Hoosier Posted April 4, 2017 Author Share Posted April 4, 2017 NAM with some particularly ridiculous runs lately. Good luck trying to pinpoint amounts with this. Lots of variables. Link to comment Share on other sites More sharing options...
Hoosier Posted April 4, 2017 Author Share Posted April 4, 2017 Here is the NAM Kuchera map. Kuchera is suggesting less than 10:1 generally, which should be the way to go for this storm with the marginal temps. The question is whether even these amounts are anywhere close to reality and how much to shave off. This is the kind of storm where forecasters really earn their money. Link to comment Share on other sites More sharing options...
Hoosier Posted April 4, 2017 Author Share Posted April 4, 2017 12z GFS is worlds apart in the all important details. Like in a different galaxy. Link to comment Share on other sites More sharing options...
Hoosier Posted April 4, 2017 Author Share Posted April 4, 2017 LOT posted a lakeshore flood watch. Link to comment Share on other sites More sharing options...
Hoosier Posted April 4, 2017 Author Share Posted April 4, 2017 What this really comes down to is which model has the best handle on the dynamic cooling? The NAM does have superior vertical resolution but if it's even slightly off on temperature profiles, you are looking at a substantially different outcome. And can't entirely ignore warm/wet ground in this setup even though rates that are heavy enough could compensate. Some images from the 3 km NAM. You can see it has a rapid transition to snow in the deformation zone tomorrow evening and overnight. Link to comment Share on other sites More sharing options...
Hoosier Posted April 4, 2017 Author Share Posted April 4, 2017 The NAM is suggesting a period of gusts over 60 mph possible near the Indiana shore... maybe even close to 70 mph right at the shore. Here's a 3 km NAM forecast sounding for GYY, which has 65 kts just off the deck and implies that it would have a chance at mixing down. Link to comment Share on other sites More sharing options...
Hoosier Posted April 4, 2017 Author Share Posted April 4, 2017 I may be wrong about this but I think there could be pretty significant impacts/power outages around Chicago metro and northwest IN. There are a series of factors that look to be coming together as touched on last night (wet soil, fairly long duration of high winds, etc), with the big lingering question being snow amounts. If anything remotely close to the NAM verifies, lights out, literally. Heavy, wet snow with those winds doesn't mix well. My unofficial advice to anyone around here would be to get prepared for a high impact scenario in the event that it happens. Link to comment Share on other sites More sharing options...
Hoosier Posted April 4, 2017 Author Share Posted April 4, 2017 GRR issued a winter storm watch. Link to comment Share on other sites More sharing options...
Hoosier Posted April 4, 2017 Author Share Posted April 4, 2017 LOT issued a high wind watch for the lakeshore counties. 18z NAM is another bonkers run. Link to comment Share on other sites More sharing options...
Don Cherry's Jacket Posted April 4, 2017 Share Posted April 4, 2017 2 hours ago, Hoosier said: I may be wrong about this but I think there could be pretty significant impacts/power outages around Chicago metro and northwest IN. There are a series of factors that look to be coming together as touched on last night (wet soil, fairly long duration of high winds, etc), with the big lingering question being snow amounts. If anything remotely close to the NAM verifies, lights out, literally. Heavy, wet snow with those winds doesn't mix well. My unofficial advice to anyone around here would be to get prepared for a high impact scenario in the event that it happens. Greetings from the mid-atlantic boards. So, I guess your suggesting my trip through O'Hare on Thursday AM will be iffy. We're watching our own mess convective stuff as the southern and northern fronts collide. Link to comment Share on other sites More sharing options...
Hoosier Posted April 4, 2017 Author Share Posted April 4, 2017 48 minutes ago, Don Cherry's Jacket said: Greetings from the mid-atlantic boards. So, I guess your suggesting my trip through O'Hare on Thursday AM will be iffy. We're watching our own mess convective stuff as the southern and northern fronts collide. Looks messy. Link to comment Share on other sites More sharing options...
Hoosier Posted April 4, 2017 Author Share Posted April 4, 2017 A couple cycles of the NAM have been spitting out a band of 4"+ precip. The 18z run has it in the area that takes it on the chin with some of the higher wind potential. Link to comment Share on other sites More sharing options...
