December Medium/Long Range Discussion

[MillvilleWx]

1 minute ago, nj2va said:

Great analysis as always.  Just hoping for at least 5” in Deep Creek from this and I’d be happy.  Hoping we all cash in.  

Good luck with studying! 

No studying over here! My school days are long gone. Working the mid shift tonight and have Aviation grids tonight. Will be easy shift for me as the day shift gets the screaming northerlies later today 

[MN Transplant]

6 minutes ago, MillvilleWx said:

Once the low surface low reflection showed to be at the mouth of the bay, it was destined to have mixing issues further inland as the 925/850mb winds would throw the warmer air back further towards I-81. The Euro is actually similar to the GFS at 5H with just different SLP placements once we get to the slot near ORF. Models being jumpy right there mean they are struggling to identify where the primary surface low will be located as there is a distinct double barrel look now on all guidance, something I pointed out last night. Until that gets figured out, it'll be doing some moving and shaking with regards to the warm boundary layer intrusion.

The CAD on the model is actually very solid leading in, and is actually the strongest surface ridge extension of all guidance. That's also another reason why the warm air made it so far west. The 1038 HP over Canada in tandem with a more tucked SLP at the mouth of the Chesapeake created a strong u-vector component to the wind field, forcing the easterlies to protrude as far west as I-81. It does correct and things improve with 3 hrs time, so it's not unreasonable to say that can easily shift back. In either case, that area of Rt15 on west is still the ground zero for this storm, IMO. I-95 to Rt15 will likely mix for a time with the further east areas mixing the longest. The deformation axis is still epic, so the back end love will be higher ratio love and can pile up quick. I still think the jack lies from WV Panhandle to the Catoctins up to HBG in PA. Northern Carroll/Balt Co into SoPA will also have the outside chance at the jack pending the overall evolution of the deformation band that is bound to establish itself. Like I said before, this is not totally figured out in the synoptic scale, so expect some movement here and there.

We are always going to be in big trouble along 95 with an 850 track that goes from central VA to the Delaware Bay per the Euro.  Especially early in the season w/o cold air everywhere.  The GFS is much more friendly in that regard with a Williamsburg to east of DE track.  

[MillvilleWx]

Just now, MN Transplant said:

We are always going to be in big trouble along 95 with an 850 track that goes from central VA to the Delaware Bay per the Euro.  Especially early in the season w/o cold air everywhere.  The GFS is much more friendly in that regard with a Williamsburg to east of DE track.  

For sure. That's one of the reasons I see mixing even back as far as Frederick as a possibility with this one. "How long?", is the question. Still a fair amount of QPF to work with and the meso aspects are far from settled. Hopefully the low can find a medium and hug the coast and not reside over the coastal plain. Someone will get rocked from this in the sub-forum and my bet is the 81 corridor right now.  

[griteater]

This is the biggest difference I see aloft between the GFS and Euro.  First off, the timestamps are different here in the comparison (hr78 for GFS and hr81 for Euro), but I'm wanting to compare the features for when the trough axis is in the same location, in this case, centered through Missouri.  The trough on the Euro is sharper with more amplitude, and the GFS has more positive tilt as it extends down thru Texas.  Also, the 50/50 low on the GFS is stronger.  Note the difference between the 2 models with the height lines over NY and PA.  The height lines are farther north on the Euro which equates to a more tucked, warmer solution.  Every little bit of difference counts.

[AmericanWxFreak]

Euro ens 

[NorthArlington101]

lotta individual ens jumped NW from 18z to 00z. hopefully 06z EPS brings better tidings. Night y’all.

[Cobalt]

bleh

[Maestrobjwa]

4 minutes ago, griteater said:

This is the biggest difference I see aloft between the GFS and Euro.  First off, the timestamps are different here in the comparison (hr78 for GFS and hr81 for Euro), but I'm wanting to compare the features for when the trough axis is in the same location, in this case, centered through Missouri.  The trough on the Euro is sharper with more amplitude, and the GFS has more positive tilt as it extends down thru Texas.  Also, the 50/50 low on the GFS is stronger.  Note the difference between the 2 models with the height lines over NY and PA.  The height lines are farther north on the Euro which equates to a more tucked, warmer solution.  Every little bit of difference counts.

