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Wintry February 19-21, 2020 Winter Storm

GSP

SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
As of 215 PM EST Tuesday: The forecast has trended a touch colder
for the period of interest Thursday into Thursday night. The setup
looks good for cool and dry air to spill into the region behind the
frontal boundary settling just south of the area Wednesday night.
The operational models and the associated SREF/GEFS plumes now all
bring accumulating snow potential down to the I-85 corridor, from
GSP to CLT. There are several wrinkles in the forecast, however. The
NAM profiles exhibit a bit more of a warm nose later Thursday as
profiles wet bulb down in the returning upglide moisture over the
frontal zone. The warm nose appears transient on the NAM profiles,
and is less prominent for all but the extreme southern tier on the
other models and blends. Thus, the thinking is that although brief
mixed ptypes are possible at times, the forecast will be
predominantly a rain/snow line issue. The deepest forcing and
moisture should cross the region Thursday afternoon as upper
divergence ramps up and a positively-tilted shortwave dives
southeast from the upper Midwest into the central/southern
Appalachians. Meanwhile, surface low pressure along the frontal
boundary will deepen along the coastal waters and a window of decent
frontogenesis will set up over the central and eastern Carolinas
into Thursday evening. The back edge of this frontogenetic axis
could flirt with our I-77 Piedmont Counties - something to watch out
for as it would mean better precipitation rates.

All told, the best 2 to 3 inch snow accumulations for this
relatively short duration event should affect the higher ridges of
the NC mountains, with lighter accumulations east of the mountains
and mainly northwest of I-85, but with a dusting southeast of the
Interstate. Some wintry weather potential will be featured for most
zones in the HWO this afternoon, but no Watches will be posted at
present.

Drying should occur rapidly behind the passing wave Thursday night,
unless any lingering bands of precipitation west of the coastal low
persist east of I-77. Dry ridging will set up over the southeast on
Friday with continued cool temperatures.



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warm nose evident still, a bit more north too.
namconus_ref_frzn_seus_39.png
 
Another impressive snowstorm on the NAM this run, and there actually been a trend to a weak low pressure around the gulf coast areas View attachment 35289
If only that was our key feature...Miller A would have been nice...should help on the backend though for those who get rained on for most of the event?
 
This is not a reflection of what scenario I’m pulling for or what I think will happen but here’s something to keep in mind; not one EPS member looks anything like the NAM.
 
wow, on 3km nam charlotte gets rid of the warm nose after hr48 and then we have an all snow sounding if sfc temps cooperate. interesting...
 
Soundings here now indicating sleet and snow versus the 12z all snow soundings.

The soundings are all snow for the most part though maybe some sleet the first hr mixed in but this is 98% all snow for PGV....this is the sounding right when it starts....not worried...

2020021818_NAM_051_35_58,-77_36_severe_ml.png
 
The temperature profiles on the 3k NAM vs 12K is ever so slight that makes this really interesting. The 12K has a warm nose of a degree or so that causes it to start as sleet for 2-4 hours and the 3K has the warm nose basically not there. The 12K still has a good swath of 2-5 inches with the sleet. The 3K around 1-4 inches. The good thing is the 3K is better at temp profiles so we could be looking at a bigger dog in the upstate up I85 to Charlotte.
 
Here’s the thing about frontogenic bands, they normally arrive earlier than forecasted, they normally have intense rates, when it moves in, snow immediately becomes heavy, not light snow for some time to heavy, it becomes heavy quick, and also areas outside the intense frontogenesis can get a nice ol minumum
 
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