December 2018 Pattern And Forecast Discussion

[AMZ8990]

5 minutes ago, TellicoWx said:

12z EPS mean:

TRI: 6"

TYS: 2" (south knox), 3.5" (north knox)

Chat: 2"

Cross: 4"

Highest run so far for northeast TN. EPS looks almost identical to GEFS mean.

@TellicoWx, what was the mean for Memphis or Jackson Tn?

[TellicoWx]

10 minutes ago, AMZ8990 said:

@TellicoWx, what was the mean for Memphis or Jackson Tn?

1" for both

[AMZ8990]

2 minutes ago, TellicoWx said:

1" for both

Cool, thank ya sir.

[Carvers Gap]

MRX evening disco...

For Friday night into Monday, models
continue to be inconsistent and have significant differences in
the details, but there is decent agreement that a significant
mid/upper level trough will dig in and a surface low will track by
to our south and east. While it currently looks like this will
likely be a mainly liquid event, especially for valley locations,
given the high level of uncertainty that far out and given that
there is model disagreement on how quickly it warms up on the
front end and cools down on the back side, will have to keep the
possibility of frozen precip in the forecast especially at onset
and on the back side. Will keep a mention of this in the HWO as
well.

[Holston_River_Rambler]

Whatever the outcome, our energy looks healthy and even has a connection from near HI.

GOES 17 image

[Carvers Gap]

Just looking at the guidance from 12z and 18z, looks like the trend today is north with weaker high pressure.  That is likely not good for many.  Maybe our folks in SE KY and SW VA can score.  Not giving up just yet.  Still about one more day before it gets much tougher.   Will check the ensembles and the Weeklies and then check back in....

Hey, @Drummer230 introduced themselves in banter.  Just moved here.  They had asked about the weather around Clarksville.  I thought you middle TN folks could chime in....

@Will (little rock), I see you down there viewing.  How does it look for you all?  You always stop in and provide valuable info.

[Carvers Gap]

Here is the 18z GEFS snow mean....this puts the operational in perspective.  The operational will have added weight beginning around tomorrow.  Right now, I give the ensemble a little bit more weight.  Tomorrow is equal.  By Wednesday, the operational and trend are the big movers...unless they are bad.  Then we talk about the Weekly. LOL.  I don't want to provide false hope w the image below, but that is where we are.  That is a pretty good ensemble mean w some not so encouraging trends for the operational models.  BTW, if it makes you feel better...that snow hole over NE TN(the really tiny one) is over MBY. 

 

[Carvers Gap]

....And if you need a pick-me-up, the Weeklies(hindcast version) look really, really....really good.  Slight warm-up and quick return to winter by the holidays.  

[Will (little rock)]

Definitely an interesting storm and certainly interesting to see the models having somewhat agreement, just hoping now that that high pressure can force some more cold air down and we see more than cold rain

[Holston_River_Rambler]

Like Carvers I don't want to provide and false hope, but there was a Met in the SE forum (page 25 of their thread for this storm) who pointed out that the GFS/ Fv3 was still substantially changing how it handles the wave run-to-run when it comes on shore in CA. That person argued that the region was "under sampled" and wouldn't put too much stock in the 18z.  I know that some are for/ against the "under sampled" as a valid argument with improved satellite data, but thought I'd throw this info out. 

I think as tnweathernut said earlier this AM, probably be some of the last significant changes once this booger gets onshore. 

[BlunderStorm]

4 minutes ago, Carvers Gap said:

....And if you need a pick-me-up, the Weeklies(hindcast version) look really, really....really good.  Slight warm-up and quick return to winter by the holidays.  

Good news to hear for a shot at a white Christmas. Also, I had just read through the euro ensemble members this time around and counted 30-32 out of the 50 members that supported a winter storm warning in my county. That makes an improvement of 5-8 members since 24 hours ago. I can't comment on last nights ensemble members as I didn't count them. As for how that applies to you all I really can't say without recounting all of the members in the specific spot. To state the obvious and already mentioned for emphasis I hope we don't see the trend between 12z and 18z continue.

[Carvers Gap]

1 minute ago, BlunderStorm said:

Good news to hear for a shot at a white Christmas. Also, I had just read through the euro ensemble members this time around and counted 30-32 out of the 50 members that supported a winter storm warning in my county. That makes an improvement of 5-8 members since 24 hours ago. I can't comment on last nights ensemble members as I didn't count them. As for how that applies to you all I really can't say without recounting all of the members in the specific spot. To state the obvious and already mentioned for emphasis I hope we don't see the trend between 12z and 18z continue.

Yeah, major teleconnection means begin to look really good between Christmas and New Year...-NAO, -EPO, and -AO.  Christmas might be a bit early for a good pattern - but w this trend, who knows?  Very cold signal for early to mid January.  They are a bit on the dry side which seems a bit tough to buy given the current pattern and what we know about Nino winters.  Now, the Weeklies have been flipping around all over the place...but they flipped cold this evening.  We suspected the BN heights over AK would be short-lived.  The 12z EPS basically shows the end of the warm pattern on that run...meaning it goes no longer than d15 and the includes the next 7-10 days of cold.  I will leave it for @nrgjeff to break it down for us since he called his shot.  As for my own personal comments, please refer to the gif below...

         

  

[IndTenn]

1 hour ago, Carvers Gap said:

Here is the 18z GEFS snow mean....this puts the operational in perspective.  The operational will have added weight beginning around tomorrow.  Right now, I give the ensemble a little bit more weight.  Tomorrow is equal.  By Wednesday, the operational and trend are the big movers...unless they are bad.  Then we talk about the Weekly. LOL.  I don't want to provide false hope w the image below, but that is where we are.  That is a pretty good ensemble mean w some not so encouraging trends for the operational models.  BTW, if it makes you feel better...that snow hole over NE TN(the really tiny one) is over MBY. 

