January 18th Event

[Chris78]

3 minutes ago, Weather Will said:

About 50 percent of the EPS members from 0z would give 2 or inches DCA north. Slight uptick from 12z.

Only a handful of shut outs but not many that give more than 3" across the area. Looks like pretty unanimous agreement on a 1 -3" snow prior to any changeover.

[Weather Will]

6z WB GEFS mean an improvement over 0z.  About 70 percent would give two inches or more DC north.

[Weather Will]

 Nice writeup by Sterling NWS this am.  Nice because it explains it very well and why Impacts still uncertain.  I do wish they would add the winter weather link back to the headlines so it would be easier to access.

The North American Ensemble Forecast System (NAEFS) guidance over
the last 24-48 hours (including the deterministic Global Forecast
System, or GFS model) has trended steadily toward the European
Center for Meteorological Weather Forecasting (ECMWF) model and
its ensemble mean, lending to increasing confidence. This also
slows down the timing of potential onset for wintry
precipitation, which makes sense given the 1000-500 hPa mean
ridge axis still overhead at 12Z (7:00AM EST) Saturday morning.
For this reason, felt it prudent to remove the Slight Winter
Storm Threat for the I-95 Corridor for Day 4/Friday and Friday
night.

The NAEFS mean prints out (liquid equivalent) precipitation
amounts about a third of an inch higher than the ECMWF mean
Saturday. The latter solution appears more likely especially
south and east of eastern West Virginia and northern Maryland
given most of the best lift will be focused further north and
west. There are also questions on what percentage of this
precipitation will fall as snow vs. sleet vs. freezing rain vs.
plain rain. Ensemble probabilities have nudged ever so slightly
lower south and east of a line from Washington DC to
Charlottesville VA, but this may well be within the model noise
level this far out in time. The antecedent surface high is quite
strong (nearly 1050 hPa Friday as it passes to the north), but
it will be transient and in a weakening state by the time
precipitation arrives. Also, the high center itself is expected
to be positioned a little farther north than what would be
considered most favorable from a climatological standpoint (just
north of the Saint Lawrence River instead of upstate New York).
The parent low track will also be well to our north and west,
with secondary low development unlikely until the attendant
mid/upper trough axis pivots toward New Jersey and Long Island
Saturday night.

Although confidence continues to increase on the potential for a
winter storm for parts of our area (above average confidence for
this time range, in fact), it is still too early to get into
specifics on timing and amounts of different precipitation types
given the above listed uncertainties and the fact that this is still
4 to 5 days away.

[WinterWxLuvr]

45 minutes ago, showmethesnow said:

I know some on here are rooting for a shallower drop of the trough in the west. At this time with what is being presented on the models I am actually rooting for a deeper drop. Let me explain.

Below we have the GEFS and the EPS at 96 hrs. What we have is the trough moving through a very broad area of lower pressures in the west. What I want you to note is the location it is deciding to initiate the development of our primary from within this large expanse of lower pressures. What we are seeing on both the EPS and the GEFS is that they are having this development on the base of the trough just on the front side. And for the most part this is what we have been seeing for the last 2 days or so on these models.

 

 

Now some may argue that this deeper drop is pumping up the ridging in front and thus the warming the temps hurting our chances for frozen. I don't really think that is a concern at this time. If you notice we have a very strong CAD signature and that will be very hard to erode out especially with the farther western track we are seeing with our low. I think at this point our far bigger concern is actually getting some decent moisture overrunning our CAD vs. any potential warming. This is where the trough drop and the primary development come into play. What it basically comes down to is the track of our low.

Below is  what we would be looking at with a shallower drop of the trough assuming that the primary initiates on its base. What we have is a good moisture source running through the southern tier of which our low will be tapping into. With the low being farther north it has a harder time tapping into this source. What we also see is the best moisture is following to the south and east of the track of this low. There is a very real danger with this of seeing the best moisture to our west and north in this scenario.

 

 

But look at we see with a deeper drop. The low is better able to tap into the southern moisture giving us a better moisture feed then the above. Also note that the track is more favorable to getting that good moisture flow running through our area.

 

 

 

Seems like you’re saying what I’m saying. Maybe I’m confusing with my language. The sharper deeper trough out there is driving the low north. We need that trough to be flatter and drive that low more East before it sharpens and begins to drive that low north. 
 