Hoosier Posted April 4, 2017 Author Share Posted April 4, 2017 LOT has been comparing the wind/wave potential to the 10/31/2014 setup, which seems like a decent comparison in general but we have a much deeper surface low and stronger pressure gradient this time, so arguably could surpass what happened then. GYY pulled off a 69 mph gust on 10/31/2014... I wonder how high they can go this time. Link to comment Share on other sites More sharing options...
OHweather Posted April 4, 2017 Share Posted April 4, 2017 52 minutes ago, Hoosier said: LOT has been comparing the wind/wave potential to the 10/31/2014 setup, which seems like a decent comparison in general but we have a much deeper surface low and stronger pressure gradient this time, so arguably could surpass what happened then. GYY pulled off a 69 mph gust on 10/31/2014... I wonder how high they can go this time. If you get 60-65kts below the inversion which the NAM shows, I could see someone right near the lake where there's better mixing pushing 70MPH. I'd have to think if it's precipitating at a quarter inch per hour like the NAM shows you'd dynamically cool enough for a decent snow accumulation even close to the lake. Even without it, I think your concerns about pretty significant tree/power impacts are pretty justified. Link to comment Share on other sites More sharing options...
Powerball Posted April 5, 2017 Share Posted April 5, 2017 On 4/3/2017 at 6:07 PM, Stebo said: Yeah I think so, I would be surprised if it turns out more than that. Fine with me. Link to comment Share on other sites More sharing options...
Hoosier Posted April 5, 2017 Author Share Posted April 5, 2017 56 minutes ago, OHweather said: If you get 60-65kts below the inversion which the NAM shows, I could see someone right near the lake where there's better mixing pushing 70MPH. I'd have to think if it's precipitating at a quarter inch per hour like the NAM shows you'd dynamically cool enough for a decent snow accumulation even close to the lake. Even without it, I think your concerns about pretty significant tree/power impacts are pretty justified. I've learned the hard way to not overlook the marine influence, but it is low 40s water temps and not 50+. Setup is just so marginal to begin with. Even if accums struggle, it should at least be snowing up to the shore if the dynamic cooling comes through. Could end up in a little bit of a sweet zone here several miles inland. Close enough to get in on some of the stronger winds with the enhanced mixed layer (but not like being right at the shore) and far enough inland to be a degree or two cooler. Link to comment Share on other sites More sharing options...
OHweather Posted April 5, 2017 Share Posted April 5, 2017 55 minutes ago, Hoosier said: I've learned the hard way to not overlook the marine influence, but it is low 40s water temps and not 50+. Setup is just so marginal to begin with. Even if accums struggle, it should at least be snowing up to the shore if the dynamic cooling comes through. Could end up in a little bit of a sweet zone here several miles inland. Close enough to get in on some of the stronger winds with the enhanced mixed layer (but not like being right at the shore) and far enough inland to be a degree or two cooler. This is not an easy forecast at all as the models don't agree on where the stronger deform develops and how slow/intense it is. It's a very robust and slow moving storm so I fully expect pockets of warning criteria snow...I'd put my money on parts of lower MI, with convection across the south I can see a last second weak/southeast trend with the low up here which would really take IL out of play for bigger snows...that's my largest concern at this point...but with impressive jet dynamics and a warm/humid airmass wrapping into the storm from the south there's some ingredients in place for a pretty robust storm...so maybe the NAM will be right if convection in the south doesn't screw it all up. If the NAM is right I'd expect accumulating snow down to the shore...but at this point I'd hedge low for accumulations in Chicago and NW IN because the NAM is sort of on its own island. This storm will be fun though because someone will get a decent snowfall and we may not know where until it starts happening, and the wind potential will be hard to miss downwind of Lake Michigan. Link to comment Share on other sites More sharing options...
