high risk

1 hour ago, WxUSAF said:

Does any snow actually occur with temps at or below freezing? Seems like rain turning to white rain and quickly ending.

       Temps just above freezing, but it's night, so maybe stickage on a few surfaces?    That said, the CAM suite consensus is for just a little bit of snow at the end, with the area of snow expanding after crossing the Bay.    One thing to watch for all of us is that any wet spots could freeze early Thursday as temps drop quickly behind the front.

4 minutes ago, NorthArlington101 said:

Taking zero credit for this analysis but what I’m hearing is that our low is developing too late and rapidly occluding - meaning we aren’t pulling in enough moisture in time. Solution could be a little more dig. 

          I think that this is very much on the right track.   If you look at the 10m wind field, the expected intense circulation on the east side of the storm just isn't there.    The 850 wind field looks like garbage too.

        I'm still very interested in tomorrow, but the simulated reflectivities all suggest very scattered activity.    Should be fun for those who get under one of those heavy showers, and we'll need that intense omega-driven cooling to combat fairly warm low levels.   The simulated reflectivities show rain except for right under the most intense cores.

41 minutes ago, Terpeast said:

Also didn’t break 50 today. Yesterday was 53. Was supposed to be the warmest days in the 60s in this January thaw. 

         It definitely looked in forecasts from early this week that today would be a taste of spring, but that idea disappeared by midweek.

1 hour ago, NorthArlington101 said:

Also some very impressive squall action Sunday… paging @high risk

      Yeah, the NAM Nest backed off a bit, while the HRRR was       All CAMs this evening show the potential, although they disagree on the amount of organization.

22 minutes ago, Weather Will said:

WB 18Z 3K NAM: and what happened to that 60-70 degree weather forecasted before Sunday????

        It has been off the table for us for a couple of days now.   The warm front is going to stay south of us, so the 60s and 70s will make it into southern VA and part of the lower Eastern Shore, but we'll be stuck in the 40s, maybe getting to the low 50s Saturday evening with a little mixing.   The good news is that the further south position of the warm front puts us in a good position for significant rain.

  Continuing what it was showing earlier, the NAM Nest still likes Sunday afternoon for some of us getting a burst of convective snow.  The CAPE field is non-zero, and other mesoscale models hint at the same idea:

39 minutes ago, WxUSAF said:

If people cared like with snow, people would be panicking at the 18z hrrr’s precip totals for the weekend 

            FWIW, the HRRR has a much weaker and more veered 850 mb wind field than most of the other guidance.      The images below show a massive difference in the intensity of the overrunning.

CAMs suggesting a few scattered heavier snow showers Sunday afternoon.

The models seem to all be coming into agreement that the warm front is going to set up to our south on Saturday.

The good news:  this puts most of our area in a really good location for overrunning, and we should get a fairly decent widespread soaking.

The bad news:  this will keep the warm sector south the DC/Baltimore metro, and you can kiss a warm Saturday goodbye.    Areas well south of DC might still get warm, and *maybe* we all break into the warm air briefly during the evening, but it right now looks like most of us will have a much chillier Saturday daytime than we were expecting.

35 minutes ago, stormy said:

I appreciate your suggestion, but No, I won't ignore them.

I fully understand that they are supposed to be more accurate than the deterministic models because of more data input across various parameters.  A higher skill score should be achieved, especially for complex systems or longer term considerations.

I will develop a comparison chart for ECM/EPS and GFS and GFS ens.

Saturdays rain will be a good first comparison.

           In the interest of "the more you know", I think you need to better understand what ensembles really are.     You are correct that the ensemble mean should outperform the deterministic run, but they don't benefit from any extra input data.    The premise of the ensembles is that the evolution of a single forecast could be extremely sensitive to initial condition errors (either due to simply not having enough observation data or even directly due to errors in the measurements) and general uncertainly of the atmosphere.  By tweaking the initial states across a larger number of run of the same system, we should in theory better sample the amount of uncertainty with the forecast.    You get a range of possible outcomes, some sense of whether the deterministic run is on the right track, and a feel for the degree of uncertainty.   If the deterministic run is way different than most of the ensemble, it isn't likely to verify.    But if a large part of the ensemble agrees with the deterministic run, the evolution of the deterministic run may have some significant merit.  (And if the deterministic run is way different than the ensembles, but many ensemble members agree on some very different scenario, that scenario is very much on the table.)    Ensemble construction has now gotten more sophisticated with things like accounting for model physics uncertainty.  

