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January 27-28 Wintry System


wisconsinwx

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Kind of an interesting event if current model forecasts hold.  Wouldn't be a pure snow event here, but would be a pretty rare 4-phase event starting with snow.  Taking the new 00z GEM verbatim we would have a few hours of decent snowfall, followed by a few hours of sleet, then a few hours of freezing rain, and then finally end as non-freezing rain.  That type of event is pretty unusual, so I remain skeptical.  More than likely it will end up being a very brief period of wet flakes followed by sleet, and then a brief period of freezing rain before going over to a predominately rain system. 

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Euro looks pretty similar to the 12z.  The biggest issue to me is similar to the event a couple weeks ago, the sneaky warm layer potential that could be the difference between a 3-5" snow event and a half inch to an inch of sleet.  The 850s look solid around here on most of the models at this early point, but the GFS runs have shown a small warm layer somewhere between 500 and 850 mb sneaking in based on the Wxcaster maps I have seen.

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Euro looks pretty similar to the 12z. The biggest issue to me is similar to the event a couple weeks ago, the sneaky warm layer potential that could be the difference between a 3-5" snow event and a half inch to an inch of sleet. The 850s look solid around here on most of the models at this early point, but the GFS runs have shown a small warm layer somewhere between 500 and 850 mb sneaking in based on the Wxcaster maps I have seen.

The GFS bufkit soundings show the 800-900mb layer above freezing so we would probably transition from snow to freezing rain and then rain at the very end as surface temps climb above freezing.

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The GFS bufkit soundings show the 800-900mb layer above freezing so we would probably transition from snow to freezing rain and possibly rain at the very end as surface temps climb above freezing.

 

 

Even you guys up there having to deal with precip issues weakens confidence in the quantity of wintry precip here prior to the inevitable changeover.  Wouldn't be surprised if this ends up being a 90% rain event down here.

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The GFS bufkit soundings show the 800-900mb layer above freezing so we would probably transition from snow to freezing rain and then rain at the very end as surface temps climb above freezing.

 

Oh, I thought sleet was likely just by having a warm layer somewhere between 500 and say 850 to 900mb.  Is 800-900 mb the standard layer for warmth that would indicate fzra?

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Oh, I thought sleet was likely just by having a warm layer somewhere between 500 and say 850 to 900mb. Is 800-900 mb the standard layer for warmth that would indicate fzra?

Usually with sleet you want your warm layer to be around 850mb or higher. The lower the warm layer is to the surface the less time the water droplet has to refreeze. The depth of the warm layer also makes a difference.

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GFS would be almost all snow this far north until after 102 hours. Twisterdata.

 

Why do you only use the 1000-850mb line to determine the all snow line?  If there's one thing I learned from the recent sleet storm, it's that none of the lines, even the 850-500mb 0C line, can be north of your location if you are to be confident of receiving snow in that period.

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Why do you only use the 1000-850mb line to determine the all snow line?  If there's one thing I learned from the recent sleet storm, it's that none of the lines, even the 850-500mb 0C line, can be north of your location if you are to be confident of receiving snow in that period.

 

 

I looked at the soundings.

 

Sounding for this location at 96 hours. All snow.

 

GFS_3_2013012400_F96_42.5000N_88.0000W.p

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