Prediction: All MCPS activities on Saturday will be canceled, MCPS building services at least delayed and a 51% chance of closure(they will monitor weather conditions and decide to close on the conditions outside).
Sorry for the delayed update, this post was supposed to come out Wednesday(1/15/2020)
The winter threat is still there, but the snow amounts have gone down lower(this usually happens). Now, there seems to be lot of other precipitation than just pure snow as well, such as sleet, freezing rain, and cold rain(the order I said these types of precipitation is what order the precipitation is expected to fall for this storm). This is a Cold Air Damming event (CAD)(meaning: a high-pressure system that goes from west to east with an associated cold front)(there is warm air above the cold front that covers the cloud)(cold front/air means 32 degrees or lower)(the above 32 degrees air is above the dome of cold air)(warm air= 32+ degree weather).
CAD Picture(from Wikipedia)(it shows and explains it better than I do):
Do you see how it uses areas of the DMV? Anyways, the clouds and precipitation fall in the above 32 degrees weather, but when the precip reaches the dome, the precip turns into either snow, sleet, or freezing rain. The type of precip depends on the depth of the cold air. If the dome is really high, we will get snow, if the dome is medium, we will get sleet, if it is somewhat low, we will get ice. Anyways, the NWS has put a winter weather advisory for all of MoCo, which starts at 7AM Saturday, and ends at 7PM Saturday(for the whole county). The advisory says, "Snow, sleet and freezing rain expected. Total snow and sleet accumulations of up to one inch and ice accumulations of up to one-tenth of an inch." It also says that the wintry mix will turn into the plain cold rain. WUSA 9 has released its first call for the wintry mix! I will show the ice and snow/sleet accumulation maps.
As you can see, most of MoCo is in the D-1" area, and Damascus(and extreme eastern/northern Clarksburg) is in the 1-2"+ area(this means that 1-2" will fall but there is a lot more potential for more than that). It says that snow and ice will accumulate quickly(because Friday and Saturday temps will barely rise above freezing). All snow and ice will stick, so anything untreated will have snow. This is a very interesting map because usually places more north and west get more snow, but this time, places north and EAST get more snow. Howard County has more of its county in the 1-2"+ area. Anyways, let's look at the ice accumulation map!
Most of MoCo is in the "Up To 0.1"" of ice area(Glazing-0.1" of ice), while the same area of MoCo who are in the 1-2"+ of snow are in the 0.1-0.25" of ice area. This means that there is enough ice to make sidewalks and roads slick and ice-covered, but in Damascus, there is a possibility of downed tree branches, and even power outages(0.25" of ice is enough to cause power outages and downed tree branches)(0.25"> of ice is enough to do those, but there is less of a chance that they will happen). If this happened on Friday, I would give 3.5/4 snowflakes for this storm. Ice is not a joke, and we're not talking about a glazing(like in December). No, we are talking about 0.01-0.25" of ice, and that's serious(in Damascus). This time, the biggest accumulations are north and far west of MoCo(Eastern West Virginia)(Frederick County, Hagerstown). East and South are the big losers here(most people will see glazing east and south of MoCo, or no ice at all). This much ice will make everything slick, and because it's so cold today and tomorrow, at least 85% of the ice will stick(probably 99% of it). Anyways, let's look at the NWS maps now!
As you can see, the eastern 13/16 of MoCo is in the 1-2" of snow area, while the other 3/16 is in the less than 1-inch area. This is the total amount of snow that will fall during this storm, and this is the most optimistic snow map out of all the snow maps I am going to show. However, the advisory says amounts "up to an inch", but this map shows at least an inch for almost the whole county, and some areas of the county could receive 2 inches, but most areas will get between 1 and 2 inches of snow(1-2"). I don't know why they don't say up to 2 inches in the advisory, according to this map, the advisory should say snow and sleet accumulations up to 2 inches. This is the most optimistic map about snow accumulations, because most of the other maps say a Dusting-1" for most of the county, with 1"+(1-2" usually) for Damascus. Let's look at the ice accumulation maps now!
