weatherwiz

I know the Euro does seem to increase QPF and total precip, however, I'm not totally sold on it. I think in these situations where we deal with a quick turnover, the QPF outputs become contaminated and end up being overdone. When I was looking at the Euro one thing I noticed regarding QPF was the majority of it seemed to fall prior and up to 12z Wednesday with not so much after that. One very difficult aspect here is the changeover probably starts occurring within the 6-hours between 6z and 12z...that's going to really throw a wrench in the QPF output. If certain things were different with this setup...I'd probably go somewhere along the lines of 6-12''+. Those mid/upper dynamics alone are about as impressive as you'll see...the lift in the mid/upper levels is going to be through the roof...but below that it's about as bad as you could want. IMO, it's that fronto zone which is going to deliver...and all indications are this will be extremely narrow...in fact, there may be even two focal areas of fronto...which would only further enhance subsidence/drying between them. Given how I think we have to rely on the fronto alone it's just for me to go on the higher side over a widespread area.

For Kevin... I will explain my step-by-step process with the forecast. I am not going to post any graphics b/c that will just eat up space. If I end up posing any it doesn't mean I am endorsing the model, just using it to illustrate what I'm saying. Mid/Upper Levels (700-250mb): Excellent jet dynamics with southern New England in a very favorable position with respect to jet streaks for upward vertical motion...and rather vigorous upward vertical motion which will be enhanced by positive vorticity advection and strong shortwave energy. Sufficient relative humidity and plenty of relative humidity with respect to ice (I'm not really sure how to explain that outside of how it's labeled on bufkit). Intense narrow zone of 700mb frontogenesis. Significance: All ingredients in place to generate clouds and the production of snow. Flag: Advection...where is the advection coming from? A WSW component to the streamlines (though some streamline convergence exists)...the key here is the component is more west than south. Why is this key? There is drier air to the west. This will ultimately advect in from the west (unless there was an off-setting force). Low-levels (925 to 700mb) Major red flags are in existence within the lowest 10,000 feet of the troposphere. These flags include a significant presence of dry air and subsidence. Significance: This is an extremely deep portion of the troposphere characterized drier air and subsidence. How is this going to influence things? IMO, we are not looking at very heft precipitation rates OUTSIDE OF WHERE THE FRONTO SETS UP...and I think this is east of CT (reasons for this are the intrusion of dry air and subsidence over our area...this is much less farther east which indicates where a boundary may be placed...boundary in this case the fronto). Whatever precipitation does fall has a tremendous way to travel before reaching the ground...having to fight both subsidence and dry air is not a good thing...especially if we can't even develop sufficient dendrites...which is a very real possibility here given the strongest lift is really not over us or in the SGZ. Wednesday morning, we'll see a radar which is very patchy and also misleading. Radar will suggest it's "snowing" somewhere but there will be a DBZ threshold needed for snow verification at the ground. Where the heavier echos are present is where you'll see snow...and a few things can happen from here... 1) Those localized areas are lucky and remain under those heavier echos or heavier echos develop over them or 2) These areas experience them but extremely brief This will be the difference between getting around a C to as much as 2-3''. But in terms of Wednesday morning radar coverage...this is exactly how I'm expecting it to look

Oh good. I was worried that front could hang around there for some time.

You can see this is just really going to come down to one narrow zone of fronto...where that happens (may very well be over the fish) is where 2-4'' of snow may fall. Outside of this zone of fronto it's just some snow showers making things slick for the AM commute

They think a cold pool in July has a chance to materialize into a snow event

That jet streak though is pretty damn impressive..180+ knots. Imagine those dynamics involved in a different type of set-up lol. Don't really see a jet streak that intense just to our west too often...usually moreso just to our north and east.

Nope. Hell...there isn't even any lift in the DZG. Something is obviously off with the precip algorithm on the GFS...it just loves to overdo QPF behind Arctic fronts.

hoping the fog won't be an issue at PWM tonight.

Look at the subsidence too below the DGZ haha

Took like 3 seconds to make...I like lol

Just for fun

My forecast for CT is up to a coating of snow...with a coating to an inch in the northeast hills. Pros: Very strong mid-level lift/forcing enhanced by a potent 100+ MLJ streak moving through the region and a 150+ knot ULJ putting us in RFQ. Narrow ribbon of impressive frontogenesis Sufficient RH with respect to ice in the SGZ Cons: Alarmingly low values of relatively humidity in the lowest 5,000 feet of the atmosphere with pockets of dry air throughout the column Still under the presence of CAA Strong subsidence within the lowest 10,000 feet of the atmosphere As front moves through it begins to do so rather progressively All in all...dynamics are great to have, but dynamics alone aren't going to get the job done or get a job done. While we have the forcing/lift to generate the production of snow the degree of dry air will quickly eat anything that falls. The result...snow showers for many but based on timing it will likely lead to a slick AM commute with delays.

I think flash freezes are overrated here...I don't think we really get many true flash freezes...(at least I don't count a few puddles icing up as a flash freeze...or a few slick spots)

I usually wait until winter is really sucking. then once i fire it up winters comes with a vengeance. Just remember though it's a copyrighted thread so if anyone else were to ever start it without my consent it must be deleted.

You're missing out

the algorithm was changed to yield precip with RH values >1% so the snow maps can still yield an output

He has great writing skills/ability. You add that to his wealth of knowledge and his method of presentation...and it creates a must read label for anyone interested in weather.

I would watch coastal RI/SE MA this evening for the possibility of convection

I still have to read your winter outlook. Have to set myself a reminder. Always enjoy reading your outlooks.

Fair point...I agree. (I'll admit I wasn't entirely incorporating that area into my post). That area I think should be favored anyways when talking about potential for 2-4''+ of accumulation. Typically with how things evolve in these situations just seem to favor those areas. Also looks like drier air is a bit slower to work that far east.

The notion of differentiating coast/inland/elevation seems odd to me...I think Scott mentioned that too. Cold air arrives uniformly...the problem is more regarding how much QPF occurs on the colder side and how much lift we have to work with. the coast isn't going to get shutout b/c they're...on the coast.

Certainly can't discount the potential. I know I've been burned in the past with under estimating lift and what it can do.

More the reason to think eastern sections stand the better chance You really know how to make me hot

What would win out in this situation? This is my interpretation... It's great to have all that lift and all, but if there is insufficient moisture...well there is nothing to really lift. It will be difficult to generate much in the way of precipitation. Plus, with that dry air...and it's pretty significant around 850...whatever precip does develop and fall will be virga. given the progressiveness of this as well we don't have time to saturate...not to mention additional dry air being advected in

Continued to be not very impressed for us here in CT...minimal, if any accumulations and by minimal I mean a dusting...maybe the NE Hills some can grab an inch to 2'' but forecast soundings (at least at BDL) show a ton of dry layers. There is a decent amount of mid-level lift though...that's for sure, but there's also a quite a bit of subsidence in the lowest 10-15K of the atmosphere. any accumulations are going to be extremely localized