Current Temps and Radar
A Flood Watch remains in effect for Davidson County. 1.5″ is expected to fall in Davidson County.
Expect a little bit less than that in Williamson County.
Rain will continue through the day Wednesday. Meanwhile, temps will start to drop, from 61° at midnight, to 54° at 6 AM, to 41° by noon.
When we hit the freezing mark shortly after dark Wednesday night, the shenanigans begin.
Ice, Sleet & Snow
NWS has issued a Winter Storm Warning for Davidson County beginning at 6 PM Wednesday.
A Winter Storm Warning means snowfall (including sleet) of 3″ or more in 12 hours or less.
NWS has issued a Winter Weather Advisory for Williamson County beginning at 9 PM Wednesday.
A Winter Weather Advisory means between 1″ and 3″ of snow/sleet in 12 hours or less.
The start times of the Warning and Advisory (6 PM Davidson Co; 9 PM Williamson Co) are a pretty clear indication of when to expect the changeover from rain to a wintry mix.
We think the changeover will begin after the evening rush hour (if not even later than that), but this will need to be very closely watch throughout the day Wednesday.
Changeover will occur first in the NW, then sweep SE, as Wednesday night progresses.
At the changeover times, rain will start to mix with freezing rain, then freezing rain will mix with sleet, then sleet will mix with snow, then eventually it will be all snow as we cruise past midnight into the wee hours of Thursday morning. Travel will quickly become hazardous immediately upon the onset of the changeover.
Ice accumulation from freezing rain measuring up to 0.10″ is expected. That’s enough to glaze roadways, especially bridges and overpasses, but it usually takes 0.25″ to begin to stress power lines and topple tree limbs. We think today’s warm temperatures and heavy rainfall will help limit ice accumulation.
Sleet accumulation is especially concerning. Those are those noisy little ice pellets, and when it gets to accumulating, it’s more punishing to travel and commerce than snow.
Eventually sleet will mix with snow. Accumulation totals have decreased because this is becoming more of a sleet event, and less of a snow event. Snow accumulates 3 times the rate of sleet. That is to say snow typically produces at a ratio of 10:1. Sleet is about a third of that. So, if this was more of a snow event, you’d be seeing those cartoon accumulations of 6″ or so.
Right now, NWS expects closer to 5″ of sleet + snow near the TN/KY line, and 2″ to 3″ closer to I-40. This is why Davidson County is in the Warning (3″), and Williamson County is in the Advisory (under 3″).
Even with 1″ to 2″ of snow/sleet, roads are going to be a mess.
Both counties are expected to face “major travel impacts from Wednesday afternoon through Friday afternoon” because “temperatures are expected to remain below the freezing mark Thursday and much of Friday.”
A north wind up to 20 MPH will slice wind chills Thursday into the single digits.
Forget wind chills, actual temps will bottom out in the single digits early Friday morning. The wind chill will approach 0°.
Melting will begin Saturday and last into Sunday. By Monday, the high is expected to be 50°.
Consult multiple reliable sources for weather information multiple times as the weather community continues to ingest fresh model data to define and refine ETAs and accumulations.
This website supplements @NashSevereWx on Twitter, which you can find here. Updated information is often posted there and is not reflected on this website.