100% agree that the low has to be further south. Way further south.

[WinterWxLuvr]

I’ll say this much on a positive note ... the gfs is flat cold to start Saturday. Guess we just need to pray for copious early precip

[Chris78]

5 minutes ago, WinterWxLuvr said:

I’ll say this much on a positive note ... the gfs is flat cold to start Saturday. Guess we just need to pray for copious early precip

I agree. At this point I dont see the low getting  further south and east where we would prefer it. Lets hope the cold maintains in future runs and we can get a decent slug of moisture in Saturday Am. 

[mappy]

35 minutes ago, WinterWxLuvr said:

Seems like you’re saying what I’m saying. Maybe I’m confusing with my language. The sharper deeper trough out there is driving the low north. We need that trough to be flatter and drive that low more East before it sharpens and begins to drive that low north. 
 

100% agree that the low has to be further south. Way further south.

like you said before, hard to have a good storm when the low is in minnesota. 

[psuhoffman]

6z eps isn’t going to make many friends. 

Problem isn’t temps. The euro is shifting the WAA precip across PA to our north.  It’s very dry here. Basically a period of light mixed precip yo dryslot then some showers with the front. 

[psuhoffman]

The temps are very similar on the gfs/gem/euro. 

But compared to the 1”+ qpf the others are spitting out during this same time period the euro is simply too weak with the WAA precip. 

keep in mind some of that (as with the others) is rain.  So it’s really only showing about .25-.35 qpf over 12 hours when we have the colder profile...not very thumpy and not good enough to mix out the warm layer so it leans more sleet than snow. 

Still not nothing. Shows the potential for 1-2” of snow/sleet across the area but it’s a more typical minor event compared to the depiction it (and some other guidance still) was throwing out there earlier.  Still time to change. 

[H2O]

5 minutes ago, psuhoffman said:

The temps are very similar on the gfs/gem/euro. 

But compared to the 1”+ qpf the others are spitting out during this same time period the euro is simply too weak with the WAA precip. 

keep in mind some of that (as with the others) is rain.  So it’s really only showing about .25-.35 qpf over 12 hours when we have the colder profile...not very thumpy and not good enough to mix out the warm layer so it leans more sleet than snow. 

Still not nothing. Shows the potential for 1-2” of snow/sleet across the area but it’s a more typical minor event compared to the depiction it (and some other guidance still) was throwing out there earlier.  Still time to change. 

Is that mainly a product of the better lift from the WAA being closer to the low which is further NW since it went to MN?

[showmethesnow]

1 hour ago, psuhoffman said:

6z eps isn’t going to make many friends. 

Problem isn’t temps. The euro is shifting the WAA precip across PA to our north.  It’s very dry here. Basically a period of light mixed precip yo dryslot then some showers with the front. 

Are we looking at the same thing? 06Z looks comparable if not just a smidge wetter then the 00Z on precip total. Now admittedly both runs are dryer then the other models but still I didn't see a degradation. 

[Chris78]

1 hour ago, psuhoffman said:

The temps are very similar on the gfs/gem/euro. 

But compared to the 1”+ qpf the others are spitting out during this same time period the euro is simply too weak with the WAA precip. 

keep in mind some of that (as with the others) is rain.  So it’s really only showing about .25-.35 qpf over 12 hours when we have the colder profile...not very thumpy and not good enough to mix out the warm layer so it leans more sleet than snow. 

Still not nothing. Shows the potential for 1-2” of snow/sleet across the area but it’s a more typical minor event compared to the depiction it (and some other guidance still) was throwing out there earlier.  Still time to change. 

I think taking a blend of the euro and Gfs is the way to go right now. Both are playing to there bias.( euro to dry and GFS to wet.) I think a middle ground between them would  still make for a 1 to 3 "  sbow then ice to rain/dryslot. 

 

After what the long range was looking like for most of January I would take that in a heartbeat.

[MD Snow]

I'm just excited about extrapolating the NAM this afternoon and tonight. 

All in all, looks like we'll get some kind of frozen. I think worst case scenario with this will be similar to what the Euro is spitting out. Canadian would probably be best case. Still think there is ample time for a shift or two in either direction.