             Ensembles can still be very wrong, as the underlying model will have limitations, and we don't always properly sample the uncertainty in the initial state.    And it doesn't help that the version of the GFS used by the GEFS is not the one used by the operational GFS.   And an ensemble system shouldn't bounce around cycle-to-cycle as some of them do sometimes.    Ultimately, we need larger ensemble systems to fully cover the range of possible outcomes, and AI methods may really help in that area.    One final comment:  be careful looking at low-res, global ensembles at short timescales, as the differences in the initial states for the members need some time to grow.   So they have limited utility in the short range.

33 minutes ago, Terpeast said:

I apologize if I came off as model bashing in the general sense, that wasn't my intention and I can see that my statement was a bit unfair. We've seen incredible advances in modeling both physical and AI, and seeing 0.6-0.8 correlations in 500mb anomalies from 10+ days out is an incredible feat. I only meant that their performance have collectively taken a hit lately in the 11-15 day range especially in the past 5-6 months. In the grand scheme of things, on a global scale, they still perform better than 10+ years ago. But regionally, they have been struggling with the trough/ridge placements such that we're seeing wild swings in our forecasted sensible weather in our back yards. 

Again, sorry about that.

            I appreciate that, but I honestly wasn't offended by your post.    It has definitely been a rough period lately in the extended range.   To me, the fact that we have higher expectations now for Week 2 forecasts speaks highly to the progress that has been made.    We just have to remember that certain patterns / transitions still give the models fits, and identifying those in advance is not trivial.

23 minutes ago, Terpeast said:

Wow. 11-15 day model forecasts have been terrible this fall/winter. Terrible. 

     I think that recent longer-range forecasting successes, part of the ever-improving state of NWP, have raised our expectations a bit too high.    We're not yet at the point where we can expect the Week 2 period to always be forecasted with skill, even for ensemble systems.

5 hours ago, Eskimo Joe said:

Latest HRRR is rather emphatic for a decent snow squall tomorrow regionwide.

       Some HRRR runs do maintain it, but some are like several other CAMS in weakening the line as it moves into northern MD/VA.   Even the previously bullish HiResW FV3 has backed off quite a bit.

26 minutes ago, brooklynwx99 said:

lol what a disaster by the ECMWF. sometimes models fuck up wave breaking blocks... it happens

  THIS.   Even though our resident third graders want to moan that poor forecasts show that NWP is useless, there are certain patterns that for whatever reason just aren't predictable.   The fact that all of the major world modeling ensemble systems showed something very encouraging for the end of the first week of January makes it clear that something about those forecasts (initial conditions generally driven by lack of observations or observational errors, the actual equations and parameterizations, numerical methods, or some combo of those) made skillful predictions impossible.     But there are plenty of periods where guidance shows remarkable skill even at extended ranges.   Here are the 500 mb anomaly correlation scores (the best measure of synoptic pattern success) for 10 day forecasts over the past 3 months for the 3 major ensemble systems (and yes, it only makes sense to verify ensembles at this range).   A score of 1 is a perfect score, and the dates on the bottom are the days on which the forecasts verify, not when they're made.    

