Where is Spring?

I'm sure many of you are wondering just when we will finally see consistently warm temperatures, because ever since the first day of Spring (March 20), we've seen below average temperatures across the Golden Triangle Region.

Unfortunately, more cooler weather is in the long-term forecast, as well as the short-term forecast as well...

Thanks to strong high pressure over the Mid-Mississippi River Valley and clear skies tonight, we will have strong radiational cooling. This means that temperatures will fall quickly tonight, and in most spots will fall below the freezing mark for the second night in a row. We could see temperatures in some locations in the 26-29 F range! And for this reason, much of east Mississippi is under a Freeze Warning for overnight tonight. But this high pressure will begin to slide east over the next 36 hours, allowing for a southerly flow to develop which will gradually increase our temperatures, but also our moisture content as well.

As per usual with Mississippi in the Spring, changeable weather is ahead. The above image shows vorticity at 500mb. We are in a generally west-northwest flow aloft here, but notice several blips of vorticity maxima: one over northeast Texas, and another near the Missouri Bootheel. In the fast moving flow aloft, these maxima, in tandem with warm-air advection occurring at 850mb (not shown), will help create some showers across the area during the day and evening of Saturday. At this point, it's not looking like a widespread rain event, but you probably will want to carry the umbrella to any outdoor plans you may have.

After a solid 24 hours of warm-air advection as well as moisture advection, your Easter Sunday could be wet at times as well. Notice another vorticity maximum over Arkansas; this feature is slated to move east during the day and consequently we will have more rain chances in the forecast. The GFS model is also showing some surface-based CAPE (convective available potential energy) for both Saturday and Sunday. We could see a few isolated thunderstorms in the mix as well, but no severe weather is expected at this time due to limited shear despite warmer temperatures....we should be in the low 70s for Easter.

Though it's tough to see thanks to the black background, a strong cold front will approach the area by the start of next week, particularly Monday into Tuesday. This system will have a bit more shear to work with, and GFS shows some CAPE as well. We will have to watch this system as some isolated severe storms are certainly possible, but confidence in frontal placement is rather low and overall confidence in any severe weather is even lower. I just want you to beware of the *potential* for there to be a few strong storms to start the work week.

As has been in the case, we really can't ditch the colder temperatures just yet, despite it being "Spring." And unfortunately, that trend looks like it will continue right on into the middle of next week as well. Here's a surface chart for next Wednesday, showing the strong cold front to our south. In its wake, we have strong surface high pressure and more cooler weather. This suggests more freezing temperatures are possible across the northern half of Mississippi.

Have a great Easter weekend, stay dry, and God Bless!

IW

A Little of This, A Little of That...

As the National Weather Service in Birmingham, Alabama put it this afternoon in their latest discussion, we have a "smorgasboard" of weather to talk about over the next several days.

Before we get into the nitty gritty of the next few days, I hope you've enjoyed the very refreshing last two days we've had across east Mississippi. The transition from winter to spring went seamless, as we had a plethora of sunshine both days with comfortable temperatures into the mid 60s with a refreshing north breeze. But as we know how the weather can behave in Spring around here, changes are right around the corner...

This map shows vorticity at 500mb valid Thursday evening at 7 PM, and we like to look at the advection of this vorticity because that can lead to areas of rising air. Here, a few maxima of vorticity are noted, most notably over central Arkansas. This coupled with warm air advection in the lower levels, especially 850mb, will help create widespread precipitation across the Mid-South beginning Thursday afternoon initially over parts of Arkansas and southern Missouri that will spread into western Tennessee and the northern half of Mississippi during the overnight hours of Thursday.

The next challenge is to determine precipitation type. The above is a modeled skew-t sounding for Thursday evening for Memphis. Notice the red and green lines almost on top of one another from the surface through around 600mb; this means the atmosphere is saturated throughout this layer. Plus, the temperature stays below freezing throughout the entire column and the area around -12 C / dendritic growth zone/ is also saturated. Therefore, it is expected that some snow will fall in around the Memphis area into extreme northern Mississippi Thursday afternoon and lasting into the overnight hours. It should be noted that this precipitation may initially begin as a rain/sleet mixture before transitioning to all snow by Thursday afternoon.

For this reason, the NWS in Memphis has hoisted a winter storm watch for the counties in dark blue. This does include Memphis and Jonesboro. Here, it is not out of the realm of possibility that 1-2" of snow/sleet could accumulate!

This is a modeled sounding for the Starkville area valid at the same time, 7 PM Thursday evening. Notice the large amount of dry air below 700mb (much different than the above sounding), but saturated above that. We here in east Mississippi will actually undergo moistening from the "top-down" throughout the day Thursday and into the evening. We will also undergo some evaporative cooling, which may actually allow for a period of light sleet Thursday afternoon as precipitation begins, despite temperatures being in the 40s. However, we will not be able to evaporatively cool far enough to get any snow here. Therefore, after the column saturates, we will likely just experience a relatively cold rain with temperatures in the upper 30s or low 40s.

