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Late Night Update

| 12:13 am April 14, 2014

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Two lines of showers and storms continue early this morning.

The first extends over western Tennessee and northern Mississippi into northern Lousiana.

The second extends across southeastern Missouri, across Central Arkansas and into northern Louisiana.

All of this activity will push across northern Mississippi overnight.  It should weaken as it does.
There are only five severe thunderstorm warnings still in effect and no tornado warnings.  Severe thunderstorm watches extend from northeastern Texas across much of Arkansas to western Tennessee.

The first round of showers/storms will enter the area around sunrise and continue to impact the area through the mornings hours.  Showers and storms will build again to our west by Afternoon and some of them may become severe Monday afternoon and evening.

Please check the latest information this morning and review your severe weather safety plans.

We will monitor the situation all night.  Expect the next update around 3 a.m. , unless conditions warrant an earlier notification.

Watching to the West

| 9:05 pm April 13, 2014

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It is an active night of severe weather in areas to the west of Alabama as a dynamic storm system continues to come together.

As we have been advertising, it is a two prong system. The first upper disturbance is moving into Arkansas from Oklahoma tonight, weakening as it goes. Showers and storms extend from southwestern Illinois to southeastern Missouri to Central Arkansas. Further south, new development is building over Central Louisiana.

Flash flood warnings are in effect around Little Rock, where water rescues are going on at this hour from West Little Rock into downtown.

A stronger, intensifying disturbance is moving out of the Rockies tonight. This disturbance is opening the door for a big Arctic airmass to come south. That impressive boundary extends from Chicago to Des Moines to Kansas City to Oklahoma City to Amarillo.

It is 68F at Springfield MO while just a short distance on the other side of the boundary, it is 39F in Salina and 32F in Hill City KS. Just yesterday, Salina was setting a record high with 91F. In Texas, it is 81F at Wichita Falls and 51F at Pampa in the Panhandle. Further back in the cold air it is 24F in Denver with heavy snow.

The main squall line extends from Central Missouri west of St. Louis into northwestern Arkansas across southeastern Oklahoma to the Red River between Texas and Oklahoma. Severe thunderstorm warnings extend from Central Missouri into western Arkansas. A tornado warning was in efect for areas near Ardmore OK a little earlier.

There have been only three tornado reports today, including two from Iowa and one from Oklahoma.

The initial activity will push across northern Mississippi this evening and reach Northwest Alabama before sunrise. The system will be weakening as it pushes through West Alabama, reaching I-59 on mid-morning.

Meanwhile, activity should intensify over northern Louisiana, northern Mississippi and western Tennessee during the day ahead of the main trough and powerful cold front. This activity should reach Northwest Alabama by late afternoon and push through western Alabama between 6-8 p.m. and into the I-59 corridor between 7-9 p.m. It will reach eastern Alabama during the late evening. Showers and storms will continue until the cold front moves through during the predawn hours Tuesday morning.

There is a chance that instabilities will be pretty impressive over western Alabama late tomorrow afternoon. In addition, wind shear values will be high as well, In fact, 0-1 km helicities may be in the 250-300 m2/s2 range. Surface temperatures will push into the middle 70s and dewpoints should be in the middle 60s.

So, we will be monitoring the severe weather potential across Central Alabama through early Tuesday. Indications are that the threat tonight is very low. But we will keep an idea on it. The main threat should come late tomorrow afternoon through tomorrow evening. Hail and damaging winds will be possible and we can’t rule out the threat of tornadoes as well. Stay tuned.

In addition to the severe weather threat, there is a flash flooding threat. Rainfalls across Central Alabama will average 1.5-2.5 inches through Tuesday morning. Flash flood watches are in effect through Tuesday afternoon.

Flash Flood Watch Issued

| 2:40 pm April 13, 2014

The NWS in Birmingham has issued a flash flood watch for much of Central Alabama, beginning Monday morning and continuing through early Tuesday afternoon.

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Counties in the flash flood watch include: Autauga, Bibb, Blount, Calhoun, Chambers, Cherokee, Chilton, Clay, Cleburne, Coosa, Dallas, Elmore, Etowah, Fayette, Greene, Hale, Jefferson, Lamar, Marengo, Marion, Perry, Pickens, Randolph, Shelby, St. Clair, Sumter, Talladega, Tallapoosa, Tuscaloosa, Walker and Winston.

1 to 3 inches of rain is expected across the watch area starting as early as Monday morning and continuing through early afternoon Tuesday. Flooding will be an issue.

Be ready to receive warnings if they are issued and to take action. Get MyWARN if you have an Android or iOS device.