As you can see most of MoCo is expected to have some ice accumulation(at least 0.01" of ice for most of the county). However, I think that the part of the county that won't get ice will get some ice, but it will be a light glaze. This shows 0.01-0.1" for most of the county, which is enough to make everything slick, but Damascus and a few other areas will get at least 0.1" of ice and could get a quarter-inch of ice. North and west of MoCo are expected to get the most ice. There's not really that much else to say about this map, because I already said it in the WUSA 9 map. Now let's look at the NBC 4 map!
As you can see, 3/4 of MoCo is in the "Up to 1" area(Dusting to 1 inch) and the other 1/4 is in the 1-2" of snow area. Even though this isn't a lot of snow, every flake that falls will stick and make icy and slick surfaces. An inch of snow will definitely cause lots of impacts and delays, it will be slick outside, and with the sleet and freezing rain, the roads/sidewalks will become really icy and slick and become very dangerous. The snow will also be much harder to remove, so I recommend salting roads and sidewalks before the storm. In this map, areas north and west will get the most snow. NBC 4 doesn't have an ice accumulation map, so we will move on to the next maps!(Note: I won't be explaining the maps because the maps are very similar and everything I will say about them will already be said).
As you can see, most of MoCo is in the 1>" of snow area, while Damascus is in the 1-2" of snow area. The amount of snow, according to this map, depends on how north or south you are(east and west don't really matter). North of MoCo will get 1-2", while south of MoCo will get less than an inch. (This doesn't have an ice map). Let's move on to Fox 5's map!
Most of MoCo is in the C-1" of snow area(some slick roads here), and the upper 1/4 of MoCo is in the 1-3" of snow area. All of MoCo will have snow-covered and slick roads according to this map. If you live north of MoCo(and west of Baltimore County), you will see 1-3" of snow. (No ice map).
Verdict for this storm: Moderate Impacts(4.25/10 for areas south of Gaithersburg)(4.6/10 for Gaithersburg and northern MoCo)(5/10 for Damascus) (1 being lowest impacts, 10 being the highest).
I put "Moderate Impacts" for this storm. Why? Well, it's because of that all snow that falls will stick to all surfaces if the surfaces are untreated, which means slick and snow-covered roads and sidewalks. There won't be that much snow, so I wouldn't put this in high impacts, but there is freezing rain, and that will make the snow harder to shovel and there is enough ice to create slick roads and sidewalks. There might be a little gap where nothing falls, and that slightly lowers the impacts, but still, temps will be below freezing, and the snow will freeze, making it harder to shovel and plow. Also, models typically tend to underestimate how long the below-freezing air will stay in these CAD events, so the whole county could see freezing rain until 5:30 PM Saturday. Damascus could have freezing rain until 7:30-8:30 PM(when temps will be at or below freezing). When it gets dark, it is going to be hard to see whether roads are wet or slick, so drivers will have to be careful at night and drive slowly, otherwise, a surface that looks wet may be icy, and their vehicle could skid. Walking slowly and carefully is advised, otherwise, you might slip. The freezing rain will make this system moderately impacted and will be the main concern, along with the sleet. Sleet basically has the same impacts as snow, so snow accumulations could also include sleet and could create totals of more than an inch of snow in areas that were expected not to get snow. The wintry mix will become rain at around 5:30- 8:30 PM(when temps will be above freezing). The impacts would be significantly higher if the storm wasn't on a weekend. Ice won't really melt when the rain falls, so even at 9PM, there could still be some slick roads. Sunday morning could have slick spots, but probably not. Overall, this storm is not that big in terms of snow accumulations but will create some impact due to the freezing rain.
Sorry for the delayed update, this post was supposed to come out Wednesday(1/15/2020)
The winter threat is still there, but the snow amounts have gone down lower(this usually happens). Now, there seems to be lot of other precipitation than just pure snow as well, such as sleet, freezing rain, and cold rain(the order I said these types of precipitation is what order the precipitation is expected to fall for this storm). This is a Cold Air Damming event (CAD)(meaning: a high-pressure system that goes from west to east with an associated cold front)(there is warm air above the cold front that covers the cloud)(cold front/air means 32 degrees or lower)(the above 32 degrees air is above the dome of cold air)(warm air= 32+ degree weather).
CAD Picture(from Wikipedia)(it shows and explains it better than I do):
As you can see most of MoCo is expected to have some ice accumulation(at least 0.01" of ice for most of the county). However, I think that the part of the county that won't get ice will get some ice, but it will be a light glaze. This shows 0.01-0.1" for most of the county, which is enough to make everything slick, but Damascus and a few other areas will get at least 0.1" of ice and could get a quarter-inch of ice. North and west of MoCo are expected to get the most ice. There's not really that much else to say about this map, because I already said it in the WUSA 9 map. Now let's look at the NBC 4 map!
As you can see, 3/4 of MoCo is in the "Up to 1" area(Dusting to 1 inch) and the other 1/4 is in the 1-2" of snow area. Even though this isn't a lot of snow, every flake that falls will stick and make icy and slick surfaces. An inch of snow will definitely cause lots of impacts and delays, it will be slick outside, and with the sleet and freezing rain, the roads/sidewalks will become really icy and slick and become very dangerous. The snow will also be much harder to remove, so I recommend salting roads and sidewalks before the storm. In this map, areas north and west will get the most snow. NBC 4 doesn't have an ice accumulation map, so we will move on to the next maps!(Note: I won't be explaining the maps because the maps are very similar and everything I will say about them will already be said).
Most of MoCo is in the C-1" of snow area(some slick roads here), and the upper 1/4 of MoCo is in the 1-3" of snow area. All of MoCo will have snow-covered and slick roads according to this map. If you live north of MoCo(and west of Baltimore County), you will see 1-3" of snow. (No ice map).
Verdict for this storm: Moderate Impacts(4.25/10 for areas south of Gaithersburg)(4.6/10 for Gaithersburg and northern MoCo)(5/10 for Damascus) (1 being lowest impacts, 10 being the highest).
I put "Moderate Impacts" for this storm. Why? Well, it's because of that all snow that falls will stick to all surfaces if the surfaces are untreated, which means slick and snow-covered roads and sidewalks. There won't be that much snow, so I wouldn't put this in high impacts, but there is freezing rain, and that will make the snow harder to shovel and there is enough ice to create slick roads and sidewalks. There might be a little gap where nothing falls, and that slightly lowers the impacts, but still, temps will be below freezing, and the snow will freeze, making it harder to shovel and plow. Also, models typically tend to underestimate how long the below-freezing air will stay in these CAD events, so the whole county could see freezing rain until 5:30 PM Saturday. Damascus could have freezing rain until 7:30-8:30 PM(when temps will be at or below freezing). When it gets dark, it is going to be hard to see whether roads are wet or slick, so drivers will have to be careful at night and drive slowly, otherwise, a surface that looks wet may be icy, and their vehicle could skid. Walking slowly and carefully is advised, otherwise, you might slip. The freezing rain will make this system moderately impacted and will be the main concern, along with the sleet. Sleet basically has the same impacts as snow, so snow accumulations could also include sleet and could create totals of more than an inch of snow in areas that were expected not to get snow. The wintry mix will become rain at around 5:30- 8:30 PM(when temps will be above freezing). The impacts would be significantly higher if the storm wasn't on a weekend. Ice won't really melt when the rain falls, so even at 9PM, there could still be some slick roads. Sunday morning could have slick spots, but probably not. Overall, this storm is not that big in terms of snow accumulations but will create some impact due to the freezing rain.
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