March Medium/Long Range Discussion

[WinterWxLuvr]

3 minutes ago, Interstate said:

This room is NUTS

Fixed it

[BristowWx]

4 minutes ago, Interstate said:

This room is bipolar. 

Probably has a lot to do with where people are posting from.  As the southern slider members fade so does the optimism the lower your latitude. I know it’s not a done deal but the chapters are being written. 

[paulythegun]

LWX did an extremely detailed write up. It still sounds like the trough’s response to the pacific/western ridging (in terms of the trough’s orientation and likelihood of amping up quickly) is a key factor…with the Hudson ULL as other important driver.
 

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Large scale troughing will reside over the western US on Wednesday. West-southwesterly flow will emanate out of the base of this trough in the Desert Southwest, and stretch across the CONUS. A disturbance embedded in the west-southwesterly flow aloft and an associated area of low pressure at the surface will track across the Great Lakes on Wednesday. A push of warm advection will ensue in response to this feature, leading to an increase in clouds Wednesday afternoon, and potentially some showers Wednesday night. Temperatures will run well above normal in southerly flow Wednesday, with highs in the 60s for most.

Thereafter, forecast uncertainty begins to increase as we move into Thursday and Friday. On Wednesday, a strong cyclone in the Gulf of Alaska will build a downstream ridge, which is modeled to progress eastward into the CONUS with an appreciable forward speed. As this ridge builds downstream, it will perturb the downstream waveguide, which has been relatively stagnant over the past week. In response to the ridgebuilding, troughing will dig into the Desert Southwest/Four Corners region Wednesday night, and then progress eastward onto the Southern Plains Thursday into Thursday night. Meanwhile, the upper ridge will progress eastward and interact with a downstream upper low over Hudson Bay. Exactly how this complex process plays out will have a major impact on our forecast. The 00z Euro and 00z Canadian have the ridge progress eastward at a higher forward speed than the trough within the southern stream. As a result, the ridge cuts overtop of the shortwave trough as it closes off, effectively keeping it suppressed to the south as it progresses eastward. In these scenarios, the potent upper level shortwave progresses directly overhead, with an intense area of low pressure at the surface progressing to our south. The 00z GFS on the other hand, doesn`t have the upper ridge build overtop the southern end of the trough, and maintains one coherent north-south oriented wave from Canada down into the Southern Plains. This scenario allows the southern stream shortwave to amplify further and gain more latitude as it progresses toward the east. This scenario results in a very intense area of low pressure tracking off to our north and west.

Such a scenario would place us on the warm side of the system, and would result in temperatures climbing into the 60s or 70s, along with heavy rainfall, and potentially even severe thunderstorms. The scenario depicted by the Euro and Canadian on the other hand would produce a significant amount of snowfall across the area, with temperatures holding in the 30s.

In both of these scenarios, Thursday would have relatively quiet weather, with northwest winds, and potentially a few showers. The main forecast uncertainty on Thursday would lie in the high
temperatures forecast. Ensemble guidance has highs on Thursday ranging from the 40s to the 70s.  The higher impact weather, whether it be in the form of heavy rain and thunderstorms, or snow, would move in on Friday and last into Friday night.

With such a highly uncertain and complex forecast, it`s important to think probabilistically. The deterministic models described above span the phase space of potential outcomes outlined in the ensemble guidance. The system being suppressed far to our south and completely missing us (as some ensemble members showed yesterday) appears to be off the table. The two main scenarios now entail the low passing to our north and west, and us ending up on the warm side of the system, and then the low passing to our south, and us ending up with wintry precipitation on the cool side of the system.

In terms of temperatures, these solutions range from highs in the 70s, to highs in the 30s. As a result, our deterministic forecast (that you see in the point and click forecast on our website) is a middle of the road solution and calls for highs in the 40s/50s, and rain across much of the area (since you can`t have snow with temperatures in the 50s). Nonetheless, the chance for snow is a very real one.

Digging a bit into the probabilistic phase space, and individual ensembles, both the EPS and GEPS trended colder and snowier with the 00z model cycle, especially across the northern half of the
forecast area. The EPS and GEPS now shows a greater than 50 percent chance for accumulating snow across nearly all of the forecast area, as well as a greater than 50 percent chance for more than a half foot of snow across far northwestern portions of the forecast area (Potomac Highlands and western Maryland). The GEFS on the other hand stand in stark contrast to the EPS and GEFS. The GEFS actually trended warmer, and less snowy, with very low probabilities for any snow, let alone significant snow. Oftentimes, the GEFS tends to follow trends in the GFS very closely, so this trend is somewhat unsurprising. In all of the respective ensembles, probabilities for snow are greater further off toward the north and west, and lesser as you progress further off toward the south and east. At the moment, this is a very challenging and highly uncertain forecast for Friday. We`ll continue to monitor trends and adjust our forecast accordingly as we progress through the week.

