March 24-25 Winter Storm Threat

[earthlight]

Honestly, I agree. Haven't the models done this most of this winter, trying to keep the storms south, only for them to come further north? I mean not every time, but most of the time.

The problem with his analysis is that although the blocking may be weakening technically, it is actually retrograding and shifting southward over Central Canada. The block and the upper level low are pressing down on the pattern more than they are now.

So I think the suppression threat is real. Right now we're kinda dealing with some bad luck on the guidance...if you carefully watch the ULL over New England some of the medium range guidance is swinging around a vort through ME/VT/NH right as the best lift from the shortwave to our SW over the TN Valley is trying to come north. That would be unfortunate but I wouldn't consider it worthy of ship jumping yet.

I like where we're at.

[IsentropicLift]

12z Euro QPF

 

NYC - 0.10-0.25"

SWF - 0.00-0.00"

MMU - 0.10-0.25"

PHL - 0.25"+

ACY - 0.25"+

[eduggs]

15-20mm of precip as snow for NYC.

 

GGEM total snow:

Maybe 15mm for Central Park.  But the gradient is extremely large and the City is large and sprawling.  Off the map it's probably 5 - 20mm south to north.  Too close to call in that setup between rain and heavy snow.  BL temps and proximity of low suggest rain but intense rates and deepening low suggest snow.  This will change several times before it gets here.  The noreaster threat is there.  All the usual questions remain.

[SnoSki14]

This whole season has been hit or miss, mostly miss and ill fated timing even in a favorable pattern so another close call would be no shocker.

[IsentropicLift]

This whole season has been hit or miss, mostly miss and ill fated timing even in a favorable pattern so another close call would be no shocker.

The suppression threat is real. It's a catch 22. Without such great blocking this would be a lakes cutter and we would torch. Seems we need perfect placement of the ULL.

[jm1220]

This whole season has been hit or miss, mostly miss and ill fated timing even in a favorable pattern so another close call would be no shocker.

It's amazing that we've been able to reach and often exceed normal snow this winter by basically getting in on table scraps from clippers and larger events that nailed New England. The only event we didn't get clipped by was the early November storm. Hopefully this one breaks that pattern because people who get clipped in this case might not accumulate much on March 25.

[Snow_Miser]

The Euro looks like it shifted a good couple hundred miles west with the positioning of the low. Still not enough for the area, but not a bad trend on the furthest south model.

[IsentropicLift]

I know it's way out of it's range but the 09z SREF's were very suppressed. They take the coastal due east off the NC coast and don't give any measurable precip north of Cape May. 

[MJO812]

JMA still shows a hit but it's further south than 0z. It looks similiar to the GFS ( low position )

 

http://grib2.com/jma/CONUS_JMA_1000-500_SLPTHKPRP_96HR.gif

http://grib2.com/jma/CONUS_JMA_1000-500_SLPTHKPRP_120HR.gif

 

Total precip

http://grib2.com/jma/CONUS_JMA_SFC_ACCUM-PRECIP_120HR.gif

1.00 + QPF for the area

[IsentropicLift]

lol does anyone in this subforum post from ulster, green, sullivan, dutchess counties? If they do its not their sub-forum thats upstate new york. 0.75-1+ for the area.

Everyone northwest is in the 0.75-1.00" range. I was simply pointing out that his statement that everyone was 1.00"+ was in fact incorrect. For the city eastward, yes, but not the entire sub-forum.

[IsentropicLift]

I'm going on a limb and say the north trend will save us all.

We're going to need a GGEM like solution to get significant accumulations up this way. The GFS/Euro are light enough that it wouldn't amount to much. We'd be lucky to get a coating on the Euro. The JMA is a comprimise but it shifted over 100 miles southeast.

 

The problem we're having is that the ULL retrograding into Maine is suppressing the wave right as it gets to the coast. So initially it begins to come north and strengthens but it can only get so far north before the flow flattens out and the low gets squashed.

[SnoSki14]

let us pray lol. Honestly though, this is all bonus snow. I never would have expected to see 2 3+ events in March in NYC. Along with decent cold, winter has really been extended. Would be a really nice bookend to an otherwise average winter.

For my local area, it's been pretty average, a few decent snow events but nothing terribly disruptive, a few cold shots, again, nothing unprecedented although that week in Jan felt beyond frigid with those winds.

It's still March, prior to the Morch's this month still featured colder weather and shots of snow so this season has more or less been what it used to be.

It's another story for parts of NE but in central and southern nj, it's felt very average and our snowfall is near normal as well.

The biggest bonus has really been the early November storm.

[earthlight]

Maybe 15mm for Central Park. But the gradient is extremely large and the City is large and sprawling. Off the map it's probably 5 - 20mm south to north. Too close to call in that setup between rain and heavy snow. BL temps and proximity of low suggest rain but intense rates and deepening low suggest snow. This will change several times before it gets here. The noreaster threat is there. All the usual questions remain.

I can envision this system having a relatively narrow stripe of significant snow if it makes it up here...owing to the warm boundary layer near the coast and the sharp northern cutoff. This is already looking like a bit of a forecasting nightmare I think...watching the medium range guidance handle the individual vorticity spokes and perturbations with the upper level low over New England gives me a headache. This is partially because of how intricate the handling becomes...and partially because you can already imagine how the higher resolution models are going to struggle as we get closer.

There's a vort max that the guidance is hinting at swinging west southwest from the upper level low through northern New England as the best lift pushes north through the mid Atlantic...that confluence is going to be a game changer if it comes to fruition. But I think the trends are positive overall now that we lost the big Midwest cutoff solution with the vort over the Central US. We have to wait for all the medium range guidance to key in on that vort moving into the TN Valley and redeveloping a surface low off the coast...and then we can work from there.

