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3/11-3/12 Winter Storm


BornAgain13

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31 minutes ago, PackGrad05 said:

Is the lack of precipitation in central NC due to subsidence as the air moves lee of the mountains?  Just wondering why the cut off...

 

5 minutes ago, PackGrad05 said:

Any chance that precip shield moves east?  What will it take?  (dynamically,  not miracle-wise)

Agree with cold rain, that you'd want to see some sharpening of the 500mb wave - that would translate down to 700mb / 850mb as well.  The limited dynamics with this system associated with the snow in terms of frontogenesis and 850mb warm advection on the NAM appear to roll thru TN to S NC / N SC then toward Wilimington.....as opposed to hooking back to the NE into NE NC

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4 hours ago, burrel2 said:

I'll gladly cash out with this.

 

It's becoming apparent that there is potential for a little accumulation in the upstate Sunday morning.  We will likely lose up to 1/4 inch of liquid to cooling the boundary layer before flipping to snow that sticks on grass.

It is all going to come down to banding and how that sets up over the area. Some models seem so have a heavy axis of precip setting up fairly far south, from say athens to columbia, SC. Other models have it more north.

If a band of heavy precip does form over area's with subfreezing 850's I think said area will get a decent 1 to 3 inch thump Sunday morning. 

nam4km_asnow_seus_21.png

It's interesting to note the higher resolution models,  nam, 4km nam, 3km nam, ICOn,and rgem all show that narrow band of heavier precip...with the 4km/3x nam being a little further south with it. For those on the edge....keep taps on the 925 to 950mb temps....as that is likely the rain/snow transition.... The 925mb temps crash really fast after 06z from the east/northeast in sc....and end up being quite cold by 09z for most of south carolina. They also fall quickly from the northwest over al/ga..but it won't happen until the tail end of the precip.  Unfortunately for the heart of north ga (atlanta to athens)....will be the  last place to see cold enough 925/950mb temps. Best chance for a change to snow before ending looks to be north/east of athens and west/northwest ga outside the mountains. 

 

 

 

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5 minutes ago, wncsnow said:

I am going to be back in Marion, NC this weekend and look to cash in and might cash in again next week in Danville.. I really think the increased amounts in SW NC could be due to some type of mechanism increasing lift such as a lee trough

Welcome home!!! Hope we can cash in for one last horrah maybe two.

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GSP disco, and they have posted some watches and warnings.

Short term /Saturday night through Monday/...
as of 230 PM EST friday: forecast confidence is gradually improving
as the NAM, GFS, and CMC are exhibiting better agreement in the quantitative precipitation forecast
and thermal fields for the weekend event. The 12z European model (ecmwf) remains the
most conservative on snowfall across the region, but the general
placement lines up fairly well with the other models.

For the specifics, a 500 mb shortwave will dive rapidly from the
plains states Saturday evening to the southern Appalachians Sunday
morning. Ahead of this wave, a 140 kt upper jet streak will stretch
across the mid-Atlantic region and maximize upper divergence over
our area by daybreak Sunday. An 850 mb baroclinic zone stretched
across the forecast area will see upglide activation Saturday
evening, with isentropic lift maximizing during the overnight hours.
Meanwhile, deep moisture will develop overhead from both Gulf
moisture sources at low levels and moisture accompanying the short
wave at mid and upper levels of the atmosphere. Any brief warm
nosing at onset in the thermal profiles will wet bulb quickly to
support all snow except in the southeast half where the surface
based warm layer may be too deep for snow for most of the event.
Warm Road surfaces could also eat into the accumulation potential,
especially in foothill and Piedmont locations. But, improved rates
during the period of peak forcing early Sunday morning should
overcome most ground temperature issues across the snowy areas. All
told, will be upgrading the watch to a Winter Storm Warning, adding
a tier of Winter Storm Watch to the southern NC mountains, and
posting snow advisories across the NC foothills and out along I-40
where accumulating snow confidence is highest. The Charlotte Metro
area and Rabun County Georgia could well need advisories at some point,
but will await improved confidence.

850 mb northwesterly downsloping flow should end precipitation
Sunday morning for most areas, with possible lingering weak banding
over the NC mountains. It does appear that mid level drying could
cut off ice nucleation over the mountains for some light freezing
rain/freezing drizzle at the very end of the event. However, that
appears to be a narrow window and lingering showers could loft
moisture into the ice Crystal zone, so no freezing ptypes will be
mentioned. A 10 am expiration on all west-southwest hazards seems fine.

A brief lull in the upper support and moisture will then occur
Sunday afternoon and Sunday night before a more prominent wave
begins to sharpen up over the Central Plains and digs through the
Mississippi River valley on Monday. Upglide moisture will return
from the south through the day on Monday as flow turns southerly
atop the strengthening cold air damming layer in place across the
region south of 1033 mb high pressure centered over NY/PA. The main
source of uncertainty for Monday will be how much separation occurs
between the lingering coastal/offshore waters system and the next
system approaching from the west. The European model (ecmwf) is an outlier in keeping
very little separation in the moisture between systems while the
GFS/NAM/CMC all feature good late Sunday drying and a longer lull.
Mixed ptype issues seem fairly certain as the 850 mb zero isotherm
moves north through the day, pinching any snow/sleet areas back
toward the northern Blue Ridge through late day. Any convection
should stay south and southwest of the forecast area in the warm
sector Monday as The Wedge intensifies. Maxes should struggle
through the upper 30s/lower 40s given the cold air damming Monday
afternoon.

&&
 

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