All solutions show us drying out on Saturday as winds turn

[SomeguyfromTakomaPark]

22 minutes ago, paulythegun said:

6z eps shut out the District more or less, aside from a couple members. Snow mean is pretty misleading and inflated for the city (fake 10 to 1 slop snow). Starting to hone in on the most likely scenario - slop SE of the fall line, good event for the NW burbs. March! 

This scenario makes sense when there is no cold air available.  Far NW burbs with elevation is the place to be for this one. 

[anotherman]

This room is bipolar. 

Are you new here?

[psuhoffman]

2 hours ago, Buddy1987 said:

I agree here. Too amped for my area down this way but I could see @clskinsfan and @WinterWxLuvrliking this setup, although the northern MD and southern PA crew are more than in it at this stage as well. Hopefully it trends south and east so everyone is happy but the way this year has gone I am not holding out much hope. 

I still think better setups are likely to happen towards mid March. But…we are in a different regime than most of winter.  Yes we had blocking in December but the mid latitude response is significantly different in December than March. A few years ago I showed how in the last 20 years we actually need the pac more so than the atl to be cold in December. That wasn’t always true and it might be a big problem in this -pdo cycle but it is what it is. So this coming blocking regime is likely to be significantly different and so not sure using persistence anymore is the best way to go. 

[AtlanticWx]

1 minute ago, psuhoffman said:

I still think better setups are likely to happen towards mid March. But…we are in a different regime than most of winter.  Yes we had blocking in December but the mid latitude response is significantly different in December than March. A few years ago I showed how in the last 20 years we actually need the pac more so than the atl to be cold in December. That wasn’t always true and it might be a big problem in this -pdo cycle but it is what it is. So this coming blocking regime is likely to be significantly different and so not sure using persistence anymore is the best way to go. 

has there been a reason why december and march have pretty much swapped places recently? march has been very snowy recently (since 2012-13, 8 winters at KIAD had >1" in march and 5 of them had >5")

 

[osfan24]

Wobbles will obviously continue to occur, but don't like seeing the EPS basically move to a bullseye on NYC. That's way north. We don't want to be on the southern edge. That's a dangerous game to play.

[psuhoffman]

2 hours ago, Ji said:

This storm is now about 120 hours out....in 99% of situations...the euro would not make any significant shifts now....especially if it was showing a cutter or rain or suppressed for us lol

Sent from my SM-A515U using Tapatalk
 

You’re just trying to gaslight yourself now.  We’re on the southern edge of the significant snowfall (which isn’t even a huge areal coverage due to marginal temps) already. So all it will take is a minor shift to take us out of the game. Even up here I wouldn’t feel safe at all. This is a thread the needle event in either direction. It’s not like 2010 or 2016 where some huge juiced stj wave in a split flow was attacking a blocker in high with cold in place. Those had wiggle room. A change in track of 50 miles or  2-3 degrees wouldn’t have a crazy impact on the outcome. Here a relatively minor adjustment would completely sink us. 
 

But you know that and you’re just saying this so you can feel justified when you go off and tirade when the euro pulls the rug out, which you likely anticipate happening. 

[Interstate]

7 minutes ago, anotherman said:

Are you new here?

I just like to point it out every once in awhile so we take our meds   

[MD Snow]

Glad to be tracking a threat inside 6 days! That's a win for this winter. 

Thinking model's lock into a general track over the next 24 hrs. At that point, we start talking details. If we land on a general euro/cmc/icon solution and the low tracks to our south, it will be interesting to see how the block effects things in the final 96 hrs. Been fun to watch the tuesday storm get punched south over the last 48-72hrs. Looks like areas in southeast PA could even start as snow now, where a few days it was southern new york. 

Obviously, a gfs track dooms pretty much everyone. If we can avoid that cutter solution, I think there's a chance even the cities get into at least some accumulations. 

[psuhoffman]

2 hours ago, CAPE said:

Some key differences influencing the track of the storm between the GFS, and Euro/CMC:

GFS- Has more interaction with NS energy rotating down around the vort near Hudson, as well as energy digging in behind associated with the next trough.

Euro/CMC- Most of the NS energy near Hudson is shifting eastward out ahead, and also more separation from the digging trough out west with more of a ridge between.

You’re definitely the best on here now at diagnosing this. Wish @showmethesnow would still post his morning briefings. 
 

But to summarize why those details are hard to resolve and could take longer than usual to get to the final solutions, there are too many waves involved in this scenario. And the wave breaking from each impacts both the high latitude configuration and the confluence but also the wave spacing under it.  It’s asking a lot of guidance to be dead on balls accurate with all these waves in close proximity but that’s what’s necessary in order to get the exact right track correct on our potential storm.  I’ve never expected this to be resolved at long leads given the setup. 

