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August 2013 Pattern & Discussion

LithiaWx

By LithiaWx,
in Southeastern States

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DCMetroWinston

DCMetroWinston

Posted
Posted

WxSouth

I'm going with RECORD COLD day on Friday in the Southern Appalachians, much of the interior Carolinas, northern parts of Alabama and Georgia. All indications are that Thursday will have a strong High Pressure in the Northeast that stays put, and this feeds cool, dry air into the "Cold Air Damming" regions. Rain will develop, become heavy and steady from Atlanta to Raleigh by Friday morning and move into Virginia...keeping temps down all day long.

Temps will start of cool, and since the rain moves in quickly, High temperatures won't budge much. Some areas stay in the upper 50's like Asheville to Boone to Roanoke.

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FallsLake

FallsLake

Posted
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WxSouth

Hi-Res NAM even faster with the cold August Rains ‪#‎scwx‬ ‪#‎ncwx‬ ‪#‎vawx‬

There is definitly cool enough dew points to support this setup. I noticed some upper 40s in eastern Virginia this morning. The models have been trying to show a strong CAD for the last few days but this may be a wait and see type event.

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Snowless in Carrollton

Snowless in Carrollton

Posted
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WxSouth

I'm going with RECORD COLD day on Friday in the Southern Appalachians, much of the interior Carolinas, northern parts of Alabama and Georgia. All indications are that Thursday will have a strong High Pressure in the Northeast that stays put, and this feeds cool, dry air into the "Cold Air Damming" regions. Rain will develop, become heavy and steady from Atlanta to Raleigh by Friday morning and move into Virginia...keeping temps down all day long.

Temps will start of cool, and since the rain moves in quickly, High temperatures won't budge much. Some areas stay in the upper 50's like Asheville to Boone to Roanoke.

Is Northern Alabama considered a Cold Air Damming region ?
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calculus1

calculus1

Posted
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Is Northern Alabama considered a Cold Air Damming region ?

 

I'm inclined to say, generally speaking, no.  Here's a map I found online of the general CAD region.  It's not perfect, because even Atlanta is subject to CAD effects from time to time, but it gives a general idea:

 

image002.gif

 

You generally need to be east of the Apps, but not too far east in order to experience the effects.

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dsaur

dsaur

Posted
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I'm inclined to say, generally speaking, no.  Here's a map I found online of the general CAD region.  It's not perfect, because even Atlanta is subject to CAD effects from time to time, but it gives a general idea:

 

image002.gif

 

You generally need to be east of the Apps, but not too far east in order to experience the effects.

And extend that right on down, because a good strong cad will get into Montgomery, but they don't spread out all that wide, so  far northern Ala wouldn't get it.  NW. Ala gets what I consider a very lucky break from the Apps. as they will get shallow cold air banking up on the western side of the mtns. and some amazing sleet storms have occurred.  Day after day of zrain and sleet, because the cold air won't so readily scour out like the gulf will do to ours after a spell.  T

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dsaur

dsaur

Posted
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I have a feeling we will have something to talk about Monday morning on the first day of classes at UNC-Asheville in the Atmospheric Science department. I am moving in on Saturday, so I hope the rain will subside for 30 minutes so I can move back in for my final semester of undergraduate studies at UNC-Asheville.

But, I do think flooding will be a concern with this weather event this weekend.

 

It's always nice to be nearing the end of a multi year task :)  Good luck!!  T

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FallsLake

FallsLake

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And CAD often reaches to Raleigh and Durham, although it tends to erode quickest in Raleigh and the eastern Triangle.

Raleigh usually does fall within CAD setups; especially strong ones. We've had many ice storms... 

http://www.nc-climate.ncsu.edu/outreach/ccms/2010/bohm_pearson/Introduction.htm

http://ncpedia.org/climate/winter-storms

http://wxbrad.com/cold-air-damming-sunday-for-north-carolina/

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GaWx

GaWx

Posted
Posted

the upped it to 4-5 and there will be two waves so this isnt an event stretched out over four days.

i think that this is a pretty good crushing for GA. JMO.

The 6z GFS gives Macon a whopping 3.57" through Monday AM, which agrees with the good crushing. However, it gives KATL only 0.77", which is well below the 2-4" projected on that same FFC forecast map. It will be interesting to see which turns out to be closer for KATL. If the 2-4" were to

verify, that would imply a legit. shot at KATL breaking their alltime JJA heaviest rainfall of over 25", which is about 5" away. However, if it gets under an inch as the 6z GFS suggests, that would mean it is going to be quite the challenge to get the record. Regardless, KATL has already set a new wettest JJA on record from sources other than tropical cyclones. Records go back to 1879.

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GaWx

GaWx

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The 6z GFS gives Macon a whopping 3.57" through Monday AM, which agrees with the good crushing. However, it gives KATL only 0.77", which is well below the 2-4" projected on that same FFC forecast map. It will be interesting to see which turns out to be closer for KATL. If the 2-4" were to

verify, that would imply a legit. shot at KATL breaking their alltime JJA heaviest rainfall of over 25", which is about 5" away. However, if it gets under an inch as the 6z GFS suggests, that would mean it is going to be quite the challenge to get the record. Regardless, KATL has already set a new wettest JJA on record from sources other than tropical cyclones. Records go back to 1879.

 

 More model data: yesterday's 12Z Euro gave KATL 1.5-2" and Macon 3-4". Today's 0Z Euro gives KATL ~2.5" and Macon ~3". so, overall the GFS/Euro agree on giving Macon a pretty good crushing whereas only the Euro gives that to KATL. So, for KATL, it looks like it may be a battle between the not so wet Goofy and the pretty wet good ole Doc. The FFC forecast office seems to be taking the Doc's side for KATL/north GA in general.

