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Wintry ❄The Christmas Miracle❄(12-24/12-25)

FallsLake said:
So this is really modernweenie but for statistics it will be interesting on when the front passes tonight. For many, the lows for today and the highs for tomorrow will occur ~ midnight. If the front doesn't pass RDU by midnight, our high for Christmas day could be 60; even with the temperature in the 30s during mid afternoon tomorrow.
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Just to add to this--according to the HRRR, the front will have cleared GSO but not RDU at midnight, with temps in the mid 30s for the Triad but mid 50s in the Triangle at that time. If true, these two climate sites will record drastically different highs for Dec. 25.
 
I haven't looked at the NWS forecast for mby in a few days, but I see this has been introduced into the forecast.
Tonight
A chance of rain and snow showers before 10pm, then a slight chance of flurries between 10pm and 11pm. Mostly cloudy, with a low around 24. West wind around 15 mph, with gusts as high as 25 mph. Chance of precipitation is 30%. New snow accumulation of less than a half inch possible.
 
Yeah these flurries and snow showers are gonna be quite difficult to forecast the exact position. But some people are gonna get lucky

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Jon said:
Interesting. So it shows potential but it’s saturated with ice? Help me out here... I’m not used to reading such funky soundings. What is the sounding that I posted showing is literally occurring? Flurries reaching the ground? Connective fatties reaching the ground? It still seems like this moisture will have to overcome dry lower levels to me.
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The lower levels aren’t dry though in that sounding, if you looked at the corresponding sounding from pivotal weather, the lower level relative humidity is still greater than 80%, with a sub saturated layer that’s only 3000-4000 feet deep verbatim on the HRRR, that’s a pretty negligible dry layer if you ask me. Yes saturation with respect to ice is an additional percent or two lower than water which gives additional one or two RH percentage points in a sub freezing environment. If the HRRR came to fruition there wouldn’t be any concerns with dry air imo based on that sounding you showed. Oth, other models like the NSSL, ARW, & NAM are drier with a shallower mixed layer and they do look more concerning in that regard and I think the HRRR may be over mixing the BL which is causing it to produce more precip than the other cams. For ex: Simply mixing two relatively moist but unsaturated parcels leads to supersaturation because the mixing occurs linearly while saturation vapor pressure is exponential. Excess boundary layer mixing begets saturation and forcing for ascent
 
The 12z NAM is still showing changeover to all snow for the FROPA.
nam3km_mslp_pcpn_frzn_seus_10.png
 
BufordWX said:
HRRR not backing down for Christmas! I will cash in now.View attachment 59844
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The HRRR has been consistent since yesterday afternoon in wanting to have that band along the NC/SC line southeast of CLT. I can remember that other convective snow events in the area, that’s a spot usually has some of the higher amounts. I wonder what causes that.
 
FallsLake said:
So this is really modernweenie but for statistics it will be interesting on when the front passes tonight. For many, the lows for today and the highs for tomorrow will occur ~ midnight. If the front doesn't pass RDU by midnight, our high for Christmas day could be 60; even with the temperature in the 30s during mid afternoon tomorrow.
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Yep and an over/under killer lol
 
NewnanWetather said:
Learned that lesson more then once. Nearly had to go back through a frozen Maggie Valley. Going back around is no fun.
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Yeah it adds an extra hour and a half and the gorge going through Haywood ain't no joke there will definitely be NW flow cranking along the border all day tomorrow. Seen a many of wrecks waited 12 hours in traffic one time due to snow.
 
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HRRR 2m RH is sitting in the 50-60% range area wide, that’s honestly not that bad. Just for some perspective and food for thought, your average summer day that produces popcorn thunderstorms in the afternoon with temps in upper 80s-low 90s with dew points in the low-mid 60s in the Carolinas comes out to a low level Relative humidity close to 50% which is comparable if not lower than the background low level RH this event will have. Given that any snow we see tomorrow will be convective and characterized by steep low level lapse rates with near absolute instability in the low-mid levels, I think this is a somewhat valid comparison although the additional water vapor in the summer does make parcels more buoyant. Starting out with RH values equal to or greater than 50-60% are good enough to get the job done for many here imo.
 
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