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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.

View attachment 35171
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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.
 
I'm curious to see what other mesoscale models think of the NAM and its bullish handle on frontogenesis. If they agree, I could see globals caving to the NAM at the last minute. Earlier on in the storm's development, I would be uneasy about the lack of Euro, but now I just consider it an outlier.
 
Not sure whether to put the SREFs in the whamby thread or here but...
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At this point I feel pretty good that we can get a general 1-3" type event....anything over that frankly is butter. I think the upside to this is bigger than the downside, don't see any real chance this bust so bad I don't see at least a few inches of snow. I think the upper end of this is 8-12" in a few streaky bands somewhere over central eastern NC if the NAM is right and all the parts come together perfectly.....would also not be surprised at all to see some 3-6" totals over a decently large area....just need the NAM to have this right.
 
Frustrating Winter so far in parts of Alabama and West Georgia. We got skunked on last system that came thru while others seen solid snow totals just to east or north and this system going to skunk all of us except for northern counties just by a hair again unless we get colder temps to pull thru and that's gonna be razor thin once again
 
malak05 said:
Frustrating Winter so far in parts of Alabama and West Georgia. We got skunked on last system that came thru while others seen solid snow totals just to east or north and this system going to skunk all of us except for northern counties just by a hair again unless we get colder temps to pull thru and that's gonna be razor thin once again
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I feel ya brother. Full skunk mode here as well. ((40 mi east of Atl). We need a Jackson miss to Maine mauler to set this right!!!!
 
Morehead city NWS putting their eggs in the euro basket. Basically calling for an inch where the Nam has almost 10 to 12.


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.
 
@Webberweather53 are there any close match analogs from previous storms in your winter storm database based on current guidance?

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Forevertothee said:
The NAM has shown more rain or sleet even for 85 N. I’m concerned the warm nose is going to be an issue.


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We really need to get rid of this thing, not just for N GA, but for yours as well. Unfortunately warm noses almost always happen. However in this case, the warm nose isn't building in through the event, it's fading out. It's how fast we can knock this thing out that matters over its presence, because it's there at the beginning.
 
Shaggy said:
Morehead city NWS putting their eggs in the euro basket. Basically calling for an inch where the Nam has almost 10 to 12.


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.
Click to expand...

Which completely makes sense, and is the right call. In my opinion, if the NAM holds serve through today and tomorrow and other short-range models such as the RGEM supports such a solution(along with the Euro caving, if it does), then I think it will be considered more by NWS offices
 
NWS Huntsville is not impressed.
"Although not indicated in the current
grids, a brief period of sleet will be possible for most of the
forecast area at the onset of precipitation, based on thermal
profiles in the 20/09-12Z timeframe. However, as the rate of
hydrometeor production increases aloft, the low-level airmass will
modify to support very cold rain or perhaps a rain/snow mixture for
portions of northwest AL/southern TN."
 
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