Who would have thought 2 weeks ago that we would have had an accumulating snowfall last week and be able to move almost right on to tracking another threat this week? Fun times. 

[Baltimorewx]

5 minutes ago, MD Snow said:

I'm just excited about extrapolating the NAM this afternoon and tonight. 

All in all, looks like we'll get some kind of frozen. I think worst case scenario with this will be similar to what the Euro is spitting out. Canadian would probably be best case. Still think there is ample time for a shift or two in either direction.

Who would have thought 2 weeks ago that we would have had an accumulating snowfall last week and be able to move almost right on to tracking another threat this week? Fun times. 

You know at some point we'll get a NAM'ing even if the storm cuts to Seattle

[psuhoffman]

1 hour ago, H2O said:

Is that mainly a product of the better lift from the WAA being closer to the low which is further NW since it went to MN?

The Euro has a sharper trough at the surface and mid levels and this creates a compact system as opposed to the GFS which has a more broad trough which directs more mid level winds (hence WAA) east into the mid atlantic vs the euro.  In essense the GFS (and GGEM) have a frontrunner wave and the euro does not.

At the surface the GFS is actually further north than the euro and warmer.  The euro is colder and less amplified with the surface system BUT you can see from the isobars that there is no energy being directed east into the cold air compared to the gfs at 12z Saturday.  Hence the lack of WAA precip extending east. 

Euro

GFS

 

It's a lot easier to see at the mid levels

H7 heights and winds

Look how the trough and winds are oriented on the euro

GFS

[aldie 22]

2 minutes ago, psuhoffman said:

The Euro has a sharper trough at the surface and mid levels and this creates a compact system as opposed to the GFS which has a more broad trough which directs more mid level winds (hence WAA) east into the mid atlantic vs the euro.  In essense the GFS (and GGEM) have a frontrunner wave and the euro does not.

At the surface the GFS is actually further north than the euro and warmer.  The euro is colder and less amplified with the surface system BUT you can see from the isobars that there is no energy being directed east into the cold air compared to the gfs at 12z Saturday.  Hence the lack of WAA precip extending east. 

Euro

GFS

 

It's a lot easier to see at the mid levels

H7 heights and winds

Look how the trough and winds are oriented on the euro

GFS

This is a fantastic and educational post...really easy to understand and straight forward as to the difference. Much appreciated

[PivotPoint]

4 minutes ago, psuhoffman said:

The Euro has a sharper trough at the surface and mid levels and this creates a compact system as opposed to the GFS which has a more broad trough which directs more mid level winds (hence WAA) east into the mid atlantic vs the euro.  In essense the GFS (and GGEM) have a frontrunner wave and the euro does not.

At the surface the GFS is actually further north than the euro and warmer.  The euro is colder and less amplified with the surface system BUT you can see from the isobars that there is no energy being directed east into the cold air compared to the gfs at 12z Saturday.  Hence the lack of WAA precip extending east. 

Euro

GFS

 

It's a lot easier to see at the mid levels

H7 heights and winds

Look how the trough and winds are oriented on the euro

GFS

Seems like trough axis in euro is slightly sharper and titled negative. Gfs flatter. Given the delay in onset talked about in the noaa discussion I’d lean more towards euro. Gfs seems to quick with flow and onset of heavier WAA

[jayyy]

Starting to look like warning level snowfall is possible for me PSUhoffman and my fellow northern tier friends

I think it’s safe to say an ALL snow event is not happening, however we could still very easily see the low track in a manner where we see a solid 4-6” thump before we go to ice and are dryslotted. In fact, analogs for similar storms and setups at h5 point to the fact that that outcome is quite possible. 

We need the storm to dig and strengthen far enough south so its able to tap into an ample moisture source, but far enough north / weak enough to not pump a ton of warm air into our neck of the woods. A tight rope to walk, but we are seeing the overall trends we want to be seeing at this point to achieve just that 

Many are focusing on the stubborn CAD in place from a 1040 H to our north and how cold it'll be leading up.  Rightfully so. However, remember that it is not surface temps that will determine when we change over to slop or rain. It can be 33 and heavily snowing, and it can be 19 out with sleet or freezing rain. What we need to worry about is the surge of warm air between the 700-900 levels.

