Snowmaggeddapocolypalooza Sunday Update

Let’s get right to it: we’re still looking at the likelihood of at least SOME wintry weather across the Midstate this evening and tonight. Exactly how much and what kind of wintry weather will depend on your location, and on how this system decides to behave as it moves through.

These things haven’t changed:
1) Rain will change to freezing rain, sleet and snow, and the transition will happen faster to the northwest of Nashville
2) This is NOT going to be a big snow-maker for the Nashville Metro: the most likely forms of precipitation in Nashville will be ice (freezing rain and sleet)
3) Even without measurable snow in Nashville, roads could be icy/slick for the Monday morning commute
4) Best chance of measurable snow will be to the north and northwest of Nashville, especially in southern Kentucky
5) Areas farther south of I-40, especially closer to the Alabama state line, are likely to see just rain with this event, perhaps just a brief period of the sleet or snow as the precipitation ends early Monday morning

Two things have changed since the forecast in yesterday’s blog post:
1) The timing of the transition from rain to ice to snow. I was a little too aggressive in pushing back that timing yesterday, and I’ve corrected it in the graphic you’ll see a little down the line.
2) Our window for freezing rain looks like it will be slightly longer than initially thought. This brings in the possibility of some ice accumulations on elevated surfaces, including power lines, before the transition to sleet or snow occurs.

Overall, the computer models have been pretty consistent over the past 24 hours. There has been a little bit of wiggling from run to run, but in general the expected evolution of this system hasn’t changed a whole lot. Here’s the latest Futurecast time series from 6pm Sunday through 6am Monday. Still some differences between the two high-resolution models that we use, but they’re pretty close:
RPM 6P SUN
RPM 8P SUN
RPM 10P SUN
RPM 12A MON
RPM 2A MON
RPM 4A MON
RPM 6A MON

And here are the latest computer estimated snowfall amounts from the Futurecast models:
RPM SNOW

Interestingly, the two most prominent models from the National Centers for Environmental Prediction (NCEP — they run the models the NWS uses) are painting a similar scenario for the snowfall pattern, even if they have differences in the snowfall amounts:
NCEP SNOW
(Once again, those are computer estimated amounts, so don’t get overly excited/worried. Those images are from wxcaster.com, a fantastic weather-nerd site.)

Here’s the tricky part about winter storms: the dividing line between all and nothing is very very narrow, on atmospheric scale. So while it’s great that most of the computer models are very close together with the “where, when, what, and how much”…the atmosphere is going to do what the atmosphere wants to do. I checked with a colleague in Oklahoma today (they’re getting sleet and snow with the system already) to see how the various models were performing with their forecasts. That information definitely factored into my version of the forecast for this evening and tonight.

That said, here is what I’m thinking in terms of how the system is going to play out. First of all, the timing. As I said above, I’ve adjusted this the most compared to yesterday’s forecast in the blog post. Areas northwest of Nashville will still see the earliest transition from rain to sleet to snow (in fact, it’s happening already), while areas farther south of I-40 may not see that transition at all. Here’s the radar image as of 2:30pm showing the mix to the northwest, and the map of expected transition times:
VIDEO RADAR SPONSOR
PAUL TIMING

(NOTE: those are the times that the snow/sleet will stick to the ground.) The National Weather Service has adjusted their timing forecast as well, so now we are thinking along very similar lines: NWS TIMING

I’m optimistic that in the metro area at least, most people should be home from Super Bowl festivities before the transition from liquid to frozen precipitation occurs.

Finally, the accumulation forecast of ice and snow:
PAUL SNOW
PAUL SNOW KEY

And, the NWS’ version of the accumulation forecasts, including the advisories that are in effect for this evening and tonight (their amounts are slightly higher, but overall pretty close):
NWS WATCH

Now that you’ve looked at those maps, let me shout this from the rooftops: DO NOT MAKE THE MISTAKE OF THINKING “NO SNOW = NO PROBLEMS”. Sleet and freezing rain aren’t fun to drive in either, and of course we’ve seen recently that even less-than-measurable snow can cause problems.

Once again, I’ll emphasize that even a slight shift in the overall track of this very large storm system will mean a significant shift in the accumulation pattern. Winter storms are tricky, which means my inner child now looks like this:
frustration

I’ll be tweeting out radar updates and quick blurbs about how the forecast is shaping up throughout the Super Bowl this evening. Of course, Twitter is going to be deluged with Super Bowl-related tweets, so your best bet is to either go to my profile page within Twitter (@PaulHeggenWSMV), or search for the hashtag #4WARN.

I plan on writing a blog post tomorrow (or if time doesn’t allow, on Tuesday) to address how the forecast shaped up compared to reality:
accountable
Yessir.

And finally…GO BRONCOS!
broncos

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About paulheggen33

Morning meteorologist for WNCN-TV in Raleigh.
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7 Responses to Snowmaggeddapocolypalooza Sunday Update

  1. Brad Brown says:

    Anyone involved in any field that has ANYTHiNG to do with communications should use Paul Heggen’s blog posts as an example of how to balance humor, pragmatism and know-how to effectively get a clear and thorough message across. The main reason I watch WSMV every morning…

  2. Barbara says:

    Thank you- thank you – thank you for being REAL, concise, honest and funny, all while avoiding the dramatic flare of having to name a daggone storm and attempt to panic the masses. This is what weather reporting SHOULD be

  3. kal busman says:

    as a 3 year meteorology student at fsu converted into another profession many many years ago, i appreciate how you present to us unfolding weather conditions. your attention to detail, humility in describing changing conditions, and honesty in admitting that although weather forecasting has much improved we are still very far away from being able to account for all of the variables that cause weather, all make us to want to follow you.
    well done.

  4. Susan Nelson says:

    Thank you! Great information and entertaining too. 😊

  5. Cecilia Riley says:

    Great posts! Love the bit of humor along with the weather.

  6. Mary Richardson says:

    Channel 4 has the BEST weather forecasters! Love your blog Paul Heggen!

  7. Pingback: Here's the latest #4WARN blog post from Paul Heggen WSMV, including the "what/wh… | NashVegas.com

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