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Archive for December 19th, 2012

Watching Overnight

| 10:42 pm December 19, 2012

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Showers and storms are developing late tonight over southern Mississippi and southwestern Alabama. This activity will likely grow to become round one of a two round system for Alabama overnight and tomorrow morning.

These showers will increase in coverage and intensity overnight and should reach West Central Alabama counties like Pickens and Lamar between 2-3 a.m. They will build northeastward from Sumter to Walker and Counties by 4 a.m.

They should weaken as they reach I-65 by 6 a.m.

They will be accompanied by some heavy rain, especially west of I-65, with lesser amounts the further east you go. Severe weather should be minimal with this first round, but it can’t be ruled out.

Some moisture laden air is sitting over southern Louisiana, waiting to be lifted northward into Alabama later tonight and Thursday morning. It is the wild card in the potential for severe weather later in the morning.

By sunrise, a line of storms currently from east of Dallas into northeastern Arkansas will be crossing the Mississippi River. It will be powered by a strong cold front and pretty potent upper level system. But the wild card is the moisture. If higher dewpoints get pulled further north into Central Alabama, the chance of severe weather will be higher. But for now, it looks like the best chances for that will be further south.

The line of strong storms will reach western Alabama by 9 a.m. and it will race eastward across the area reaching I-65 by late morning and exiting eastern Alabama by mid-afternoon.

Winds aloft will be strong and it will not be hard for those strong winds to get pulled to the surface. We will have ample low level shear too, so we can’t rule out a few isolated tornadoes. But again, the instability may be so limited that even the shear won’t have anything to work with.

We will keep our finger crossed that no severe weather develops. But keep your source of warning information on alert and handy.

We will have periodic updates through the night here as the situation unfolds.

Tornado Watch To The West

| 7:49 pm December 19, 2012

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A tornado watch is up for much of West Arkansas and East Oklahoma tonight until 2am CST. This batch of storms will roll into Alabama tomorrow morning, but our severe weather threat is somewhat marginal. Scroll down for a complete discussion, and see the afternoon Weather Xtreme video for details…

Dynamic Storm System On The Way

| 1:54 pm December 19, 2012

An all new edition of the ABC 33/40 Weather Xtreme video is available in the player on the right sidebar of the blog. You can subscribe to the Weather Xtreme video on iTunes by clicking here.

THIS AFTERNOON: What a beautiful day. Lots of sunshine with streaks of cirrus clouds overhead; temperatures are headed toward the upper 60s. But, to the west, a major storm system is stirring up a huge fuss over the nation’s mid-sections.

Blizzard warnings are in effect for parts of Colorado, Kansas, Nebraska, Iowa, and Wisconsin… in the broad area from Denver to Milwaukee. And, in the warm sector of the developing storm system, strong to severe storms are expected to form tonight west of Alabama; SPC maintains the standard “slight risk” of severe weather for much of Mississippi, Louisiana, and Arkansas. The convective initiation should begin in the 5-7 p.m. time frame, and those storms will blow into Alabama after midnight.

STORMY THURSDAY MORNING: Not much change in our thinking for tomorrow’s event. The main window for storms in Alabama will come from 3:00 a.m. until 12:00 noon (for our part of the state), and the severe weather threat is somewhat marginal due to the lack of buoyancy/instability.

The 12Z model runs show a little surface based instability over the southern half of Alabama, and SPC maintains the standard “slight risk” of severe weather for Alabama generally south of I-20. It is your classic cold season high shear, low instability event. Very high shear values will be in place, so we will have to watch for any small, brief spin-up tornadoes along the low topped squall line that will move through, but the main threat will come from strong straight line winds in the 40-60 mph range. This would be enough to knock down a few trees and power lines.

We should mention that tomorrow will be a very windy day, even away from storms. West winds will average 15-30 mph, with gusts to 40 mph… meaning we might even see some trees toppled by the gradient wind away from thunderstorms.

Take a few minutes to watch the Weather Xtreme video for all of the maps, graphics, and details.

COLD SHOT TOMORROW NIGHT: The weather turns windy and sharply colder. Temperatures will reach the upper 20s by Friday morning, with a gusty northwest wind wind chill index values should reach the teens. Friday will be sunny, but windy and cold with a high in the upper 40s.

PRE-CHRISTMAS WEEKEND: Expect a low in the 20s early Saturday, with low 30s at daybreak Sunday. The high Saturday will be in the mid 50s, with a high closer to 60 by Sunday. The weekend will be rain-free.

CHRISTMAS WEEK: We won’t be able to give you a high confidence forecast for next week until we get past tomorrow’s storms.

A few showers should break out Monday, and now the GFS (the 12z run) develops a deep surface low northwest of Alabama Christmas Day, meaning Tuesday would be breezy with occasional showers and storms. A few strong to severe storms would be possible Tuesday night into Wednesday morning with this setup.

On the other hand, the ECMWF (12Z run) shows a batch of showers Monday, then generally dry conditions on Christmas Day, followed by a big storm system with potential for strong to severe storms on Wednesday.