            There were periods of poor performance by all 3 systems (early October and around November 9),  periods of poor GEFS and GEPS performance but with the Euro doing fine (around November 12 and at the very end of December), periods of fair performance by all 3 (mid October), and periods of fantastic performance by all 3 (third week of November and especially the third week of December).    Those scores between December 18 and Christmas are remarkable for 10-day forecasts and are numbers we could have only dreamed of 20 years ago.   Advances in data assimilation and coupling of the ocean to the atmosphere in models will lead to even bigger improvements, and AI offers tremendous opportunities to run the massive size of ensembles needed to truly represent the uncertainty and potential for extreme events with more lead time.     That doesn't mean that frustrations like those with the upcoming pattern will completely disappear, and it REALLY doesn't mean that we should soon expect models to lock in on a snowstorm 12 days out and never waver up until the day it happens.   We just need to remember the current limitations and focus on consistency in patterns (and not details of deterministic runs at extended ranges) in ensembles, understanding that progress in forecasting the extended ranges doesn't preclude huge busts.    I'll end with this plot of Day 5 anomaly correlation by year over the past 40 years (apologies for not having the values for Day 10).   While the lines have flattened more than we'd like in the past 10 years (I think that AI is the way we'll see these rise again), and the GFS needs to catch up to the Euro, the progress is undeniable.    Thanks for coming to my TED talk, and Happy New Year!

pa

I know that we're all chasing big dogs, but this would be a nice start to 2026 if it happens.   NAM Nest and RGEM aren't as tasty as the HiRes FV3, but they all have the idea of some sort of quick-hitting band right on the front.

31 minutes ago, bncho said:

It was stuck on hour 66 on TT, Pivotal, and WeatherBELL for about ten minutes.

      Understood, but while that means that it wasn't an issue with the processing on those sites, it's a dissemination issue with the data.   The model chugged along just fine; issues with the actual runs are extremely rare.

Friendly reminder that graphics updating slowly on someone's website does not mean that there is anything wrong with the actual mode run.

55 minutes ago, SnowenOutThere said:

Storm looks to be over and the grand total is possibly an optimistic 1-2 inches thanks to a flip back to snow for a bit… I would not envy the email addresses of any meteorologist in NYC right now 

         Fascinating late evening radar on Long Island, with synoptic snow moving west-northwest to east-southeast, while ocean-effect snow streams from south to north across Long Island.

4 minutes ago, WxUSAF said:

Line did a nice split around you @MN Transplant

      Same here!    As for the overnight rainfall, a bunch of HRRR cycles late yesterday showed a significant minimum in the precip for most of the area.   I dismissed it, because it really didn't fit the narrative, but it was spot on.   

It's remarkable that every CAM has a forced line of convection tomorrow morning arriving on the west side of DC around 7AM and hitting the eastern side around 8.   I'm also very intrigued by all CAMs showing a broken line on the secondary front in the early afternoon.   This environment will have some CAPE and some low freezing levels, so I suspect that these could be accompanied by small hail or graupel.

9 minutes ago, 87storms said:

Just posted this in another thread. Saw it on LinkedIn. Should have looked here first lol. That’s quite a speed increase re AIGFS.

   It is indeed remarkable how fast these AI-based models run.   It really opens the door to running larger ensembles than ever thought possible, although getting meaningful spread still needs research

14 hours ago, WxUSAF said:

If all you wanted for christmas or Hanukkah was one more global weather model, you got it! AIGFS is now on tropical tidbits. I think this is the “hybrid” AIGFS and not the graph cast GFS? @high risk?

           All of the new AI NOAA global model products are using Graphcast.   Tropical Tidbits is displaying the deterministic GFS, called the AIGFS.    There is also an AIGEFS, but it's not yet displayed here.   The HGEFS is the hybrid GEFS, which combines the 31 members of the "regular" GEFS with the 31 members of the AIGEFS.     Note that the AIGEFS has been shown to be somewhat underdispersive, so treat high probabilities with caution.       https://www.noaa.gov/news-release/noaa-deploys-new-generation-of-ai-driven-global-weather-models

This is the Round 2 for midday / early afternoon tomorrow that I referenced in the above post.   Interesting to see some impressive modeled reflectivities with that.

1 hour ago, wxmeddler said:

LWX is confident too much sfc stability, but I’m not so sure we don’t get some sort of dynamics that could break through. Won’t be widespread.

    Every CAM has a nice forced line just ahead of the front, with consensus showing it passing through DC around 6 or maybe 7AM.   Most of these events end up being just heavy rain, but they do occasionally surprise us with more.

    Another thing to watch is that all of the guidance has another round of scattered heavy showers around midday in a well-mixed environment with a bit of low-level CAPE and low freezing levels.   Would not be surprised to see some graupel out of those.