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December Medium/Long Range Discussion


WxUSAF
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23 minutes ago, Bob Chill said:

12z eps at the end of the run looks a lot like a smoothed version of the 12z gfs op. uh oh

Now that I ain't concerned about...lol (besides, that would look like a more typical Niño!)

And overall...I think we could all use some down time from tracking (I know I could...there is Christmas music to be prepared!)

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Yay flooding returns!  And this will probably make 2018 the wettest year in DCA history... from the afternoon LWX AFD:

.LONG TERM /THURSDAY THROUGH MONDAY/...

A shortwave disturbance will depart off to the northeast Thursday
morning, and ridging will build in aloft. As a result, dry
conditions are expected. There could be a bit more cloud cover than
previous days as high clouds start to stream in ahead of a more
significant system located off to our southwest. High temperatures
will reach into the low-mid 40s.

Meanwhile, a high amplitude trough will eject from the Four Corners
region onto the Southern Plains during the day Thursday. This trough
will become meridionally elongated in nature Thursday Night, and
eventually become cut off from the northern stream flow during the
day Friday as it tracks across the lower Mississippi Valley. This
trough will be highly anomalous in nature, with standardized
anomalies of 500 hPa height dipping to -5 to -6 over Louisiana at
12z Friday. The highly anomalous nature, and slow forward motion of
the trough will allow it to draw moisture northward out of the
tropics. By midday Friday, a fairly expansive plume of precipitable
water values between 1.5-2 inches will be located just downstream of
the trough over the southeast US. As the system progresses further
along, this plume of moisture will reach our area, with most
model guidance indicating precipitable water values around
1.25-1.5 inches locally. Those values would be near, or
potentially above the record daily values for the IAD sounding
location. Given the high moisture content and strong forcing for
ascent downstream of the potent mid-level trough, heavy
rainfall appears likely across the region Friday afternoon
through much of Friday Night. Nearly all of the deterministic
guidance, as well as the ensemble means of the GEFS and EPS
produce well in excess of an inch with the system. As a result,
flooding could become a concern, especially over areas that have
residual snowcover from yesterday`s storm.

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10 minutes ago, yoda said:

Yay flooding returns!  And this will probably make 2018 the wettest year in DCA history... from the afternoon LWX AFD:

 

 

Good. We need the rain......we've been suffering from a terrible drought. The water table is low and it's been looking entirely possible that we never get rain again. Also we've been in moderate drought conditions for months. And I think we're not going to get any snow this winter because of atmospheric memory and the drought. :whistle: :ph34r:

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1 hour ago, Bob Chill said:

I was actually be more serious than troll...

qhWoe5A.jpg

 

gfs_z500a_nhem_53.png

I actually think the EPS pattern would be ‘okay’, especially if you got the PV to sink a bit S. You could end up with an overrunning pattern. You wont get big MECS with this look, but you could get ice/thump type events if it worked out on timing 

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Just now, Wentzadelphia said:

I actually think the EPS pattern would be ‘okay’, especially if you got the PV to sink a bit S. You could end up with an overrunning pattern. You wont get big MECS with this look, but you could get ice/thump type events if it worked out on timing 

Sorry. Too many IFs and COULDs here. Low probability front end slop? Not what we are looking for. Not after the south got plastered with an historic snow event in early Dec while we got bupkis. Take all your misguided optimism elsewhere.

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7 minutes ago, Wentzadelphia said:

I actually think the EPS pattern would be ‘okay’, especially if you got the PV to sink a bit S. You could end up with an overrunning pattern. You wont get big MECS with this look, but you could get ice/thump type events if it worked out on timing 

It's generally a -AO look.. ignore the RNA ridge, it's El Nino. 

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23 minutes ago, C.A.P.E. said:

Perhaps the new edition of the weeklies might brighten the mood a bit. I kinda doubt it though. Probably going to suggest closing the shades until mid January. Those of you close to full panic mode, proceed with caution this evening.

If the shades really were to close until mid-January, there would likely be panic, and it would not necessarily be completely off-base.

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3 minutes ago, C.A.P.E. said:

@Bob Chill you need to step it up dude. I am in a bitter mood.

Not trolling here....

