Severe Potential Saturday 10-13-12 (updated at 10:30AM on 10-13-12)

Updated Info (Updated at 10:30AM on 10-13-12):
Forecast models have shifted the best parameters even further south for today. This means there should be little or no severe weather threat in southern Minnesota with mainly a damaging wind threat into Iowa. The curse of 2012 has struck yet again it seems. I updated my ‘area at risk’ image to reflect these changes.

Area at risk (IMO):

Updated Info (Updated at 1PM on 10-12-12):
I once again updated my ‘at risk’ area for severe weather tomorrow. Model trends have continued to weaken this storm system though there still should be some severe weather in the area. The biggest threat continues to look like damaging wind though there may be some tornadoes and supercells early on as the storms first start to form. This looks most likely in southwest Iowa down into parts of Missouri, etc. Otherwise there may be a few isolated tornadoes elsewhere in the risk area – especially if any isolated storms develop ahead of any lines that form that can remain discrete long enough to produce a tornado.

In any case, forecast models have trended south some with this storm system so the heavy rain may actually stay south of our area into Iowa which would be unfortunate of course. I guess we will see though. At this point we are planning to still chase tomorrow. I’m unsure of exactly where just yet though. Remember to watch us live though as we are chasing tomorrow afternoon by going to http://www.majorleaguestorms.com/live and like usual, please remain weather aware tomorrow!

Area at risk (IMO):

Updated Info (Updated at 2:30PM on 10-11-12):
Based on the latest model guidance there still appears to be a threat for severe weather across southern MN and much of the northern plains on Saturday. However, recent model runs have depicted a weaker storm system moving into the area and/or has been splitting the storm system into 2 pieces – one part going north into southern MN and the other part staying down in Kansas.

In any case there appears to be less of a chance for tornadoes on Saturday now compared to how things looked as recently as yesterday. Things could easily change back though so don’t let down your guard just yet but both the GFS and NAM have been showing this weakening trend for a couple of runs now.

The biggest threat at this time appears to be damaging wind with the storms that develop – and there will be some much needed rain to fall across the area. A tornado threat can not be ruled out either but unless things change it will be very limited.

Updated Info (Updated at 11PM on 10-10-12):
I decided it was time to update my ‘Area at risk’ image. This is based on both the 12Z and 00Z NAM as well as some blending with what the GFS has been showing. It still looks like a tornado threat will exist but it will at least partially depend how quick precip moves out of the area in the morning.

I outlined an area where I personally think has the highest tornado potential based on the latest model guidance. Don’t be surprised if this changes some in the coming days as we get closer and closer to the event. There also will probably be a pretty high damaging wind threat across much of the area due to the amount of shear being depicted.

It appears the severe weather will probably start fairly early on Saturday. I wouldn’t be surprised to see storms fire around Noon in eastern Nebraska or western Iowa that could possibly be severe/tornadic though between 2-6PM it will be more likely. These storms will likely move fast off to the northeast so now is the time to get prepared. Severe weather could continue well after dark, especially in Iowa and Illinois.

Area at risk (IMO):

Updated Info (Updated at 2:30PM on 10-10-12):
Based on the latest model guidance, I still feel there is a good chance of severe weather with possible tornadoes in the northern plains this coming Saturday.

The GFS continues to be consistent with timing, strength and general track of the storm. However, the amount of CAPE being depicted on this run has decreased some since the 12Z GFS yesterday though it still appears to be sufficient for severe weather.

The 12Z NAM was fairly similar to the GFS as far as timing but the track of the storm was slightly south of what the GFS was showing (meaning most of the severe stuff would remain south of MN) and the storm itself was a bit weaker. However, a bigger concern may be the amount of ‘crapvection’ being depicted on the NAM. While I still expect severe weather to occur and probably some tornadoes (some maybe strong tornadoes), this ‘crapvection’ (if it verifies) may limit things and at the very least may make it difficult to know the area most at risk until Saturday morning so I can see exactly what areas are clearing out and what areas are not.

I still feel my ‘area at risk’ that I posted in my original post below is still pretty accurate as far as areas that are most likely to see severe weather at this point. I will probably update it tonight though once the 00Z NAM comes in.

Updated Info (Updated at 7:30PM on 10-9-12):
I’m starting to feel more and more confident that a widespread severe weather event will occur on Saturday and chances seem to be increasing that tornadoes will be a good possibility. In fact, strong and fast moving tornadoes are looking more and more likely as we get closer to this event.

For the time being I will not change my ‘at risk’ area that I posted below as it looks fairly accurate at this point. It still may need to be altered though, especially as we start to get closer to the event and details become a bit more clear. The 12Z GFS actually showed more CAPE then previous runs. If this verifies then the instability will not be an issue. There is still some differences in timing and track between the GFS and ECMWF which is not surprising. Hopefully the NAM will help clear those things up though.

We are planning to chase on Saturday at this time. If you live anywhere in the northern plains, please keep a close eye on things this coming Saturday – it continues to look like a very dangerous day.

Original Post:
For the last several days, the GFS has been very consistent with showing a potentially strong storm system moving into the northern plains this coming weekend. At this time it appears that Saturday (October 13) would be the most likely day for us to see severe weather in southern MN (and surrounding areas).

I typically hold off with making an outlook for severe weather until we are closer to the actual event (partly because I like seeing what the NAM shows) but this particular event appears to have the potential of being a very dangerous one (could be tornadoes). That said, since we are several days out, I want to make sure everyone understands that things can and likely will change (in particular the exact location of areas that may be affected). In addition to this, forecast models have struggled with the amount of moisture that actually makes it into systems this year. With it being so dry, the GFS could easily be over estimating how much moisture will be available with this storm system (if it verifies) which would limit the severe potential. Also, there could easily be ‘crapvection’ (non-severe storms/rain) in the area which will limit potential among other things. In other words, there are many ‘unknowns’ at this point – we could even end up with linear storms where damaging wind will be the primary threat.

In any case, IMO its worth making a post to start warning people of the potential. At the very least I’d expect some severe weather with probably some heavy rain across portions of the northern plains on Saturday (unless things dramatically change – which they could) or we could even end up with tornadoes in the area. Stay tuned as I will keep updating this post in the coming days with the newest information.

Area at risk (IMO – will likely change):