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Winter mix Sunday dec 20th

Nam 3km actually isn’t far off for wet snow flakes even near Charlotte per wet bulb, but it’s quite a stretch 71BD6490-6A4D-44FC-8C6C-17461417BD98.png72FF1192-786E-4626-B25A-9CACF838571E.png
 
Gfs has some onset snow showers for foothills and western piedmont of nc Sunday morning

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This sounding is from the Nam for upstate sc. about the only model with snow sounding in the upstate.


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Myfrotho704_ said:
View attachment 58669View attachment 58670View attachment 58671View attachment 58672
Me and Tim have been talking about this one and he’s going as far as saying this one could have accums, that’s a big could tho, because it could easily just be a Virgo event
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This one has the potential to be a sneaky little event for some. It could be a event that never gets a advisory but someone gets a surprise dusting to half an inch in the grass and on cars before ending as rain. That departing high pressure seems to be the reason for some marginal cold air. We will see best chance outside the mountains is likely the triad NC areas maybe Charlotte although I’m hoping for a little snow in upstate sc to but doubt it happens.


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Can’t see at work how are the WPC snow odds for tomorrow
 
Soundings from the 12k NAM stink and are similar to the 12z hrrr with most of us just way too warm in the lower levels.
 
Brad p just said flakes north of I-40 for tomorrow

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Myfrotho704_ said:
?View attachment 58736View attachment 58737
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Man that is so close. I mean, I think that sounding would produced a few flakes mixed in. It would be nice not to have to rely on an isothermal layer all the way up to 800 mb, and I think that's really what's going to kill this event. It looks like we're already forcing a ton of ascent, so it's difficult to imagine the precip could get much heavier to cover those last few degrees at the surface. If we could just get things a degree or two cooler anywhere aloft, we could see a more widespread changeover at least.

I bet there will be a few people, though, who get to see some huge mangled aggregate flakes. That's what you get when you are melting so much above the surface.
 
I guess he doesn’t know. Friday morning he said low 20s and places were upper 30s when I woke up.
 
RVD said:
Man that is so close. I mean, I think that sounding would produced a few flakes mixed in. It would be nice not to have to rely on an isothermal layer all the way up to 800 mb, and I think that's really what's going to kill this event. It looks like we're already forcing a ton of ascent, so it's difficult to imagine the precip could get much heavier to cover those last few degrees at the surface. If we could just get things a degree or two cooler anywhere aloft, we could see a more widespread changeover at least.

I bet there will be a few people, though, who get to see some huge mangled aggregate flakes. That's what you get when you are melting so much above the surface.
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Yeah it’s not impossible for last minute trends, but unlikely, 3km is close while the hrrr slightly mixes out the BL which kills it, (I though that was a bias the old hrrr has, I guess they didn’t fix it)
 
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Myfrotho704_ said:
1 degree less in all layers is all I’m asking View attachment 58768View attachment 58769
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The first sounding you showed here actually looks like wet snow to me and not cold rain w/ it being isothermal all the way down to about 950mb. In most situations, we can typically work with a near-surface warm layer that's ~2500 feet or so deep before a snowflake completely melts into a raindrop before hitting the ground. When you perform a back-of-the-envelope calculation for the height of the non-isothermal layer near the surface & account for Charlotte's surface elevation, with an above freezing layer emerging ~950mb, it's only ~1000-1250 feet deep, plenty shallow enough for frozen hydrometeors just above the surface to make it to the ground as wet snow.
 
SD said:
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RGEM for tonight looks to be significantly colder at the surface than the NAM or any other model. That cold air sticks around as precip sets in. But I guess RGEM doesn't have heavy enough precipitation to generate a strong isothermal layer like the 3km NAM?

These surface temps are a known bias, right?
low_temps_rgem.png
 
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