If the epo ridge goes up but the ridge in the west sets up off the west coast then we're in some trouble for a while. I liked what the gefs was doing and the eps started following but that's changing now. If the epo cold is centered out west and there's even the slightest hint of a SE ridge then the storm track will be north and west of our area. We'll get cold but not without rain first. I'm not a fan of anything I'm seeing right now. We have recent experience with what happens when the epo dumps cold in the west first. That's not a good or high prob for snow in these parts. If the gefs starts drifting towards cold in the west then it's close the shades here except for flukes. 

 

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1 minute ago, psuhoffman said:

If the epo ridge pops its only a matter of time before we get cold. If the AO is also neutral to negative it helps our chances. If the first dump goes into the west so be it. We have time. 

We clearly have a dead period coming up. Trolling aside, it appears the EPO/AO combo will be favorable going forward. It would be great if the pattern evolved quickly so we are cold by Xmas, but I have had my doubts about that. The week after seems more realistic, and it might be early Jan before we have established cold in the east. People get freaked about 'punting' Dec, but more often than not, it ends up that way.

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3 minutes ago, Bob Chill said:

Not trolling here....

If the epo ridge goes up but the ridge in the west sets up off the west coast then we're in some trouble for a while. I liked what the gefs was doing and the eps started following but that's changing now. If the epo cold is centered out west and there's even the slightest hint of a SE ridge then the storm track will be north and west of our area. We'll get cold but not without rain first. I'm not a fan of anything I'm seeing right now. We have recent experience with what happens when the epo dumps cold in the west first. That's not a good or high prob for snow in these parts. If the gefs starts drifting towards cold in the west then it's close the shades here except for flukes. 

 

I am in complete agreement with this post. Now, back to trolling..

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47 minutes ago, North Balti Zen said:

If the shades really were to close until mid-January, there would likely be panic, and it would not necessarily be completely off-base.

But given our history with ninos...and that strange occurence of us not typically getting snows in early January (even in our best years)...would that really be cause for concern? Sounds more typical to me, lol

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Weeklies look like about what you would expect given the 0z EPS at the end of its run. Western trough/eastern ridge, then a gradient pattern with WAR early Jan, then things really get good mid to latter third of Jan with -NAO and cold anomalies along the east coast. Looks like a -AO/-EPO throughout.

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4 minutes ago, C.A.P.E. said:

Weeklies look like about what you would expect given the 0z EPS at the end of its run. Western trough/eastern ridge, then a gradient pattern with WAR early Jan, then things really get good mid to latter third of Jan with -NAO and cold anomalies along the east coast. Looks like a -AO/-EPO throughout.

Has degraded quite a bit over the last 5 runs. AN temps in the east through early Jan now. The good stuff is getting kicked down the road. Luckily the weeklies have been really jumpy and unreliable. Week 3 skill is half decent though and week 3 is not a good snow look for us. 

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Just now, Bob Chill said:

Has degraded quite a bit over the last 5 runs. AN temps in the east through early Jan now. The good stuff is getting kicked down the road. Luckily the weeklies have been really jumpy and unreliable. Week 3 skill is half decent though and week 3 is not a good snow look for us. 

Yup, not to mention the EPS has been wishy-washy lately with the pattern evolution. This edition of the weeklies might look different (colder in the east earlier) if it was based off the prior EPS run. It is what it is.

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Just now, C.A.P.E. said:

Yup, not to mention the EPS has been wishy-washy lately with the pattern evolution. This edition of the weeklies might look different (colder in the east earlier) if it was based off the prior EPS run. It is what it is.

One thing of interest that normally doesn't interest me is the strat. @frd has been posting a bunch of interesting stuff. Looks like the most sig warmth/displacement of the season is setting up and it's not far away now. The ao/nao are notoriously hard to predict beyond 7 days so what we see now and what may happen could be very different. I wouldn't be surprised one bit if the ao or nao or both tank before the end of Dec. Strong blocking episodes on average last 45 days. If that happens before the end of the month then it changes the entire landscape of the rest of winter and no model is going to get it right until it happens. 

Week 3 of the weeklies looks pretty good for SNE though. More often then not they go on a heater before us. We've waited our turn many times. If the weeklies have it right then I wouldn't be surprised to see the NE get multiple events. 

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