows a band of heavy snow that moves throughout the county through that time period. That could be the main bulk of the snow accumulation. I am not even gonna try to explain what is happening, its a mess of precipitation switches. The total snowfall from this storm, as the NAM shows is 1-2 inches, which I agree with. However, with sleet, the totals go up drastically. It shows 3-7 inches of snow and sleet for a county, with totals close to a foot, or even OVER a foot in some areas! This is what I am hoping for in terms of snowfall. This would be a boom scenario. However, realistically, I don't think we will get THAT much snow and sleet. But we will see.

GFS:

The GFS shows the storm starting out as rain for the lower quarter, freezing rain for the middle quarter, and snow for the upper quarter. It then shows mostly ice for the county before transitioning over to rain. It shows pretty much no snow for the entire county, in terms of accumulations, but it does show ice. Depending on where you live, the GFS shows a glaze of ice all the way to two tenths. The more northern and eastern you are in the county, the more ice accretion you will get. However, CAD usually lasts for longer than the models show. At this point out, I trust the NAM and HRRR more than the GFS and European, because they are better at predicting close-range conditions. However, the GFS and European models are still important.

Euro:

The European model shows the storm starting as a mix/snow, and then shows it transitioning to rain before it leaves. However, this model skips 6 hours every time it shows the storm moving, so I am pretty sure that the wintry precipitation will fall for a while before turning into rain if this model plays out right. This model shows a dusting - 1 inch of snow in the county, NE areas will see more, SW areas will see less.

HRRR:

This model, in my opinion, handles cold and warm air very well. It is a good model for short-term forecasting. This model shows the storm starting as rain first, and then switching into snow/mix, depending on where you live(northern sees snow, southern sees mix). It keeps switching back and forth, from a mix to snow, and back. The mix will be heavy at times, increasing snow totals. This model doesn't show any rain for the county, other than the initial onset(for the most part). This shows 2-4 inches of snow for our area, which is a nice amount. It doesn't show that much ice accumulation, the more south you are in the county, the more ice you will see, which makes sense(totals range from glaze to around a tenth).

Capital Weather Gang:

The Capital Weather Gang shows 1-3 inches of snow for the upper third of the county and a coating to 1 inch for the rest of the county. The models have been showing more snow than this for some of the areas in the C-1" of snow area, but I can understand why they were conservative and went for the lower totals. 

WBAL 11: 

WBAL 11 shows 1 inch or less, in regards to snow, for most of the county, and for the western side, it doesn't show any snow, just "Ice Accumulation Possible". They lowered the totals for this storm, and I can understand why though, since the main forecast for this storm is mixed precipitation.

National Weather Service Snowfall Map:

This map has increased! It shows 2-3 inches for about all of the county and 3-4 inches for Damascus. That means they are starting to gain more confidence in more snow and ice, which is good. I bet the HRRR and NAM affected this decision!

Same with the snowfall map, the ice accumulation map increased their totals too! The upper part of the county(more on the eastern side) is in the 0.10-0.25 inches of ice, while the rest of the county is in the 0.01-0.10 inches of ice range. This storm is going to be very messy, to say the least. From this map, I expect an advisory for the WHOLE county and maybe even a warning in the upper part of the county? As of 6:10 PM, there have been no alerts issued for MoCo.

I can understand why there aren't many maps for this storm, it's because it is nearly impossible to predict, with temps playing with the freezing mark. This storm requires a nowcast kind of prediction. But what about impacts? Well, it depends on where you live. Any area north and west of MoCo, like Frederick County and the general Shenandoah region, will be hit pretty hard by this storm. There, you could see amounts of ice enough to make power lines fall and create outages. And the snow and sleet doesn't help too. I could see school closures, even in virtual learning, due to power outages. But what about MoCo? Well, the criteria for no school in MoCo, as MCPS has stated, is "countywide power outages". Although it's definitely a possibility in the northern regions, I don't think we will see enough winter precipitation to cause power outages throughout the whole county. And the timing of the storm isn't that great for school closures either. But, during heavy ice accumulation, the crews won't be able to help until the storm is done and over, even in the interior NE and Canada(somewhat). And in the DMV, where we have been snow-starved for a very long time, I don't think the crews will be able to fix it during the storm.  Even after the storm, it will be hard to get power back up to the whole county that fast. So my prediction for school impacts are: A 35% chance of a 2-Hour Delay on Tuesday and a 30% chance of a closure. If conditions start out really bad, we could see a closure on Tuesday, but I am pretty sure we won't get an early release on Monday because that kind of stuff has to be planned out before the storm hits, and that's very difficult to do in this storm. South of MoCo, it's probably just going to be a cold rain for you, but you might see a brief period of a mix.