December 15: Turbulent Forecast, Daily Links

WEATHER

We’re finally going to see some sunshine today, but temperatures will remain cold through tomorrow morning.  Highs today will only reach up to around 30°…
thursday-highs
…with wind chills remaining in the teens and low 20s all day:
thursday-wind-chill
1

Air temperatures will start off in the teens Friday morning, then the warm-up kicks in.  There are no typos in this 4-day forecast — this is what I really think is going to happen:
wsmv-4-plus-4-am-1
9
Southerly winds will strengthen on Friday, helping push temperatures up to the upper 40s in the afternoon.  Temperatures will continue to rise Friday night and Saturday, all the way up to around 70° by late Saturday.  Off-and-on showers will develop late Friday night and Saturday, then thunderstorms are likely Saturday evening, THEN the cold air crashes back in by Sunday morning with a mix of raindrops, sleet pellets, and snowflakes as the lingering showers wind down.  That’s a lot to digest, so let’s take it bite by bite…
3

The showers Friday night and during the day Saturday don’t look overly impressive.  It will be hit-and-miss light rain, as Futurecast’s clouds-and-radar simulation shows:
rpm-12a-sat rpm-4a-sat rpm-8a-sat rpm-12p-sat
The bigger story during the day Saturday will be the warm and windy conditions…highs will reach the upper 60s, with southerly winds around 20-30 mph:
paul-rpm-wind-gusts
I wouldn’t be surprised if the National Weather Service hoists a Wind Advisory for Saturday.  (Yet another day to make sure your outdoor Christmas decorations are secure.)
4

As the dividing line between “unseasonably warm” and “insanely cold” approaches us Saturday evening, the squeeze it puts on the atmosphere will produce some thunderstorms and heavier rain, moving west-to-east into Saturday night:
rpm-4p-sat rpm-8p-sat rpm-12a-sun
5
There’s even a chance some of those storms could be severe — but the limiting factor this time of year is always instability.  If the atmosphere warms up enough, and if there’s enough moisture in place, some of the storms could get pretty feisty.  Right now the Storm Prediction Center has outlined areas farther to our southwest for the greatest severe weather potential:
paul-severe-risk-region
That said, the SPC’s own short-range ensemble forecast model estimates a 40-50% chance of severe thunderstorm ingredients in our neck of the woods Saturday evening:
sref_prob_combined_supercell__f066
That model has shown a northward bias recently, so you shouldn’t be overly worried about it at this point.  Damaging straight-line winds would be the main threat — we’ll keep a close eye on it as the weekend approaches.
7

Once the heaviest rain moves through, the cold air invasion will catch up to the last of the lingering showers — Futurecast paints that as a messy mix of rain/sleet/snow in the pre-dawn hours of Sunday morning:
rpm-3a-sun
At this point, I’m not concerned about accumulations, for several reasons:
1) The computers always over-estimate wintry precip in this time frame (48-72 hours out)
2) The moisture will be meager, and the mixed showers very light
3) The ground will be wet and warm
6

The wintry temperatures will be factor all day Sunday — temperatures will hover around 30, with wind chills in the teens.  Next week brings another slow warm-up, but not the wild ride we’ll be on over the weekend:
wsmv-4-plus-4-am
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LINKS

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About paulheggen33

Morning meteorologist for WSMV-TV in Nashville.
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