Sun's going to take a break...

It's been a while since I've posted on here! I felt it was time to change that!

A quick check of the radar shows an elongated cold front across the eastern half of the country:

Rain stretches from the Gulf of Mexico all the way to Canada! There's also quite a bit of snow! That's because a surface low pressure has formed over east Texas;

Notice in the picture above that the winds are in a counter-clock wise flow, this is drawing down the MUCH colder air from the plains into central Texas. This is why they are seeing snow! Portions of Texas also have another chance of snow as an Upper Level Low (ULL) moves in, energizing the surface low. It is this ULL that will shove the surface low to the northeast, dragging a cold front through our area Wednesday.

Now that I've talked about the snow in Texas enough, let's talk about our weather the next few days!

We continue to be on the southern side of the cold front mentioned above. This will allow us to be in a strong southerly flow, warming us into the low to mid 70s the next few days. This southerly flow will allow for some patchy dense fog to be around tomorrow morning, before the rain moves in.

Ahh... Yes. RAIN! It is MUCH needed across the Deep South, but don't expect a ton of it with this system. In fact, as with many of the previous systems, we won't pick up as much rain as our neighbors to the north and west. We will catch the tail end of the cold front, meaning a thin line of showers will move through the area. It will be slow moving so hopefully we'll get some training to occur. If not, then we won't reach the half inch of rain I have forecast at this time...

After the front passes, we'll cool off quite a bit! A longwave trough will set up across the eastern half of the county, allowing cooler temperatures to linger through the weekend. Check out the 7 day forecast to see how cool we get!

Rainy period takes hold

Current radar imagery shows the low over the state of Alabama. We are on the moist side of the front and will be there for the next couple of days. Here's the latest radar loop:

As the loop shows above (TIME SENSITIVE! (10:45 AM EDT)); there is another batch of rain heading our way. Also, another piece of energy is providing rain for southern Georgia, east of Interstate 75. This band of rain will continue to lift north and MAY scrape our eastern counties of Talbot, Taylor, Schley and Sumter. The bulk of the rain effecting our area will be coming from the south and west.

There's a nice conveyor belt of moisture moving in from the Gulf of Mexico, as illustrated by all the rain on radar. This shows up nicely in this morning's Peachtree City, GA sounding:

The precipitable water, or PW, is 1.74, while Birmingham has a PW of 1.92 so there's PLENTY of moisture to work with! The only thing stopping all this water in the atmosphere from raining out is a significant lifting mechanism. The NWS from Peachtree City, GA (FFC) indicated from their morning discussion that a lot of the rain this morning was from isentropic upglide, or air moving toward a region of the same density. For example; warm air, less dense, riding over cold air, more dense, to be with the other pockets of warm air creating light to moderate precipitation. This will be the case for another couple of hours until we get the sun to help destabilize the air. Speaking of the sun, it's peeking out to our west so we'll destabilize some this afternoon:

That's why I'm calling for a few isolated thunderstorms, below severe levels, later on today.

Taking a quick look at the rest of the week shows the moisture sticking around until at LEAST Friday morning! That's allowed me to forecast off and on rain showers for the duration of the workweek. Originally, I was forecasting between 0.50" to 1.00" for our area. That seems a tad high right now so I've backed it down to 0.25" to 0.75" for the immediate viewing area as there's been a trend to be drier than forecast, locally. Those reading elsewhere in the southeast; I anticipate most of us will managing to eek out at least 0.50" though, higher elevations could see 1.00"+.

Oh! Here's the 00Z GFS showing the cut-off low I mentioned last week:

This thing is going to SIT here for a few days before finally being kicked to the northeast. This will result in a slightly warmer weekend than originally thought but still below average with highs in the low 80s.

Thank you!

