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Feb 1-3rd GHD III Part 2


Chicago Storm
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32 minutes ago, OHweather said:

Anecdotally, I don't trust this system not to mix all the way up to at least Akron, OH, which the Canadian/RGEM insist on. And maybe the Canadian models are doing better with the PV over Canada. That's my analysis for the day ;)

But for real, I think how the PV interacts with the storm is quite important here for wave 2. With a jet streak to the north providing plenty of divergence aloft and with the precip largely being driven by warm air advection processes...to go along with what should be a lot of latent heat release from convection in the Gulf Coast states and from the anomalously high PWATs getting wrung out as the moisture gets lifted over the front, I feel like if the PV doesn't press down more there is room for last second northwest bumps with the wave on Thursday. If the PV presses down more it will overwhelm these processes, but if it holds steady or backs off slightly I'd expect a bump back NW. Can argue we've stopped the trend of the PV pressing down more in recent runs at the least.

gfs-ens_z500a_namer_fh48_trend.thumb.gif.cc6570a8e9a2ba805b6cb46cb104f123.gif

This got me thinking & poring over a bit of data, only to find a fascinating quirk in the data. Per Environment Canada, the GFS is, by far, the worst performer of all models in the 24-hour timeframe - even worse than the JMA (monthly RMSE over North America, 500mb GPH).

... Which seems really strange, so here's the webpage for anyone who wants to spot-check https://weather.gc.ca/verification/index_e.html

monthly_ts_rmse_GZ500_NA_24.png

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1 hour ago, Chicago WX said:

Tornado siren test right now is a nice touch. :lol:

Going with a final call of 15” for MBY. Jackpot call in LOT’s CWA is somewhere in Ford County with 19”.

Good point. Our monthly test is tomorrow during the heavy snow. I better call dispatch and have them cancel it. lol

Expecting similar amounts here. I'm going for 14" here since we will have at least 1/4" of rain before the flip, otherwise it could have been the higher amounts that the GFS was previously advertising.

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Up in the suburbs of Cincy, I'm hoping that this storm shifts a bit further southeast. We're about 2 counties away from hopefully not dealing with a crippling dose of concrete, but if this thing comes northwest, I could see it being a devastating ice storm especially for the city. 0.5 would be enough, 1 inch would be bad.

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1 minute ago, StormChaser4Life said:

At this point do we trust globals though or start looking more at short range hi res guidance? Honest question. Always wondered at what point do you shift away from globals. I see 12z euro joined nam in missing wave 2 here and also downing my totals for wave 1. Not sure what to think. 

Definitely can start incorporating the shorter term models for tonight's portion.

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6 minutes ago, Sciascia said:

Speaking of…Snow swath on newer HRRRs has slightly gone more NW. 3 inches in ORD at 4am when 12z had under an inch 

Yeah, just watch for trends.  I think it was Stebo who made the point that stuff like the HRRR/RAP has a limited domain and really only uses obs/data from inside the US, which is probably why they are prone to large error in their latter timeframes. 

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1 minute ago, Stevo6899 said:

The 12z rgem animated simluation does look pretty sexy with the first round for metro detroit. Good luck and enjoy it up there.

 Thanks. I will say this about DTX warning, they still talk about Thursday. Which is really looking more like a graze job of light snow.  This is all gonna be about tomorrow and it's gonna come down to the ratios. Pretty solid model agreement, give or take some noise, on about 1.20" qpf with about an inch falling as snow.  Temperatures will be steadily dropping as the storm progresses.

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2 minutes ago, michsnowfreak said:

 Thanks. I will say this about DTX warning, they still talk about Thursday. Which is really looking more like a graze job of light snow.  This is all gonna be about tomorrow and it's gonna come down to the ratios. Pretty solid model agreement, give or take some noise, on about 1.20" qpf with about an inch falling as snow.  Temperatures will be steadily dropping as the storm progresses.

Yea as always will depend where the banding sets up. Rgem looks to have them nearly stationary over the area for 20+ hours.

My gut is telling me someone still may get a foot plus. Im still tempted to hop on a plane tonight lol. Havent seen 6+ storm in person in over 3 yrs as i havent been home in the winter and nothing has been worth traveling for.

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It's basically nowcast time, in terms of position of key features, with the short range/high resolution guidance used as a tool. You can check obs and radar vs the hourly RAP/HRRR runs. Can also check the short range forecasts of the globals vs obs and radar to have an idea which one has a more correct trend for tonight.

SPC mesoanalysis will be a good place to check the position of maximum low and mid level f-gen. For the gradient area in Northern Illinois, frontal timing and position, how quickly the dry HP is building, and positioning of the surface frontal trough post fro-pa are all very important to whether we over or underperform. This is in addition to radar trends for mesoscale banding position and orientation.



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