December 11th 2019 Snow Potential

sroc4 wrote:Pretty easy to see that there are still MAJOR differences in the evolution at 500 between euro and GFS. NAM CMC Ukie all look much more like euro.  On the Euro map below 6 hours faster to the Vort max digging in from the north located over the NW GL and you start to phase energy and a LP will pop.

So how does the comparison of the Euro looking like the CMC not treanslate the same at the surface? Euro has all rain mostly,whereas CMC has a warning level snow for most, I dunno what UKIE has.  Are you leaning towards snow or rain? I know its going to initially be a rain storm monday/tuesday but then it looks to change but then I wonder after all that rain will it even be able to stick.

So Jman and everyone else.  A quick down and dirty analysis.  

A warm front approaches our area late tonight into the early morning hrs Monday.  Depending on exactly where you live Precip in the form of rain will break out prob between about 5am-9am tomorrow am.  As the day progresses rain will become more steady and increase in intensity and likely last well into Monday eve and overnight hr.  By the early morning hrs on Tuesday there should be a break in the the rain and most of Tuesday will be hit or miss showers and temps will warm as the warm front will have pushed up through the area.  

By late afternoon on Tuesday, as you you can see below, temps are into the 50's and even 60's along the coastal plain.  

As you can see the 32*f line on the surface is way up by the US/Canadian boarder.  So how is it going to snow AND accumulate on Wed??  







NOTE: First image about is valid for approx 4pm Tuesday; the second and third image above are valid 4am Wed morning

So as you can see above a cold front will crash the area overnight Tuesday into Wed such that a mere 12hrs(+/-) the 32*f surface line(second image above) is now essentially down to the coast, and 2meter dew points(third image) are crashing.  An important feature I want to highlight in the second image above is take note at the temperature gradient.  A mere 100-150 miles to the S&E separates the 60's and 70's from the freezing line.  And a mere 100-150 miles N&W temps are in the teens.  This sets up an impressive baroclinic zone along the cold frontal boundary that WILL enhance vertical lift.

Now I want to zoom out real quick and look at the big picture.  Unlike the last storm set up the source region for the cold air behind the front is straight out of the Arctic and frigid Canadian tundra, because you have a steep ridge along the WC of NA and resultant arctic/polar trough digging into the Eastern CONUS.  This is a key factor for a successful event here and is why the baroclinic zone I showed above sets up.  






Now once the cold front sweeps through overnight Tuesday and into early Wed it should stall just to our SE.  A new round of enhanced precip will develop Wed am.  It will likely begin as light rain then begin to mix and change over to snow as we progress into mid-late am Wed from NW to SE as the arctic air sweeps in.  

I think a general 1-3" for most of us on the board with possibly higher numbers (ie:3-6") is def doable in this set up.  The reason for this is this:

There will be a potent jet streak(JS) between 300-250mb favorably positioned to our north at just the right time.  This should/would enhance lift in the areas I have circled if modeled correctly.  This combined with the potent temp gradient I highlighted above should lead to a period of decent banding.  As is always the case the banding will likely be in some areas and not in others.  The most likely areas that will see the heavier banding will be along the coastal plain.  




The final piece to the puzzle Id like to point out are snow ratios.  As you can see by the 925mb and 850mb maps below respectively, the temps just above the surface will rapidly drive the snow ratios up.  Once the Precip changes over snow ratios for everyone will get better and better as the event unfolds.  






And so Jman to bring your original question back around full circle, I fully expect that the crashing arctic air combined with crashing dew points will rapidly cool the surface once the precip falls such that the enhanced lifting mechanisms outlined above, favorably positioned JS, and baroclinicically driven vertical lift enhancement, combined with climbing snow ratios will allow for everyone or almost every one to cash in on some accumulating snow fall on Wed.  

Now a few quick notes on the models.  Euro, CMC, GFS, (yes even the GFS) all shoiw what Im outlining above; however, the NAM which usually over does precip/QPF is actually showing very little in the way of precip as of current modeling.  So we will see how this plays out as we head through today.  


WE TRACK!!

 

Thanks Sroc, great analysis and it makes sense now that you painted the picture, man the temps really change quick. Yes we track!

Frank_Wx wrote:Latest 12z NAM valid this Wednesday:

4am



7am:



10am:



TOTAL SNOW



6-10" of high ratio snow N&W of NYC. WOW

It’s very possible that as our S/R hi res models come into range we see just how much enhancement the JS and temp gradient can proved combined with ratios. The Trop tidbits map you posted was only 10:1

SENJsnowman wrote:Wow, great analysis SROC and Frank...thanks! And great questions JMAN, I was thinking the same things. Hard to believe 60's to accumulating snow in 15-18 hours, but such is the force that is nature.

The Jersey Shore has not had an intense, prolonged snowfall since the giant spring blizzard of '18. And I remember a few seasons recently where there was just no sign of snow down here until like mid-January. So, all this early season action, hit or miss, is awesome!

As far as the actual temp crash/heavy precip timing nature of the event, these tend to not work out well for the Jersey Coast due to warm noses and mid level intrusions and such. Not sure if that's in play here, but I figure it will be...usually is. So, low expectations, high hopes and ready to track!

Snow man. This set up isn’t going to involve any warm noses. This is all about where the front stalls and when not if the temps crash, then can you get under a heavier band. I know it’s 50-60* the afternoon before but this set up screams overachiever IMO for most.

GfS coming in colder sooner

A coating to 2 inches might be a bit low no? Well still perfect timing to keep me home ad long as it's snowing in morning we likely won't go in.

Euro holds serve. Wide spread 2-5”

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