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Wintry February 19-21, 2020 Winter Storm

Rain Cold said:
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.
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For now an inch or two definitely is but I do think the NAM provides us w/ a reasonable ceiling if everything lines up in our favor the next day or two. The lack of run-run consistency in the Euro & EPS certainly makes me skeptical to put a ton of stock into it and the UKMET is progressively adjusting to the wetter solutions provided by the GFS, ICON, & CMC & some of their respective ensembles. A GFS - ICON blend is the consensus solution atm and one I'd momentarily lean towards.
 
Nerman said:
You have to like this trend from the GFS for the Carolinas.

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When the GFS ticks NW inside day 2-3, it's almost always a permanent change. That along w/ the SREFs supporting the ECMWF plus stereotypical global NWP biases w/ overrunning precipitation and the lifting mechanisms that augment it, make me really skeptical of the drier solutions offered by the EPS, Euro & UKMET atm.
 
Webberweather53 said:
When the GFS ticks NW inside day 2-3, it's almost always a permanent change. That along w/ the SREFs supporting the ECMWF plus stereotypical global NWP biases w/ overrunning precipitation and the lifting mechanisms that augment it, make me really skeptical of the drier solutions offered by the EPS, Euro & UKMET atm.
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I agree. The CMC, GFS, ICON are all basically identical to the NAM in regards to precip extent. They just have less qpf.

From a forecasting standpoint I’d still cut the NAM totals in half for now. But if it continues to show this solution and 3km backs it then maybe it’s legit.
EURO seems to be out to lunch struggling with this setup.
 
Despite how reliable the ECMWF & UKMET typically are, it's really, really hard for me to buy into the drier solutions offered by the Euro & EPS given that most of our precipitation will be driven largely by low-mid level warm air advection. I legitimately can't recall a single instance where WAA has been generally overestimated.

gfs_temp_adv_fgen_700_seus_11.png


gfs_temp_adv_fgen_850_seus_11.png
 
Fountainguy97 said:
The NAM has been trending north with the precip and low pressure for a day now. We need to watch for this to stop over the next day. Then we can dive into amounts.

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While the LR NAM is often not the most reliable, I actually don't think it's a coincidence whatsoever that given most of our precip in this event will be driven by warm advection (plus frontogenesis), that the NAM also happens to be the most aggressive with the precipitation here. I suspect this might simply be a fatal flaw in the globals, especially the ECMWF unless of course the synoptic pattern changes wildly between now and late tomorrow.
 
Webberweather53 said:
When the GFS ticks NW inside day 2-3, it's almost always a permanent change. That along w/ the SREFs supporting the ECMWF plus stereotypical global NWP biases w/ overrunning precipitation and the lifting mechanisms that augment it, make me really skeptical of the drier solutions offered by the EPS, Euro & UKMET atm.
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So the SREF is only good for showing what’s not gonna happen? Lol


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Webberweather53 said:
While the LR NAM is often not the most reliable, I actually don't think it's a coincidence whatsoever that given most of our precip in this event will be driven by warm advection (plus frontogenesis), that the NAM also happens to be the most aggressive with the precipitation here. I suspect this might simply be a fatal flaw in the globals, especially the ECMWF unless of course the synoptic pattern changes wildly between now and late tomorrow.
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I guess that’s why the NAM is a mesoscale model.
This precipitation is driven by mesoscale forces that globals probably will have a tough time locking onto.

It will be interesting to see if the NAM backs off of qpf any.
 
ForsythSnow said:
Still have that warm nose early in the event over N GA. Might not end well and be too far north for many.
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Yeah, this simply just won't work for North GA. This is from Lake Lanier. It's amazing the consistency across the models for this too. I can't find a single one to hug at the moment.

Nose.png

MS, AL, GA need a lot to change in a little over 48 hours.

namconus_T850_us_43.png
 
In my opinion, this can only adjust so far to the NW, given the press of HP and relatively flat flow. At this point the concern is precip amounts and timing, with the northward extent of precip likely being extreme southern VA.
 
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