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NorthHillsWx

February 18-19 MAJOR Ice Storm Threat

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13 minutes ago, BullCityWx said:

12k NAM cut freezing rain totals in some of the triad because of sleet. 

12k keeps a large area of sleet through the storm. Could be the saving grace 

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For the Hickory area(including Morganton, Valdese, and  points west) GSP upped totals on my forecast grid point in Valdese to 0.60 once you add it all up for tonight/tom. Was 0.50 this morning good trends my friends. As long as you want this ICE Storm like me :) Also my low temp tonight is now 29 was 30 and high is now 34 was 36.

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There's a reason that the NAM family initialized dew points way too high- NAM consistently has less boundary layer mixing than GFS. On a day like today when when the sun is out and updrafts are bubbling up, there will be a lot of mixing up to about 850. The air at that elevation is drier; the more mixing there is, the more dry air is able to mix down to the surface. 

I don't know if current dew points (RDU holding at about 26 right now) will hold or whether they will shoot up once the sun goes down, but that's why we're seeing NAM dewpoint busts right now.

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Just now, wncsnow said:

Jason Boyers thoughts for WNC

FB_IMG_1613598940826.jpg

Wow big difference when you compare to GSP which gives you and me both 0.25 to 0.60 and Brad P. who gives us both 0.30 to 0.50. 

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9 minutes ago, btownheel said:

Soundings line up with that?

Imo no. 850s +5-7 seems too warm for sleet. 925’s are marginally conducive for sleet and i think that’s what the NAM is catching, but south of the va border looks like a freezing rain event to me with limited sleet

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Just now, wxduncan said:

Wow big difference when you compare to GSP which gives you and me both 0.25 to 0.60 and Brad P. who gives us both 0.30 to 0.50. 

I actually think his forecast looks good for McDowell County, can't blame him for being a little conservative 

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16 minutes ago, NorthHillsWx said:

Imo no. 850s +5-7 seems too warm for sleet. 925’s are marginally conducive for sleet and i think that’s what the NAM is catching, but south of the va border looks like a freezing rain event to me with limited sleet

One thing to think about with respect to sleet vs freezing rain when looking at soundings...the general rule is that once the warm layer exceeds +3C, the snowflake dropping down will completely melt (instead of partial melting of the snowflake when the warm layer is between +1C and +3C).  Once full melting of the snowflake occurs, the raindrop can't refreeze back into sleet because it no longer has ice nuclei to refreeze onto.  As long as the snowflake only partially melts, it can refreeze back into sleet because it still has ice nuclei contained in it.

See the bolded text below from: https://www.mentalfloss.com/article/91745/7-wintery-facts-about-ice-freezing-rain-and-sleet

Freezing rain forms when there’s an inversion layer present during a winter storm. An inversion layer occurs when a layer of warm air gets sandwiched between two colder air masses. Snowflakes fall through the warm layer and completely melt before reentering the subfreezing air near the surface. This newly formed raindrop can’t freeze back into ice because it doesn’t have a nucleus around which to freeze, so the raindrop becomes supercooled, meaning it remains in liquid state even as its temperature drops below freezing. Once the supercooled raindrop reaches the ground, the water instantly freezes into ice.

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1 hour ago, Iceagewhereartthou said:

Some roads near Easley have been brined, I guess bc of the WWA. Not expecting any issues here though.  

Same here..hwy11 and 123 brine city..my silver truck is kinda ashy now...lol

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3 minutes ago, griteater said:

One thing to think about with respect to sleet vs freezing rain when looking at soundings...the general rule is that once the warm layer exceeds +3C, the snowflake dropping down will completely melt (instead of partial melting of the snowflake when the warm layer is between +1C and +3C).  Once full melting of the snowflake occurs, the raindrop can't refreeze back into sleet because it no longer has ice nuclei to refreeze onto.  As long as the snowflake only partially melts, it can refreeze back into sleet because it still has ice nuclei contained in it.

