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Wintry February 19-21, 2020 Winter Storm

Write up by MHX, guess they are going with the Euro over the NAM/GFS

CAA is expected to commence late Thursday as the low departs to
the east, and it appears increasingly likely there will be
enough moisture in place for colder air to realize, resulting
in a change from rain to snow overnight Thursday night into
Friday. Almost all the global models now show some form of
accumulating snow for eastern NC during this period although the
forecast totals vary quite a bit. The GFS/NAM are by far the
most aggressive, bringing snow into the picture by late
afternoon resulting in higher accumulations (north of 4" in some
spots). The ECMWF delays the onset of snow until evening and
has much more muted amounts. Today`s forecast leans toward the
ECMWF for a couple of reasons:

1.) The deterministic ECMWF and the EPS (Euro ensembles) are in
strong agreement, with the ECMWF being the most stable solution
the past few runs. The EPS probability of 1" of snow or greater
has been around 45-50% for the last few runs.

2.) The GFS ensembles average a bit lower than their
deterministic counterpart, and in fact are close to the ECMWF
and its members.

Have put snowfall accumulations in the grids, although even then
this is under the ECMWF solution due to expected warm surface
temperatures which should initially melt the snow (apart from
grassy surfaces and higher elevations) and the fact that coastal
winter storms like this generally feature SLRs well below 10:1.
For now, show generally under an inch for interior zones with
lower amounts towards the coast. It should be emphasized this
forecast is fluid and will be closely monitored, but at this
time it does not appear to be a high-impact event.
 
Myfrotho704_ said:
If the euro craps the bed and starts agreeing with other models, NWSs are really gonna start scrambling and upping the threat
Click to expand...

Yes, but it is much better to increase totals going into the event than the opposite. Conservative forecasts by the NWS/TV Mets should not be surprising at this point--and they are right to point out the potential limiting factors. The lack of support from the EC/UK remains disconcerting. Maybe the NAM is leading the way...or maybe not. lol
 
Seeing the model spread now, there really isn't clear guidance - it may come down to just watching the event unfold and seeing how things are verifying.
 
I have to say over night trends for the upstate was a step back. This is clearly a big hit for Eastern sections of the southeast though more specifically north eastern NC. But areas north of 85 in upstate. We be lucky to see a Dusting to 1.5 inches while high elevations close to sc/nc border gets 2-3 inches. Temps will be a struggle for upstate with .25 Qpf to work with which some falls as rain


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WPC 12z snowfall graphic (95 percentile)
5074e803b43b999c0f3b8cb14353ee0e.jpg


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metwannabe said:
NAM doubles down, GFS increased and Euro step back.... hard to go all in without the Euro. Big 12z runs today

Yet seeing the WPC maps, going to be interesting ti see how this unfolds
Click to expand...

I generally agree with this 50th percentile forecast for now given how much uncertainty there is atm, maybe an inch or two in favored areas of the south-central coastal plain is a conservatively reasonable outlook for now. This is obviously almost certainly going to change.

wpc_snow_72h_50_northcarolina_72.png
 
metwannabe said:
NAM doubles down, GFS increased and Euro step back.... hard to go all in without the Euro. Big 12z runs today

Yet seeing the WPC maps, going to be interesting ti see how this unfolds
Click to expand...

Imo the euro 7h maps don’t match up well with what it’s showing at the surface. I think it may be having an issue resolving this tbh and wouldn’t be surprised to see it start caving soon. It already has caved some in recent days when it was the southern outlier and then finally jumped north.
 
Jessy89 said:
I have to say over night trends for the upstate was a step back. This is clearly a big hit for Eastern sections of the southeast though more specifically north eastern NC. But areas north of 85 in upstate. We be lucky to see a Dusting to 1.5 inches while high elevations close to sc/nc border gets 2-3 inches. Temps will be a struggle for upstate with .25 Qpf to work with which some falls as rain


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Click to expand...
I didn’t see that at all. The NAM was decent and 3K actually had snow breaking out along and north of 85 as precip began rolling through.
 
iGrey_X said:
I didn’t see that at all. The NAM was decent and 3K actually had snow breaking out along and north of 85 as precip began rolling through.
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There’s a lot of sleet sounding north of 85. That’s probably why snow totals could be kept down.


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Here is what CAE is thinking at the moment:

Some questions about precipitation type Thursday
nt, mainly to our NE. Latest model ensemble means indicate some
light snow accum across our E/NE FA. Local top down tool
indicates a period of rain/snow mix Thu nt for the central and
east FA. Confidence limited due to several key factors in our
local perfect storm approach for significant winter weather not
being met. Main issue is cold air not being in place before the
onset of precip but rather is coming in as the
precipitation/moisture is shifting out. Even if a period of
light snow occurs, surface temps appear will be above freezing
and warm soil temps would lead to melting and reduced impacts.
Will leave in rain/snow mix for Thu nt but will not indicate
snow accum at this time.
 
Webberweather53 said:
I generally agree with this 50th percentile forecast for now given how much uncertainty there is atm, maybe an inch or two in favored areas of the south-central coastal plain is a conservatively reasonable outlook for now. This is obviously almost certainly going to change.

View attachment 35164
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I still think an inch or two is probably the most likely outcome, but it is good to see moisture increasing slightly as we move in. I feel like we're getting scammed by the NAM, though. I mean, I figured we'd get a couple of these big snow maps, but I thought it wouldn't start that until later today or overnight tonight.
 
Nerman said:
This is well before the moisture even arrives. If it verifies I think you've got a very quick changeover to all snow.

View attachment 35167
Click to expand...
Which is really what the 3K was showing. There’s a warm nose along from Anderson to Laurens to Union SC north that is 32 degrees at around 825 which really isn’t even a warm nose. I’m not really even looking at globals at this point as they have been too reckless at this point and are just now even getting moisture into the areas.
 
The NAM is not backing down. Thing is the Canadian agrees with it, so it is not alone. The GFS is showing more than the Euro, too. Not sure how you can go with the Euro instead of it being an outlier when it is so far off from the other models.
 
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