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CandymanColumbusGA

CandymanColumbusGA

Posted
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:lol: Columbus has had over 7" in the past 21 hours... 4.51" of that fell in an HOUR yesterday. :lol: I don't think models caught that... ;)

 

Then Beauregard, AL, just southeast of Auburn, AL, picked up 7.5" in about 6 hours in the overnight hours that lead to even more flash flooding.

 

I'm saying that because those are just general rain totals the models are predicting... Some spots could see a LOT more!

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GaWx

GaWx

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Posted

:lol: Columbus has had over 7" in the past 21 hours... 4.51" of that fell in an HOUR yesterday. :lol: I don't think models caught that... ;)

 

Then Beauregard, AL, just southeast of Auburn, AL, picked up 7.5" in about 6 hours in the overnight hours that lead to even more flash flooding.

 

I'm saying that because those are just general rain totals the models are predicting... Some spots could see a LOT more!

 

 Wow, what a mess!! Did Columbus attain a 24 hour record outside of the daily record or was it spilt up too much into two calendar days?

 

 Agreed. Isolated much higher amounts vs. models in summer due to isolated slow moving heavy convection or training go without saying as you know. My point is that the forecasted FFC general rainfall amounts for N GA (2-4") agree much better with the Euro's general rainfall amounts than the 6Z GFS' general rainfall amounts. So, they're clearly favoring the Euro.

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GaWx

GaWx

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The 6z GFS gives Macon a whopping 3.57" through Monday AM, which agrees with the good crushing. However, it gives KATL only 0.77", which is well below the 2-4" projected on that same FFC forecast map. It will be interesting to see which turns out to be closer for KATL. If the 2-4" were to

verify, that would imply a legit. shot at KATL breaking their alltime JJA heaviest rainfall of over 25", which is about 5" away. However, if it gets under an inch as the 6z GFS suggests, that would mean it is going to be quite the challenge to get the record. Regardless, KATL has already set a new wettest JJA on record from sources other than tropical cyclones. Records go back to 1879.

 

The 12Z GFS comes in much wetter than the 6Z GFS for the period through 12Z Mon. due to more Gulf tropical moisture with 2" for KATL and a whopping near 6" for Macon!

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dsaur

dsaur

Posted
Posted

Yeah, I knew I shouldn't get hopped up on Mwx and CMan's giddy model readings, lol.  All the rain was north of me, and now it's all south.  It rained... read drizzled.... most of the night starting about dusk and I've heaped up a huge .3 for it, lol.  I knew as soon as Cad was mentioned I'd just get drizzle...the cad would push out the front, and the tropical juice, and here it is.  Sun has been out and the drizzle is patchy mist now.  Unless the ts can find me...not looking likely, I think the cursed lands will remain dry surrounded by a sea of flooding :)

  To add insult they had near 5 inches a few miles up the road, while I was getting slapped around by a tenth of drizzle.  And now I read Cman piled up the inches too.  Oh, well, at least it's cool, so I can cut the grass without too much discomfort in the afternoon sun.

It takes a tough manly man to live in the cursed lands!!   T

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CandymanColumbusGA

CandymanColumbusGA

Posted
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 Wow, what a mess!! Did Columbus attain a 24 hour record outside of the daily record or was it spilt up too much into two calendar days?

 

 Agreed. Isolated much higher amounts vs. models in summer due to isolated slow moving heavy convection or training go without saying as you know. My point is that the forecasted FFC general rainfall amounts for N GA (2-4") agree much better with the Euro's general rainfall amounts than the 6Z GFS' general rainfall amounts. So, they're clearly favoring the Euro.

We had 5.73" yesterday, which was 0.01" shy of the all-time daily record set on April 1, 1981 (aka the EF3 Hurtsboro tornado). The 24 hour record of 7.22" was set in March of 1990, which we missed by 0.08". :(

 

And my comment was more for the people not saying we'd get crushed... because we certainly did! haha! I've favored the Euro a bit more than the GFS in my forecast the past few days. Although the GFS did a decent job of placing the front & CAD. It's just having trouble with the tropical moisture in the Caribbean. 

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LithiaWx

LithiaWx

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Not sure why FFC is so optimistic about rain chances today. 70% chance of rain and pretty much the only rain I see in the northern half of GA is in East and Central GA. With this cool air mass in place I seriously doubt we get any rain.

You do realize it also means there is a 30 percent chance you will get nothing

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GaWx

GaWx

Posted
Posted

The 12Z GFS comes in much wetter than the 6Z GFS for the period through 12Z Mon. due to more Gulf tropical moisture with 2" for KATL and a whopping near 6" for Macon!

 

 Per the 12Z Euro: KATL gets ~2.5-2.75" and Macon ~3.25" through 12Z on Monday...so pretty decent crushings for both and in agreement with the 0Z Euro. With the wetter 12Z GFS (vs. 6Z GFS) of 2" for KATL and 6" for Macon and the last two Euro runs, the FFC forecast that MariettaWx showed has very good model support as of now. It is largely going to depend on the tropical moisture's trajectory once it comes out of the Gulf, of course. So, the variance is quite large. IF KATL does actually receive, say, close to 3", it would then be within only 2" of the alltime JJA record of 25"+ set in 2005 with still 12 days yet to go. Records go back to 1879. KATL has already set a new alltime record for JJA for rainfall not connected to tropical cyclones.

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calculus1

calculus1

Posted
Posted

very good news for the northern half of Alabama and NW and West Central GA, including atlanta. Looks like 1/2" or a little more so shouldn't be any flooding.

 

I think you enjoy being a contrarian, don't you?   :)  You seem to take the opposite viewpoint of MariettaWx (or anybody else who happens to post concerning GA weather recently) pretty much all the time, which is perfectly legal and all.  I just find it interesting.

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