Webberweather53
Meteorologist
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Wintry Potential Dec 13-14 Ice Threat
- Thread starter Webberweather53
- Start date
Ethan80963!
Member
NAM's not backing down
Ethan80963!
Member
FWIW the ICON has temps in the CAD areas just above freezing with heavy precip falling at hr 69
Blue_Ridge_Escarpment
Member
And the ICON is horrible with 2m temps. So that’s a good sign.
according to SREF mean, likely freezing rain advisory up to 0.1” for Surry/Wilkes and Winter Storm Warning for Ashe, Alleghany and Watauga up to 0.3”. A little sleet or mix will likely prevent any ice storm warnings. NWS GSP counties mostly the same for northern mountain counties near the blue ridge but very little immediate foothills.
Little to nothing for Yadkinville, Statesville to Charlotte. Maybe special weather statement if temps are there with precip. ~sref mean
Plumes are trash..but I mostly agree
NWS Blacksburg going with 0.1 to 0.2 for most which prevents any Winter Storm Watches in NC. AFD also says mix of a sleet/snowflake will mean Winter Storm Warning over Ice Storm Warning if amounts increase.
Moderate Risk issued for western NC from WPC. If trends do not worsen, I expect a Winter Storm Watch for Alleghany, Ashe and Watauga. 
A light coating of snow/sleet would certainly help the freezing rain stick better. Hard to tell if we have precip reaching the ground when temps are low to mid 20s and dry air. These micro-features won’t be picked up on models or soundings. Mostly talking about elevations 1,000 to 2,500ft. If you go to high up it will hurt you in this setup and likewise if you are to far south or East.
Dont you need temps solidly below freezing to get significant icing ? Seems like 31 or 32 is too warm to do major icing.
packfan98
Moderator
Not for tree tops and power lines. Anything below freezing will do the trick, especially at night. The ground and road temps can be a factor with any potential accumulations there. The duration and rate of precip is important as well.
Usually, the duration of the precipitation is the issue when you have temps just at or below freezing. You'll get more runoff at 31 than you will at 27. If it rained for 5 days straight at 31, you'd see major icing. But that's unrealistic. At 32, you really reach an equilibrium due to the freezing process and you don't get significant accrual.
Yeah heavy rain at 32 is hard to accumulate. I think the thought of lighter precip moving in ahead of everything is what’s causing WPC to up these risk percentages?
It also matters where those temps are. Bridges and overpasses remain colder after being in the 20s just prior. Also how much significant ZR is wasted if it starts as sleet/snow mix? And a surface of sleet would be colder than actual temp. GFS is showing pockets of 32 or less at lunch time Friday after quiet a bit, so I wouldn’t rule out frozen precip for much of the day given how stubborn CAD is to erode esp Mount Airy to Hickory.
ForsythSnow
Moderator
Light rain will accumulate greatly at temps just below, but more heavy or moderate will actually raise the temperatures up and melt the ice that already has accumulated unless the temps are around something like 28 or below.
Ethan80963!
Member
I'm not writing this system off just yet. I'm waiting until after the first system moves through so models can see what comes from it first. Tomorrow's 12z models will be in their prime after this first system moves. I'm also not writing it off after seeing that the WPC is pretty confident with it.
Temps will need to be 29 to 30 for a good period of time to see anything on roads. At 30 on bridges, overpasses and tree tops you will see some glazing. Possible shaded areas but at those temps minor event unless stays around 30 for long period
WxBlue
Meteorologist
WPC only have KML/shapefile available for greater than 0.25 inch... but the odd of that isn't looking very likely per them.
