Nowcast For Wednesday - Friday Storm

Go check out my forecast first before reading this nowcast: https://mcpsweather.blogspot.com/2021/02/final-forecast-for-wednesday-friday.html

Thursday:

11:40 AM Update: 

The snow from the first wave is gone now as we wait for our second wave. It won't really drop that much snow though, a coating to 2 inches if we do see some measurable accumulation. Now we focus on our next threat, the one on Saturday. As soon as models come in, I will start making a post.

9:45 AM Update:

I have gotten many reports in the county of people getting winter storm warning levels of snow. 4 inches in Clarksburg, 6 inches in Damascus, 2 inches in northern Germantown. Honestly, even for northern areas in our county, you can see such a difference, ranging from 2 all the way up to 6 inches. It just depends on who had the most precipitation and cold air. I was surprised how much less Clarksburg got than Damascus; that's a 2-inch difference! That's not the much of a mile difference too. It just shows how much of a difference in amounts two places can have when they are a short distance away. I wouldn't be surprised if someone pushed over 7-8 inches, but most of the snow accumulation is done. A coating to two more inches of snow will fall in the second wave, but I expect totals to be on the lower end of this scale.

8:38 AM Update:

I measured 2 inches of snow on the ground in Gaithersburg. Snow is still falling at a moderate rate. One thing that I did not really take into account was the amount of mixing that happened last night. I knew some mixing would happen, but not to the extent it was. I still think that another 1-2 inches of snow may fall when this storm is said and done, but I am not so sure anymore. Mt. Airy(technically in Carroll and Frederick counties but still very very close to MoCo) has reported 5 inches of snow and is still counting. It does have higher elevation though, but I think some areas in our could(not probably) reach 4-6 inches. It's a possibility. We will see how it plays out. I do guarantee at least a coating of snow to fall everywhere. We will start to see precipitation dry out as we go through the morning. Then, in the night, some snow will fall again. Temps will be much colder than what we had yesterday, but there will be less moisture. Dendritic flakes will help us get some more snow through Friday. Overall, my forecast seems to be holding up ok, but we will see. I will shortly be working on a post not for this storm, but for the storm on Saturday-Sunday.

Wednesday:

10:45 PM Update:

This is where the snow/sleet line is right now. Only more interior upper MoCo is seeing snow. The rest of the county is seeing sleet or a snow/sleet mix. In Gaithersburg, a snow and sleet mix is occurring. There may be some localized areas in the sleet area that may be seeing snow, but even there sleet will probably mix in at one point. Precip types will go back and forth.

10 PM Update:

Heavy snow should be continuing into the night and into Thursday. It should start to taper off late Thursday morning/afternoon before our second wave. Precip types will probably switch back and forth, but the snow should win out overall(southern MoCo will probably see some mixing, but they will see some good snow too). This wave will drop most of the snow accumulation though. The second wave will drop a little bit more and might drop an inch or two. Temps should be below or at freezing. Roads and sidewalks completely covered; everything covered in snow. Wet areas turning into ice. Right now, it's looking a bit better than expected, at least for snow lovers.

9:10 PM Update:

The heavy snow has reached us, and I can definitely confirm it coming down here in Gaithersburg. It is falling at a very heavy rate, causing low visibility, and is now sticking to sidewalks/roads. Temps are at or below 32, so now snow should accumulate easier. This snow will last throughout the night and will start to clear up on Thursday late morning/afternoon. 

8:20 PM Update:

This tweet from Tom Tasselmyer shows an image from what I assume to be the SPC(Storm Prediction Center). It says that snow intensity will pick up in the area in Tennessee, West Virginia, and Kentucky, as "strong jet-induced upward vertical velocities" move in. So what does mean for us? That area of heavy precipitation(snow for us) will be heading RIGHT our way. This will help us get more snow accumulation. After what everyone made out as a hopeless, terrible storm this afternoon, there may be some hope.

7:45 PM Update:

The snow seems to have tapered off into light snow, cause I don't see anything falling. The snow still seems to be slowly accumulating but I don't really know. Even if nothing is falling, that is ok. The main course of the precipitation and the one that will bring us the main accumulation from this storm is far west of us, and it's coming east. Should be here in the next 2-4 hours.

7:12 PM Update:

We have officially reached 32 degrees here in Gaithersburg. Lots of surfaces that aren't snow-covered are wet, and along with the heavy snow still falling, there will be black ice underneath the snow. Snow should accumulate rapidly now.

6:40 PM Update:

The snow is falling at a very heavy rate here in Gaithersburg. I can't see much; it looks like there is a lot of fog. All surfaces(excluding sidewalks and roads) are covered in snow. I assume roads and sidewalks will get covered once temps drop below 32 in the night. This isn't even the main precipitation course, we will be seeing heavier, consistent snow during the night today, and midnight to morning hours tomorrow, before it starts to taper off. With the updated NWS map, I am now going to change my snowflake prediction to a 55% chance of school buildings being close. Conditions are colder than expected, and at these rates, snow will stick on untreated surfaces rapidly.

6:20 PM Update:

The NWS has updated their snowfall map for MoCo, and boy does it look a lot better for snow lovers. 4-6 inches for the eastern half of the county(and northern) and 3-4 inches for the rest(southern half). The main reason they upped their map by a lot(at least from what I think) is because of the first band dropping a coating, which meant that the snow had to fall at a heavy rate, especially with temps above freezing. That cooled the atmosphere and ground enough everywhere to where there will be more snow accumulation, and there will also be more moisture(not so sure about this one). Right now in GBurg, it's coming down really well here. Almost 32 degrees.

6:00 PM Update:

Snow still coming down at a pretty heavy rate. The temperature has dropped by 6 degrees and I assume it will drop to at or below freezing in the next hour or so. Warnings have been set up for counties right north of us(Cecil, Upper Baltimore County, Harford). I wouldn't be surprised if the warning gets extended a bit south, to upper MoCo. It could happen if precipitation is heavy enough, and could even drop to southern MoCo. Already a decent coating on the ground.

5:30 PM Update:

The heavy snow is causing major dynamic cooling in the atmosphere, meaning that temperatures are quickly dropping. The temperature has already dropped 4 degrees in just an hour. And as the sun starts to set, temperatures will drop even more as there will be no sun angle to worry about. Snow starting to accumulate on surfaces. 

5:12 PM Update:

The snow rate is picking up fast. It's really coming down here. Big, wet flakes falling at a heavy rate means that snow will be accumulating on any untreated surface soon, especially when we drop below freezing. Areas that usually pick up the snow accumulation first and fastest were wet for a while, and now becoming snow-covered as the ground cools. If it keeps falling at this rate, I wouldn't be surprised if roads and sidewalks get fully covered.

5:00 PM Update:

I can confirm that light snow is falling and reaching the ground here in Gaithersburg, and many other people have reported snow falling in MoCo too. It's not sticking and probably won't stick until we get into the night. There are warnings for Frederick and Caroll counties due to afternoon models being aggressive with snow there. Still an advisory in MoCo.

4:20 PM Update:

The snow that was reported across the region(mainly west of us) was just the pre-teaser; not actually part of the storm. The main snow is still far west of us and is coming our way in the next 1-3 hours.

3:30 PM Update: 

Snow has been reported in our western neighboring counties(Loudoun, Fairfax). If we are snowing at 36-42 degrees, it may be a good sign that we can support all ❆ throughout the night.