The weather roller coaster continues Friday as we begin a gradual warming process. As the image above depicts, another lobe of energy is progged to move across the area Friday afternoon and evening. Expect more rain showers and even some elevated thunderstorms Friday afternoon/evening with the main threat being some hail. These storms will not have any tornado threat because they are elevated, i.e. rooted above a stable surface layer.

This image is the forecast upper level wind pattern by the 12z GFS for Saturday evening at 7 PM. This would suggest a severe weather setup as the LMRV would be positioned favorably in the broadly diffluent upper-level flow, which would favor enhanced surface lift. Sufficient instability at the surface would aid in the development of thunderstorms, some of which could be quite strong or severe.

On the other hand, here's the 12z ECMWF for 12z Sunday. This model shows the surface low near Demopolis, AL with any severe weather threat confined to southeast Alabama, southern Georgia, and into the Florida Panhandle, keeping us here in Mississippi (with the exception of coastal areas) likely clear of any severe weather issues.

The bottom line is that forecast confidence is very low after Friday evening. One thing is for certain, however, and that is Spring in the Southeast always poses weather surprises!

Have a great week, and God Bless!!

IW

It's Spring Break!

Wow what a week it has been weather-wise...we had some snow flurries across the area this past weekend, a day or two of very windy conditions Tuesday and Wednesday, and now we are finally beginning to feel like some springtime temperatures are in the air!

As you can see, temperatures even at the 5 pm hour are pretty comfortable with a gentle north wind making it feel quite fabulous outside. And if you like warmer temperatures, you'll love the forecast tomorrow and Saturday!

Here's why: Notice the height lines at 500mb kind of "arch" toward the north over Mississippi toward the Great Lakes. This is a weak, but noticeable mid-level ridge that is caused by warming in the lower-levels causing these particular heights to expand. Thus, we can expect temperatures into the low 70s and maybe mid 70s closer to the MS coast not only for Friday, but also for Saturday as well.

Unfortunately, we have to deal with rain and potentially thunderstorm chances Sunday evening into Monday morning. But the good news is that this system should exit the LMRV fairly quickly and we'll see a return to sunshine by Tuesday.

The rest of the week looks to be fairly benign weather-wise with no real dips in the jet stream of which to speak. Therefore, we can expect temperatures to slowly increase through the week right back to the low 70s by next Thursday! And if you're going to the Gulf Coast, you can expect temperatures in the mid to upper 70s with no chances of rain at this time...so I think the timing of Spring Break was perfectly planned!

Have a great Friday and Spring Break, and God Bless!

IW

A Little Snow? Plus, A Look into Past March 1 Weather Events

Well, here we are the first day of March and it feels more like a late January day outside with temperatures struggling only into the middle 40s later today underneath an overcast sky. We even are seeing a few flurries already in portions of north Mississippi!

Here's a sounding valid at 6 AM tomorrow morning across the GTR into adjacent parts of Alabama. While not a classic setup, sub-freezing temperatures are found hroughout most of the column with some moisture seen in the lower 5-7k feet AGL As this moisture and cooler air moves across north MS/AL later tonight into early tomorrow morning, a window of opportunity exists for a brief snow shower or moderate flurry activity, but no appreciable accumulations of snow are expected. Temperatures are expected to warm, relatively, during the day Saturday but will struggle to get out of the low and mid 40s as strong cold air advection occurs.

A brief warmup is expected Monday before more cold air arrives in advance of our next storm system poised to impact the area during mid-week. Here's a 500mb vorticity chart valid for Tuesday morning. East Mississippi is certainly experiencing PVA which combined with warm air advection at 850mb will lead to widespread rain showers Monday evening lasting through the day Tuesday.

But things get interesting Tuesday night as this strong shortwave begins to close off into an upper level low. Strong cold air advection occurring beneath this feature would be sufficient for snow to form, but I think this is a deal where the moisture will outrun the cold air and prevent any snow chances from developing. But, this is still several days and this system certainly bears watching throughout the weekend into next week.

Here's a quick look at some recent weather events that occurred on March 1 throughout the past several years. Notice, this day can have anything from flooding, tornadoes, to snow!

Here's March 1, 2009. Notice over 6" of rain fell in Tuscaloosa over a 48 hour period!

Believe it or not, this is just hours after the flooding rain event shown above. As much as 3-5" of snow fell across Alabama as arctic air interacted with wrap-around moisture!

Above are images obtained from SPC from the major tornado outbreak from March 1, 2007. Unfortunately, 68 tornadoes occurred that day, including an EF-4 tornado that killed 9 people in Enterprise, Alabama, in Coffee County of Southeast Alabama.

In light of these events, I've always been intrigued by the forecast on March 1 because it can be so many things, especially in the wild-weather capital known as the Southeast!

Have a great Friday and weekend, and God Bless!

IW

Data obtained for this post were collected 2/28/13