Going to be blunt here. Think there’s going to be a huge gradient in snowfall between DC and Baltimore. Points SE of DC may only see snow TV, while points NW of BAL see upwards of 6”. We will have a solid idea of where this boundary will setup by 00z Thursday. Until then, models will continue to waffle. Important that we stick to the trends and don’t jump off the ledge from run to run. Dissecting surface temp / QPF total specifics 3+’days out is a waste of time and energy. We’ll get into that in the short term. Let’s just keep rooting for the snowier trend to continue for now!

[psuhoffman]

@H2O

The effect is even more dramatic at 18z

GFS

Euro

 

There are 2 ways to look at this...

The Euro is actually the colder solution with a better SLP track and CAD.  If it adjusts towards a broader mid level trough which allows a front runner wave with more mid level WAA directed into the mid atlantic...the euro might actually end up BETTER than the GFS/GGEM.  Keep in mind it still manages 1-2" across our area Saturday evening even though it has NOTHING during the day Saturday when the GFS is thumping us.  It is significantly colder.

On the other hand if the euro is right and the system ends up with a very sharp mid level trough that directs all the WAA to our west there is a severe cap on how much frozen we can really get with this given the primary low is most definitely going to track well northwest of us.  

[MD Snow]

ICON pretty much whiffs with an all snow start except far northern and eastern areas. Slightly drier to start which allows upper levels to warm enough for mix. Primary stronger and less strung out as well. 

[Baltimorewx]

1 minute ago, anotherman said:

The ICON is hot garbage.

Its probably a decent amount of sleet or ice for many of us but yeah not much snow

[MD Snow]

2 minutes ago, anotherman said:

The ICON is hot garbage.

YUP, ICON doesn't show mix. Check surface temps. 

[psuhoffman]

5 minutes ago, MD Snow said:

ICON pretty much whiffs with an all snow start except far northern and eastern areas. Slightly drier to start which allows upper levels to warm enough for mix. 

From the precip distribution pattern I would guess the ICON is in the euro camp wrt the mid level flow.  

[MillvilleWx]

2 minutes ago, anotherman said:

The ICON is hot garbage.

Wish I could look at thermals, but just given the algorithm in place and the surface temps, looks like a quick burst of snow in the beginning, then a nasty ice storm west of the Fall line. East of the fall line is a minor event with some snowfall, short period of ice, then ice cold rain. This is a verbatim take, and it's the ICON. I'll wait for the better models and withstand judgement. 

[psuhoffman]

up until 12z runs...the GGEM/GFS are in agreement with a broader mid level flow and lead wave, the Euro/ICON agree on no lead wave.  I haven't seen anyone post the UKMET so no idea what it's doing.  I will be interested to see what the high resolution guidance does once it gets into range.  

[psuhoffman]

1 hour ago, showmethesnow said:

Are we looking at the same thing? 06Z looks comparable if not just a smidge wetter then the 00Z on precip total. Now admittedly both runs are dryer then the other models but still I didn't see a degradation. 

It beefed up precip slightly towards the end...AFTER we lose the column for snow.  Might be more "icy" 6z v 0z but less snowy...I am NOT a fan of ice so for those that want ice 6z could possibly be a better run.  Preference.  But if you look at precip early on when we have the column it was a slight reduction hence the cut in snowfall totals across MD.  

[MD Snow]

I don't really foresee this going much further west than already depicted. Could see runs today and even tomorrow trending the wrong way before an overall positive trend for the final 48hrs, with incremental improvements as CAD begins to be better modeled and the low trends slightly further east in or favor. I'm probably just being optimistic but I've seen it happen plenty of times before. 

[showmethesnow]

6 minutes ago, psuhoffman said:

It beefed up precip slightly towards the end...AFTER we lose the column for snow.  Might be more "icy" 6z v 0z but less snowy...I am NOT a fan of ice so for those that want ice 6z could possibly be a better run.  Preference.  But if you look at precip early on when we have the column it was a slight reduction hence the cut in snowfall totals across MD.  

Got you. Didn't look in depth was just a quick and dirty glance after seeing your post. Nice post on the mid-level winds by the way.

[clskinsfan]

Hi Res Euro is a mix of the GFS and regular EURO. People in northern Md should love it. Verbatim it is a nasty ice storm for the 81 corridor.

[Scraff]

GFS looks too mixey to me. Not much of an initial thump.