 

The Eastman snow shield is operational

[John1122]

The models are actually amazingly steady on the track of this system. The run to run differences we see are relatively minor wobbles. It's just that these 75-100 mile wobbles have major effects on the sensible weather on the ground for our region because as we often are, we are on the borderline for rain vs snow. Sometimes it's like they designed and implimented 40 just south of classic snow vs rain areas. 

[BlunderStorm]

10 minutes ago, IndTenn said:

The Eastman snow shield is operational

Ahh, the good ole Kingsport Snow Hole of Approval as I call it. 

[Holston_River_Rambler]

Just add this to play devil's advocate to my own post. As far as I can tell guy is a NWS forecaster and has several tweets on this specific storm today besides the one I'm posting.

Basic summary: N. stream may end up being more difficult to peg down than southern. Wed night to early Thursday for some clarity for features east of the Mississippi

This one was number 3 out of 11. Number 10 in the series offers a good guide to using ensembles. (not putting that out there as a critique of how anyone is using ensembles here, but since we have a thread about education, thought I'd add it in too in case anyone was curious)

 

[nrgjeff]

Agree the northern Stream will probably determine the outcome. Southern stream with surface low south looks good. Exact track of PVA is still up in the air, and that 75-100 miles is crucial. Northern stream will influence both the PVA and the cold air. Sure the southern stream will influence PVA too; but, I think the northern stream will be most crucial here.

European weeklies are cold. Mid-December warm period now looks only about 5 days long vs 7-10. Week of Dec. 17 is now shown slightly cool here. I figure it will take a couple cold fronts to fully cool off though. The big GOA trough responsible for the mild 5 days will also scour the cold supply. However by Dec. 24 the new AK ridge will have been in place several days, replenishing cold air supply. So I like the gradual step slightly BN temps Dec. 17 week (perhaps still near normal). Then go more solidly BN temps Dec. 24 week. January starts pretty cold too. If week 5-6 is right, then things could finally get interesting here in January.

[BlunderStorm]

Tonight the ICON took another step in the right direction. Hopefully this is the story for the whole model suite.

[Bango]

5 minutes ago, BlunderStorm said:

Tonight the ICON took another step in the right direction. Hopefully this is the story for the whole model suite.

Dreamy path for the low on the ICON for much of i40 north, which for that particular model, is about all I take away.  As john stated, the route, for 5 days out, is really honed in even if the wobbles and details remain subject to change

[jaxjagman]

55 minutes ago, *Flash* said:

0z a smash for NC. Seems this storm is trending as another Carolina special. 

No doubt and we get the nose job

 

[John1122]

I actually like that run of the GFS pretty well. The high is stronger in the Midwest. The air is colder than it was showing a few days ago. The track is really great as well. With all those factors it just feels like the GFS is overestimating the 850s.  

The other day Holston posted some reanalysis animations. This exact set up was on one of the major December snowstorms.  HP over SE Minnesota, low along the panhandle. I just don't see the 850s hitting the Ohio River in this set up. That is a 1008 lp, not a 997 cranking in the Gulf. 

 

[John1122]

The FVS is hanging in for 40 and north basically. I won't bother with the crazy tropical map that puts down 2 feet of snow right on top of me. But the snow depth looks like a reasonable compromise.

[John1122]

The FVS also gives my area around .30-.40 freezing rain.

[BlunderStorm]

37 minutes ago, John1122 said:

The FVS is hanging in for 40 and north basically. I won't bother with the crazy tropical map that puts down 2 feet of snow right on top of me. But the snow depth looks like a reasonable compromise.

I would take that in a heartbeat and cash out til January with that look. That's a solid 10".

[John1122]

Euro snow depth map is similar in areas north of 40 to the snow depth map from the FV3. 12+ inches on the Northern Plateau with some 16+ areas where elevations approach or exceed 3000 feet near me and into SEKY, 2-4 right along the TN/KY line from Clarksville to the Eastern Highland Rim. 8-12+ inches in NE TN/SWVA. 16-25+ in Western NC. Just insane, if it were to come to pass there'd be a ton of power outages and it'd be a truly old school storm. My largest has been 13 inches in the 2000s. February of 1998 I had 17+, February of 1996 I had 15, March 1993 I had 25.  I think 13 is the biggest December event I recall seeing listed here. But I would have to go back and look again.

Warm nose up the Eastern Valley to probably Jefferson City or a little further, and for all of Middle and Western Tennessee below the border areas with Kentucky.

This is probably the biggest Euro run yet for the areas in SEKY, Plateau, NETN, SWVA that get the snow.

Also, that is as I noted, the snow depth map, not the snowfall map. I'd imagine it might look like the FV3 map.

[BlunderStorm]

Snow depth at peak extent among models on weather.us

German 0z 

 

GFS 0z

 

ECMWF 0z

Outside of the NE portion it's not looking good for the Tennessee Valley atm. Models are starting to carry a little more weight. As for myself I'm feeling pretty excited! I'd say we should probably start up a thread tomorrow if were still looking good on 06z.

[TellicoWx]

0z EPS is almost identical to 12z, only change really was it increased the mean across NE TN.

[jaxjagman]

GFS keeps going back and forth with the winds.

 

 

[Carvers Gap]

41 minutes ago, jaxjagman said:

GFS keeps going back and forth with the winds.

 

 

I think this is one of those winters where the PV is just going to take a beating.  

[John1122]

Neighboring WFO in Kentucky, NC and VA have issued winter weather advisories for snow overnight and into tomorrow. Waiting to see if MRX follows suit. Fairly robust wave working through the area over the next 24 hours. Just had a burst pass through that was blinding for about 10 minutes. Hopefully they increase in frequency overnight.