December Med/Long Range Discussion Part 2

[mappy]

Just now, pasnownut said:

One run is not a trend.  Its a bad run.  The only trends right now are the volatility meter being off the charts.

Several solutions left until we know in this butt ugly pattern.  Still better than last year....so far.  That may change, but I'm not closing any blinds yet.

Nut

 

you said it better than i did. thank you. 

[pasnownut]

7 minutes ago, mappy said:

you said it better than i did. thank you. 

 

Just trying to stay ++++ in this trying pattern.  Like I suggested yesterday, and Bob showed a little hope using the roll forward approach, we need that NAO to show up, and we all know that doesnt just appear.  that said its gonna be a long....and many times rocky sleigh ride into the New Year.  Doesnt mean we cant eek out some opportunities.

 

Nut

 

[Wxdavis5784]

Forgive me if I am wrong, but if you take the 12z and 18z from yesterday and look at last nights 0z and this mornings 6z, I would say there is a trend backing off of snow. So you are correct in the fact that one run isnt a trend but the last 2 havent been overly impressive IMO.

[H2O]

6z GFS still has a p decent ice event for DCA up until 18z Sat.  There is a blob of precip that falls between hr102-108 with temps still <32

[mappy]

Per cobb for westminster

06z GFS has 3-4" of snow before the flip, but even the flip is a brief 3 hour period of FRZA before precip stops. I can totally get on board with that. 

[mappy]

Also -- 06z GFS was better for Westminster than 00z. 

[mappy]

LOL -- ignore all that. Cobb has 00z/06z flipped around. 

 

06z much worse  

[Bob Chill]

6 minutes ago, mappy said:

LOL -- ignore all that. Cobb has 00z/06z flipped around. 

 

06z much worse  

Don't worry. The para will save you. 0z para was good again. 

This brings up some between the lines thoughts. We're just coming up on inside of d4 so ops will become more useful than ens. Ens spread is fairly tight already so they aren't adding too much value as it is.  Considering the front running precip is waa driven and not so much synoptic it could easily trend better at shorter ranges. 

Psu made a great post yesterday about small bullseyes due to best lift at the battleground between air masses. It may not be until Thursday before that is honed in on. 

[mappy]

5 minutes ago, Bob Chill said:

Don't worry. The para will save you. 0z para was good again. 

This brings up some between the lines thoughts. We're just coming up on inside of d4 so ops will become more useful than ens. Ens spread is fairly tight already so they aren't adding too much value as it is.  Considering the front running precip is waa driven and not so much synoptic it could easily trend better at shorter ranges. 

Psu made a great post yesterday about small bullseyes due to best lift at the battleground between air masses. It may not be until Thursday before that is honed in on. 

thanks, hadn't looked at the para. 

i did see psu's post yesterday, definitely a great post that everyone should read a few times and take a step back from the ledge. 

i'm just excited we have something to track

[WxMan1]

20 minutes ago, Bob Chill said:

Psu made a great post yesterday about small bullseyes due to best lift at the battleground between air masses. It may not be until Thursday before that is honed in on. 

This.

In instances like these, we want that flatter, faster wave, even one that doesn't look like your typical (dampened) shortwave, rather one that shows up on a 500 mb chart as an innocuous warm frontal arc or lobe of higher vorticity before the first initial round of height rises. The colder/deeper the retreating arctic air to work with (denser theta packing), the more bang for the buck with the initial waa. Especially if the thermal stratification in that best isentropic ascent/moist layer is optimal for crystal growth (i.e. between -12 to -18°C).  This is most certainly where those bullseyes come into play.  

[Bob Chill]

15 minutes ago, WxMan1 said:

This.

In instances like these, we want that flatter, faster wave, even one that doesn't look like your typical (dampened) shortwave, rather one that shows up on a 500 mb chart as an innocuous warm frontal arc or lobe of higher vorticity before the first initial round of height rises. The colder/deeper the retreating arctic air to work with (denser theta packing), the more bang for the buck with the initial waa. Especially if the thermal stratification in that best isentropic ascent/moist layer is optimal for crystal growth (i.e. between -12 to -18°C).  This is most certainly where those bullseyes come into play.  

Much more eloquent than what I said :). 

That's the interesting part of the storm obviously. Even as HP is nearly overhead it's still doing it's dirty work with return flow in the middle of the country. Using the nam sim as an example (NOTE EXAMPLE lol), it shows how things can really get juiced up far in advance of any synoptic feature. 

