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Jan 24-26 Weekend Snow and Sleetfest Model Thread Part Tres

H2O

By H2O,
in Mid Atlantic

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wxmeddler
wxmeddler

My call before the flip-over: Southern MD & Eastern Shore: 6-10" I-95 Corridor: 8-12" Parr's Ridge and NW: 10-14" Allegany & Garrett: 12-16" (Unlikely to Flip)

stormtracker
stormtracker

You white as hell

psuhoffman
psuhoffman

Finishes looking at the HRRR

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konksw

konksw

Posted
Posted
Just now, balltermen said:

23/2 here near Braddock Road metro. 

Just saw the 3k NAM.   5" snow followed by 3" sleet.  Would still be quite the storm.  You can't toss it unfortunately.  Too many times we've seen mid level warm air punch its way well north and west than the globals suggested at 36 hours out.  

How many times has that happened with this level of significant cold in place?

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balltermen

balltermen

Posted
Posted
1 minute ago, konksw said:

How many times has that happened with this level of significant cold in place?

a million. You never think a warm nose can find a way through.  But it does. 

That said, the NAM is also wrong a lot and I think it is probably early with the flip time

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wxmeddler

wxmeddler

Posted
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1 hour ago, WxMan1 said:

Typically the degree of the warm air (MaxT aloft) will be proportional to the depth. In other words, the highest the MaxT aloft, the deeper the warm or >0C air.

In many studies I've seen though, no matter how deep or shallow the warm air is, when you hit 3C or 37F, you're completely melting the hydrometeor. Once that happens, there's no going back to sleet or anything "pellety" unless the air somewhere within the subfreezing layer can get down to -13C/8F or lower. Unless that happens, the rain drop does not refreeze. When we see sleet, it's typically associated with an elevated warm layer temp between 0.5C and just below 3.0C. When it's closer to 0.5C, it's probably more of a sleety & rimed snow mix. When the MaxT aloft is closer to 2.5C, it's more like a sleet ball, with little if any evidence of a mangled snowflake. 

We're in for some real sh*t if that's the case. Most guidance gets the fall line and SE at or above +5C as early as 11am tomorrow. Would love to see those studies if you have the links. 

I don't recall ever having a situation where there is a +7 to -8 swing in a single profile in this area. That is some southern high plains ice storm levels of cold air wedging. We do not see this here.

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IUsedToHateCold

IUsedToHateCold

Posted
Posted
Just now, JenkinsJinkies said:

Now what if NAM stays the course but the other models do not cave to it?

If a model is on an island it's probably wrong unless it's in it's wheelhouse doing something it's proven to excel at. NAM is good at thermals, so it is a wheelhouse, but we've seen the NAM be wrong outside of 24 hours. This is within 24 hours, so we are to assume it could be on to something, but I wouldn't necessarily conclude that verbatim. 

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nj2va

nj2va

Posted
Posted
Just now, Chris78 said:

Sounds like an improvement?

Honestly, I’ve been so busy at work I haven’t paid much attention during the day.  A quick look vs 18z and the flip was  a touch later than 18z.  I honestly don’t really put much confidence in UK thermals but a nice data point for the better lol

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SnowenOutThere

SnowenOutThere

Posted
Posted
6 minutes ago, wxmeddler said:

We're in for some real sh*t if that's the case. Most guidance gets the fall line and SE at or above +5C as early as 11am tomorrow. Would love to see those studies if you have the links. 

I don't recall ever having a situation where there is a +7 to -8 swing in a single profile in this area. That is some southern high plains ice storm levels of cold air wedging. We do not see this here.

Seems like multiple studies disagree with each other. One I read/skimmed said that if we have a freezing layer of 3000+ feet below the elevated warm layer it’ll refreeze to sleet regardless. Just such an extreme setup to where it all breaks down. 

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pazzo83

pazzo83

Posted
Posted
4 minutes ago, SnowenOutThere said:

Seems like multiple studies disagree with each other. One I read/skimmed said that if we have a freezing layer of 3000+ feet below the elevated warm layer it’ll refreeze to sleet regardless. Just such an extreme setup to where it all breaks down. 

wild to think we'd have a layer of 40+F air when it's around 20F at the surface.  That would seem to produce a catastrophic ice storm if it occurs though.

 

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LordBaltimore

LordBaltimore

Posted
Posted
4 minutes ago, SnowenOutThere said:

Seems like multiple studies disagree with each other. One I read/skimmed said that if we have a freezing layer of 3000+ feet below the elevated warm layer it’ll refreeze to sleet regardless. Just such an extreme setup to where it all breaks down. 

I'd imagine besides the depth of freezing layer there's also variability based on if the drops contain ice nucleating particles which then becomes a matter of if they were homogenously nucleated in the first place. Probably no way to tell

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