That there (what you said about the 50/50)...you're saying that being weaker is what's causing the Euro result? And I'm wondering...is Monday’s wave weaker on this run as well? (Thinking about that whole inverse reaction @psuhoffman mentioned)

[griteater]

1 minute ago, Maestrobjwa said:

That there (what you said about the 50/50)...you're saying that being weaker is what's causing the Euro result? And I'm wondering...is Monday’s wave weaker on this run as well? (Thinking about that whole inverse reaction @psuhoffman mentioned)

Correct, when the trough for the storm is over Missouri on both models, the 50/50 low on the GFS is stronger and farther southwest compared to the Euro.  That, and the other reasons given are at least part of the picture for why there is a more amplified, warmer, solution on the Euro (sfc low farther NW).

[Maestrobjwa]

5 minutes ago, griteater said:

Correct, when the trough for the storm is over Missouri on both models, the 50/50 low on the GFS is stronger and farther southwest compared to the Euro.  That, and the other reasons given are at least part of the picture for why there is a more amplified, warmer, solution on the Euro (sfc low farther NW).

Hm...so I'm wondering if we need to watch the first system more closely then...to see if it trends stronger or weaker...now it's practically on the doorstep, so you'd think we'd have more clarity on that by the end of today?

[MillvilleWx]

12 minutes ago, griteater said:

Correct, when the trough for the storm is over Missouri on both models, the 50/50 low on the GFS is stronger and farther southwest compared to the Euro.  That, and the other reasons given are at least part of the picture for why there is a more amplified, warmer, solution on the Euro (sfc low farther NW).

Good catch. I remember seeing on the Euro early on there was a bit of a difference in the strength of the surface reflection on Monday compared to other guidance, so that makes sense that it would provide a slight negative feedback. We're getting down to the nitty gritty on the synoptic scale, so that piece on Monday will be important to resolve before we have a distinct idea on what to expect with the SLP positioning on Wednesday. @MN Transplant said it best earlier with regards to the SLP track. Thanks for the trend gif Grit

[griteater]

1 minute ago, MillvilleWx said:

Good catch. I remember seeing on the Euro early on there was a bit of a difference in the strength of the surface reflection on Monday compared to other guidance, so that makes sense that it would provide a slight negative feedback. We're getting down to the nitty gritty on the synoptic scale, so that piece on Monday will be important to resolve before we have a distinct idea on what to expect with the SLP positioning on Wednesday. @MN Transplant said it best earlier with regards to the SLP track. Thanks for the trend gif Grit

In the old days, we would say the Euro is correct and the other models will move to it...but in the past 8 years or so, it hasn't been that way from what I've seen.  Maybe the Euro is correct here, but time will tell.

[Maestrobjwa]

3 minutes ago, griteater said:

In the old days, we would say the Euro is correct and the other models will move to it...but in the past 8 years or so, it hasn't been that way from what I've seen.  Maybe the Euro is correct here, but time will tell.

Sounds like we'll be sweatin' it the next 24-48 hours to see who caves to who, lol

[BristowWx]

I literally fell asleep at 1045..just woke up and picked up where I left off.  The GFS pbp was like meeting the hottest girl ever...then 2 hours later the Euro pbp was like finding out she was a dude. 

[yoda]

23 minutes ago, MillvilleWx said:

Good catch. I remember seeing on the Euro early on there was a bit of a difference in the strength of the surface reflection on Monday compared to other guidance, so that makes sense that it would provide a slight negative feedback. We're getting down to the nitty gritty on the synoptic scale, so that piece on Monday will be important to resolve before we have a distinct idea on what to expect with the SLP positioning on Wednesday. @MN Transplant said it best earlier with regards to the SLP track. Thanks for the trend gif Grit

We may have to wait till Monday IMO when the h5 pieces/SLP for the Monday "event" finally moves into the NE/Canadian Maritimes before we get a better idea of where the players for our snow will be on Wednesday.  As griteater pointed out... the 50/50 low positioning seems to be crucial to us down here. 

ETA:  seems like you ninja'd me above... my bad

[MillvilleWx]

I know it's the NAM, but keeping an eye on the Monday storm progression. I took a look through 42hr and the NAM is almost lock-step with the CMC in the evolution at 5H and the SLP movement and strength. The GFS was way stronger and the Euro was much weaker. The CMC is the compromise right now, so I'm curious to see what the NAM shows the rest of the run (Yes, it's at range, but it's something to compare with what we have. Not taking as gospel. Just for reference). 