However the rain/storm event unfolds early in the week, we should turn much, much colder over the latter half of the week. But we simply don’t have enough skill in forecasting weather 4-8 days in advance to be very specific. Again, I encourage you to watch the Weather Xtreme video for details, thoughts, maps, and graphics.

WEATHER BRAINS: Don’t forget you can listen to our weekly 90 minute netcast anytime on the web, or on iTunes. This is the show all about weather featuring many familiar voices, including our meteorologists here at ABC 33/40.

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Look for the next Weather Xtreme video here by 7:00 a.m. tomorrow… and stay tuned for updates on storms to the west of Alabama as they develop tonight.

Storms Blow In Tomorrow Morning

| 6:19 am December 19, 2012

An all new edition of the ABC 33/40 Weather Xtreme video is available in the player on the right sidebar of the blog. You can subscribe to the Weather Xtreme video on iTunes by clicking here.

ONE MORE DRY DAY: A pretty chill morning to start the day; Gadsden and Fort Payne report a freezing 32 degrees at daybreak; most places are somewhere between 37 and 41. We rise into the upper 60s today with ample sunshine, although high clouds will begin to show up and increase this afternoon.

TO THE WEST: SPC maintains the “slight risk” of severe weather for much of Mississippi, North Louisiana, Arkansas, and West Tennessee tonight, where strong to severe thunderstorms should develop in the favorable warm sector environment ahead of a major storm system over the nation’s mid-section, which promises to bring lots of snow and wind all way way from the Rockies to the Great Lakes. Blizzard warnings are up for parts of Colorado, Kansas, Iowa, and Wisconsin.

THE ALABAMA SEVERE WEATHER THREAT: SPC hasn’t changed tomorrow’s severe weather risk much; they define a standard “slight risk” for roughly the southern half of Alabama, or the part of the state south of I-20. But, I think storms over the northern counties will be very gusty with potential for high winds.

There is very little surface based instability with this system tomorrow morning, which is the primary limiting factor in our severe weather threat. But, there is a tremendous amount of dynamic forcing, and the wind fields are strong. The main risk with the band of storms tomorrow morning will come from straight line winds of 30-50 mph, and some spots could see severe gusts (over 58 mph). This could knock down some trees and power lines.

We also note there is very high amount of shear; surface-925 mb bulk shear values are around 45 knots, so we will need to watch the radar closely for signs of rotation. But, we all know it is almost impossible to warn for the small, short lived spin-up tornadoes within a squall line.

I should note that the day tomorrow will be very windy, even away from storms, with southwest winds averaging 15 to 30 mph, with occasional gusts to 40 mph. Wind advisories will be needed.

TIMING: The main window for storms in Alabama will come from about 3:00 a.m. until 12:00 noon. Rain amounts of 1/2 to 3/4 inch are likely. See the Weather Xtreme video for more details on the situation tomorrow along with all of the maps and graphics.

COLD SHOT TOMORROW NIGHT: As the storms move out, much colder air rolls into Alabama, and we will be in the upper 20s by daybreak Friday. The winds will stay up, and the wind chill index could very well drop into the teens early Friday. Friday will be sunny, but windy and cold with a high in the upper 40s. A northwest wind of 15 to 25 mph will make it feel colder.

PRE-CHRISTMAS WEEKEND: Mornings will be cold; we expect a low early Saturday in the 25-29 degree range, with low 30s early Sunday. The weekend will be dry with a good supply of sunshine both days… the high Saturday will be in the mid 50s, and close to 60 on Sunday.

CHRISTMAS WEEK WEATHER: Let me say up front that we really won’t be able to be very specific about next week until tomorrow night, after the next round of storms is out of here. Like football coaches, we take storm systems one at a time. Model madness is coming to play, making the forecast a real can of worms.

We are confident in these things…

*The weather will be wet at times Monday, and on Christmas Day
*Very cold air, perhaps the coldest so far this season, will blow in here by the middle of next week

Beyond that, it is just hard to say. The 00Z GFS/ECMWF runs have taken severe weather off the table for now with the surface low much more to the south. In fact, we might have to look at some risk of snow Tuesday night into Wednesday for parts of Arkansas and Tennessee as the cold air takes over. Even some hint at a snow flake or two on the back side of the departing storm system over North Alabama Wednesday night. All voodoo and noise now… let’s wait until tomorrow night to really get specific.

Take some time to see the Weather Xtreme video for maps, graphics, and more information on the possibilities next week.

WEATHER BRAINS: Don’t forget you can listen to our weekly 90 minute netcast anytime on the web, or on iTunes. This is the show all about weather featuring many familiar voices, including our meteorologists here at ABC 33/40.

CONNECT: You can find me on all of the major social networks…

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Don’t forget our Toys for Tots marathon continues today; I will be live at Legacy BBQ on Highway 150 in Hoover to wrap things up at 4, 5, and 6:00 this evening on ABC 33/40. The next Weather Xtreme video will be posted here by 4:00 this afternoon…