 

 

Unlike clippers, dry air will be much easier to overcome because moisture will be much deeper. Of course this also means a switch to sleet will probably happen earlier than models predict. The very simple view is that it seems unanimous that the snow column is in peril around 12z give or take. We want the fastest onset possible. The synoptic low is trailing by quite a margin so the best trend to watch is onset time and expanse of the shield. This is one thing the ops may be underestimating at this point. Hard to say. All we can do is hope things juice up on the front end as we approach. Chance for significant snow has dwindled considerably but we can still have an "acceptable" event out of this. 

[Bob Chill]

Just now, Bob Chill said:

Much more eloquent than what I said :). 

That's the interesting part of the storm obviously. Even as HP is nearly overhead it's still doing it's dirty work with return flow in the middle of the country. Using the nam sim as an example (NOTE EXAMPLE lol), it shows how things can really get juiced up far in advance of any synoptic feature. 

 

 

Unlike clippers, dry air will be much easier to overcome because moisture will be much deeper. Of course this also means a switch to sleet will probably happen earlier than models predict. The very simple view is that it seems unanimous that the snow column is in peril around 12z give or take. We want the fastest onset possible. The synoptic low is trailing by quite a margin so the best trend to watch is onset time and expanse of the shield. This is one thing the ops may be underestimating or misplacing at this point. Hard to say. All we can do is hope things juice up on the front end as we approach. Chance for significant snow has dwindled considerably but we can still have an "acceptable" event out of this. 

 

[WxMan1]

3 minutes ago, Bob Chill said:

Much more eloquent than what I said :). 

That's the interesting part of the storm obviously. Even as HP is nearly overhead it's still doing it's dirty work with return flow in the middle of the country. Using the nam sim as an example (NOTE EXAMPLE lol), it shows how things can really get juiced up far in advance of any synoptic feature. 

 

 

Unlike clippers, dry air will be much easier to overcome because moisture will be much deeper. Of course this also means a switch to sleet will probably happen earlier than models predict. The very simple view is that it seems unanimous that the snow column is in peril around 12z give or take. We want the fastest onset possible. The synoptic low is trailing by quite a margin so the best trend to watch is onset time and expanse of the shield. This is one thing the ops may be underestimating at this point. Hard to say. All we can do is hope things juice up on the front end as we approach. Chance for significant snow has dwindled considerably but we can still have an "acceptable" event out of this. 

Well put!

[Bob Chill]

8 hours ago, psuhoffman said:

I know a few have discussed the disconnect between the temperatures and the H5 means on the long range ensembles and I think I discovered the disconnect.  Looking at the last few op runs of the GFS I suspect the means are giving a false impression of what the period may actually be like.  The first issue is that north America will be flooded with cold air when this +epo +nao period starts.  That means for a while the cold may well be able to push and encroach further into the area of h5 ridging then you would normally expect.  Also, the op runs seem to imply storms will be cutting across into the area of general ridging in the east during this period.  If you look at the links below, you can see that overall the heights are high along the east coast if you take an average of the entire period, but twice storms are able to cut into the ridging and end up in a place that puts us in the game.  however, due to timing differences at this range, any ensemble mean is simply going to show ridging in our area and not indicate the storm that cuts through for a day since the ridging is in place 70% of the time during the 10 day period.  It is a much more fluid and volatile pattern then the means suggest.  Now the longer we stay in such a pattern the worse it will get.  The cold will relax and once it does it could get ugly.  But the pattern may not be stable and lock in for long so if we can hold off the torch for a week we may not have to suffer long before things reshuffle.  Just wearing my rose glasses tonight. 

 

Good post about the disconnect. We're already starting to see colder features embedded in the flow that were smoothed out into orange lameness on the means several days ago. EPS last night again has mean hi/low temps d11-15 that are completely normal and cooler than a few days ago. Mean highs in the low to mid 40's and lows in the upper 20's every day. Certainly doesn't mean in reality that we have a day or 2 in the 50's/cold front/day or 2 in the upper 30's of course but clues outside of the mean h5 plots continue to indicate we are not going to have a balmy week straight of weather. 

D15 h5 member plots show a huge range of possibilities irt sensible wx on the east coast. Def a bias for higher heights in the SE but not by a big margin or anything. The mix of plots imply pretty much normal winter wx in our region with nothing exciting or devastating. I've seem much worse. That's for sure. Last december's member plots required medication to look at. LOL

 

 

 

I'm a touch on the pessimistic side about how long the lower heights stick around AK and the west. That is a feature we can do without. If you aren't going to have any atlantic help then you can't have height patterns like that for an extended period. Screws up everything because it will warm our source region #1, and #2 it will be difficult to impossible to maintain any colder air we get in the area. Basically hit and run modified continental air will be the norm. The only saving grace is time of year. We are quickly moving towards our best climo period where we don't need major departures to support frozen precip but the overall look pretty much sucks. Barring a fluke/miracle, my guess is Dec offers no chances at a clean and/or decent event. Frozen scraps at best. I hope I eat these words....