See the bolded text below from: https://www.mentalfloss.com/article/91745/7-wintery-facts-about-ice-freezing-rain-and-sleet

Freezing rain forms when there’s an inversion layer present during a winter storm. An inversion layer occurs when a layer of warm air gets sandwiched between two colder air masses. Snowflakes fall through the warm layer and completely melt before reentering the subfreezing air near the surface. This newly formed raindrop can’t freeze back into ice because it doesn’t have a nucleus around which to freeze, so the raindrop becomes supercooled, meaning it remains in liquid state even as its temperature drops below freezing. Once the supercooled raindrop reaches the ground, the water instantly freezes into ice.

Skew-T Parameters and Indices (weather.gov)

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Just now, griteater said:

One thing to think about with respect to sleet vs freezing rain when looking at soundings...the general rule is that once the warm layer exceeds +3C, the snowflake dropping down will completely melt (instead of partial melting when the warm layer is between +1C and +3C).  Once full melting of the snowflake occurs, the raindrop can't refreeze back into sleet because it no longer has ice nuclei to refreeze onto.  As long as the snowflake only partially melts, it can refreeze back into sleet because it still has ice nuclei contained in it.

See the bolded text below from: https://www.mentalfloss.com/article/91745/7-wintery-facts-about-ice-freezing-rain-and-sleet

Freezing rain forms when there’s an inversion layer present during a winter storm. An inversion layer occurs when a layer of warm air gets sandwiched between two colder air masses. Snowflakes fall through the warm layer and completely melt before reentering the subfreezing air near the surface. This newly formed raindrop can’t freeze back into ice because it doesn’t have a nucleus around which to freeze, so the raindrop becomes supercooled, meaning it remains in liquid state even as its temperature drops below freezing. Once the supercooled raindrop reaches the ground, the water instantly freezes into ice.

One thing that is completely boggling my mind is the strength of the warm nose- I cant ever remember a sleet/zr event with such a strong warm nose (10-12C, which feels completely ludicrous) - We're in uncharted territory in that regard and I am completely flummoxed on if the algorithms that govern model phase changes will be able to handle this.

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Seeing Reports of 32 and and IP/FRZN (I doubt it’s Sleet) about 5 miles SE of Lafayette LA that’s DEEP South. 32 And FRZN Abbeyville LA Directly On Gulf Coast. My point is let’s start checking 18Z suite to see who had <32 that far south..... Basically I-10 Corridor 

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2 minutes ago, PantherJustin said:

Seeing Reports of 32 and and IP/FRZN (I doubt it’s Sleet) about 5 miles SE of Lafayette LA that’s DEEP South. 32 And FRZN Abbeyville LA Directly On Gulf Coast. My point is let’s start checking 18Z suite to see who had <32 that far south

While an interesting note, the air this system will be working with here has absolutely no connection to the cold air that settled west of the apps. I’d be looking north of here for temp/dew point trends vs model outputs in terms of verification of our winter event 

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1 minute ago, NorthHillsWx said:

While an interesting note, the air this system will be working with here has absolutely no connection to the cold air that settled west of the apps. I’d be looking north of here for temp/dew point trends vs model outputs in terms of verification of our winter event 

Gotcha thanks!

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16 minutes ago, BornAgain13 said:

The Weather Channel App has my area reaching 37 degrees tomorrow afternoon... nothing that I have seen in the guidance shows that...

Like I’ve always said, checking The Weather Channel for weather info is like reading People Magazine for investing advice.  :P

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5 minutes ago, ILMRoss said:

One thing that is completely boggling my mind is the strength of the warm nose- I cant ever remember a sleet/zr event with such a strong warm nose (10-12C, which feels completely ludicrous) - We're in uncharted territory in that regard and I am completely flummoxed on if the algorithms that govern model phase changes will be able to handle this.

This has been the fly in the ointment for this forecast for DAYS. It’s inexplicably warm for a LP track such as this. The 2002 event had +5 850’s and some models, as you pointed out, are predicting nearly double that, an absolute mid level torch! My thoughts are they are overdone somehow. Will be interesting to see how the mid levels actually play out through tomorrow, I have a gut feeling it’s overdone and models are too warm based on the warm 850’s, but we will see. As you said, uncharted territory 

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