David Reese

A look back at the CAD that didn't really develop

I had advertised a Cold Air Damming setting up across portions of the southeast. That didn't really happen. Yes, we did see some cool and cloudy mornings, but we saw partly to mostly cloudy skies in the afternoon allowing us to get into the middle 80s Friday and Saturday. Here's the current situation from space this morning: 

There's a pretty good layer of cloud cover over most of Georgia, extending into east central Alabama. This has been the view the past few mornings, but the clouds haven't been thick enough to hold up with the heating of the day. You may ask yourself, what heating? There's a ton of clouds, there's no heating! Au contraire fellow reader. The atmosphere extends miles into the sky. Here's a view of the soundings to illustrate the points I'm about to make: 

Peachtree City, GA 12Z Sounding from this morning:

The green, dew point, and red, temperature, lines are very close together near the surface. That's the cloud deck we are seeing across much of Georgia! Now, here's the 00Z Sounding from last night (technically today but I'll say last night since it was from 8PM Sept. 17, 2011 ;))

There's the same inversion, where the red line starts going back to the right as you go up, near the same pressure level, but notice the temperature line near the surface is WAY right of the dew point line. This is why we didn't see much cloud cover yesterday afternoon. The atmosphere mixed itself out bringing slightly drier air from aloft. Another reason the NWS pointed out was the absence of confluence, where air flows inward toward an axis parallel to the general direction of flow. We've had zonal flow, west to east winds, aloft, meaning the atmosphere had a chance to mix itself out and dissipate the clouds. 

That's a look back at the weekend, but what about the upcoming work week? Well, Monday appears mostly dry with the better rain chances to our west. The rain will likely move in sometime Tuesday and be off and on through Friday. Here's the model output in a nice graph for you: 

The NAM, which only goes through Wednesday afternoon, or 84 hours, has the rain moving in early Tuesday morning. I feel it brings it in a TAD early and will forecast better rain chances by early afternoon Tuesday. As we look at the GFS, it gives us almost 1.5 through Friday night/Saturday morning. This appears plausible, the good rain chances that is, with a cut-off low developing over the Ohio River Valley. A cut-off low just means it's not in the jetstream anymore and got left behind. Here's a picture of what I'm talking about: 

The low just sits over the state of Illinois for a day or so before being nudged to the northeast by the end of the week. It should be noted that a quick glance at the 06Z GFS has the cut-off low a little further to the northeast. Overall, I don't think we'll get as much rain as the GFS is putting out, but somewhere between 0.5" to 1.0". Of course, there could be locally heavier amounts in thunderstorms, but that's just a generalization for the area. 

It will be interesting to see all of this develop the next few days. As always, I'll keep you updated with my latest thoughts!

Thank you,

David Reese

Cold Front on our Doorstep and SNOW in Wisconsin!

The cold front is finally here! Current analysis shows the front moving through Birmingham:

We can tell where a front is by the wind shift. The winds in southeast Alabama and much of Georgia are from the southwest, while those across northwest Alabama are from the northwest. That's how we can locate a cold front on surface analysis! The colder temperatures are still across northern Mississippi, but they will get here later tonight. If we see the front slow up just a little, we'll see a broken line of showers move through our area. However, latest model guidance indicates we'll be on the wrong side of the front, the northern side, once it finally taps into some warm and moist air. I'm still leaving in the possibility of a few scattered showers this afternoon, but the confidence in any one spot seeing rain is pretty low. If you do see rain; don't expect much. Current QPF, liquid precipitation, output has us only getting about two tenths of an inch the next few days.

After the front passes to our south, an area of high pressure will build into the northeast. I detailed this in a blog post a few days ago. With the high over the northeast, a CAD, or wedge, will set up where there will be some VERY chilly temperatures for this time of year in the Carolinas and northeast Georgia. There's going to be a big contrast of temperatures between North and South Georgia. Northern Georgia will see a ton of clouds while south Georgia will see a good deal of sunshine. I'll be sure to post a picture of where the CAD sets up and the clouds and station plots to go with it.