[psuhoffman]

15 minutes ago, AtlanticWx said:

has there been a reason why december and march have pretty much swapped places recently? march has been very snowy recently (since 2012-13, 8 winters at KIAD had >1" in march and 5 of them had >5")

 

My guess…March was historically more snowy and we simply had a bad stretch. I think it’s the law of averages evening out. As for December, the warning SSTs are likely impacting December the most of all our winter months. Ian showed a great graphic how our first snowfall is consistently moving later over the last 50 years. If the avg SSTs continue to increase we are likely losing Dec as a “winter” month. 

[Interstate]

What did the NAM say?

[Stormchaserchuck1]

12z NAM
 

[stormtracker]

Deep down, I think we all know how this is going to turn out, but we're just desperate to track something, anything, so we just keep going until the last second.  We all know what our fate is, but we gonna keep on keeping on.

Because we're sick people.  

[Imgoinhungry]

Just now, stormtracker said:

Deep down, I think we all know how this is going to turn out, but we're just desperate to track something, anything, so we just keep going until the last second.  We all know what our fate is, but we gonna keep on keeping on.

Because we're sick people.  

Only question is when will the euro cave to the gps!  

[stormtracker]

Just now, Imgoinhungry said:

Only question is when will the euro cave to the gps!  

We'll get a preview of 12z when the ICON caves and looks nothing like it's 0z run

[Blizzard22]

My guess…March was historically more snowy and we simply had a bad stretch. I think it’s the law of averages evening out. As for December, the warning SSTs are likely impacting December the most of all our winter months. Ian showed a great graphic how our first snowfall is consistently moving later over the last 50 years. If the avg SSTs continue to increase we are likely losing Dec as a “winter” month. 

Why was March historically more snowy ? Are average temps colder in March than December ?


.

[psuhoffman]

1 minute ago, stormtracker said:

Deep down, I think we all know how this is going to turn out, but we're just desperate to track something, anything, so we just keep going until the last second.  We all know what our fate is, but we gonna keep on keeping on.

Because we're sick people.  

Agree but there is a chance. The blocking does make this more realistic than those past mirages I’ve been making fun of all winter. This one while unlikely has a legit “chance”.  But the thermal boundary still just isn’t right yet. We need a lot to go perfect with wave spacing to make up for the fact the  thermal boundary base state is still to our northwest. I think come mid March we will get some waves where the boundary is to our south and we have less atmospheric hostility to overcome in the snow equation. 

[psuhoffman]

5 minutes ago, Blizzard22 said:

Why was March historically more snowy ? Are average temps colder in March than December ?


.

Going forward March is least likely to be impacted by warmer SSTs. As for the past is seems during the last -pdo March was snowier. That could be random coincidence though. Sometimes it’s just chaos since snow is a pretty random fluke thing in our region. 

[Stormchaserchuck1]

March is a wetter month.. this would give us snow a lot of times, but we average 2-3" in December

[Ralph Wiggum]

ICON going towards the GFS. Pretty significant shift tbh. Northern areas are snow tho at 120. 

[StormyClearweather]

28 minutes ago, stormtracker said:

We'll get a preview of 12z when the ICON caves and looks nothing like it's 0z run

Nailed it. 

[stormtracker]

1 minute ago, StormyClearweather said:

Nailed it. 

Betting on fail here will never let you down.

[Ralph Wiggum]

I'm not sure the icon look is horrible. It isnt that SW->NE oriented look like the gfs that's tries to cut. Has more of a look sliding W->E with cold pressing to the N. That would make for a much juicier or prolonged overunning for areas N of the boundary. Definitely isn't a strong amped look. A gfs track with weaker system crawling along could work if it can get displaced a bit S

[Superstorm]

I'm not sure the icon look is horrible. It isnt that SW->NE oriented look like the gfs that's tries to cut. Has more of a look sliding W->E with cold pressing to the N. That would make for a much juicier or prolonged overunning for areas N of the boundary. Definitely isn't a strong amped look. A gfs track with weaker system crawling along could work if it can get displaced a bit S

Agreed.


.

[Ji]

4 minutes ago, stormtracker said:

Betting on fail here will never let you down.

remember when the euro shows rain/cutters.....it never budges...not once in 20 years of tracking

[brooklynwx99]

the ICON isn’t a cutter, it’s a Miller B. it gets shunted due E from the confluence, quite different synoptically from the GFS

[Ralph Wiggum]

1 minute ago, brooklynwx99 said:

the ICON isn’t a cutter, it’s a Miller B. it gets shunted due E from the confluence, quite different synoptically from the GFS

That's what I posted above. I mean it isnt a fail proof setup, nothing is. But I would take this anywday vs an amped cutter in Pittsburgh at this range.