1/26/17-1/30/17 Clipper/NW Flow Event.

[John1122]

This event is only around 36 hours from first flakes if models are to be believed. GGEM is lighter snows of 1-2 inches but more widespread. GFS has been consistent with heavier totals in all but one of the last 8 runs, but in all but two of those 8 runs, most snows greater than 1 inch occur over terrain areas in the East. Otherwise they are spread out enough to where areas may pick up 3/4ths of an inch from one system, then have it melt and pick up 3/4ths from the second.  So even though you see these snowfall totals, it will not likely be reflected at these amounts on the ground at a given time outside the terrain areas.

GGEM through Mon evening.

 

GFS through Monday evening.

[Greyhound]

MRX NWS mentions it in their forecast discussion....so I'm cautiously optimistic.  Of course the higher elevations are favored, but does mention the possibility for an inch in the Valley from the Sunday/Monday system. 

http://forecast.weather.gov/product.php?site=MRX&issuedby=MRX&product=AFD&format=CI&version=2&glossary=1

[tnweathernut]

Nice trend.  Take a look at the vort pass from 12z.  It's honestly not bad at all.  There is a piece of energy coming quickly behind the main vort that (to me) looks like it washes it out.  IF the main piece of energy is a little more consolidated or the trailer is a little more separated, I wouldn't be surprised to see something a little stronger.  

Obviously, the ceiling is still pretty low, regardless... Since it's the ONLY game in town though, it's not like we won't be watching it in east TN..  lol

[John1122]

This is a take what you can get winter. I'll take an inch or two. I just want to see snow in the air and feel some cold. I actually managed to get below freezing this morning for the first time in weeks. 

[nrgjeff]

Upper Plateau to Tri Cities should get some light snow, esp Sunday. Knoxvegas will need a lot of luck. Nashvegas would need even more. Not watching it at all for Chatty. Post may sound a little terse, but it is an easy pattern recognition forecast around here with that light QPF and 500 mb PVA overhead in NW flow. Cheers!

[BlunderStorm]

16 minutes ago, flash43 said:

 

Generally if it doesn't snow where I live in the head waters of the Tennessee valley it doesn't elsewhere in this forum. I'm sure you have a shot at it albeit slim.

[John1122]

0z GFS was further west and more vigorous with the second  again. Hopefully this is a trend like last year's clippers. 

[John1122]

4 hours ago, BlunderStorm said:

Generally if it doesn't snow where I live in the head waters of the Tennessee valley it doesn't elsewhere in this forum. 

I do disagree with this statement. Because of the geography of our forum, the biggest snow events for the western half will very often feature rain for the eastern half. 

[BlunderStorm]

Are you referring to examples in which a low tracks through our area causing warmer layers of air to cause rain and in some cases ice lowering snow totals. Sort of like what happened a year ago. I received 4 and a half from "snowzilla" due to what I just mentioned and a dry slot. When I think about a text book setup for an awesome storm I like to think of February 2015 specifically for lack of a better word what the weather channel referred to as "Octavia". I think the winter storm happened sometime between Feb 15-20ish with a full plethora of precipitation types resembling a layer cake as it crossed through the upper south and Appalachia. My town was pinned with 15 inches of snow. It may be years until another "Octavia" occurs but it was one of the two major events which increased my interest in meteorology the other being the 2011 tornado outbreak. I can still remember to this day vividly hearing the thunder rumble violently as the winds rushed by swaying the trees in ways I never seen before along with the rush of fear and adrenaline as our local meteorologist Dave Dierks spoke of a tornado warning over Russell county https://www.youtube.com/watch?v=B5k13-abTVM at 0:25. This video as well https://www.youtube.com/watch?v=1GEl1S_TpYU

 

*NOTE IMAGES SHOWN DO NOT RELATE WITH CURRENT EVENT BEING DISCUSSED*

[John1122]

36 minutes ago, BlunderStorm said:

Are you referring to examples in which a low tracks through our area causing warmer layers of air to cause rain and in some cases ice lowering snow totals. Sort of like what happened a year ago. I received 4 and a half from "snowzilla" due to what I just mentioned and a dry slot. When I think about a text book setup for an awesome storm I like to think of February 2015 specifically for lack of a better word what the weather channel referred to as "Octavia". I think the winter storm happened sometime between Feb 15-20ish with a full plethora of precipitation types resembling a layer cake as it crossed through the upper south and Appalachia. My town was pinned with 15 inches of snow. It may be years until another "Octavia" occurs but it was one of the two major events which increased my interest in meteorology the other being the 2011 tornado outbreak. I can still remember to this day vividly hearing the thunder rumble violently as the winds rushed by swaying the trees in ways I never seen before along with the rush of fear and adrenaline as our local meteorologist Dave Dierks spoke of a tornado warning over Russell county https://www.youtube.com/watch?v=B5k13-abTVM at 0:25. This video as well https://www.youtube.com/watch?v=1GEl1S_TpYU