From Summer to Winter!
Portions of the upper Mid-West are in the ice box this morning! Look at the current temperatures:

International Falls dropped to 20 and Embarrass dropped to 19! There was also another rare event yesterday in the Mid-West, well for mid-September anyway: SNOW! Here's the local climatology report from Rhinelander, WI:

 

This is the earliest EVER Rhinelander has seen a trace of snow! Just another hint that winter is right around the corner ;) 

Thank you,

David

The Final Countdown!

Summer is on its last legs, but it it holding strong for one final day. The area of high pressure providing us with the spectacular, albeit warm, weather the past 5 days will finally be nudged out to sea by a cold front. Yes, our second cold front of the season, remember Tropical Storm Lee's attached cold front ;), will arrive tomorrow afternoon. Our in house RPM has a bit of moisture making its way into east central Alabama tomorrow morning. I'm not totally buying that solution, but it's certainly possible. One thing I know for sure; there will be more clouds tomorrow than there will be today! We'll see a few fair weather cumulus clouds this afternoon, but not enough to keep us from reaching the lower 90s again...

Now, we usually talk about showers or thunderstorms in advance of cold fronts, but this one isn't going to have much moisture to work with thanks to the high pressure currently in place. Here's the latest QPF output by the North American models (it should be noted that the scale isn't the same as yesterday's version I showed...):

  

The 00Z GFS yesterday was putting out over .30" of rain locally... The 00Z GFS today has only .13 inches! With each model run, we've gotten drier and drier. That's not good news for the prolonged drought our area is currently experiencing. 

After the front passes, some MUCH cooler air will settle over us. Take a look at what some of the models are putting out this morning: 

Our highs go from the lower 90s today, as forecast, to the upper 70s by the weekend! Also notice, we don't rocket back into the upper 80s next week. This is fantastic news for those weary of the heat and humidity we had to go through this summer. The CAD I talked about yesterday is still being picked up by the models, which is why we are expecting cooler temperatures this weekend. I will tell you that our forecast still hinges on how strong of a CAD signature we see. If the CAD is stronger, we could see highs only in the upper 60s to low 70s; if it's not that strong, we will see highs in the mid to upper 70s, which is what I'm going with at this time.

Tropics:
I want to give you a quick update on the tropics: Tropical Storm Maria is still churning in the Atlantic Ocean, but the forecast track takes it well away from the United States. In fact, Bermuda will be brushed by Maria's tropical storm force winds, but that's the only land area that will be affected.

Looking into the extended period, the 00Z GFS has a storm forming in the western Caribbean Sea:

The subtropical ridge in the Atlantic is then forecast to break down in response to a long-wave trough moving through the Eastern United States. This trough will then drag the tropical system into the Gulf of Mexico and aim it at Florida:

This is a LONG way away in model land and should be taken with a grain of salt. It's just something I'll keep an eye on and will keep you up to date on the model's latest thinking.

Have a great Wednesday!

David Reese

Warmth won't last much longer

Good Tuesday morning everyone! It's starting to feel a little like summer again.... Highs yesterday topped out at 91 in Columbus, while Auburn had a high of 86. You can expect more of the same today, as high pressure continues to dominate our weather pattern.

By Thursday afternoon, a front will have nudged far enough south to give us a chance of rain late in the day. It will take its time moving through, so I'll leave a chance of rain in all day Friday and the beginning half of Saturday. The rain won't be terribly widespread or heavy though; as illustrated by this plot of precip from numerous computer models:

In fact, the GFS is the only model spitting out any rain locally, with the 06Z coming in drier than the 00Z run. I do have to say that the NAM doesn't forecast far enough out to capture a potential rain event as it brings the front in a tad later than the GFS. The only thing this front is assured of doing is bringing in MUCH cooler air! Highs are forecast to be in the upper 70s to low 80s by the weekend... Can you say fall is here!?

