Issues with surface temperatures until you get north of the Mason-Dixon, and there are some mixing issues along the southern and eastern parts of the snowfall. First snow map of the year!
The wintry mix of snow, sleet, and rain appears to be creeping closer to I-95 on the models, so I tightened up the gradient a bit to reflect lower totals from D.C. to Baltimore. The same is true for Long Island, and could be true for eastern New Jersey and New York City as well.
On the flip side, higher QPF across most of Pennsylvania into northern New Jersey and eastern Upstate New York increased the snow total forecast for these areas. Some small increases also occurred along the Appalachians.
Highest risk is still how far north and west the sleet/rain mixing line gets tonight, which could cut deeply into totals along I-95. Once you get far enough north and west and enter the “safe zone” where no mixing is expected, locally higher snow totals are possible.
Oh yeah, and don’t forget about those winds, especially along the coast. Gonna be fun.
As has been the pattern of recent Marches, we in the Mid-Atlantic find ourselves with a late-season snow storm that contains significant snowfall. While the storm evolution may not be classic, it seems that we will see a fairly common snowfall distribution, with the highest snow totals hitting mostly north and west of I-95 while areas south and east see more of a rain and a wintry mix.
The two main questions are where the rain/snow line ends up, and how warm will the surface temperatures be when the snow is falling. For the D.C. to Philadelphia corridor, this will mean a lot. The models differ on just how cold it is along the I-95 corridor as the precipitation is falling, which is where most of the uncertainty with this forecast lies.
The QPF is also a bit of an issue, but taking a model blend seems to be the best way to go at this point. I wouldn’t count hugely on anomalous pockets of minimal QPF, and I’m sure there will be some area that gets sweet deformation banding and ends up with more snow than expected.
I ended up going more bullish with the southern fringe of the different snow contours east of the mountains and across south-central Pennsylvania, otherwise my thoughts are pretty similar to yesterday.
Still looking at a fair amount of uncertainty regarding snow accumulation east of the mountains due to the very warm temperatures leading into this event. A good pasting of snow is expected once temperatures cool down early Thursday morning, but a 1-2 hour shift in either direction with the introduction of colder air could add or remove some 1-4″ of snow. That being said, once the changeover to snow is made, it will be snowing quite hard, and heavy snow can overcome marginal surface temperatures.
This time it’s the 40N crew that will cash in with this upcoming snow storm. After a very mild Wednesday along the East Coast, temperatures will come crashing down overnight as a disturbance develops over Virginia and tracks just south of Long Island.
Ultimately, the strengthening and position of the surface low will have a large impact on how far north/south the 1″+ snow amounts end up. The snow will also be battling against a very warm antecedent air mass that will keep most spots as rain for at least the onset of precipitation. This means places like D.C. and Baltimore will struggle to change over to snow overnight. Heck, D.C. stands a risk of never changing over to snow at all Thursday morning if the more northern model solutions are correct.
As the initial storm system moves out Thursday morning and early afternoon, a second upper-level vort. max will slide through the Mid-Atlantic. This could trigger snow showers across more of the Mid-Atlantic Thursday afternoon and evening. Most places around/south of D.C. will still be too warm to see this light snow stick, but a little “snow TV” is better than nothing… I think?
Over Christmas break, my brother (who lives near Boston) asked me a very interesting question that I don’t have a definitive answer for. His question was about ice forecasts, and why it seems like meteorologists forecast it way too often compared to what actually happens.
I’m torn on this one. Being in the Boston area, my brother does not get many “good” ice events compared to areas further inland in the Northeast. Inferring that my brother was basing his question mainly on storms that have a quick transition from snow/sleet to freezing rain to rain, I want to attempt to answer this as logically as possible.
I think the answer varies based on perspective. Whether you’re a meteorologist, Joe Q. Public, an emergency manager, a utility company, etc., ice accumulation and its potential impacts can be a huge problem for some, and a minor nuisance for others.
Meteorologists try to verify a forecast to the best of their abilities. If it looks like even a couple hundredths of an inch of ice is possible before a changeover to rain, it will likely end up in the forecast. Then the ice happens and the meteorologists pat themselves on the back for a job well done. But is it a job well done?
Verification aside, what did including ice in the forecast actually accomplish? Assuming the storm quickly changed over to rain after the brief period of freezing rain, did that minor, short-lived ice accumulation actually do anything? Was it even noticed?
And this is the point where my opinion becomes split. As a meteorologist, not only do I want the forecast to verify, but I also want to build in a contingency to my forecast in case something goes awry. What if the freezing rain lasts an hour or more longer than I expected, and it becomes much more of a problem than I had anticipated? What looks more foolish, mentioning ice with little to no impact, or not mentioning ice and then having some scale of disaster happen due to a more prolonged ice event?
For me, the answer depends on the storm evolution as well as the forecast confidence. Unless it’s a high confidence forecast with a very short transition period from snow/sleet to rain, it’s probably better to include ice accumulation in the forecast. Given how little ice it can take for things to go from okay to really, really bad, I think most people will forgive meteorologists for being a little overcautious.
As the event is unfolding, time for a final update. A slight shift north and west, but overall similar thinking to yesterday’s forecast.
I think that there is a little more room for this to shift a bit further north and west compared to moving it south and east. The area of significant snowfall seems pretty locked in at this point, with concerns about mixing on the southern edge of the snow accumulation in the Carolinas.