[schinz]

It appears to me this NAM run would be a pretty warm solution for many of us.  Low looks to track North through Eastern Virginia 

[yoda]

great disco from LWX this morning

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Synoptically, the forecast has not changed much for the Wednesday
through early Thursday timeframe as strong Canadian high pressure
looks to situate itself over Quebec and northern New England on
Wednesday, helping pump cold air down the eastern slopes of the
Appalachians in a classic cold air damming situation. At the same
time, a deep upper level trough will be pushing eastward from the
Mississippi River Valley, progressing into the Tennessee and Ohio
Valley by Wednesday evening. Down at the surface, broad low pressure
over the Southeast will lift northward along the Carolina coast
Wednesday afternoon and evening, strengthening in the process.

Locally, we will see wintry precipitation overspread the area
Wednesday morning and midday from southwest to northeast, with snow
the likely ptype initial with the colder air locked in the boundary
layer thanks to the high to the north. As the low strengthens and
moves up the coast Wednesday afternoon and early evening, warmer air
will be drawn in off the ocean on an increasing easterly flow at the
surface and aloft. This will allow for mixed precipitation to
encroach in the vicinity of the I-95 corridor with plain rain
favored further eastward near the Bay and eastern shore of Maryland.

The upper trough will take on a negative tilt Wednesday night as
upper jet support moves overhead. This will combine with the
increasing moisture thanks to the strengthening onshore flow. The
latest guidance guidance continues to highlight the potential for
significant snow accumulation along and west of the Blue Ridge
Mountains, where a moderate winter storm threat exists. Further
east, confidence is lower due to mix precipitation limiting snow
accumulations. When this transition takes place and where it sets up
is the million dollar question in these type of events, and that
will be something we`ll get a better handle on as the the event
nears.

As mentioned, plentiful moisture will be associated with this
system, as ensemble guidance indicates 1 to 1.5 inches of QPF.
Meanwhile deterministic models highlight a potential for 1.5 to in
excess of 2 inches of QPF across north central Maryland and adjacent
areas in eastern West Virginia and extreme northern Virginia. Thus,
those areas that hang on to the cold air and see snow as the
dominate ptype, significant snow accumulation is quite possible.
Still 4 days out, so plenty of time for models to get a better
handle on the situation and exactly where that rain/snow line sets
up, which will all hinder on the exact track of the low. Keep up to
date on our latest winter forecast at weather.gov/lwx/winter over
the next several days.

The low will be pulling away from the Delmarva Peninsula Thursday
morning, with precipitation lingering across our northern zones and
upslope areas. The second half the day Thursday will be on the dry
side as the low lifts northeastward and high pressure to our west
builds eastward through Thursday night. Below normal temperatures
and dry conditions will prevail behind the system with high pressure
in control to finish out the work week and heading into the first
half of the weekend.

[MillvilleWx]

20 minutes ago, yoda said:

great disco from LWX this morning

 

 

I'm glad I'm in agreement with LWX. This system will not be moisture starved, that's for sure. How far west can that boundary layer warmth protrude into the region, and then when does it shift back for those that mix. 6-8" of snow with 1" of sleet is on the table along with areas that see 12-18" of snow with local to 22". All on the table with this setup. 

[Weather Will]

WB 6Z GFS 850 400 pm Wed

[Thanatos_I_Am]

The places that stay frozen get mauled. Maybe a tad less cold air this run. 

[Weather Will]

WB 925 at 7pm is warmest then starts to sink SE again.  Surface maps are lagging behind temp maps,

[Cobalt]

Just now, Thanatos_I_Am said:

The places that stay frozen get mauled. Maybe a tad less cold air this run. 

2M temps and 850s seem basically identical, if not just super tiny changes. I'd imagine that's just noise, or maybe due to rates? Idk, but I guess it's a step back but not a Euro type step back. I'll take that track any day and hope the mesos get a good grip on the thermal setup. 

[Cobalt]

Snowhole bingo card incoming???

[yoda]

lol 0.2 at DCA... nice try

[Weather Will]

I am no expert but surface temps struggle in 30s in 95 corridor throughout Wed afternoon/evening

[yoda]

06z GFS is a mauling for i95 corridor and west

[Cobalt]

1 minute ago, yoda said:

06z GFS was a mauling for i95 corridor and west

I think that's the best way to describe it. Whoever stays frozen is gonna bank on those rates piling on the snow. I'll roll the dice with the potential mixing, really excited to see the mesos get a hold of how that mixing will set up

[Weather Will]

WB 6Z GFS....why the mix when all the thermal profiles are below freezing?

[yoda]

Rates are silly in the CCB at 96...