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January 21-24 Winter Storm Potential


Hoosier
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National Weather Service Quad Cities IA IL
1129 AM CST Mon Jan 21 2019

.UPDATE...
Issued at 1119 AM CST Mon Jan 21 2019

The 12Z set of data continues to support temperatures near
freezing at the surface Tuesday morning, with rain indicated south
of Highway 30 aloft. That signal is enough that a winter weather
advisory is likely to be issued this afternoon for Tuesday morning
through the end of the storm.

 

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37 minutes ago, Chicago WX said:

12z Ukie went south. Takes the low over LAF. 99% wrong most likely, but kinda funny.

Haha.  At 36 hours, it's a weak surface tough/low in Missouri.  Meanwhile other models are several mb deeper with a surface low in Iowa at that time.

I'm guessing LOT goes advisory for at least I-80 north, and quite possibly the entire cwa since the bar for icing is low and to account for the lagging response in pavement/road temps.

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My thoughts from last night are generally the same for the QCA after looking at 12z.  Looks like an hour or less period of light freezing rain, perhaps with a few wet flakes changing to all rain by early afternoon.  Should stay all liquid till at least midnight when 95% of precip event is over.  The northern DVN cwa def has a tougher forecast.  Looks like Cedar Rapids to Dubuque could get a nice little snow, but I'd be concerned about WAA tempering amounts some.  Could see a messy mix even there.  If they can stay all or mostly snow they could pick up several inches.

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Haha.  At 36 hours, it's a weak surface tough/low in Missouri.  Meanwhile other models are several mb deeper with a surface low in Iowa at that time.
I'm guessing LOT goes advisory for at least I-80 north, and quite possibly the entire cwa since the bar for icing is low and to account for the lagging response in pavement/road temps.
Agree we'll be needing an advisory in all likelihood. Also wonder how long it'll remain in effect with the rapid temperature fall tomorrow night pointing toward flash freeze potential.

Sent from my SM-G965U using Tapatalk

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Amazing to eventually see the snow maps out of this one. Someone 25 miles apart is going to get an ice storm and someone else is going to get 3-6 inches of snow. Basically you can forecast a county or two as a guide of potential conditions but a minor shift has a lot of impact. Add to that the timing (Tuesday PM rush hour) and I don't envy Ricky and crew now...

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8 minutes ago, Hoosier said:

The GFS currently looks a little too far north with the freezing line out in KS/MO.  Have to see if that continues as the hours go by but it might be a good idea to take a blend and not ride the GFS thermal profiles verbatim.

And the 12z ECMWF is way off out there in that regard.  For example, it had KC in the mid 30s at 1 pm central and it's still below freezing there.  Just something to watch.

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For some proof of what I mentioned earlier, here is the 12z Euro vs actual temps valid at 3 pm central.

us_model-en-087-0_modez_2019012112_9_472_210.thumb.png.1abf2763885756a488769d0238d247ea.png

mo_sfc.gif.3e7d9860e0d8a4b4636e22802bd4270c.gif

 

It's not a cloud cover issue either, as the Euro had extensive clouds progged.  So why look at this area?  Well, it's downstream of the surface low and there is snowcover in a significant part of the area.  Sounds familiar for areas farther north/east tomorrow.  

Now, there's a risk in overreacting and thinking well, done deal, it's going to end up warming more slowly from here on out.  Not necessarily.  If the temperatures don't drop off as much or warm more quickly than progged tonight and into tomorrow, then it cancels out.  So it means you watch actual observations (especially the northward climb of the 32F isotherm) and compare to the models.  

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46 minutes ago, Hoosier said:

For some proof of what I mentioned earlier, here is the 12z Euro vs actual temps valid at 3 pm central.

us_model-en-087-0_modez_2019012112_9_472_210.thumb.png.1abf2763885756a488769d0238d247ea.png

mo_sfc.gif.3e7d9860e0d8a4b4636e22802bd4270c.gif

 

It's not a cloud cover issue either, as the Euro had extensive clouds progged.  So why look at this area?  Well, it's downstream of the surface low and there is snowcover in a significant part of the area.  Sounds familiar for areas farther north/east tomorrow.  

Now, there's a risk in overreacting and thinking well, done deal, it's going to end up warming more slowly from here on out.  Not necessarily.  If the temperatures don't drop off as much or warm more quickly than progged tonight and into tomorrow, then it cancels out.  So it means you watch actual observations (especially the northward climb of the 32F isotherm) and compare to the models.  

Well explained Hoosier. I certainly don’t envy a forecaster in this position. SREF ensembles nearly literally spilt in two over my area. Half the members give us rain with little snow accumulation and the other half gives us a respectable amount of snow. The NWS torn on which direction to go so they go right down the middle. In my experience when you have high heights to your E/NE and skin temps at 0-10° for over 48 hours, a storm system is really going to have to pack quite the punch with WAA to boost temps to near 40° (as some models are hinting at) and this system just isn’t that robust. Don’t see it happening as some global models are depicting especially when some don’t even have a handle on current temps. Short range models will hopefully have a better handle on this. 

 

Another interesting system to watch. 

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In the LOT area, the zone I'd watch for the possibility of somewhat more substantial ice would be roughly the I-88 corridor and perhaps a tad south.  Farther north may be more snow/mix and less ice but it's a close call.  Shouldn't get too crazy, maybe like a tenth or areas of two tenths, but it should be fairly breezy despite the inversion locking up the stronger winds aloft.  Even one or two tenths of ice can start to cause some scattered electrical issues when you throw in gusts of 25-30 mph. 

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Just now, Hoosier said:

It's 10 with a dewpoint of -10 here.  You would never guess that precip would be transitioning to rain 24 hours from now.  How the heck did meteorologists do this stuff back in the day?

Yeah...and ORD has a dewpoint of -7. 

Hard to fathom the Td increasing by 35+ degrees over the next 24 hours. Normally you'd lean against it, but the model support seems overwhelming.  Hopefully the Ukie and NAM can win out...but, unfortunately, WAA can overwhelm everything if the conditions are right. :(  

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1 minute ago, beavis1729 said:

Yeah...and ORD has a dewpoint of -7. 

Hard to fathom the Td increasing by 35+ degrees over the next 24 hours. Normally you'd lean against it, but the model support seems overwhelming.  Hopefully the Ukie and NAM can win out...but, unfortunately, WAA can overwhelm everything if the conditions are right. :(  

Forecast of 17 at 7:30 AM tomorrow.  Rain by 1:30pm

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