A Gulf Low, A Pattern Change, and Severe Season: 4-2-13 Update

Spring has sprung, and other than this upcoming Thursday (April 4), it looks to stick around. We have a lot to talk about regarding the upcoming pattern so lets get started.

A Gulf Low

First off on the discussion plate today: our upcoming Gulf Low.

Despite a lack of these type systems during the winter when they would have produced snow, we have a gulf low on the way for Wed/Thu. Below is the precipitation map for the next 96 hours.

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As you can see, a widespread 1″+ is expected across the area, with isolated areas receiving up to 2″ of rain before the low heads up the coast. I can’t rule out some isolated thunder with this system but I don’t expect much at all as daytime highs will only reach the mid-40’s to low 50’s for areas north of Atlanta. Behind this system, temperatures will return back to normal with widespread low/mid 70’s for Sunday through most of next week.

A Pattern Change

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Above is the current pattern at 500mb as modeled on the 0z GFS ensembles. As you can see, there is a large trough (the blue) across the Eastern US, that has been responsible for the cooler temps we experienced through most of March. The dip in the 564 height line is the wave that is going to produce our Gulf Low. This trough is going to begin to lift out behind the low, however, and you can see major changes afoot as early as 144 hours with a trough developing to the west and rising heights across the southern US. A strong positive height anomaly has developed over the Atlantic by this time (Bermuda high) which will help to stream warm, moist air into the south-eastern US. By 192 (next Tuesday), the pattern has completely rearranged with a western trough and a southeastern ridge fully in place. Below, you can see the GFS/Euro/CMC all agree on this being the upper level pattern by this weekend into next week.

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As this upper level pattern evolves, we will have to watch closely for severe potential, and the models are already hinting at potential next week.

Severe Weather Potential

The Storm Prediction Center has already given this system some mention in their 4-8 day outlook, however I will start this off with a disclaimer that details are very murky at best but the potential exists for widespread severe weather across the central and eastern US next week. We are headed into the climatologically favored time of year for major severe events, and so it is important to pay attention to any and all threats. The GFS has been the most adamant about next week, however it has been all over with timing bringing a strong Great Lakes Low through as early as next Wednesday (4/10) and as late as next Fri/Sat (4/12-13). IF this solution verifies, there will certainly be widespread severe, possibly an outbreak, across the central and southern Plains in the Sun-Tue timeframe, with the threat potentially spreading east with time. It is FAR too early to determine how far east the threat may make it, but one thing that appears very likely is that moisture/instability won’t be a problem with this system as it has been with previous. As far as the North Georgia area is concerned, we are entering the time of year when wedges become less of a problem (as they were with the last two systems) and currently I don’t see a wedge setting up across the area with this system. So, since the set-up doesn’t look wedge-y, I will be keeping a very close eye on this time-frame and update as we get closer.

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