March Medium/Long Range Discussion

[AtlanticWx]

2 hours ago, BristowWx said:

If the 6z ICON went past 120 it would have been not good compared to this run.  It’s warmer and norther

looking at h5 this is exactly what we want tbh, our shortwave is making a pass right under the NS. sure it might start off as rain like the icon shows but it's dynamic enough and would pass south enough to be snow if we're extrapolating it. 06z icons actually faster which could be a good thing

[CAPE]

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.

[AtlanticWx]

taking a glance at the 06z cmc just for fun, below is the 6z cmc compared to 0z - it looks virtually the same but maybe the western trough is a little held back but overall its the same which is encouraging

[AtlanticWx]

and 06z shifted favorably from 0z too. at hour 90, the shortwave is less amped and faster and the NS is stronger + faster - good to see! 

[nj2va]

8 minutes 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.

Thanks for this. I also wonder if the orientation of the block is impacting too - GFS is pressing further south with the block. Maybe that’s allowing more ridging/separation out west on the Euro/CMC? 
I’m probably wrong so feel free to use the thumbs down emoji

[Ralph Wiggum]

2 hours ago, CAPE said:

IWe still can't know yet. 

But what about Scotty? One would think Scotty would have to know by now. Iykyk 

[CAPE]

33 minutes ago, nj2va said:

Thanks for this. I also wonder if the orientation of the block is impacting too - GFS is pressing further south with the block. Maybe that’s allowing more ridging/separation out west on the Euro/CMC? 
I’m probably wrong so feel free to use the thumbs down emoji

There are definite differences in the character of the ridge across Greenland at that point. If you read my somewhat rambling post yesterday about all the interactions between waves over time, it is nearly impossible to discern cause and effect. In this case I think 'in phase' interaction with NS energy will tend to pull the low further NW.

[Stormchaserchuck1]

1 hour 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
 

This storm?

wow.. what a miss

Pattern is really wet through the whole model run...

[AtlanticWx]

looking at eps from 0z -> 6z, at hour 84 looks like our main trough is weaker and maybe digging a bit more while our NS is a bit faster, gonna see how this plays out in a second

[brooklynwx99]

the main difference between the GEFS and EPS (& GEPS for that matter) is the handling of the N and S streams and their effect on the confluence in SE Canada

the GEFS keeps much of the vorticity in the trough itself, leading to a higher amplitude S/W and not as much confluence scooting out over SE Canada. this leads to higher heights and the mean storm track to the west of us

however, the EPS and GEPS have more of the northern stream moving ahead of the trough, allowing for significantly more confluence over SE Canada, leading to the opposite effect. therefore, we get much a much snowier solution with most of the SLPs tracking offshore

tough to say which model has the right idea. I would lead against the GEFS only because it's been inconsistent and it doesn't have as much support as the EPS. the GEFS is also underdispersive and often times will follow the OP, which has been erratic. look how awful of a job it did with the Monday system. the GEFS solution is certainly possible due to a lack of a true semipermanent 50/50 ULL, but so are the solutions of the EPS and GEPS

either way, there remains the potential for a significant snowfall event over the NE US, even down to the coast. we should see one camp cave over the next model cycle or two, as we're getting into the 5 day range now

[AtlanticWx]

Just now, brooklynwx99 said:

the main difference between the GEFS and EPS (& GEPS for that matter) is the handling of the N and S streams and their effect on the confluence in SE Canada

the GEFS keeps much of the vorticity in the trough itself, leading to a higher amplitude S/W and not as much confluence scooting out over SE Canada. this leads to higher heights and the mean storm track to the west of us

however, the EPS and GEPS have more of the northern stream moving ahead of the trough, allowing for significantly more confluence over SE Canada, leading to the opposite effect. therefore, we get much a much snowier solution with most of the SLPs tracking offshore

tough to say which model has the right idea. I would lead against the GEFS only because it's been inconsistent and it doesn't have as much support as the EPS. the GEFS is also underdispersive and often times will follow the OP, which has been erratic. look how awful of a job it did with the Monday system. the GEFS solution is certainly possible due to a lack of a true semipermanent 50/50 ULL, but so are the solutions of the EPS and GEPS

either way, there remains the potential for a significant snowfall event over the NE US, even down to the coast. we should see one camp cave over the next model cycle or two, as we're getting into the 5 day range now

what's interesting is that the 6z eps continues the trend of more separation between the NS and our actual trough. gonna be interesting to see what it does

[AtlanticWx]

there have to be some amazing members in there, overall it looks like there's less spread but the same as 0z, will post snow map when it comes out

[Weather Will]

WB 6Z EPS, tick north but not a cave to GFS.

[AtlanticWx]

6z eps was a nod to the gefs/gfs in the sense that it went nw but really there were so many members that slammed us just the nw camp skewing it

[Stormchaserchuck1]

Ensembles are south of the OP with the rising-out of-NAO block-potential/storm. -NAO/50-50 low/wet pattern

They really pop this SE ridge strong, but it's not going to be this bad, (unless models shift toward an Aleutian high).

mustering up potential energy

The hit.. restrengthening 50/50 low after -NAO wanes (rising up out of NAOindex#research).. EPO's are colder at the surface if it holds. It's a window of time. I'm still generally worried about warm air, but it could be a big hit before it melts. 

[Weather Will]

WB 6Z control which does closely follow the operational 

[Ralph Wiggum]

4 minutes ago, AtlanticWx said:

6z eps was a nod to the gefs/gfs in the sense that it went nw but really there were so many members that slammed us just the nw camp skewing it

Agreed. A 971 and a couple 976 lows n and w will definitely do that. Majority of clustering is still pretty much centered around the mean maybe slight lean N.

[AtlanticWx]

it's good that the eps is flip flopping from nw to se ever since 00z yesterday, we're at a good place rn

[Chris78]

4 minutes ago, Weather Will said:

WB 6Z control which does closely follow the operational 

Can you post the 24 or 48 map so it takes out the snow up north from Tuesday?

[paulythegun]

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! 

[AtlanticWx]

Just now, 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! 

what??

[midatlanticweather]

Definitely seeing the shift North. We are in a bd spot on all models being just barely in the game. We need to be on the northern edge of the snow and not the southern to make me feel this is in a good spot. One or two more ticks north in the Euro and we are out. Seems almost inevitable based on this year's trends. 

[Ralph Wiggum]

Not a terrible place to be. Obviously farther N and W would fare better in this setup, but close enough that any adjustments will have a significant impact. Hopefully we are starting to stabilize any big shifts and we can start seeing more influence from confluence. Would love to start seeing model adjust S now and start windshield wiper effects. 

[Weather Will]

3 minutes ago, Chris78 said:

Can you post the 24 or 48 map so it takes out the snow up north from Tuesday?

WB is very slow…,

[Interstate]

This room is bipolar. 

[Ralph Wiggum]

3 minutes ago, midatlanticweather said:

Definitely seeing the shift North. We are in a bd spot on all models being just barely in the game. We need to be on the northern edge of the snow and not the southern to make me feel this is in a good spot. One or two more ticks north in the Euro and we are out. Seems almost inevitable based on this year's trends. 

See my last post. I think we r starting to stabilize general track. You're not in a bad spot. It isnt going to continue N every single run for the next 5 days. Big jumps might be over. Probably going to see a fair amt of wobble (windshield wipers) back and forth, NW and SE next several days. Buckle up.

[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.