Arctic Air Arrives Tonight; Wednesday Snow Update

Current Radar 

Summary…high today 41°…very cold tomorrow…below freezing until Wednesday…Wintry mix changing to rain Wednesday, but confidence still low.

Arctic Blast

We should see the sun late this morning or sometime this afternoon. But, only briefly.

Dry, arctic air bottled up to our Northwest will pass the Ohio River Valley by noon then land in Middle Tennessee for Martin Luther King Jr. Day.

Once we go below freezing tonight, it might be Wednesday before we see above-freezing temperatures.

Monday will be deceptively sunny, with the high only 28°. Dewpoints will go negative, making the air the driest it has been in a very long time.

Snow Update

Sunday Night — as the Arctic front arrives sometime between 8 and 9 PM, one of the models is squeezing out a few flurries. This seems unlikely, but even if it happens, it will be of little to no consequence.

Wednesday — as discussed yesterday, we are still expecting something to happen. Possibilities are rain, snow, maybe some sleet, but there is low confidence on the “when” and “how much.” Right now, it looks like we could see a very brief episode of freezing rain or wintry precipitation early Wednesday morning, then changing over to rain later in the morning and Wednesday afternoon.

The following forecast sounding illustrates the “what type of precip will we see?” problem. This model, the GFS, thinks that on Wednesday morning, temperatures just under 5,000 feet will be above freezing as the precip is starting to fall, but then it would refreeze when the rain reaches the ground. That would mean freezing rain for a very brief time Wednesday morning.

There are many reasons this could prove wrong. If it’s off by just a handful of degrees, it would be all snow, or it could be all rain. This may not be properly taking into account the effects of evaporative cooling. Or, the sounding might turn out to be correct 40 miles away, but for us be vastly different — creating a different result.

So, to review, the GFS model thinks we will see some mixed wintry precipitation to our west early Wednesday morning, perhaps starting as freezing rain here . . .

. . . then changing over to all rain late morning and in the afternoon:

The European model agrees with keeping the snow north and east of us on Wednesday.

Yesterday, the models thought this would be all snow for us. As usual, we are right on the rain/snow line. The models are going to continue to oscillate this far away. Right now, we think this will be a potentially hazardous driving situation Wednesday morning, but only very briefly before everything turns over to rain. I will bet this forecast will change at least a few more times. Remember, confidence in the accuracy in this forecast is low. I’m going to reuse this from yesterday:

This website supplements @NashSevereWx on Twitter, which you can find here.