Overunning Mixed Event 12/18-12/19/21

[40/70 Benchmark]

1 hour ago, qg_omega said:

NAM /GFS?  No more model talk in the storm thread?

The last several pages summarized the fact that not much snow is expected in SNE...I'm not sure how you missed that.

[qg_omega]

Just now, 40/70 Benchmark said:

The last several pages summarized the fact that not much snow is expected in SNE...I'm not sure how you missed that.

Thought this was the New England sub thread, my bad

[40/70 Benchmark]

Just now, qg_omega said:

Thought this was the New England sub thread, my bad

It is..what is your point?

[ice1972]

Wait wuts happening here?

[40/70 Benchmark]

Here is my Final Call:

 

Weekend Mixed Bag to Supply White Christmas for Portion of Area: Final Call

Situational Synopsis:

The larger scale synoptics of this weekend's storm system remained largely unchanged from that which was discussed in Wednesday's First Call, however, the storm system now looks to track slightly closer to the region, which means that warmer air in the mid levels of the atmosphere will advance farther north into the region. This means that while a white Christmas remains possible across the northern portion of the region, it is now much less likely across the vast majority of the area than it appeared on Wednesday. What has not changed is that seasonably colder air still looks to advect into the region ahead of the storm during the day on Saturday.

This sets the stage for a complicated forecast because at the same time colder air is being drawn in from the north, the storm is forecast to ultimately draw close enough to the air to begin to counter this advance of colder air, especially in the mid levels of the atmosphere. This could lead to a myriad of precipitation type issues.

 

 

 

Anticipated Storm Evolution:

Colder air at all levels of the atmosphere is forecast to be seeping southward beginning early on Saturday morning in advance of the onset of any precipitation across the region, around midday west, and late afternoon east. The bulk of the precipitation will fall Saturday evening through midnight.

 

This could cause the leading edge of the rainfall to change to sleet and freezing rain across northern Connecticut and Rhode Island, and sleet an snowfall across interior southeastern Mass. However, as the mid level area of low pressure approaches and passes to the north of the area during the peak of the storm Saturday evening, warmer mid level air will begin to advect northward again.

 

1pm Saturday

 

Earlier during the week, when First Call was released, it looked as though several inches could accumulate as far south as the Mass pike region before any mix and transition occurred. However, since that time it has not only become apparent that the storm would track closer, which allows mid level warmth to advance northward more liberally. But it has also become clear the meager dynamics with this system would also be a mitigating factor with respect to this initial  burst of snow, which now looks to limit snowfall in the pike region to just an inch or two before the arrival of mixed precipitation.

 

Note the sounding above for Lawrence, MA in the Merrimack Valley, a locale that was originally anticipated to receive several inches of snowfall. In this case, since warmer air is advancing north, it is imperative for snowfall to accumulate efficiently since there is a limited window of time in which it will fall, especially with the further north track. Ordinarily in order to forecast rapidly accumulating snowfall, the forecaster must be confident that not only snowfall will be heavy, but the flakes will be able to develop into well formed dendrite crystals, which in conjunction with heavy fall rates aid in rapid accumulations. There are a specific set of criteria that need to be met for this to take place. First of all, the snow flakes need to develop within the maximum snow growth zone, which consists of temperatures between about -12c and -18c at approximately the 700mb level of the atmosphere. Secondly, this area needs to be co located with the lift (OMEGA) that creates the moisture necessary to facilitate the development of well formed dendrites. The first  issue in the above sounding is that the atmospheric column remains so warm that the snow growth temperature range of between -12c and -18c is found all the way up at 500mb, which is well above the maximum lift (OMEGA) found down at the 700mb level. This means that the snowflakes are going to be developing well below the optimal temperature range. Thus given that the lift is generated in warmer than ideal temperatures at a lower level of the atmosphere, snowfall will likely consist of snow grains, as opposed to well formed flakes (dendrites), which means that they will not accumulate proficiently or rapidly in the short amount of time that the precipitation is in fact snowfall. This inferior snow growth also means that the advancing mid level warmth will encounter even less resistance via evaporative cooling. This is also evidenced in the annotation above, as there is a warm sliver of air arriving in the mid levels of the atmosphere by the time steadier precipitation arrives around 7pm in Lawrence. Further to the south in the Mass pike region, sleet is already mixing in as early as 4pm.

 

4pm Saturday

 

The image below illustrates the sleet reaching the route 2 corridor, including the Merrimack valley by 7pm, at which point the transition to plain rainfall is occurring along the south coast and south shore of Mass.

