A much calmer day today, but could it snow Friday night?

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SUMMARY

Whew! That was a rowdy line of storms last night. All that activity has moved well off to our east, leaving us with some partly cloudy skies and much cooler temps. We’ll struggle to get into the mid 40s today, after dropping to 36 degrees this morning.  Tonight, we’ll fall off into the 20s. If you have any tender, frost-sensitive plants outside you may want to protect them. We break out into sunshine on Thursday before clouds increase ahead of our next headache, I mean storm system (ha).

Temps should warm to the low to mid 50s on Friday as we find ourselves in a weak southerly flow ahead of the next storm. As this system passes to our south, enough cold air should move in to give us a rain/snow mix. If precip is heavier than forecast, or if that low moves just a bit farther south, or if the cold air coming down is a bit colder we could get all snow. Need less to say, it’s a tricky forecast, folks. And to top it all off, snow is so unusual this time of year that models handle it very poorly.  The bottom line is that this is a close call (when are our snow chances not close calls?) and if you have travel plans for early Saturday morning, it’s just something to keep in mind. Saturday looks very chilly and wintry. Definitely a day to stay inside if you can. Or do like everyone else on days like this…go to Walmart. haha

I’ll keep you posted on the snow chances. It still feels weird saying that, since we’re now in APRIL.

Below is one model’s depiction of Saturday morning, showing heavy snow just to our north and a rain/snow mix across the plateau. This is the model that has refused to give up on us getting snow Friday night. The next run of this model will be available this afternoon.

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And below are the storm reports from last night. Blue dots represent wind damage, red dots are tornado reports, and green dots are large hail (>1″).

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DISCUSSION

Now that our severe weather threat from last night is over, our attention can now turn to our snow chances for Friday night. Snow. In April. It’s happened before. Back in 1987 we had half a foot of snow fall on April 3. Knoxville had 10.5 inches. So, it can happen but it’s extremely rare.

There are a few things that interests me about Friday night’s snow chances. First, if snow does fall in March and April it tends to be very heavy, wet snow.   Some call these “warm” snows, as the temp barely gets cold enough for snow. The good news is that these snows melt so very fast and are often gone within hours of falling. Another thing  is the track of the low. If this were January I’d be excited about snow. But, this is April and temps may not get cold enough to support an “all snow” solution. Or if it snows, will it get cold enough to stick? Forecasting wintry precip is hard enough in the winter. It’s basically a fool’s game in April.

And wouldn’t you know I have a race Saturday morning. I never dreamed I’d have to worry about snow for a race on April 7!

If the precip falls hard enough, we may get snow because of something we call evaporational cooling. As precip falls, some of it evaporates on the way to the ground. That’s always the case, especially with wintry precip, because it falls into colder air and colder air is, by nature, drier. Warm air holds moisture but cold air can’t.  That’s why your skin dries out in the winter, but you can cut the air with a knife in August because it’s so muggy.

Evaporation is a cooling process. If precip falls hard enough, it can sometimes drop the temp enough to turn rain to snow when temps are right on the rain/snow line. This happens a lot when snow falls into drier air. The drier air evaporates more precip and that evaporation causes more cooling and can significantly drop the temps. I’ll wait until Friday to see just how dry our air is and if that’s something we may have to throw in the pile of uncertainties (ha).

I’m earning my pay this week! ha

I’ll keep you all posted on this and I’ll let you know as soon as anything gets clearer.

Next week looks continues unsettled but I’m not seeing any severe weather. We’re now in a cooler pattern that may spare us significant storms for the next week or so.

You all have a great day! Tomorrow, I’ll have some info for you about a storm that really gave me some concern last night as it moved into southwest Cumberland County. Those of you who were following me on FB know what I’m talking about. I’ll tell you why storms like that one can cause unpleasant surprises in tomorrow’s blog. Prepare to learn some meteorology! ha

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