WxMan1

A little less than 3" here in Crofton MD as of 9 pm.

Yeah...about that... The Rapid Refresh Forecast System -- RRFS -- will ultimately replace the current CAMs, including the NAM, HRRR, ARW, ARW2, and HREF suite. Many aren't on board with that, at least right now, given (a) the poor verification of the RRFS at this point, and (2) while the RRFS is an ensemble, it's ensembles are of the same system. Whereas the HREF is comprised of an ensemble of multiple (different) systems. Not looking forward to that day...hopefully it'll be put off. Rapid Refresh Forecast System GSL, NCEP/EMC, and other partners are working together on a project to design a single-model, convection-allowing, ensemble-based data assimilation, and forecasting system called the Rapid Refresh Forecast System (RRFS). This project aims to develop advanced high-resolution data-assimilation techniques and ensemble-forecasting methods while supporting the unification and simplification of the NCEP modeling suite around the FV3 model. (<-- But the FV3 has been pretty crappy verification-wise). Within the NOAA model unification effort, the RRFS represents the evolution of the NAM, RAP, HRRR, and HREF systems to a new unified deterministic and ensemble storm-scale system. This new system is targeted for initial operational implementation in late 2024 as a planned replacement for the NAMnest, HRRR, HiResWindows, and HREF. While the standalone regional (SAR) FV3 model is being developed for convection-allowing forecasting of a limited area (CONUS), other possible components of the RRFS are being tested now in the experimental, WRF-based High-Resolution Rapid Refresh Ensemble (HRRRE). Experimental runs of the HRRRE at GSL are focused particularly on: Improving 0-12 h high-resolution forecasts through ensemble-based, multi-scale data assimilation Producing spread in 0-36 h ensemble forecasts through initial-condition perturbations, boundary-condition perturbations, and stochastic physics. GSL is the owner and responsible for all data in this AWS S3 Bucket.

I'd be wary of the NAM folks, even the 3km. Mainly because, well, it's the NAM (btw NCEP can't pull the plug on that model soon enough). I know it's in the shorter range when the NAM could actually be right. But look at some of the CAMS, including the latest (18Z) HREF are all farther south with the axis. I mean, look at the latest HRRR (the one Pivotal Wx map)...heaviest stays south! And were within 24-36 hours of go time. Will be interesting to see the 18Z GFS trends. ECMWF and UKMET, while not as far south with the max QPF and snow axis (into central VA), are definitely more muted with more widespread 2-3" for most, which is consistent with the NBM. Proceed with caution with the NAM3..

Latest NBM v4.1 and v4.2 snow for Mon-Tue. Lots of 2-3" for the DMV. Not sure why the 4.2 version is a touch higher; might be because of SLR, but I'll take that one.

Should have posted this earlier, but the ECMWF ML FuXi model ("Foo-chi") is pretty optimistic for the Friday system as well. All totaled, at least ~10mm total, perhaps more since we don't really see the full resolution. That's like 0.4"-ish. Not bad. It should be noted that the FuXi was consistent in having 0.15-0.30" with the Mon-Tue system, which appears pretty reasonable now. https://charts.ecmwf.int/products/fuxi_medium-mslp-rain?base_time=202401140000&interval=12&projection=opencharts_north_america&valid_time=202401150000

GFS is solid but boy oh boy still quite a bit of spread when compared to the high res guidance. I mean we go from 4-6+ south of the DMV area on the GFS to heavier snow north towards Balt north with warm ~925 mb layer issues along/east of 95 here, esp in So. MD, per the NAM and high res guidance. All within 36, maybe 24 hours from go time. Weird.

Frontogenesis with a narrow ribbon of enhanced isentropic ascent always seem to overperform with events like these when the Arctic chill follows suit.

Since we're dealing with the NFL playoffs, the GFS vs. ECMWF battle to me feels like...

Oh believe me, I did too! I think it's pronounced "Foo Chi".

If it helps (and no it doesn't), the 0.25 degree experimental FuXi ECMWF ML model gives our area (I think) between .15 and .25 of liquid equivalent QPF Mon night into Tue. A band of overrunning snow north of a flat wave/eventual weak low off the Mid Atlc coast. MSLP and 850 mb wind speed: https://charts.ecmwf.int/products/fuxi_medium-mslp-wind850?base_time=202401121200&projection=opencharts_north_america&valid_time=202401160600 12 hr QPF (4-5mm through 12Z Tue...another 0.5 to 1 mm through 00Z Wed...: https://charts.ecmwf.int/products/fuxi_medium-mslp-rain?base_time=202401121200&interval=12&projection=opencharts_north_america&valid_time=202401130000 This particular version has been verifying fairly well of late.