The cooler air will be aided in what we call Cold Air Damming (CAD). The high pressure moving in behind our frontal system will move from the Great Lakes to the Northeast, which will put it in prime position to develop CAD. Here's the model representation of it:

Notice how the isobars, lines of constant pressure, kink around the Appalachians? That's CAD!

You see, winds around high pressure flow clock-wise, meaning if you're south of it, you will see easterly winds. These easterly winds around a high situated in the northeast runs into the Appalachian Mountains and isn't allowed to flow up and over. This means the cold air gets dammed up and must go somewhere! That somewhere is usually to the southwest along the spine of the mountain chain and into northern Georgia. If the high is strong enough, it can filter that cold air all the way into our area! We aren't forecasting it be to QUITE that strong, but it is certainly possible. Another result of CAD is a thick stratus deck, low level clouds. You'll certainly be able to see that along the Appalachians this weekend and I'll be sure to grab a satellite image for you! Clouds help keep temperatures down during the day and if the high is strong enough, we could see temperatures even cooler than what I'm forecasting right now... Either way, we are going to see temperatures below average for the duration of your weekend.

Tuesday: A few high clouds but otherwise mostly sunny. Highs near 92.
Tuesday Night: Mostly clear with lows dipping into the mid 60s.
Wednesday: Partly cloudy with highs near 93.
Wednesday Night: More clouds move in, in advance of the front. Lows in the mid to upper 60s.
Thursday: A slight chance of rain later in the day. Otherwise, we'll be partly to mostly cloudy with highs near 90.
Friday: The cooler weather filters in! First, we have to deal with some rain, but as noted earlier; the rain won't be all that widespread nor heavy. Highs in the low to mid 80s.
Saturday: Mostly cloudy with highs near 81. (Subject to change cooler....)
Sunday: Partly to mostly cloudy with highs near 80. (Subject to change cooler....)
Monday: The high pressure in the northeast moves east, out of CAD positioning. This will clear our skies but temperatures will still be near 80.

Looking in the extended range, I notice the GFS (and the Euro to a certain extent) bringing a longwave trough into the eastern half of the country next Wednesday/Thursday. I'll watch the models closely to see if they continue this trend, which could bring some cooler air (and maybe rain!) our way next Thursday and Friday.

Thank you,

David Reese

Near Record Lows this AM

We bottomed out at 59 degrees this morning, one degree shy of our old record of 58. The cool mornings will last for the next two days before we see an influx of moisture Sunday afternoon. The weather the next few days will be FANTASTIC! Plenty of sun, pleasant temperatures and low humidity. Does it get any better than this in the beginning of September?

Our weather pattern will start shifting Sunday night, as the upper level low spinning over the Ohio River Valley forms into a trough and ejects out of the US. When the trough does form, it will bring enough instability to create a stray shower or two further to our south, near south Georgia/north Florida, where the better moisture is situated.

The 90s will return by Tuesday and linger thru at least Thursday. In the extended period of next Friday and Saturday, it appears the GFS is bringing a front through the Deep South which would bring our highs back into the middle 80s. It would certainly be refreshing, but I want to see a little more consistency before I fully jump on.

The tropics are still active.
Tropical storm Nate is located in the Bay of Campeche with a northwesterly motion of 3 mph. The trough, mentioned above, WILL miss Nate as forecast, thus making Nate to go into Central Mexico Sunday afternoon. I'm still thinking Nate gets to a category 2 before making landfall, but it still has the CHANCE of a Cat. 3. Again, Nate will NOT effect the United States.

Maria is still hanging on to Tropical storm status as of 11AM. It is forecasted to go through the northern Lesser Antilles, as forecast a few days ago, as a tropical storm. It will then pass over Puerto Rico, where they DON'T need to the rain! In fact, they've seen almost 30 inches of rain for July and August ALONE!!! Maria will then track east of the Bahamas, as the trough mentioned a few times already in this post, will kick Maria out to sea!

Thank you,

David Reese