7pm

 

While it is possible the mid level warmth encounters a little more resistance in the Merrimack Valley of northeastern Mass, the sleet should have reached well into southern New Hampshire by mid to late evening. Rainfall is likely over the vast majority of the region south of the Mass Pike by this point, with the possible exception of some higher terrain. It should also be raining near the coast inside of route 128 in the Boston area.

 

10pm Saturday

 

 

The area of low pressure should be making its closest approach around or shortly after midnight, which will also be the warmest point of the storm. Rain should be prevalent south of the pike with possible exception of the highest terrain in the Berkshires and hills of NW Connecticut.

 

1am Sunday

 

Snow and mixed precipitation should began collapsing back to the coast with the approach of dawn on Sunday, as the low moves away and pulls the colder air back in its wake.

 

4am Sunday

 

 

The precipitation may end as a period of light snow or flurries to the coast around sunrise on Sunday with seasonably cold airmass remaining in place throughout the day as skies clear.

 

7am Sunday

 

 

Final Call:

 

 

[weathafella]

We were hoping our daughter would leave tonight but she was exhausted.   Hopefully she gets up early enough tomorrow.   Heading out of Burlington to Boston should be ok is she’s out by 10–11 it seems.

[powderfreak]

Cooled off real nice since yesterday.

High of 46F yesterday and sitting 28/17 now, wet-bulb in mid-20s.

Nice cold air drain.

[powderfreak]

7 hours ago, qg_omega said:

NAM /GFS?  No more model talk in the storm thread?

Models haven’t changed in days it seems.  Not much to talk about.  If one came out congrats Montreal or congrats ORH, then it’s probably discussed.

I’d say if you see something worth mentioning, drop it in.  We all know we are checking them out.

[Ginx snewx]

Tiny sleet pellets biatch

[The 4 Seasons]

Man this storm really took a big fat dump on the subforum. At least i was never in the game, so there's that. We're off to good a start.

[The 4 Seasons]

41F with some light rain here and there.

[dendrite]

31/23

Primed and ready to snow. 

[Ginx snewx]

1 minute ago, dendrite said:

31/23

Primed and ready to snow. 

And we have the real first Congrats Dendrite of the long winter

[moneypitmike]

1 minute ago, dendrite said:

31/23

Primed and ready to snow. 

Enjoy.  I'll be envious reading the posts from you, Jeff, and Lava.

[HoarfrostHubb]

34/26 here.   Won’t have to waste too much to get to frozen.  But still expecting to be underwhelmed.  My 4” call earlier for my house will prob come in half that. 

[ORH_wxman]

Is Kevin getting a burst of snow? Looks like that precip is snow on CC. Or he’s right near the line. 

[The 4 Seasons]

CC:

[ineedsnow]

5 minutes ago, ORH_wxman said:

Is Kevin getting a burst of snow? Looks like that precip is snow on CC. Or he’s right near the line. 

looks like its not  far from him but looking at radar scope looks like the mix line is sw of him

[MBRI]

Freezing rain Sleet here already. Western RI

[Ginx snewx]

Just now, MBRI said:

Freezing rain Sleet here already. Western RI

You are below 32?

[Damage In Tolland]

Flakes in the air . Hopefully can manage icing later 

[512high]

36F /this sucks..

[Damage In Tolland]

I certainly wouldn’t call it a burst , but it did begin as all snow. Light snow 

[dryslot]

OVC, 31/18°F, The sky has that snow look to it.

[Baroclinic Zone]

38/28

Heading out soon to meet some clients.  Should make for some fun driving.

[Ginx snewx]

1 minute ago, dryslot said:

OVC, 31/18°F, The sky has that snow look to it.

Lock

[moneypitmike]

32 minutes ago, Ginx snewx said:

And we have the real first Congrats Dendrite of the long winter

Hopefully it's a long winter!

 

3 minutes ago, dryslot said:

OVC, 31/18°F, The sky has that snow look to it.

It really does.  Although here is that snow to sleet to rain look to it.

[Ginx snewx]

5 minutes ago, dryslot said:

OVC, 31/18°F, The sky has that snow look to it.

Like you said uniformity 

[WinterWolf]

5 minutes ago, dryslot said:

OVC, 31/18°F, The sky has that snow look to it.

You deserve it after last years disaster Jeff. Enjoy it. Nothing like the look, feel and the inevitability of an impending winter system.
 

Hopefully we all can join in soon as the pattern change takes hold.  

[Sugarloaf1989]

37F here and overcast.  Dry ground with no precipitation yet.