A Nice Sunday, Severe Weather in the Offing Though

| 12:31 pm April 13, 2014

A pleasant spring Sunday is in progress with partly cloudy to occasionally mostly cloudy skies at time. High clouds are starting to stream across the area, and thickening and lowering clouds are to the west. Back over Mississippi, we see a healthy field of cumulus clouds in a plume of moisture surging up into the Magnolia State. By the time you get to the Mississippi River, a thick overcast is in place.

The nearest rain to Alabama is some rain over northwestern Arkansas and some showers over eastern Texas. Thunderstorms are in progress in the Dallas/Ft. Worth area, but they are not strong nor severe at this time.

Temperatures are in the upper generally at this hour. Birmingham and Anniston are at 78F and 77F respectively, Tuscaloosa checked in with 73F at noon, a little cooler since skies are already cloudy. It has become quite breezy, with southerly winds averaging 10-20 mph and gusts to near 30 mph at times.

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A quick check of the weather early this afternoon shows that the forecast is on track for Central Alabama.

Severe weather is expected today and tonight to the west of Alabama. There is a large slight risk severe weather outlook area in effect today and tonight in an area roughly bounded by Austin, Wichita Falls, Oklahoma City, Wichita, Kansas City, Peoria, St. Louis, Memphis, Meridian, Alexandria and back to Austin. The moderate risk area that was included in the forecast earlier has been removed due to the clouds and precipitation over Texas and Oklahoma that is reducing instability.

The storms to our west will move eastward overnight, weakening as they move across Mississippi. They should make it into Alabama well after midnight.

As a second surface low develops to our west early tomorrow and instability rises with some daytime heating, storms should ramp up during the day. They should be enough instability and shear in place for some of the storms to become strong to severe by afternoon. It now appears that all modes of severe weather are possible, with hail, damaging winds and even tornadoes. We will be able to refine the exact threat as we move into the daylight hours tomorrow, but for now, review your severe weather safety plans and check your sources for receiving watches and warnings.

Much colder weather is in the offing for Tuesday behind the cold front. Highs will remain in the 50s all day with the threat of some frost Tuesday night as the mercury drops into the middle 30s generally with a few spots reaching freezing. Growers and planters should be aware of the threat and plan accordingly.

Atlantic Hurricane Season Forecast from Klotzbach/Gray

| 11:31 am April 10, 2014

Dr. Bill Gray just finished speaking at the Tropical Meteorology Conference at South Padre Island, discussing the challenges of seasonal hurricane forecasting and the precursors that they use.

He turned it over to Dr. Phil Klotzbach to announce their 2014 Atlantic Hurricane Season Forecast. Here are the numbers, showing their forecast and the 30 year average (1981-2010).

KB photo

Named Storms: 9 (12.0)
Named Storm Days: 35 (60.1)

Hurricanes: 3 (6.5)
Hurricane Days: 12 (21.3)

Major Hurricanes: 1 (2.0)
Major Hurricane Days: 2 (3.9)

ACE*: 55 (92)
*ACE is Accumulated Cyclone Energy, a measurement of the wind energy expended by tropical cyclones. It is a better parameter for looking at the overall intensity of a storm or season.

NOTES
…Klotzbach credits the pending El Nino for the below average forecast.
…The Atlantic is at its coolest since 1994 as well.

ANALOGS
Some analog seasons cited:
…1957 Hurricane Aubrey killed at least 416 people in SW Louisiana
…1963 Flora killed over 7,000 people in the Caribbean
…1965 Hurricane Betsy struck Bahamas, South Florida and Louisiana
…1997 Hurricane Danny flooded Alabama coast
…2002 Lili impacted Gulf Coast

I cite the example storms from the analogs as a reminder that it only takes one story to make it a bad hurricane season. So even though a below average season is forecast, that is academic if storm hits you.

Here is the full forecast.

A Late night Look at the Alabama Weather Situation

| 11:52 pm April 6, 2014

There still is a significant threat of severe weather overnight across Central Alabama.

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An impressive 850 millibar jet is acting like a firehose tonight, pouring warm, moist air into West Central Alabama from Mississippi.

This area of inbound warmth and moisture is resulting in widespread heavy rain and thunderstorms over West Central Alabama. The storms have produced some wind damage in places like Pickens and western Tuscaloosa Counties, as well as Marengo County. Numerous trees were reported down along US-82 near Buhl.

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They have also triggered a flash flood warning for four counties in West Central Alabama including Greene, Pickens, Sumter and Tuscaloosa Counties where radar estimates show 2-3 inches of rain had probably fallen. A flash flood warning was just issued for Fayette, Jefferson, Lamar and Walker Counties until 5:30 AM CDT.

