Cold Christmas (was: Chance of a bit of snow here Sunday)

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Old thread:

Friday Dec 9th

Chance of a bit of snow here Sunday night/early Monday morning that will melt by itself during the day Monday. Zero to half an inch, likely mixed with rain. Might have some impact on the Monday morning commute.


Saturday Dec 10th

Timing on the system has sped up a little bit. This means less overall chance of accumulating snow, but now there is a slight chance of snow at both the beginning, tomorrow morning, and end, Monday morning. In either (or both) cases, chance of light snow, with perhaps a bit of accumulation Sunday if the snow comes before sun up that the changeover to rain will clear later in the morning. Should have little or no impact on the commute either Sunday or Monday. Some rain or showers in between.


Thanks, Max! You're the best!


This pattern is starting to look fun. Very pronounced response to tropical forcing a few weeks back. 


We saw a wee bit o' snow accumulate on the back deck table yesterday.


I had to scrape the car windshields this morning. And had to be careful not to slip on the deck and land on my keister. 


Looks like 3 days of snow...  12/23, 24, 25.   


Not major.... but could cause some traffic troubles. 


Formerlyjerseyjack said:

Looks like 3 days of snow...  12/23, 24, 25.   

Not major.... but could cause some traffic troubles. 

Are you telling me my beloved family may not be able to descend upon my house for Christmas?


Formerlyjerseyjack said:

Looks like 3 days of snow...  12/23, 24, 25.   

Not major.... but could cause some traffic troubles. 

way too early to know the magnitude of an event at this range. There could very well be big snowstorm or two buried in this pattern. 


This has been developing for a while.  The pro mets and weenies have pushed it out from this weekend's system now to the 23rd

WxNut2.0 said:

way too early to know the magnitude of an event at this range. There could very well be big snowstorm or two buried in this pattern. 

Driving down to Virginia on the 23rd, so hoping that the snow line stays to the north, if it does develop.


max_weisenfeld said:

This has been developing for a while.  The pro mets and weenies have pushed it out from this weekend's system now to the 23rd

I’d be reticent to really assign a particular date to this. The pattern is such that it “loads the dice” toward something cold and snowy — but it’s far from a guarantee. I think really any time in the last ten or so days of the month has enhanced snow potential. 


Disclaimer: The following is a forecast for a period 7-10 days out, so please take with at least a grain of salt.

Ensemble model guidance is coming into rather good agreement regarding the possibility of a deep east coast trough and associated risk for a higher-end snow event around Christmas. Details regarding specifics (i.e., snow vs. rain, snow totals) are still too far out to be resolved accurately, but from a pattern perspective this is a pretty classic NYC/I-95 snow event setup. There’s still plenty of things that can change, but given the fact that the broad December pattern has played out as a predictable response to tropical forcing from over a month ago, I personally have slightly higher than normal confidence that the risk is heightened.


 I will stress again that there is a LOT of time for this to go pear shaped, but Christmas could be a bit messy if things hold up as currently shown. 


A quick Saturday update:

Uncertainty remains quite high on the finer details regarding the evolution of the pattern mid-/late-next week. The past few models cycles have begun to push the storm further inland, mitigating higher snow totals in our area. I would urge quite a bit of caution here though as a 100 mile shift east is the difference between a cold rain and a foot of snow. If you are planning on traveling late this week, I’d suggest maintaining your plans while paying close attention to the forecast. 


Wxnut 2.0 - thank you for these updates. They are about a bazillion times more informative and helpful than any other weather news I ever hear or read.  I really appreciate your posts here. 


finnegan said:

Wxnut 2.0 - thank you for these updates. They are about a bazillion times more informative and helpful than any other weather news I ever hear or read.  I really appreciate your posts here. 

Glad to hear! It’s a bit tough with these events because they’re obviously high impact and separating the signal from noise can be tough. I feel quite confident in some kind of storm developing but don’t have any inclination on what the impacts will be yet. 


Thank you WxNut 2.0. Your posts help me anticipate how I should plan ahead in response to potential high impact weather. You are a treasure.


I don’t even pay attention to Lonnie Quinn or Craig Allen anymore. I go right to Wx and Max for my extended forecasts question


WxNut2.0 said:

finnegan said:

Wxnut 2.0 - thank you for these updates. They are about a bazillion times more informative and helpful than any other weather news I ever hear or read.  I really appreciate your posts here. 

Glad to hear! It’s a bit tough with these events because they’re obviously high impact and separating the signal from noise can be tough. I feel quite confident in some kind of storm developing but don’t have any inclination on what the impacts will be yet. 

 Whatever happens next week is almost besides the point. Your analyses are valuable because they are always science based and historically informed and they are not driven by advertisers or some desperate need to get as many eyeballs as possible on your website.  Thanks again. 