Hoosier Posted April 5, 2017 Author Share Posted April 5, 2017 Some April snow numbers for Chicago Last 1" calendar day: 4/14/2014: (1.4") Last 2" calendar day: 4/5/2009: (2.1") Last 3" calendar day: 4/11/2007: (3.0") Last 4" calendar day: 4/5/1982: (9.4") Link to comment Share on other sites More sharing options...
cyclone77 Posted April 5, 2017 Share Posted April 5, 2017 Looks like a good 1-1.5" of cold rain for tomorrow. That could put us up over the 2" mark for the month already. Not expecting any snow here. Link to comment Share on other sites More sharing options...
smoof Posted April 5, 2017 Share Posted April 5, 2017 Nice 22" jackpot zone 15miles from here on the 0z NAM! I'm trying not to get excited though since it's by far the coldest model still. Link to comment Share on other sites More sharing options...
hawkeye_wx Posted April 5, 2017 Share Posted April 5, 2017 I'm not sure how much rain I'll get from this (0.30-1.00+", depending on the model), but the models did come back north some after they are began whiffing south a couple days ago. The 00z NAM removed nearly all the snow west of Lake Michigan. If anyone in Iowa sees any, it shouldn't be much more than a few flakes mixed in. Link to comment Share on other sites More sharing options...
cyclone77 Posted April 5, 2017 Share Posted April 5, 2017 1 hour ago, hawkeye_wx said: I'm not sure how much rain I'll get from this (0.30-1.00+", depending on the model), but the models did come back north some after they are began whiffing south a couple days ago. The 00z NAM removed nearly all the snow west of Lake Michigan. If anyone in Iowa sees any, it shouldn't be much more than a few flakes mixed in. Where was this storm a month or two ago? We'd both be sitting pretty for later tonight and tomorrow morning. HRRR keeps temps AOA 40 in the heart of the deformation band tomorrow. Link to comment Share on other sites More sharing options...
Hoosier Posted April 5, 2017 Author Share Posted April 5, 2017 Not overly optimistic on the snow aspect here at this point. I think it will snow and probably accumulate respectable for April, but I think there's going to be a large amount of precip wasted on rain. If I knew that temps would at least get down to 33-34 with the kind of precip rates that are being modeled, I'd probably be a bit more bullish on significant accumulations, but various raw output has trouble dropping temps below the mid 30s here for any prolonged period. Now it's possible there could be a positive surprise, but things certainly look better just to my northeast with slightly colder low levels progged. Still watching with interest though given the overall heavy precip/high wind potential, and there aren't many times that I can remember pairing winds of this magnitude with wet snow... it's been drier/fluffier snow more often than not. Link to comment Share on other sites More sharing options...
harrisale Posted April 5, 2017 Share Posted April 5, 2017 If these 3km NAM snow totals are anywhere close to correct, there are going to be a lot of folks caught completely off guard in Southern Ontario. Saw tons of people lying out in the sun in the parks today. Take with a grain of weenie salt of course: Link to comment Share on other sites More sharing options...
Hoosier Posted April 5, 2017 Author Share Posted April 5, 2017 Couple sites in IL/WI reporting some flakes. Dynamic cooling is trying but generally not enough. Link to comment Share on other sites More sharing options...
Hoosier Posted April 5, 2017 Author Share Posted April 5, 2017 Still some differences in the placement of the enhanced deformation band later tonight (a number of SREF members and the UKMET are farther west) but overall it would appear that areas from around extreme north central IN and northeastward in Michigan have the best chance to rip tonight. Given the intensity of this band, and assuming temperatures cool close to freezing, I would not be surprised to see some 1-2" per hour type rates in there, favoring Michigan but possibly extending into Indiana. Link to comment Share on other sites More sharing options...
Hoosier Posted April 5, 2017 Author Share Posted April 5, 2017 LOT is calling for occasional waves to 28 feet on Lake Michigan. Link to comment Share on other sites More sharing options...
HillsdaleMIWeather Posted April 5, 2017 Share Posted April 5, 2017 I'd imagine the WFO's will go with WWAs due to the massive uncertainty Link to comment Share on other sites More sharing options...
Hoosier Posted April 5, 2017 Author Share Posted April 5, 2017 LOT upgraded to high wind warning. IMO, the wind potential looks a tick less impressive than yesterday, but still pretty impressive. Link to comment Share on other sites More sharing options...
Hoosier Posted April 5, 2017 Author Share Posted April 5, 2017 4 minutes ago, HillsdaleMIWeather said: I'd imagine the WFO's will go with WWAs due to the massive uncertainty GRR upgraded part of their area to a warning and went with advisory elsewhere. Link to comment Share on other sites More sharing options...
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