 

 

*NOTE IMAGES SHOWN DO NOT RELATE WITH CURRENT EVENT BEING DISCUSSED*

 

I'm referring to events like the one in the historical thread that is the worst winter storm in Nashville history. Middle Tennessee had 8+ inches of snow, several inches of ice and temps in the 20s and NE Tn/SWVA was near 60 for 3  days while this happened. Probably the most extreme example, March 21st and 22nd 1968 it snowed 17.5 inches in Memphis. It was 79 degrees in Tri-Cities those two days.  Middle and West scores best when an arctic front hangs up over the Apps and a wave tracks up it. This usually results in cold rain in the Eastern Valley and wintry precip there.  So whats bad for further east sections is often what's good for further west and vice versa. Miller A events get the eastern areas and leave them out. As do most clippers. 

[Daniel Boone]

Good discussion between you guys, blunder and John. 

     In the large scheme of things, blunder's location does receive more annual snowfall than most of the forum area, hands down for obvious reasons. Some monster storms of note in Russel county; January 1998, 3 feet reported near Lebanon. December 2009, 2-3 feet .

 John is correct in how certain setups produce snow in Western areas with rain , even in higher elevations Eastern sections. Late January or early February of '85(I'm sure u know John) comes to mind for me as Memphis got 10" while we got rain that ended as a little sleet.

  Clippers seldom affect Western areas but can. March 2009 comes to mind here as a plains diving system dove all the way to miss.,Ala, and Georgia dumping heavy snow Memphis to Nashville to Atlanta before cutting NE and covering Asheville to Roanoke . we were blanked here but, Marion, VA eastward got 4" or more. Made a complete horseshoe hook around the great Valley.                                            That storm was probably classified by some as a Miller b, Miller a transfer but, it did come down from the Alberta/Saskatchewan area.

 

[Mrwolf1972]

06z gfs

[BlunderStorm]

At what point in time should we transition to showing shorter high resolution models generally? Also My memory of historic events is little due to my age. I am 16 so my memory of events before 2010 is less relevant because I rarely ever payed attention to the weather when I was a younger child. Though I can recall the winter of 2009-2010 being huge. School was closed for most of January that year I believe.

 

[John1122]

44 minutes ago, BlunderStorm said:

At what point in time should we transition to showing shorter high resolution models generally? Also My memory of historic events is little due to my age. I am 16 so my memory of events before 2010 is less relevant because I rarely ever payed attention to the weather when I was a younger child. Though I can recall the winter of 2009-2010 being huge. School was closed for most of January that year I believe.

 

As of last year, the RGEM was the best at handling the timing, placement and strength of clippers imo. It was very good inside 36 hours.

[John1122]

12z is a bit lighter on totals in East Tennessee but the trough placement was further west and the snow area grew westward.

[John1122]

GEM is still really sharp with it's trough and really doesn't do much outside of the Eastern areas and it doesn't even do much there. 

[AMZ8990]

1 hour ago, John1122 said:

12z is a bit lighter on totals in East Tennessee but the trough placement was further west and the snow area grew westward.

Thanks for sharing John.  That gives me hope that we still have a chance of some accumulating snow on the west side of the state.  Hopefully the models continue to move westward as we get closer to the end of the month.  All in all though, That is a pretty decent model for the whole state.  As you know, it is tuff to get the whole state covered in snow from west to east.

[John1122]

If the trough is that broad it will allow the clipper to come down further west before it heads east. Look where it enters the upper midwest to see where it's going. If the trough it more east based it will enter in the eastern Dakotas or Western Minnesota. If it enters in the Western Dakotas or Eastern Montana western areas have a better shot at snow. The snow totals were lower in the eastern areas because the further west the track, the flow is more westerly instead of NW and that eliminates some of the NW flow snow.

[John1122]

This is from yesterday with a sharper/easterly trough vs today. Notice the snow breaking out over eastern ND/Minn. Today at 12z that hit west TN the snow arrives as far west as Western ND/Eastern Montana. That is why West Tn had some 1+ inch potential on the GFS.

Yesterday

 

[AMZ8990]

14 minutes ago, John1122 said:

If the trough is that broad it will allow the clipper to come down further west before it heads east. Look where it enters the upper midwest to see where it's going. If the trough it more east based it will enter in the eastern Dakotas or Western Minnesota. If it enters in the Western Dakotas or Eastern Montana western areas have a better shot at snow. The snow totals were lower in the eastern areas because the further west the track, the flow is more westerly instead of NW and that eliminates some of the NW flow snow.