The flash flood watch continues for Autauga, Barbour, Bibb, Blount, Bullock, Calhoun, Chambers, Cherokee, Chilton, Clay, Cleburne, Coosa, Dallas, Elmore, Etowah, Fayette, Greene, Hale, Jefferson, Lamar, Lee, Lowndes, Macon, Marengo, Marion, Montgomery, Perry, Pickens, Pike, Randolph, Russell, Shelby, St. Clair, Sumter, Talladega, Tallapoosa, Tuscaloosa, Walker and Winston Counties until 1:00 PM CDT Monday.

As of 11:50 p.m. tonight, there were no severe thunderstorm warnings nationally, but that will change.

The warm, moist airmass the jet is bringing north will eventually lead to significant instability, especially over southwestern and North Central Alabama. Right now, all of the surface based CAPE is limited to counties near the coast.

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This will change rapidly over the next few hours as the jet continues to pump in the warm, moist air.

The upper level trough is becoming more negative in its orientation. The negative orientation increases the severe weather threat as colder air aloft is able to destabilize the atmosphere. It also increases the amount of wind shear present as well.

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Finally, the wind shear over Alabama is significant.

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0-1km helicity is very high over western sections of Alabama. If that hangs in there until the instability arrives, it will enhance the threat of severe weather. Bulk shear numbers are high as well, meaning storms will have no trouble getting and staying organized.

WATCHING RADAR

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Supercell storms over Louisiana and Mississippi are triggering severe thunderstorm and tornado warnings. The storms will push northeast into Central Alabama later tonight. If they encounter an airmass with a moderate amount of instability and the current high shear, there will be problems.

IN SUMMARY
Where the instability values can reach 750 j/kg or more overnight, there will be a significantly enhanced threat of severe weather because of the shear. The SPC just noted that there is a 60% chance they will issue a watch for Central Alabama soon. Here is the MCD Graphic:

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A Few Notes Before Noon

| 11:41 am April 6, 2014

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A severe thunderstorm watch has been issued for parts of eastern Texas and Louisiana. Storms are widespread in that region ahead of an upper level warm front is pushing into South Texas and southern Louisiana.

The 850 mb front extends all the way across Mississippi and into Alabama. Rain and storms were pushing north ahead of the front over much of Pickens, Sumter, Greene, Hale, Bibb, southern Tuscaloosa and southern Bibb Counties southeastward across Montgomery to near Union Springs. This activity will continue to push north and northeast this afternoon overspread much of the area.

You can see from the lower left panel that instabilities are still limited to GUlf Coastal areas. This will change as we get into the afternoon and for us here in Alabama, into the overnight hours.

Temperatures are still in the 50s across Central Alabama. Since the rain has not arrived yet over parts of North Central ALabama, temperatures may manage to get into the lower and middle 60s in those areas.

The SPC maintains a slight risk of severe weather, their standard severe weather outlook, for today and tonight over much of eastern Texas, much of Louisiana, a good bit of Mississippi and Alabama.

In Alabama, storms tonight will become severe with the potential to produce damaging winds and even some tornadoes. The best chance of tornadoes is south of a line from Demoplis to Pine Apple to east of Evergreen, but we can’t rule one out anywhere in the slight risk area. The slight risk area runs generally south and west of a line from Phil Campbell to Springville/Pell City to Tuskegee to Ozark.

Pay attention to forecasts, watches and warnings tonight and Monday morning. Review your severe weather safety plans and be ready to act if warnings are issued for your location.

Slight Risk Area Expanded Slightly

| 10:05 am April 6, 2014

On the 7:30 a.m. CDT update to the Day One Severe Weather Outlook, the SPC slightly expanded the Slight Risk area, moving it north of Birmingham. Here is a sneak peek at the latest severe weather info for this afternoon’s forecast package.

TIS THE SEASON: Alabama is a climatologically favored place for severe weather the first week of April. On this map from the SPC, you can see where significant tornadoes are most likely across the nation during the first week of April.

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There is a bulls eye over North Alabama the first week of April where the probabilities are highest for having a significant tornado (EF2 or greater). This peak period actually blooms over North Alabama around March the 11th and expands until April 22nd, when it begins to shrink and consolidate with a similar maximum over Oklahoma and northern Texas. The Sooner State becomes the sweepstakes winter in the significant tornado department. The maximum sets up over Oklahoma and North Texas by April 15th. It peaks at about a probability of over 0.35% and expands, but gradually lessens and shifts north toward Iowa and Nebraska by the middle of June.

FORTUNATELY even though this is prime season for significant tornadoes in our area, the probability that one will occur within 25 miles of any place in the maximum area is only 0.25%. Not 25%, but 0.25 percent, so well less than 1%.

