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scottd

What precip type is reaching the surface at CLT?

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Based on the GFS forecast sounding shown here in the WeatherSpork app below, what precipitation type would you expect to see reaching the surface at the Charlotte Douglas Int'l Airport (KCLT) at 18Z on Sunday? And of course, credit for the correct answer involves also answering why.

 

PrecipType.thumb.png.d3dbf19c5ccd17e2713045d3dd57b40a.png

 

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3 minutes ago, Marauder said:

Snow?

 

Can't get credit for the answer unless you give some details as to why. ;)

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2 minutes ago, scottd said:

Can't take credit for the answer unless you answer why. ;)

Well, from my untrained eyes, it looks like the temp & dewpoint at and near the surface will be below freezing. Parcel seems to be saturated with a cloud layer hovering around 1000'. Getting warmer? 

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Freezing or frozen rain?  Inversion layer down low below freezing, temps at dewpoint above freezing up high falling through it

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Sleet given the narrow band of warm air and thick layer of below freezing air below it.  Freezing rain would be more likely if the band of warm air were much thicker and the cold air band thinner.

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Freezing rain maybe sleet mixed with rain, just below 0 c on ground with a slight temp inversion, clouds are quite thick, great time for boots, tks or staying home watching TV

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All good instincts so far.  The answer is that it's could be just about any precipitation type or mixture given this profile.  The cloud top temperatures are still kind of warm, but cold enough to start to build ice crystals and snowflakes.  The temps only climb a degree or two above freezing over a 3,000 ft layer.  This isn't typically enough to melt snow completely.  But if any melting does occur in that layer, you will likely see the drop maintain a slushy core and there's a pretty generous layer of cold air just above the surface to refreeze the slushy core into an ice pellet.  

Here's the tough issue.  If complete melting occurs, you may get freezing rain at the surface - if the surface temperature happens to be below freezing (it's pretty close).  If it's above freezing, it's just rain (although freezing rain aloft).  If it freezes into an ice pellet, then it'll reach the surface as an ice pellet.  If it doesn't melt much at all, then you will get snow and if it melts just a little you may get graupel or snow grains.  And the final catch-all is that there could be a mixture of snow, freezing rain and ice pellets...that would be my forecast at this point.

So something like -FZRAPLSN    

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Hmm.  Well the atmosphere is saturated up to about 17000 ft with the temp and dew point running together below that.  The temperature inversion briefly goes above freezing, but that's clear up at 5000' or more.  That's too far to fall through freezing air to not refreeze before hitting the surface, so no freezing rain.  I'm saying sleet.

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Actually the GFS MOS valid at 18Z says "Z" which means freezing precip or a mixture.

MAV.png.94522d63ae85e714ee4e57b93cfc1497.png

 

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I really enjoy these little tid-bits of knowledge to learn from. Thanks Scott.

These type of exchanges are what make this site so valuable. 

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8 hours ago, L. Trotter said:

I really enjoy these little tid-bits of knowledge to learn from. Thanks Scott.

These type of exchanges are what make this site so valuable. 

You are very welcome.  You'd really like the next live workshop I'm doing starting in the Spring.  It'll be a one day program that will discuss inflight weather hazard avoidance.  The workshops I've done in the past 15+ years have all been (for the most part) oriented around preflight weather analysis...this will be one that focuses on the actual flight hazards with a little preflight analysis thrown in.  

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9 hours ago, L. Trotter said:

I really enjoy these little tid-bits of knowledge to learn from. Thanks Scott.

These type of exchanges are what make this site so valuable. 

Lee I second your statement, illustrations followed by results IMO allows my brain to absorb the content, 

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3 hours ago, Danb said:

Moderate ice pellets at 15Z

Looks like I got two out of the three precip types right. Not going to mix in snow because the warm nose turned out to be too warm. So, just -FZRAPL. This shows, however, that it is snowing aloft, but the snowflakes are partially melting and refreezing into little nuggets. 

SurfaceOBS-CLT.thumb.png.f3a89cbf63168ceba88a6e41e0a10d32.png

CLT-Skew-T.thumb.png.6c1c40a572d674ecc7eb4f74791a27a0.png

Overall in the S. Charlotte area, this turned out to be a very cold rain for the most part. Got some moderate ice pellets overnight, but nothing really to write home about.

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