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5/18/20 - 5/23/20 Upper Low Flooding & Severe Threat

Webberweather53

Meteorologist
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Desert Southwest ?
Figured it was time to start some sort of thread on this given how impactful this event may be and that we may have several days in a row w/ both a legitimate threat for flash flooding and severe weather (including damaging winds & tornadoes) across a pretty respectable portion of the southeastern US (esp the Carolinas).

While the maximum intensity of the severe &/or rain threat may not be quite up to par with the Easter Weekend tornado outbreak, this event is going to be a marathon instead of a sprint, lasting possibly most, if not basically all of this coming week.
 
To give some a sense for just how long this overall event may last, most models hint at precip onset sometime later on Monday into Monday night (ish), and potentially lasting all the way thru next Saturday, basically a 5-6 day event.

1589663906291.png
 
To give some a sense for just how long this overall event may last, most models hint at precip onset sometime later on Monday into Monday night (ish), and potentially lasting all the way thru next Saturday, basically a 5-6 day event.

View attachment 41542

Been noticing for next Saturday as it exits, we get caught on the SW side of it with NW flow and 40-50kts of 500mb flow, some OPs/ensemble members hint at a more organized severe weather threat with that NW flow, this pattern coming up next week is honestly something else
 
Been noticing for next Saturday as it exits, we get caught on the SW side of it with NW flow and 40-50kts of 500mb flow, some OPs/ensemble members hint at a more organized severe weather threat with that NW flow, this pattern coming up next week is honestly something else

Oh yeah, I noticed that as the upper low pulls away and the ridge begins to come back, we may have renewed threats of rain/storms going into the following week! The more water we put into the ground, the more edge we're gonna take off the heat when it does finally come (& of course feedback to creating more storms).
 
Been noticing for next Saturday as it exits, we get caught on the SW side of it with NW flow and 40-50kts of 500mb flow, some OPs/ensemble members hint at a more organized severe weather threat with that NW flow, this pattern coming up next week is honestly something else
ECMWF likes that day to be Friday as it departs 22BA4065-B57A-4B94-96B9-BE41EF09F0DD.png405B84CD-EAAB-471A-BB3E-3004DA77DB9E.png
 
Oh yeah, I noticed that as the upper low pulls away and the ridge begins to come back, we may have renewed threats of rain/storms going into the following week! The more water we put into the ground, the more edge we're gonna take off the heat when it does finally come (& of course feedback to creating more storms).

As we go ahead and if we do get all this rain plus more storms, early this summer we may get away with significant boundary layer mixing which is a cape killer on summer days, kinda neat that this may effect that
 
I remember how bad last June was with boundary layer mixing until those MCSs
 
This is something to watch, models haven’t been handling this MCV well, as someone said in the comments this could have a effect on the upper level low here
 
This is something to watch, models haven’t been handling this MCV well, as someone said in the comments this could have a effect on the upper level low here


This stronger than forecast mesolow creates a southward tug on the parent s/w over Iowa that leads to our eventual upper low, causing it to slow & dig earlier, leading to more rain in the SE US this week

1589665434282.png
 
This stronger than forecast mesolow creates a southward tug on the parent s/w over Iowa that leads to our eventual upper low, causing it to slow & dig earlier, leading to more rain in the SE US this week

View attachment 41547

These forecast errors in the GFS have propagated forward to ~36 hours in the forecast period, internal changes mask them thereafter. Also notice the immediate & downstream diabatic ridge from TD One/Arthur is much stronger on more recent GFS forecasts (red shading), this also slows our upper low down and causes it to dig sooner and w/ more vigor, also favoring more rain in the SE US & the Carolinas this week.

I don't think our wet trend on the NWP models is over yet either, especially on the GFS
 
These forecast errors in the GFS have propagated forward to ~36 hours in the forecast period, internal changes mask them thereafter. Also notice the immediate & downstream diabatic ridge from TD One/Arthur is much stronger on more recent GFS forecasts (red shading), this also slows our upper low down and causes it to dig sooner and w/ more vigor, also favoring more rain in the SE US & the Carolinas this week.

I don't think our wet trend on the NWP models is over yet either, especially on the GFS

This also increases are severe chances each day and allows more warm sector which In turns causes more Convective precip, which In turns causes more rain, yikes
 
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I could go for a couple good thunderstorms soon, especially considering that it has been dry. But hopefully the flood threat in the Carolinas doesn't turn out to be as bad as it's being modeled.
 
This also increases are severe chances each day and allows more warm sector which In turns causes more Convective precip, which I’m turns causes more rain, yikes

Concerning that the models are bringing TD 1 so close as any added rain from that will just add to the totals over eastern NC next week.
 
It still fascinates me watching the GFS/GEFS do its thing....

5D9B9B1F-C4F3-44FC-ADE3-98191B4A6098.gif
 
So we are looking at 5 or 6 days of severe weather chances in NC starting Monday? Did I read that right?
 
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