Today’s guidance has continued to show a slower evolution with our area largely staying in the rain. That said, the impacts in this general area could still be rather large with wind becoming something of a concern. The deterministic ECMWF (which at this lead time should still be used carefully) is showing a very impressive 972 millibar low sitting over Michigan this coming Friday. Should this come to pass it would be quite rarified air as far as continental cyclones go; it is quite hard to get such a deep and intense area of low pressure without the influence of the ocean. While I’d expect the main snow threat (given a similar configuration to what is shown in guidance) to remain well to the west over the Ohio Valley and points west, flight cancellations/delays would be almost guaranteed across the country. If you have flight plans for Thursday/Friday, I’d suggest starting to look for alternatives now. 


This is what I posted this morning on facebook, where we havent had the benefit of the ongoing conversation that wxnut has provided here:

Monday, Dec 19th

Keeping an eye on the end of the week.

Looking at some significant NOT SNOW weather Thursday 22 through Saturday 24 this week. Although there might be a snow shower at the outset Thursday morning, the main events are a likely 1 - 2" of rain Thurs evening and overnight, likely strong gusting winds Thurs night, and rain and cold Friday. No significant snow accumulation is expected although conditions could be slippery for a brief period Thurs if we get a snow shower, and there is a possibility for flash freezing of puddles and wet areas Friday as the temperature is likely to drop rapidly from the 50s, possibly into the teens, in a matter of hours as the system moves off. Saturday likely to be dry but quite cold.

Although it is not likely to be snow here, or regionly, this is a big powerful storm and could impact travel at the end of the week and into the weekend.

As usual, this is a complex system and things could change so stay tuned. That said, the models are in fair agreement for this far out and the fine tuning will likely be around the wind strength and how cold it will get Friday.


One aspect that we should emphasize as the bigger risk right now is the cold that comes behind this. Persistent cross-polar flow has brought an airmass from Siberia to our doorstep. As the system passes this weekend an arctic front will bring temperatures into the teens. 

Pretty good explainer: https://twitter.com/nickpbassill/status/1604923418381615104?s=46&t=0BOj25XRMbCDz3_BI09NLQ


WxNut2.0 said:

One aspect that we should emphasize as the bigger risk right now is the cold that comes behind this. Persistent cross-polar flow has brought an airmass from Siberia to our doorstep. As the system passes this weekend an arctic front will bring temperatures into the teens. 

Pretty good explainer: https://twitter.com/nickpbassill/status/1604923418381615104?s=46&t=0BOj25XRMbCDz3_BI09NLQ

I would so much rather have snow ... sigh!


Forecast remains likely wind and rain Thursday and Friday.


The models remain quite consistent this morning. Temperatures remain warm throughout the storm, with a cold front right behind that will drop temperatures from the 50s to the teens Friday afternoon and night. A flash freeze is possible but not likely Friday afternoon.

Thursday morning starts with a slight possibility of light snow, then a midmorning lull, followed by very likely rain becoming heavy by evening. Winds likely to develop Thursday evening and night, steady 15 - 20 with gusts up to 40 mph possible. Wind and rain likely to continue through midday Friday or Friday afternoon. Winds near the coast (including the airports) could be stronger, impacting travel Thursday and Friday. Total rain 1 - 2" over the period so quite wet but flooding less likely.

Saturday and Sunday likely cold, with highs in the mid 20s and overnight lows in the teens.


Only change to the forecast this morning is to add a chance of localized road and field flooding, which also speaks to an increase risk of ice patches after the freeze on Friday.

Thanks Max and WxNut 2.0!


From a scientific perspective, this is a storm that PhD dissertations will be written about.

TL;DR: The attached chart shows a model forecasted, vertical cross-section through the core of the storm. What makes this so cool is that the forecast actually shows that the stratosphere is found at about 900 millibars -- or a little bit less than a mile above the surface! As the lower stratosphere is characterized by the famous "ozone layer", it is possible that you may get a whiff of some of that ozone in the coming days.

Longer: Potent storms like this require a disturbance within the jet-stream as a precursor to the cyclogenesis (the birth of a cyclone). These disturbances are often found along tropopause -- the interface of the troposphere (lowest level of the atmosphere) and the stratosphere. Ozone is a very good absorber of solar radiation and as a result temperatures in the lower stratosphere are quite stratified in the vertical (hence the name stratosphere). Due to this stratification, air from the stratosphere will have a tendency to spin as it descends. Once it has descended far enough, this spinning air aloft induces a circulation and ultimately a cyclone at the surface. The tropopause can be seen in the attached chart as the dashed line labeled ' --- 2 PVU'  with warmer colors above the 2 PVU line indicating the location of the stratosphere. At the point in the forecast for which this chart is valid, the cyclone at the surface is already well underway and is being maintained through its link directly to the stratosphere. The fact that the column of stratosphere that is impinging on the surface has a slight westward tilt as you move up in the atmosphere also indicates the storm is continuing to grow; this tilt shift vertical as the storm reaches peak intensity and ultimately eastward as the storm begins to decay.


    WxNut2.0 said:

    From a scientific perspective, this is a storm that PhD dissertations will be written about.

