Saturday, January 24, 10AM
The arctic airmass has obviously arrived, and global models have come to some agreement, but the mesoscale models, which should be in range at this point, are concerning. They drive the primary low into the arctic mass to the west of us which brings a relatively warm layer aloft. So, although at the surface it’s well below freezing, snow falls from high altitudes, passes through a warm layer, melts to rain (or least no longer snow), then after passing through the warm layer, hits cold air and refreezes. If the cold layer at the surface is deep, the rain refreezes before hitting the ground as sleet. If the surface layer is shallow, the rain hits surfaces as a liquid and refreezes (freezing rain). Freezing rain is the most dangerous because it coats everything, including trees and power lines, with a heavy coating of ice. Sleet is terrible for roads and walkways, but it doesn’t stick to surfaces. Think ball-bearing ice pellets. It still is going to snow, but if the short range models are right, then the snow totals will be on the lighter end of the totals I’ve said the past couple of days. I’d be only guessing as to which scenario is correct, but the end result will still be extremely impactful.
In summary, snow develops around midnight, becoming heavy by morning with significant accumulations. I’m sticking with the totals from the past couple of days, but it depends on when the changeover occurs. After the change, there will be significant accumulation of sleet. In some areas it is going be really impressive. Hopefully we don’t get any freezing rain or drizzle because that would just make the glacier worse. I’ll update this evening with more details.
Finally, a reader asked a couple of questions and wanted my thoughts. First, they wanted to my opinion on when to start clearing a messy system like this. It’s a great question. Just my opinion, but for a storm like this, I would say to wait for all precipitation to end to start shoveling and clearing vehicles. Yes, it’s going to be much heavier, but getting under the fluffy snow is much easier than trying to get under ice. If it was going to be an all snow event, then I would say try to keep up, but with possibility of freezing rain, I am waiting. Also, we always read stories about heart attacks from shoveling, so go slow, and take breaks. You’re in no hurry as we are likely not going anywhere tomorrow or Monday.
The second question was about phone weather apps and why they show ridiculous snow totals. I never look at my iPhone app, but I just did and even now it say’s 20″ for tomorrow. That’s comical. I don’t know the algorithm that they use, but I suspect it is AI and obviously has no human input. I googled “why my phone app says high snow totals” and ironically, the AI response is pretty good, though there are a lot of human articles too. But here’s what AI wrote (the highlighting is not mine):
“Your phone’s weather app is likely showing high snow totals because
it is pulling raw, automated data from a single computer model—often the American GFS model—without any human meteorologist to interpret or adjust the numbers. These models often over-calculate, particularly when they cannot accurately differentiate between heavy snow, rain, or a wintry mix.
Here is a breakdown of why your app is showing high, and potentially inaccurate, snow totals:
- Raw Model Output (No Human Touch): Apps often take direct, unedited output from computer simulations. Human meteorologists analyze multiple models and local factors to filter out these “fluke” high numbers, but apps generally just display the automated result.
- The “10:1 Ratio” Fallacy: Many apps calculate snow by assuming 1 inch of rain equals 10 inches of snow. However, if the atmosphere is warmer or the snow is lighter, the ratio changes, and the app will significantly overestimate the total.
- Wintry Mix Miscalculations: If the storm includes sleet, freezing rain, or rain, the computer model may mistakenly interpret this as heavy snow, leading to massive, inaccurate, and “eye-popping” numbers.
- Model “Flip-Flopping”: Computer models often produce wildly different totals with every update (every 6 hours). The app may be showing a maximum potential model run rather than a likely scenario.
- Timing of the Forecast: If the high number is for a storm several days away, it is highly likely to change as the storm gets closer and forecasters get more precise data.
What to do instead:
For more accurate, localized, and context-driven forecasts, it is highly recommended to check with your local TV meteorologists or the National Weather Service. “
The Weather Mill 