Final Prediction

The all-important question that will determine snow accumulations in Lake Orion tonight is...will we be dry-slotted? Dry-slotting occurs when dry air moves in behind the low pressure system, resulting in a break in snowfall. We probably need 4+" to get a snow day tomorrow, and as long as we don't get dry-slotted for an extended period of time, that will probably happen. This is a heavy, wet snow that will make rush-hour traffic tomorrow morning terrible, especially as there is probably a layer of slush under the snow. What I will say is that it is a tough call as to whether or not we in Lake Orion will get a snow day tomorrow, as we will probably be right on the edge of the extended dry-slotting. However, I think we manage to pick up around 4.5" of snow tonight for a storm total of around 6", which is probably good enough for a snow day tomorrow.

Therefore, my prediction is YES, we will get a snow day tomorrow. A tough first prediction to make for sure though, and I'm not just saying that so I have an excuse if we have school tomorrow. If we have school tomorrow, I will freely admit that I was wrong.


Here is my snow day chances map. What is the 50% line? It is the general snow day line. Areas to the N of the line have a greater than 50% chance of a snow day, and areas to the S of the line have a less than 50% chance of a snow day.

EDITED MAP: Because I mixed up Lake Orion and Flint.

Update

The forecast seems to be on track. Although the low pressure system is tracking further west than expected, we somehow have managed to have all of our precipitation fall as snow. The National Weather Service therefore upgraded Oakland County to a Winter Storm Warning. Although we only have 1.4" of snow so far (at my house), 3-7" more of snow is expected tonight. Therefore, I will keep the snow day alert level at high

To the person from Carmen-Ainsworth High School: I will make a prediction for that high school and include in my prediction tonight a graphic showing the general "snow day" line. Areas to the north of this line will likely close school tomorrow, while areas to the south of this line will likely not close school tomorrow.

Update

One problem with this storm is that the area of precipitation is not as large as expected. This may lead to the precipitation ending early, and less snow falling. Another problem is that the surface low track may be further west than expected. If this occurs, the changeover from rain to snow could occur faster than expected. If these trends continue, I will put out a new snowfall map with lower snowfall totals in a few hours, and also downgrade our alert level to medium. For now though, I'll stick with the going forecast.

Everything on track; raised alert level to high

Snow Day Alert Level: [Low] [Medium] [High] [Very High]

Read my detailed discussion in the last post, and my snowfall map in the last post, as those are still valid. And as I said in that discussion, if they were still valid this morning, I would raise the alert level to high. Currently, the National Weather Service is forecasting Lake Orion to get 4-7" of snow. I'm forecasting 5-9", and I believe that the NWS will join me in forecasting that much this afternoon. This is because the snow is occurring further south than where the NWS forecast it to fall. Therefore, we will likely get a quicker changeover to snow than is currently forecast, and thusly more snow. Other National Weather Service offices have bumped up snow totals for this event, and I believe that our National Weather Service office will soon follow.

I will make a definitive "yes" or "no" prediction on whether or not we will have a snow day by 7:35 p.m. tonight.

Use the comment feature! Ask me a question about this storm and our snow day chances through the comment feature, and I will answer it. I'll be updating this blog several times throughout the day, and will answer your questions in the updates.

MEDIUM risk of a snow day Monday.

Lead Story: Temperatures likely cold enough for snow; alert level raised to medium.

Snow Day Alert Level: [Low] [Medium] [High] [Very High]

Discussion: A low pressure system currently located in Western Kentucky is going to move to the NNE tomorrow and bring an area of heavy snow to SE Michigan from the early afternoon on. The forecast models are likely initiating temperatures a little too warm, so most of the precipitation should fall as snow. Therefore, my snowfall map will bump totals up a little bit over what most people are saying, as the heaviest precipitation will fall at the start of this event, and therefore we could receive a good more snow than forecast if precipitation starts out as snow, or if precipitation turns over to snow more quickly than expected. I expect a quick period of rain at the start of this event, turning over to snow sooner than expected. Why? Well for one, temperatures tonight are already 1-2 degrees lower than what was forecasted. Now, I know, 1-2 degrees doesn't seem like a big difference, but it could make all the difference with this storm. See, the heaviest precipitation will fall at the start of this event, so even a changeover to snow an hour quicker than expected could result in an additional inch or two more than what was forecast. Another thing that points to possible heavier accumulations is that the precipitation is starting quicker than expected. The earlier precipitation starts tomorrow, the less time temperatures have to rebound. Therefore, I expect it to start snowing sooner than expected tomorrow, resulting in the higher accumulations than generally forecast in my snowfall map below.

So, expect precipitation to begin around noontime tomorrow. It will likely start as rain or a wintry mix, transitioning over to heavy snow sometime in the early afternoon. The snowflakes at the start of this event could be huge, and snowfall rates could easily exceed 1" per hour. Snow will then continue to fall into the evening and overnight, and this snow will continue to be heavy at times, especially if we can get some lake enhancement going overnight as winds shift to the Northeast. Wraparound snow showers will then occur on Monday as the low moves away from MI.

Now, to discuss snow day chances. Why didn't I move our alert level to high? One reason: the high bust potential with this system. Just as a quick changeover to snow will result in an additional inch or two with this system, a slow changeover will result in an inch or two less than forecasted. Therefore, I played it safe for now and kept it at medium. If the current forecast holds up tomorrow morning, I will raise our chances to high. There are a lot of things going for a snow day with this system. Firstly, this will be a long event, with snow potentially falling for 24 hours from Sunday Afternoon to Monday Afternoon. This means that the plows will have to focus on the main roads, not the back roads. Also, there will be a lot of blowing and drifting of snow, resulting in major snow drifts on the back roads that will simply be impossible for buses to move through.

The bottom line: Currently forecasted accumulations would be enough for a snow day, but I will hold off on raising our alert level to high until the bust potential minimizes for this event.

Snowfall Map:

New Snowfall Map

Why the changes in the map? Well, the main difference is that the rain/snow line is probably going to be over SE Michigan. This will severely cut down on snowfall accumulations at the start of this event. However, a quick burst of heavy snow is still likely at the end of this event. Due to the fact that I am forecasting Lake Orion to get only 2-4" of snow now, I have lowered the snow day alert level back down to LOW. This is subject to change though, as a little further east track of the low could increase snowfall totals.

NOTE: After this system moves through, I'll be keeping an eye on a strong cold front that will come through on Wednesday Night. There could be blizzard conditions for a few hours with this cold front, and I'm actually a little more excited about that system right now, to be honest.

First Snow Map for Sunday Afternoon/Evening Snow Event

I'll post a detailed discussion of our updated snow day chances tonight, but for now, here's my first snowfall map for this system. As you can see, if these accumulations come to pass, it would be unlikely that we would get a snow day on Monday. Therefore, if future model runs support my current snowfall map, I will likely bump our snow day chances back down to low in my discussion tonight. However, there are still two days before this system hits, so snowfall totals still have a lot of time to be trended upwards. Stay tuned to this blog for details, and my detailed discussion will be up around 11:30 p.m. tonight!


EDITING to say sorry, but I won't have an update tonight. I'm tired, and the forecast models are all over the place. Suffice it to say, the chances of a snow day are diminishing. I will have a full discussion, and a new snow map, out when I wake up tomorrow morning.



Here's the map: