Severe weather threat looks to shift a bit westward, more in line with 11/17/13

The bullseye area has retreated a bit westward, but the scenario is still looking quite strong.

Mainly, the question is how much moisture is going to be present over the lower Great Lakes as this monstrous storm system develops. The more moisture, the better chance of severe weather. As of now, this scenario looks on par with November 17th in terms of upper level winds, a bit below that day in terms of lower level winds, and the-same-to-much less in terms of moisture content, depending on where you are.

The stronger low level winds caused a widespread area of very warm moist air across the region back in 2013. As the low level jet isn't looking quite as strong, the highest moisture content is confined to a much smaller area. Those that do have the moisture should have a lot of it, though - both the GFS and NAM are predicting dewpoints at or above 60° for areas of Illinois and Indiana. The question is, how high will the dewpoints be in Southwest Lower Michigan? That depends on the model you look at, and the time of day.

The NAM tends to 'overdo' moisture content in its forecast, but with 60° dewpoints just to the south I don't think it's far-fetched to think that a wide area of SW lower MI will achieve dewpoints of 55° or higher. With this kind of system, that should be more than enough for a solid line of severe storms to develop and produce a very strong damaging wind threat. The tornado threat will also be present, but my thinking is that storm mode should be more linear (possible LEWP segments), so strong tornadoes wouldn't be especially likely, but can't be ruled out.

As goes the saying, the situation looks strong, but a bit disjointed. The strongest forcing will be along the Lake Michigan shoreline and will build into our area. The best conditions for severe weather, however, will be to the south of our state line. If there's enough forcing in those areas for discrete storms, they're looking at a possible whopper of a tornado outbreak. The further east you go in our state, the less the threat should be present, as I have a feeling cool air coming off of Lake Huron will choke covection it moves east.

Big time nastiness this Tuesday in the Great Lakes region

Everything is beginning to come into focus, and it isn't looking good for the southern Great Lakes region/Ohio Valley.

Jet core forecast by GFS 06z model run for Tuesday March 15th

Jet core forecast by GFS 12z model run for Tuesday March 15th

Jet core forecast by ECMWF 00z model run for Tuesday March 15th

Currently, I don't believe the bullseye will fall on us for this scenario. The models are in fairly good agreement for what could essentially be a repeat of the situation, with Illinois and Indiana or even northern Kentucky bearing the brunt of this system. The setup doesn't look quite as mean (yet) as the November 17th 2013 situation. For example, the jet core for that event was around 140kts, and the jet core for this is forecast to be about 120kts. Nonetheless, that could change in either direction. I don't see it particularly *decreasing*, as that 120kt forecast has been fairly consistent in both models for the last several runs.

The low level jet and moisture content are what's going to make or break this situation. For now, the GFS is forecasting a 45-50kt low level jet intensifying to 50-60kts as the surface low matures. Again, that's a little less mean than the November 17th event, but that can always go up once the short-range models start coming in. Either way, that amount of shear should be strong enough to drop some significant tornadoes across a widespread area. Instability will be marginal - 500-750j/kg of SBCAPE - but that matches the November 17th event.

I will be actively monitoring this situation as it develops, and should start being able to plot the exact bullseye for the event in the coming days. For now, I've introduced a widespread severe risk for the two southernmost lines of counties, a general risk for the two lines north and easternmost of that area, and a marginal risk up to the Arenac County line.

GFS moves storms up to Tuesday, ECMWF in another universe

The GFS continues to flip-flop on severe weather potential next week. This morning's and last night's run backed off a bit from yesterday afternoon's in terms of potential, but that's because it had the system speeding up. Today's midday run has it speeding up even more, with a surface low just shy of the tenth level of hell in terms of strength developing in the "sweet spot" to our north west. This forecast predicts what I'd call a rather robust tornado threat for the southern half of lower Michigan on Tuesday afternoon.

That supercell composite is yellow-to-orange with only a maximum level of 500j/kg of SBCAPE being forecast. That tells you something about the wind speeds being predicted.

I'm not going to lie - this 100kt upper level jet depicted scares the hell out of me. When that upper level jet points in a southwest/northeast direction and you see contours separating to the east and west like that, you have an indicating of rising air. The more perpendicular the 500mb jet is to your location, the more 'spin' storms will have. A 200-300mb jet core of 130kts is being forecast by this run. This picture alone indicates a tornado threat all the way from lower MI into Ontario...

...But let's throw in this one for shits and giggles. Take a look at that warm air coming up from the Gulf of Mexico and mixing violently into the air at the base of this negatively-tilted monster.

A very powerful cold front would be occluding a fairly strong warm front. This would lead to extraordinary forcing for ascent, meaning that even in weak instability, you'd likely have big thunderstorms

A couple of forecast soundings for southern lower MI. The first (above) is for around 5PM Tuesday. No quality analogs to any documented supercell thunderstorms, but a clear pronounced "TORNADO" threat (note, not "WEAK TORNADO"). 

The second is around 8PM a little further east. As can be seen, the same solid "TORNADO" threat is present. This sounding actually does have an analog weak-tornado producing supercell thunderstorm associated with it. 

Now, throw everything you see above out the window for the Euro model's forecast. The ECMWF is in a completely different dimension. Yesterday's run forecasts a backdoor cold front to descend from the north/northwest and pretty much destroy any chance of thunderstorms along with any chance of temperatures in the 70s:

A "back door" cold front is one that comes from a direction opposite typical weather patterns - usually from the north or northeast - and typically in the spring time. The ECMWF is forecasting such an event, caused by high pressure further north. This would choke any hot days/severe weather chances. The model also places the center of the much-weaker storm much further north and west, centered over Alberta/Saskatchewan. This would be way too far east to influence our weather yet. 

With the spread between the models being this large at this point, this is one of those situations where you can't count on anything. The GFS has definitely been consistent regarding this cyclone developing, and intensifying very, very quickly. If it's forecast verifies this could very well wind up being a bomb cyclone, which could do very nasty things in our neighborhood. The ECMWF has only had a couple runs that can even see this point, though, so it's important to give it some time to crunch numbers. As the week goes on, more samples will be collected and a more accurate forecast will be put together. My gut is pretty neutral. Storms from the northwest have intensified pretty good this year, but the GFS may be overblowing this one a bit. We could wind up with something forming, but not quite the bomb that the model is currently spitting out. I'll revisit this tomorrow and hopefully have more solid data to interpret.

Rain forecast revised down quite a bit - Severe thunderstorm chances up

The models have been having trouble predicting stormtrack days in advance as of late. Last week, we were on the pummeling end of such an error when the Little Storm That Could™ wound up tracking north and dumping 13"+ of snow on the Thumb.

Now we're going to be on the opposite end of the error, and all the rainfall from this system is going to go to the south of us, tracking through Ohio, Pennsylvania and New York.

More details can be found here.

On the topic of next week, I'm still a bit concerned about the possibility of severe thunderstorms.

The latest models actually do have the front speeding up which would likely bring us some strong storms, though the wind profiles are a bit more unidirectional and a bit less intense, and the system itself is more positively tilted, which means the tornado threat would be a bit muted, though the damaging wind threat appears higher than it did last night. This forecast could easily change again, but based on what I see this afternoon I'll likely introduce a dark green or yellow outlook for next Wednesday.

Chance of severe thunderstorms next week worth a mention

After watching the last few runs of the GFS with great interest, I think it's safe to say that there's at least a slight chance of strong to severe thunderstorms in Michigan next week. I'd place this chance around Wednesday or Thursday.

It's important to note that if the current GFS forecast were to verify, we probably would not see any severe weather. This would be because the storms would likely manifest to our west and not quite coincide with the maturing of the surface low, which would turn up the wind speed at all levels - and most importantly, the low levels - to around 11. See the image below.

