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November 26-28 Coastal Storm Discussion and Obs


DCAlexandria

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This is the precip that may legitimately be snow on the 12z NAM.  Seems like the column is supportive of snow by 17-18z or so for DC/Balt and points west.

nam_namer_009_precip_p03.gif

The dca sounding is not all that great though. We're going to need some high rates. http://www.twisterdata.com/index.php?sounding.lat=38.9796&sounding.lon=-77.0523&sndclick=y&prog=forecast&model=NAM&grid=221&model_yyyy=2013&model_mm=11&model_dd=27&model_init_hh=12&fhour=09&parameter=SNOWIN&level=SURFACE&unit=none&maximize=n&mode=singlemap&sounding=y&output=image&view=large&archive=false

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:huh:  That sounding is perfectly fine for snow.  It won't accumulate, but it will snow.  

 

Edit...you linked the 21z sounding, at which point the precip is done or very nearly done.  At 18z it's more of a borderline sleet/snow sounding with a warm layer around 750-800mb that has temps near freezing.  

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What is the highest altitude on a sounding that can correlate to precip-type at the surface?

I'm not entirely sure I understand the question, but any altitude in which clouds and precip particles are forming is temperature dependent.  Precip typically forms in winter storms below 500mb (about 1 mile altitude), but in summertime thunderstorms can form higher.  Even in summer, rain droplets typically start as snow at those altitudes unless you're in the tropics but then warm as they fall.  

 

For winter precip type determination, it gets more complicated because the vertical temperature profile can waver back and forth above and below freezing with altitude.  The 18z NAM sounding for DC, for example is borderline sleet or snow as I mentioned.  The reason is that the snow might melt in that warm layer near 750-800mb if temps are above freezing, but then the column is below freezing from about 800mb-950mb.  Then the rain droplets would refreeze into sleet.  From 950mb to the surface it's not warm enough (and the warm layer isn't deep enough) to remelt those sleet pellets.  

 

FLIZZARD TIME!!!!

SNOVEMBER!  

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I'm not entirely sure I understand the question, but any altitude in which clouds and precip particles are forming is temperature dependent.  Precip typically forms in winter storms below 500mb (about 1 mile altitude), but in summertime thunderstorms can form higher.  Even in summer, rain droplets typically start as snow at those altitudes unless you're in the tropics but then warm as they fall.  

 

For winter precip type determination, it gets more complicated because the vertical temperature profile can waver back and forth above and below freezing with altitude.  The 18z NAM sounding for DC, for example is borderline sleet or snow as I mentioned.  The reason is that the snow might melt in that warm layer near 750-800mb if temps are above freezing, but then the column is below freezing from about 800mb-950mb.  Then the rain droplets would refreeze into sleet.  From 950mb to the surface it's not warm enough (and the warm layer isn't deep enough) to remelt those sleet pellets.  

 

 

SNOVEMBER!  

Thanks, the inability for the falling precipitation to fully melt near the surface is what confused me.

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Impressive temps early this morning on my way to work. 68 degrees at 4am and a few hours later, 20 degrees cooler.

 

I'm not going to enjoy the winter here am I? :( #easternshoreproblems

 

attachicon.gifsbyobs.jpg

my daughter just moved there; I like SBY and am pretty familiar with it as an old law school bud lives there and have visited him quite often in the last 30 years

as you know, there have been more than a few storms over the years that we saw the sun through cirrus or had spits of snow while SBY had 6-12"

that area seems to be on a roll the last few years too so I wouldn't count yourself out by any stretch

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