Morning Notes at 10 a.m.

Just a few dot…dot…dot notes as we continue to anticipate a significant early winter severe weather outbreak across the Lower Mississippi Valley, Mid-South, Southeast and Ohio Valley on this first official day of winter. (The winter solstice occurs at 11:11 a.m. CST.)

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…Mist, drizzle and light rain has been the order of the day across Central Alabama so far. The BMX and Columbus radars show this very light precipitation streaming north in the warm advection pattern that is bringing moisture north on strong southerly winds.

…It is quite warm, with temperatures in the middle and upper 60s. It is 68F at Tuscaloosa. Highs should top out in the lower 70s. The record high for the date at BHM is 73F.

…It feels humid out there as well. Dewpoints at this hour include 67F at Tuscaloosa, 65F at Calera and 66F at Jasper. BHM was reporting 63F.

…Winds will be increasing. Across Central Alabama, they are averaging 10 mph now. Over the Tennessee Valley, winds are stronger as they are under the leading edge of an increasing low level jet stream at 5,000 feet. Those winds extend back into southern Louisiana. Wind advisories are in effect all across the region, including all of Alabama except for the Dothan area.

…All this will give the air a stormy feel today. It feels like “tornado weather”. And that is borne out in the forecast for severe weather.

…No severe thunderstorm or tornado warnings to our west now, but a tornado watch was just issued for Louisiana, eastern Texas and southern Arkansas. It goes until 6 p.m.

Much of Alabama is covered by a severe weather risk for the late afternoon and overnight hours, including an enhanced Moderate Risk over the Northwestern quarter of the state and a slight risk as far east as a line from Andalusia to Wedowee.

This thinking is based on the latest 4 km NAM output this morning and is in line with our current forecast:

…Patches of very light rain and drizzle will continue to stream northward today across the area. Rainfall will be light.

…Clouds are thick, although there is a little thinning from Bibb/Hale Counties up through Chilton, Coosa, Clay and Cleburne Counties. There is a little fog too.

…A couple of isolated storms could form around 4 or 5 p.m. across Central Alabama. Instabilities will be running 1,200-1,500 j/kg over West Central Alabama. By that time, bulk shear values will be over 50 knots, which will plenty sufficient for rotating updrafts. Low level helicities will be in the 200-300 m2/s2 range, so we will be watching for a rotation and the possibility of a tornado warning during the late afternoon, like we saw yesterday in the Jackson area when a confirmed tornado occurred.

…By midafternoon, a mass of thunderstorms will cover much of Arkansas and northern Louisiana. A tornado watch was just issued for those areas valid until 6 p.m. Prefrontal bands of thunderstorms start forming over Mississippi during the evening, extending into western Alabama around midnight. These storms will have the potential to produce damaging winds and isolated tornadoes.

…The tornado risk is highest over the Mississippi Delta, to the west of us in places like Alexandria LA, Memphis and Jackson MS. To put it in perspective, the SPC put the chance of a tornado occurring within 25 miles of a point in that area at 15%. That doesn’t sound like much, but actually, it is significant. Not like April 27th when the chance was 45% over Alabama and eastern Mississippi. The 10% risk covers areas west of a line from Livingston to Tuscaloosa to Jasper to Decatur. The rest of the slight risk area in Alabama carries a 5% chance of seeing a tornado within 25 miles of any point.

…The threat for damaging winds is higher, with the chance that points over Northwest Alabama will have a severe wind report within 25 miles of them at 45%. Areas down to a little past I-59 carry a 30% chance. The rest of the slight risk area carries a 15% chance of damaging wind reports.

…These storms will continue through the pre-dawn hours, pushing east of I-59 by mid-morning. There will still be sufficient instability through the morning hours over Central Alabama, and during the afternoon over South Central and East Central Alabama for continued storms. With the main dynamics already to the north of us, the threat for severe weather will be less, but there will still be a few warnings I would imagine.

Bottom line: we are waiting to see the storm system show the whites of its eyes. We will be monitoring it continuously until it is out of Alabama tomorrow night. Be able to receive watches and warnings, especially if you are sleeping, since much of the event will occur overnight. And review your severe weather safety plan with your family in order to be ready to take action immediately if a warning is issued.

Category: Alabama's Weather, Severe Weather