Saturday, December 7, 2013

Recapping yesterday's icy day and details on round 2 of wintry weather

Winter weather forecasts, at least from MWN and as far as we could tell most other local outlets, were pretty accurate for yesterday's winter weather system... with one critical exception: surface temperatures.

Rather than reaching the freezing mark by mid-morning (which they did) and then continuing to slowly fall, they stopped falling.  In fact, between periods of precipitation, there was actually a very slight rise to 32.5-33 degrees.  This made ALL the difference in the resultant amount of ice in the Memphis metro.  Instead of 0.25-0.50" of ice, which would have been likely had temps remained just below freezing, most places saw 0.10-0.20" and up to a quarter inch of sleet.  (Totals were MUCH higher just to our north where the air at the surface and aloft was colder.) Once precip tapered off and ended by late afternoon, the temperatures began falling, reaching the upper 20s by early evening.

Ice-covered trees in Bartlett Friday afternoon

The WXLIVE! weather station at MWN, covered in ice

The bottom line: one or two degrees of error on the forecast resulted in half or less the predicted ice, better road conditions that anticipated, and thankfully many less power outages. MLGW reached a peak somewhere above 8000 outages Friday afternoon and had nearly 100% restored by early Saturday morning. Kudos!  I won't say that any cancellations or postponements were for naught - the forecast and expected impacts were based on what we knew going into the event.  MWN picked up 0.60" of liquid (melted) precip after the temperature first hit 32 at 8:15 Friday morning. We were basically 1 degree from having a completely different scenario by last evening.

What's Next?

Looking ahead, we promised another round of wintry weather and that is still in play.  The NWS has issued Winter Weather Advisories for the entire area for the overnight hours tonight, ending at 6am Sunday.  Though precipitation amounts are not expected to be as high with the next round, there are a couple of key differences. Surface temperatures (at least overnight into tomorrow morning) will not be hugging the freezing mark - they'll start in the upper 20s.  In addition, very little melting today will mean trees and power lines START with minor ice accumulations, so anything additional will mean extra ice weight. One tenth of an inch to start and another one to two tenths falling totals a quarter inch of ice - which is Ice Storm Warning criteria.

Winter Weather Advisory posted for a large part of the area Saturday night until 6am Sunday


As for what to expect, I've just hinted at it, but temperatures will not reach freezing today as clouds thicken ahead of tonight's storm and ice remains around the area. Light precipitation will start again tonight after 8pm, and maybe as late as midnight, continuing off and on overnight with light precip amounts expected. Most precipitation should taper off shortly after sunrise Sunday with 0.10-0.20" of an inch of freezing rain and minor sleet accumulation expected. Temperatures then rise above freezing by noon Sunday before another small round of precipitation moves through late in the day Sunday. I expect this late day light rain stay liquid with temps in the mid 30s.  For a complete forecast, including even COLDER temperatures in the week ahead, click here or check out our mobile apps (links below).


So, while this does not appear to be a major event, additional power outages could result from the cumulative effects of icing (8000+ lost power with about the same amount of ice yesterday). There will also be less wind to dry the streets and they are starting off much colder than yesterday. I expect we could see some slick bridges and overpasses again late tonight and Sunday morning until temps rise above freezing. More trees branches will likely fall, especially those weakened by yesterday's storm.  If you have plans in the morning, be cautious.  If you don't have to go out early, things should improve by mid-day to early afternoon considerably.

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