If you're in, I'm in! Just an FYI, and not even taking into account the latest (12Z) guidance, but the probabilistic WSSI kinda sorta gives us an areal extent of what most likely would be minor impacts. We'll see. Also attached the 13Z NBM 50% percentile snow (most likely total or mode). I think, or I'd like to believe, this is a good 'floor'...with hopefully going forward an increasing trend. The main shortwave driving this event is still south of the Gulf of Alaska, well west of the WA/OR coast.

Meh, good time to start a thread. I mean, it's going to be something. Even if an inch or less of cold smoke before the coldest air of the season so far. Best to get this separated from the medium range thread that will probably have other trackable systems around Jan 19-20 and beyond. I like it. LFG!

Those twin systems in Jan '87 were so awesome. I was 16 at the time, living in Springfield.

That's what she sa... oh nevermind.

SIAP...This will be the first 'test' for the growing list of machine learning runs from the ECMWF suite. Verification has been pretty good, especially for some. Not going to get the specifics (i.e. ptype, snow totals, etc.), but at least we can see what the ML runs have in terms of the track into the medium range. https://charts.ecmwf.int/?facets={"Product type"%3A["Experimental%3A Machine learning models"]}

Well said PSUHoffman. The fact that El Niño episodes are a bit less frequent "these days" is another potentially interesting by-product of climate change. We didn't always need to have an El Niño to get lucky with a bona-fide Miller A. It does help to have that overly active so tropical jet. But I think of the A storm in Feb 2014 -- which was during a Niña winter. Matter fact, I believe so many of us would take winters of 2013-14 and 2014-15 -- both ENSO Niña or neutral yet PLENTY of productive Miller Bs that were able to reach us south of I-70 (those 3-6" events that we can't seem to buy these days). My hunch is we'll get lucky, or unlucky depending on where you live, with a slider that happens to be timed perfectly with a transient cold air surge. Much like last January. Problem with those is it's going to be quite frontogenetic -- meaning a sharp northern gradient. We happened to do well here in central AA County...areas to the south towards Fredericksburg and Southern MD even better...but that's just pure luck.

Snowing decently here in Crofton with the backside deformation banding setting up. Before the lull, we may have gotten a quarter inch or so. Happy to hear the NW-W areas doing well. For me, this winter was more than okay, especially after a disastrous December. 10.25" on January 3rd was really all I needed. That was a great storm at a great time of the season.

Good sized wet aggregate flakes here in Crofton/central AA County. 36°F.

Looking forward to the 2-4" IMBY. A little jealous of eastern New England, then again I'm not overly partial to crippling wind chills and snow drifts at the same time. Give me a foot of pasty dense snow without the brutal cold like we (almost) had Jan 3rd and I'm good.

https://twitter.com/MikeTrout/status/1486854871743610881?t=g6qqB584yfS5ccOi5m4m1Q&s=19

It's like a Cowboys fan (like me) recalling the glory days, now over a quarter century ago. Thankfully we don't have to wait that long for a historic, at least Top 10 snowfall around these parts. Reminisce with these GEFS panels just before the 1/22-23 event 6 years ago. Every member had at least a foot for DCA. We'll get there again someday, and it will be oh-so-sweet when it happens!

They're already on it...wowzers...their storm thread is over 300 pages now. I already know 2 folks flying out of BWI tomorrow to go chase.

Op GFS reminding us that the in-situ dry slot can be a real deal with a transfer/low deepening offshore. What's more, I think we're all wary of several hours of pixie dust snow/lack of dendritic growth and light rates when it actually does snow. I have no idea what the 'bar' for this storm is yet. 2-4" for the Beltway region? Sure, let's start there..

Nice lift in the dendritic growth zone at FH084 around DCA.

I had a heck of a time getting the cities to match up with the graphic. Thankfully the shift before last night got the key messages started. Notice how the probs went up, especially in New England. We also now see the storm in the day 4 WSO! Let's hope the probs keep going up for us!!