    TL;DR: The attached chart shows a model forecasted, vertical cross-section through the core of the storm. What makes this so cool is that the forecast actually shows that the stratosphere is found at about 900 millibars -- or a little bit less than a mile above the surface! As the lower stratosphere is characterized by the famous "ozone layer", it is possible that you may get a whiff of some of that ozone in the coming days.

    Longer: Potent storms like this require a disturbance within the jet-stream as a precursor to the cyclogenesis (the birth of a cyclone). These disturbances are often found along tropopause -- the interface of the troposphere (lowest level of the atmosphere) and the stratosphere. Ozone is a very good absorber of solar radiation and as a result temperatures in the lower stratosphere are quite stratified in the vertical (hence the name stratosphere). Due to this stratification, air from the stratosphere will have a tendency to spin as it descends. Once it has descended far enough, this spinning air aloft induces a circulation and ultimately a cyclone at the surface. The tropopause can be seen in the attached chart as the dashed line labeled ' --- 2 PVU'  with warmer colors above the 2 PVU line indicating the location of the stratosphere. At the point in the forecast for which this chart is valid, the cyclone at the surface is already well underway and is being maintained through its link directly to the stratosphere. The fact that the column of stratosphere that is impinging on the surface has a slight westward tilt as you move up in the atmosphere also indicates the storm is continuing to grow; this tilt shift vertical as the storm reaches peak intensity and ultimately eastward as the storm begins to decay.

      TLDR.

      Translation?  smile


      jimmurphy said:

      WxNut2.0 said:

      From a scientific perspective, this is a storm that PhD dissertations will be written about.

      TL;DR: The attached chart shows a model forecasted, vertical cross-section through the core of the storm. What makes this so cool is that the forecast actually shows that the stratosphere is found at about 900 millibars -- or a little bit less than a mile above the surface! As the lower stratosphere is characterized by the famous "ozone layer", it is possible that you may get a whiff of some of that ozone in the coming days.

      Longer: Potent storms like this require a disturbance within the jet-stream as a precursor to the cyclogenesis (the birth of a cyclone). These disturbances are often found along tropopause -- the interface of the troposphere (lowest level of the atmosphere) and the stratosphere. Ozone is a very good absorber of solar radiation and as a result temperatures in the lower stratosphere are quite stratified in the vertical (hence the name stratosphere). Due to this stratification, air from the stratosphere will have a tendency to spin as it descends. Once it has descended far enough, this spinning air aloft induces a circulation and ultimately a cyclone at the surface. The tropopause can be seen in the attached chart as the dashed line labeled ' --- 2 PVU'  with warmer colors above the 2 PVU line indicating the location of the stratosphere. At the point in the forecast for which this chart is valid, the cyclone at the surface is already well underway and is being maintained through its link directly to the stratosphere. The fact that the column of stratosphere that is impinging on the surface has a slight westward tilt as you move up in the atmosphere also indicates the storm is continuing to grow; this tilt shift vertical as the storm reaches peak intensity and ultimately eastward as the storm begins to decay.

        TLDR.

        Translation? 
        smile

        The ozone layer over NJ on Thursday will be at a slightly lower altitude than Denver. 


        WxNut2.0 said:

        jimmurphy said:

        WxNut2.0 said:

        From a scientific perspective, this is a storm that PhD dissertations will be written about.

        TL;DR: The attached chart shows a model forecasted, vertical cross-section through the core of the storm. What makes this so cool is that the forecast actually shows that the stratosphere is found at about 900 millibars -- or a little bit less than a mile above the surface! As the lower stratosphere is characterized by the famous "ozone layer", it is possible that you may get a whiff of some of that ozone in the coming days.

        Longer: Potent storms like this require a disturbance within the jet-stream as a precursor to the cyclogenesis (the birth of a cyclone). These disturbances are often found along tropopause -- the interface of the troposphere (lowest level of the atmosphere) and the stratosphere. Ozone is a very good absorber of solar radiation and as a result temperatures in the lower stratosphere are quite stratified in the vertical (hence the name stratosphere). Due to this stratification, air from the stratosphere will have a tendency to spin as it descends. Once it has descended far enough, this spinning air aloft induces a circulation and ultimately a cyclone at the surface. The tropopause can be seen in the attached chart as the dashed line labeled ' --- 2 PVU'  with warmer colors above the 2 PVU line indicating the location of the stratosphere. At the point in the forecast for which this chart is valid, the cyclone at the surface is already well underway and is being maintained through its link directly to the stratosphere. The fact that the column of stratosphere that is impinging on the surface has a slight westward tilt as you move up in the atmosphere also indicates the storm is continuing to grow; this tilt shift vertical as the storm reaches peak intensity and ultimately eastward as the storm begins to decay.

          TLDR.

          Translation? 
          smile

          The ozone layer over NJ on Thursday will be at a slightly lower altitude than Denver. 

          TLDR means "here's the short version" 

          literally, "too long; didn't read"


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