UNFORTUNATELY: Today is one of those days when there may well be a few significant tornadoes across the state. The best chance of a significant tornado is over southwestern parts of the area, south and west of a line from Cuba to Pine Hill to Atmore, except for southern Mobile and Baldwin Counties. But there is a decent chance (5%) that there will be a tornado within 25 miles of you if you live north of the significant risk area, but south of the official Slight risk issued by the SPC. The northern boundary of the 5% tornado probability and slight risk area extends from near Hamilton to Carbon Hill to Hoover to Tuskegee. We will have to watch out for damaging winds as well, especially late tonight as the threat transitions from discrete supercells to a squall line.

SECRET WEAPON: You say it doesn’t feel like severe weather out there today. But the secret weapon of severe weather outbreaks will be brandished by our system tonight: the low level jet. As a strong upper level trough progresses eastward, surface low pressure near the Texas coast will move northeast and intensify this afternoon and evening. By 10 p.m., it will be near Vicksburg. As the low strengthens, an area of strong winds at about 5,000 feet will develop over Louisiana. This low level jet as it is known, will do two things. It will transport lots of warm, moist air northeastward rapidly and the fast moving air will cause significant wind shear in the lower layers of the atmosphere. Neither of these pieces of news are ever good in a severe weather situation.

PARAMETER PARTY: Let’s peg the geek meter for some severe weather parameters off the morning run of the 4 km NAM. As noted in the previous paragraph, low level wind shear will not be a problem. The low level jet will produce 0-1 km helicities on the order of at least 250 m2/s2, and they will most likely be higher. Bulk shear values, which is a measure of the difference in wind speed with altitude will be high as well, meaning storms won’t have any trouble staying organized. The question will be whether there is sufficient instability. The models might actually be downplaying the eventually CAPE values over Alabama tonight. Currently, the NAM depicts around 500-750 j/kg. That Is sufficient for severe weather in Alabama, especially in light of the shear available. And they could go higher.

DYNAMIC SYSTEM: I am always concerned when I see rapid transformations of the atmosphere like this one. As noted earlier, the morning and early afternoon did not have a typical severe weather feel. The low level jet will take care of that, pushing temperatures from mostly 50s in the rain-cooled air this afternoon to the middle 60s after midnight. And dewpoints will climb from around 50F this afternoon to the lower 60s tonight. That sort of dynamic change is troublesome. So this will be a system we have to watch carefully. The NWS Birmingham noted this morning that similar systems in the past almost always have produced at least one tornado, but that they were usually weak. At the same time, they noted that the prospects of underestimated instability might make for a more serious situation.

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While we can’t rule out a tornado anywhere across Central Alabama overnight and early Monday morning, the best chance will be south and west of a line from Haleyville to Springville/Pell City on to Tuskegee, Ozark and Seaside. This area, which is also the slight risk area for the day, was expanded slightly on the 8:00 a.m. update from the SPC. There is an enhanced area of slightly higher tornado probabilities (10% chance with in 25 miles) over southwestern parts of Alabama, south and west of a line from Livingston to Camden, Pine Apple and then east of Evergreen. It does NOW include coastal Mobile and Baldwin Counties.

HOW THE SYSTEM WILL UNFOLD: Moderate to heavy rain with embedded thunderstorms moved over South and South Central Alabama this morning. More light to moderate rain was moving northeast by mid-morning and will affect the rest of Central Alabama into the afternoon, increasing with time. Most of the thunder should be limited to South Alabama, although some lightning was showing up southwest of Demopolis at 9:30 a.m. There will be some more thunder through the afternoon.

As the surface low moves into Central Mississippi this evening, a warm front will be pushed north over Central Alabama. This will be accompanied by increasing rain and storms. While those shouldn’t be severe, they will be loud. Locations south of the front will be in the warm sector with rising temperatures and dewpoints and increasing instability leading to strong to severe thunderstorms. Discrete storms ahead of the front will be especially troublesome given the magnitude of the wind shear. Rain and thunderstorms will continue for much of the night across much of the area. The main activity should push east of I-65 by lunchtime, continuing to affect East Central and Southeast Alabama with a severe weather threat. There will be some lingering showers into the afternoon over western sections into the afternoon and eastern sections into the evening.

FLASH FLOOD THREAT: A Flash Flood WAach went into effect at 10 a.m. CDT for all of Central Alabama. It will be in effect until Monday afternoon. Widespread 1 to 2 inch rainfall amounts with some locally higher amounts between 3-4 inches could cause flooding.

TEMPERATURES: Readings have been slow to climb over Central sections due to the clouds and increasing showers. Areas that get rain earlier may hae their highs limited to the upper 50s today, while you will find 60s the further north you go. Lows tonight will actually come early in the evening in many spots as the warmer air moves in. Official lows will probably be in the upper 50s, but by morning, readings will be in the middle 60s. Highs tomorrow will likely rise to near 70F, before tumbling back into the lower and middle 40s Monday night.