That makes sense.  I will definitely be watching to see how everything unfolds.  I hope we all get some enjoyable weather out of this system, Although I know that would take a lot of pieces coming together to get everyone in the forum involved in a good snowstorm.  I'm not gonna lie though, It is nice just to have some sort of system to track again.

[AMZ8990]

Also, it is interesting to see how the snow totals go from good in far eastern Tennessee but then the snow totals fall off drastically on the other side of the mountains in North Carolina.  

[John1122]

NAM is not the best at the end of it's range. But this would not be rain falling in the areas it's showing rain. The 850s are frigid. The 540 line is in central Alabama.

 

[tnweathernut]

The trend has been for a bit deeper trough a little further west.  The last run (12z) was a decent jump as we get closer in....

[John1122]

2 minutes ago, AMZ8990 said:

Also, it is interesting to see how the snow totals go from good in far eastern Tennessee but then the snow totals fall off drastically on the other side of the mountains in North Carolina.  

The Apps eat clippers up usually.  Downsloping  dries out everything outside the higher peaks there. Sometimes a clipper can redevelop off the coast and get eastern NC involved. There will still often be a precip game from the Foothills to the I-95 corridor.

North Carolina areas usually either get a major snow event from a miller A type system or not much at all outside of Western Mountain areas. But they are more likely to get massive snows over 12 inches over larger areas at low elevation due to the coastal influence. 

[tnweathernut]

6 minutes ago, AMZ8990 said:

Also, it is interesting to see how the snow totals go from good in far eastern Tennessee but then the snow totals fall off drastically on the other side of the mountains in North Carolina.  

Just like the wind rising up the mountain will wring out moisture the wind heading down the mountain on the other side has a drying effect.  It isn't very often a clipper helps the bulk of NC. They would have to dive in VERY far west and south to accomplish that goal.

[John1122]

The final element will be timing of the system. GFS had been showing it mainly impacting from say Sunday afternoon into Monday morning. Now it's arriving earlier Sunday, especially on the NAM. It'd be better to arrive in the dark if possible.

[tnweathernut]

1 minute ago, John1122 said:

The final element will be timing of the system. GFS had been showing it mainly impacting from say Sunday afternoon into Monday morning. Now it's arriving earlier Sunday, especially on the NAM. It'd be better to arrive in the dark if possible.

Absolutely, great point.  Clippers that arrive during the day with marginal temps will almost always disappoint.  Get one to come in after dark with supportive temps and it's not that hard to create road problems.

[John1122]

1 minute ago, flash43 said:

Saw this on another forum, but it's worth mentioning the potential for dry air intrusion during this event. Now I may be interpreted the skew-T's incorrectly, but it doesn't look like the dry air ~ 800 mb is around for the entire event. For the onset, yes. But given the trough sharpening trends, at least on the GFS, a stronger system yielding more potential QPF output would saturate the column more quickly, right? At any rate, to temper my expectations, I'm just going to divide modeled snow totals in half until further notice. Wouldn't hurt...

Time of arrival, track, temp etc will impact snow amounts that are able to accumulate. The fact that we can get some lows in the 20s and highs that are cold for a few days leading into it will help some. The soil temps are way above normal for the area right now. But cutting the totals in half is never a bad idea in my experience. Though last year's nice Jan 20th clipper never saw the models catch up. The RGEM at around 36 hours started beefing up totals but the other models were at about 50-60 percent of what happened until very late in the game. The track wasn't nailed down until 6-12 hours before hand too.

[tnweathernut]

4 minutes ago, flash43 said:

Saw this on another forum, but it's worth mentioning the potential for dry air intrusion during this event. Now I may be interpreted the skew-T's incorrectly, but it doesn't look like the dry air ~ 800 mb is around for the entire event. For the onset, yes. But given the trough sharpening trends, at least on the GFS, a stronger system yielding more potential QPF output would saturate the column more quickly, right? At any rate, to temper my expectations, I'm just going to divide modeled snow totals in half until further notice. Wouldn't hurt...

Haha, probably not a bad idea with ANY potential snow.  My guess is you'd be closer to correct using that method.  I will note the 12z Euro came in a little wetter overall.  Not a great snow map, but better than prior runs.

[Jed33]

How does the Euro look on this event? It's so hard to tell much from the free maps.  Not much talk of it. Must be very weak. The GEFS looked ok. Just not as much as the GFS, which continues to have the highest snowfall output.

Edit: I just saw I posted that about the same time TNweathernut posted about the Euro. Thanks!