griteater

It's out on the NOAA eval site - https://mageval.ncep.noaa.gov/model-guidance-model-parameter.php?group=Model Guidance&model=GFS&area=NAMER&ps=model

Yeah, that's what you see with the various ensemble members....some west and well developed...some east and well developed.....some east and weaker

FV3 doesn't develop the low and precip very much this run (low is farther east), but it has light snows in E NC. h5 wave looked similar to 18z overall.

It had an h5 improvement though

The overall setup is pretty good for a northern stream system. We get an arctic front to plow thru on Friday, then before there is time for a warm-up, the next wave dives into the trough fairly sharply. A good version of this type of setup would be the storm from just a year ago in mid-Jan...i.e. a Saskatchewan Screamer that manages to be sharp enough where it actually draws up some warm advection and forcing for ascent to generate precip

GFS is improved this run for next Sunday (yikes, long way out). Kind of looks like the decent FV3 run from 18z

Could be, I didn't think anyone could out snowmap WxBell, but maybe this one does lol. You know the SV map says total snow and doesn't indicate ensemble mean, so maybe it's a total of all members. It's showing some action at least

12z EPS has below normal temperatures (850mb) from day 6 to the end of the run at day 15, so that's a start. Here is mean snowfall on the 18z GEFS for days 7 to 16. I've seen worse

Southeast winter climatology doesn’t really warrant the hang wringing we see in here, but it’s part of the deal with watching model runs

NOAA temperature outlook for days 8-14 (Jan 25-31) "FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: WELL ABOVE AVERAGE, 5 OUT OF 5, DUE TO VERY GOOD AGREEMENT AMONG 500-HPA HEIGHT, TEMPERATURE, AND PRECIPITATION GUIDANCE ACROSS MOST OF THE FORECAST DOMAIN."

All NAO blocks aren't created equal. This is what a good one looks like on what I believe must be from the Euro Seasonal for February (image courtesy of @bennollweather). All long range caveats apply, as we won't be able to kick the can much longer.

Now here is a trend loop of the last 16 runs over the past 4 days of the GFS Ensemble Mean for Jan 28 (at day 10). The axis of the western ridging has trended east with it initially more thru Alaska, but now it's closer to the W Canada coast. This is a good position in between pure Alaska ridging (-EPO) which can sometimes be too far west (sometimes the U.S. trough can be too far west), and pure Western Canada ridging (+PNA) which can sometimes be too far east (cold, but sometimes on the dry side). Also, the polar blocking on the trend loop has waxed and waned, but the latest few images show a bit more Greenland blocking (-NAO).

Seeking out a winter storm prior to next weekend is a bit cart before the horse IMO (and as others have mentioned). Here is the GFS Ensemble Mean for days 0-10. As long as it continues to hold, the kickoff to a colder regime begins with this ridge building up along the western North America coast. That ridge goes up at day 5 now.

Today's Euro has one of the bigger arctic blasts you'll ever see at day 10

So the MJO deals with where convection is being enhanced / suppressed in the tropics, and this typically has a large influence on the EPO and PNA patterns across the Pacific and North America. For this time of year, when the convection is enhanced from the Eastern Indian Ocean, to the Maritime Continent (Indonesia), to the Western Pacific (phases 3-6), a +EPO / -PNA pattern is favored (central / eastern U.S. ridging). When the convection is suppressed in those same regions (phases 7-8-1-2), a -EPO / +PNA pattern is favored (central / eastern U.S. troughing). But that is what is "favored". Other processes will influence the overall pattern. With the NOAA MJO update I posted a few pages back, they favor the MJO making a quick trek through phases 3-4-5 in week 1, before making a move toward phase 7 in week 2, and they state that the MJO is not expected to have a large influence on the pattern. In spite of that, for a cold eastern U.S., we never want to see the MJO in the warm phases (3-4-5-6), so it remains to be see whether forecasted -EPO / +PNA patterns come to fruition - https://www.americanwx.com/bb/topic/51836-mid-to-long-term-discussion-2019/?do=findComment&comment=5117686 The MJO does have some influence on the AO and NAO but the processes which produce AO/NAO blocking are complex and can be largely separate from the MJO, including stratospheric influences.

The day 15 EPS analogs have both Atlanta Snowjams, lol - Jan 1982 and Jan 2014 (image courtesy of @commoditywx)

From NOAA's latest MJO Weekly Update...

Winter temperatures to date

I asked Anthony (HM) about him seemingly predicting the upcoming polar blocking. Obviously, the Euro Weeklies and other weeklies are showing it, but it's nice to see that he feels there are legit physical mechanisms for the blocking. So when he says momentum loss, my interpretation is that he is referring to typical strong westerly flow in the upper atmosphere and stratosphere slowing down (post-SSW effect and other processes I'm sure), which opens the door for waviness in the flow and blocking. Also, he mentions typical Nino trough/ridge positioning to go along with the blocked flow (western ridge / eastern trough).

Last Thursday's Weeklies (above) compared to tonight's for the same dates (Jan 24 - Feb 13)

^ -NAO is much better in the analog composite compared to the actual EPS

In the meantime, here are the top 10 analog match dates (your favorite Mack, lol) for day 11-15 from the 12z EPS (courtesy of @ChrisDevitoWX) 12z EPS Day 10-15

It’s happened before - Jan 1994. Rainstorm sandwiched in between 2 big arctic blasts with single digit lows. 500mb configuration has to be right along with having the cold air

Yes, it was an official SSW with zonal winds reversing from westerly (+) to easterly (-) at 10mb in the stratosphere averaged over the globe at 60N, and also occurring at a time when the strat PV should be at its strongest of the winter. The wind reversal has lasted 10-11 days now and may end in a week or so (pending). The red/purple/orange line is this year. The blue line is last year, where the SSW wind reversal lasted 17 days in February. I don't know of the exact definition of an SSW split vs. displacement, but I would think this one qualifies as a split just based on the 10mb height images. However, it wasn't a violent split like we saw last year and in other years where there is strong heat flux that comes up from the troposphere in conjunction with heat flux in the stratosphere. With this one, the heat flux that weakened the strat PV was focused in the stratosphere alone - note the focused orange colors above 100mb in the stratosphere near Christmas. As far as the SSW's effect on the AO, we see that the effects have been hard to come by so far. "Northern Annular Mode" here is essentially the AO, so the blue coloring shows that the AO has turned negative in the stratosphere, and is trying to work its way down into the troposphere on the right side of the image, but it remains to be seen how forceful it will propagate downward.

Here's the WSI version of the Euro weeklies. Week 4 looks fantastic