[WxUSAF]

1 hour ago, Bob Chill said:

Don't worry. The para will save you. 0z para was good again. 

This brings up some between the lines thoughts. We're just coming up on inside of d4 so ops will become more useful than ens. Ens spread is fairly tight already so they aren't adding too much value as it is.  Considering the front running precip is waa driven and not so much synoptic it could easily trend better at shorter ranges. 

Psu made a great post yesterday about small bullseyes due to best lift at the battleground between air masses. It may not be until Thursday before that is honed in on. 

6z GFS still has the "thump" between 12-15z Saturday morning near DC/Baltimore.  Except it brings in slightly warmer air aloft relative to 0z, so at least some of that thump is sleet.  If you assume 50/50, it's still 2-3" of snow for our area, some sleet, fzdz, then a few rain showers and it all melts Sunday.  

[WinterWxLuvr]

1 hour ago, wdavis5784 said:

Forgive me if I am wrong, but if you take the 12z and 18z from yesterday and look at last nights 0z and this mornings 6z, I would say there is a trend backing off of snow. So you are correct in the fact that one run isnt a trend but the last 2 havent been overly impressive IMO.

So it might not snow.  It's not the end of the world.

[Joshfsu123]

47 minutes ago, WxUSAF said:

6z GFS still has the "thump" between 12-15z Saturday morning near DC/Baltimore.  Except it brings in slightly warmer air aloft relative to 0z, so at least some of that thump is sleet.  If you assume 50/50, it's still 2-3" of snow for our area, some sleet, fzdz, then a few rain showers and it all melts Sunday.  

I would take this in a heartbeat... just want to see a little snow to get into the Holiday mood.

[eurojosh]

12z NAM (12k) 84 hrs is 

 

 

[nflwxman]

1 minute ago, eurojosh said:

12z NAM (12k) 84 hrs is 

 

 

Mostly virga, verbatim.

[yoda]

06z GFS snowfall maps on TT show 4-6 in DC region though... I guess some of that is sleet?

[yoda]

2 minutes ago, nflwxman said:

Mostly virga, verbatim.

Precip is still down in C VA... but it would look nice if that is the radar look

[WxUSAF]

2 minutes ago, yoda said:

06z GFS snowfall maps on TT show 4-6 in DC region though... I guess some of that is sleet?

For sure, but not sure exactly how much.  Still has that WAA thump right around DC/Baltimore from 12-15z, but by 15z, everyone but maybe mappy and folks E and N of her are pinging.  So, it flips sometime between 12 and 15z, but don't know exactly when.  Going to be later the farther N and E you are. 

[mappy]

5 minutes ago, yoda said:

06z GFS snowfall maps on TT show 4-6 in DC region though... I guess some of that is sleet?

most, yes. maybe an inch of actual snow, rest is sleet/frza, then plain rain. 

[MN Transplant]

I know that the 12z is rolling, but this sounding from 06z is just great

[WinterWxLuvr]

When I look at the h5 map on the NAM (yes, I know), I don't see how the storm isn't even more north and west than it is.

Even as it's been modeled, reliance upon precip from a low in Kansas is an iffy proposition IMO.

Still 4 days out though, and that means a lot lately.

[mdsnowlover]

1 minute ago, MN Transplant said:

I know that the 12z is rolling, but this sounding from 06z is just great

i still cant read them, shoot!!

[yoda]

I guess then 06z GFS at 105 would be heavy freezing rain?

[MillvilleWx]

2 minutes ago, MN Transplant said:

I know that the 12z is rolling, but this sounding from 06z is just great

Nose goes...

[MN Transplant]

Just now, mdsnowlover said:

i still cant read them, shoot!!

Just look at the red line, which is temperature.  Bottom is the surface, top is way above the jet stream.  This one shows how dramatically it warms from the surface to just above the surface (few thousand feet). 

[mdsnowlover]

1 minute ago, MN Transplant said:

Just look at the red line, which is temperature.  Bottom is the surface, top is way above the jet stream.  This one shows how dramatically it warms from the surface to just above the surface (few thousand feet). 

thank so much.