SIGNIFICANT SEVERE WEATHER LIKELY ACROSS NORTH GEORGIA 4/28-4/29
It is looking rather likely that we have a lot to deal with weather-wise over the next 48 hours. Damaging wind, hail, and tornadoes are all in the cards, along with extremely heavy rainfall that will likely lead to localized flooding.
The following are the SPC’s latest probabilities for tornadoes, wind, and hail respectively through the day today and overnight tonight. As you can see our largest threat appears to be damaging winds, however tornadoes will still be possible, and a few long-track tornadoes cannot be ruled out, especially for areas from Blue Ridge to Jasper to Cartersville and west. This area could easily be extended south/east depending on how things play out with potential secondary surface low development today/tonight.
The following is the “significant tornado ingredients” index from the SPC’s SREF model, basically giving an idea of where the highest probabilities of a strong tornado would be, valid at 8PM tonight.
As you can see, the highest threat is to our west, however it shifts east overnight while weakening, as seen in the frames below valid 11PM and 4AM.
From the last few runs of the NAM, it appears the main band of precip, possibly a broken line of supercells vs a solid line, is expected to move through from 3-9AM tomorrow, followed by a period of clearing allowing the atmosphere to reheat. Then by tomorrow afternoon, another round of storms/supercells is expected to impact the area. The SREF again pumps up the sig-tor index across the area from late afternoon through early Wednesday morning before the front finally clears the area.
I’m sure there are a few of you saying “don’t take the sig tor at face value without looking at everything else” so here’s everything else.
The SREF is plotting instabilities of 1000-2000 CAPE, which will be PLENTY for supercell development, and it has support from the NAM/GFS/Euro on this widespread instability. The last few runs of the RAP increase low-level helicity to extremely high levels across primarily the north-central and northwest part of the state, and bulk shear is being progged at 30-40kts overnight (higher if secondary low development occurs, and this area of enhanced helicity will probably expand on all sides).
So…. for the non-weather geeks in the audience, what does this mean? The potential exists for an outbreak of severe storms, possibly including a few strong/long tracked tornadoes across northern GA from late tonight through early Wednesday morning. I STRONGLY advise you to have a way to receive warnings, whether with a weather radio or phone app (link to a free one on android, also available through Iphone): https://play.google.com/store/apps/details?id=com.globalcanofworms.android.simpleweatheralert).
Also, have a severe plan in place before bed tonight. Waiting until the severe weather is here will not cut it. I will be updating on the Facebook page as well as on my twitter @negawxman throughout the day today as things develop and update as the SPC puts out new outlooks later this afternoon.
Everyone have a great day.~TW