Essentially, it will take a few more things to come together to produce anything nasty. First and foremost, there'd need to be enough instability for thunderstorms. The cold front would have to arrive a bit earlier than what's being forecast for that to happen. Our hottest day next week should be Wednesday, when temperatures could actually reach the mid 70s, and dewpoints could reach the upper 50s, if not 60°. The GFS tends to be pretty good with temperatures so I'm thinking it's safe to bank a little bit on this being the case. Were the cold front to arrive Wednesday afternoon, it'd be chasing the warm sector with a vengeance, and would probably initiate storms. My cause for concern is that this looks to be a powerful cyclone that's building, and when that upper level disturbance is strong enough to drive a storm system like this, the models typically underball its speed by a few hours. Should the storm pick up steam, it would mean that the above image displaying the low level jet intensification on Thursday could come a day early and possibly bring even more of a punch than what's being displayed.

So what types of hazards would we see if this were to happen? Damaging winds would be a given, as any time the wind speeds get that strong, a thunderstorm tends to bring them down to the surface. A jet core intensifying to 130kts and an 110-120kt upper level jet is currently being forecast, so we're looking at a lot of horsepower. Throw in the mid and low level jets of 60-70kts and that's severe wind pretty much guaranteed. These would be fast moving, powerful storms similar in speed to what we saw on August 2nd last year. There would also be a pretty solid tornado risk, and I'd say with those wind speeds being what they are, strong tornadoes would be possible should discrete storms be the mode.

Again, this is very, very preliminary and should be taken as only a marginal risk at this point. That means about a 1-in-20 chance of any hazard manifesting. The system could just as easily slow down or stay the same as what's being forecast, in which case we'd probably wind up seeing nothing but rain and perhaps some gusty winds. I do think it's worth a mention to get people thinking about severe weather again, though, as we will almost certainly be in the warm sector and that's where thunderstorms happen.

Could be a bad year for gardening/fruit - March 16-18th potentially strong cold front

This could be one of those springs that bounces back and forth between April/May-like temperatures and what we traditionally see in March, which is highs in the upper 30s and nights well below freezing. The latest GFS in particular is suggesting that a storm system would develop and thrust northward into Manitoba/Ontario (similar to our spring/summer-style patterns), bringing very warm temperatures - we're talking potentially low-to-mid 70s - and dewpoints in the upper 50s. This could set up some strong thunderstorms that week.

What comes after that week has me a bit alarmed for the fruit trees, though:

This indicates a potential dip back down to the 30s in the wake of what would likely be a strong cold front. This forecast puts northern Michigan clearly under the gun, and Mid-Michigan right on the threshold. This is very preliminary, and that freezing line could go 100 miles in either direction, north or south, but you get the picture. Even a single night below freezing at this point could damage new buds, which are likely to come out in the wake of these upcoming weeks of high temperatures. There are a few points between where it could freeze, too, so hopefully that'll slow things down, but in using the "wave" crest/trough visualization, this would definitely be the highest and lowest points in the timeline.

Again, this is way far out, and things could change significantly, but one thing the GFS model does well is temperatures. In another week the Euro should be able to see this point, so we'll have some more clarity on what to look for. Either way, gardeners, do not give in to temptation - don't plant until mid April at the earliest!

As a side note, today's chance of thunderstorms in lower MI has all but disappeared. I do suspect there'll be thunder in areas of the U.P., but down here we're just too stable (no disrespect, yoopers).

Fronts slow down a bit - 10% thunderstorm risk shifts to tomorrow, includes all of Michigan

The SPC has revised their initial outlook and is now calling for a general thunder risk for all of Michigan tomorrow, including the U.P.

I don't know if I'm feeling this one very much, at least down here in the lower peninsula. While the NAM4KM does suggest some thunderstorms in the upper peninsula tomorrow, down here it doesn't see any as of late, and the warm front may move through during the early morning hours which will temper instability. We'll have to wait and see.