[IsentropicLift]

The 12z Canadian ensembles are a mixed bag but the mean is well SE of the op. The coastal tracks from the Outer Banks to just south of the benchmark. The mean has 0.50"+ NW of the city and 0.75"+ from the city south and east.

 

FWIW taking a look at the 12z JMA more closely on storm vista, the surface is below freezing for everyone at hr 72, at hr 96 we're all at 32 or above for 90% of the area. By 120 the surface freezing line is right along I-95. A majority of the precip falls around hr 96. Just wanted to point out that while 850 temps are cold, we have BL issues.

[jm1220]

The Euro ensembles were apparently a little north of the operational. Fairly encouraging sign for at least a notable impact here.

[MJO812]

Euro mean is way north of the 0z mean.

12z mean

http://raleighwx.americanwx.com/models/ecmwfens/12zecmwfens850mbTSLPUS096.gif

0z mean
http://raleighwx.americanwx.com/models/ecmwfens/00zecmwfens850mbTSLPUS096.gif

[IsentropicLift]

Euro mean is way north of the 0z mean.

12z mean

http://raleighwx.americanwx.com/models/ecmwfens/12zecmwfens850mbTSLPUS096.gif

0z mean

http://raleighwx.americanwx.com/models/ecmwfens/00zecmwfens850mbTSLPUS096.gif

Yeah but how far NW does the meaningfull precip make it?

[Snow_Miser]

Yeah but how far NW does the meaningfull precip make it?

 

Looks like the Meaningful Precip makes it to around Sussex NJ. Nice precipitation signal for the area. A lot better than 00z.

[bluewave]

The ensemble mean is going easier on the confluence than the OP.

 

 

 

[MJO812]

12z GGEM ensemble mean

http://raleighwx.americanwx.com/models/cmcensemble/12zggemensemblep12096.gif
http://raleighwx.americanwx.com/models/cmcensemble/12zggemensemblep12108.gif

Total precip
http://raleighwx.americanwx.com/models/cmcensemble/12zggemensemblep72108.gif

 

Southeast of the operational model

[Snow_Miser]

The 18z GFS was rather unimpressive for the NYC Metro area. Nice hit for Philly on southward.

[bluewave]

The evolution looks a lot like 2/6/10. Hopefully, the sharp precip cutoff edges north of us in future runs.

 

http://www.meteo.psu.edu/~fxg1/NARR/2010/us0206.php

[SnoSki14]

All about the confluence really, there's still a few days for things to change so let's hope for the best. The general public will be furious if we do get this event, but oh well you can't change what mother nature will do.

[earthlight]

The ensemble mean is going easier on the confluence than the OP.

 

This will undoubtedly end up being a down to the wire type situation for someone on the northern edge of the precipitation shield and better lift. I can almost see the weenie band on the fringe of the precipitation already -- but it really is too hard to say where it will set up at this point. It is beginning to look like our area will be somewhere within the biggest forecast uncertainty area though that should come as no surprise...we seem to end up there very often. The NAM has a confluent flow and vorticity overhead with the main shortwave over the MS Valley already which is rarely a good look for our area. But my interest is piqued at some of the lead energy flying ahead of the main trough axis over the Southeast states. Perhaps this is deamplifying the ridge axis and amplification ahead of the main shortwave and allowing the secondary surface low development to slip a little farther southeast than it would otherwise. 

 

There are many features to watch in this setup but the three ones below are the main players. All of the medium range guidance has that confluence and vorticity almost rotating southward around the upper level low north of New England right around the time that the shortwave is amplifying into the MS and TN Valleys. That would be unfortunate as it would really press on the mid and upper level flow and make it difficult to get precipitation up north past PHL. 

 

[PB GFI]

The evolution looks a lot like 2/6/10. Hopefully, the sharp precip cutoff edges north of us in future runs.

 

http://www.meteo.psu.edu/~fxg1/NARR/2010/us0206.php

I have a hard time believing that the precip field in a 992 slp east of southern nj moving to just east of the BM is getting wrapped up so tight like one would see in a hurricane.

I thnk the precip field is more robust

[earthlight]

I have a hard time believing that the precip field in a 992 slp east of southern nj moving to just east of the BM is getting wrapped up so tight like one would see in a hurricane.

I thnk the precip field is more robust

 

It makes plenty of sense as modeled. The models are showing a very strong confluent flow over much of the Northeast just before the shortwave begins to shift towards the TN Valley which is pretty much game time for us as far as advecting in the moisture and getting the best lift into the area. The jet dynamics wont support the northwest expansion of the precipitation shield because the upper level height field is not just collapsing but being forced eastward as well. You can see the sharp pressure gradient to the northwest of the surface low..and look aloft at how the mid level height field is shunting the vort max to the south and east instead of allowing it to come up the coast. 

 

This is a perfect situation for a sharp cutoff on the north-northwest side of the precipitation shield. The good thing for our area is that we are still on the fringes on most of the medium range model guidance, and the trend has been (albeit a slow one) to orient the upper level low to our north in a more favorable position. Once this occurs there is a window for the secondary surface low to track farther northwest tucked in a bit more towards the coast. We aren't very far away from seeing robust solutions on the GFS and NAM but as it stands now this is a Central NJ gradient as the surface low doesn't have room to get past Ocean City Maryland when it's within striking distance of the coast.

 

[MJO812]

18z GEFS is more north than the operational model

http://raleighwx.americanwx.com/models/gfsensemble/18zgfsensemblep72120.gif

 

4 hits on the ensemble members

http://www.meteo.psu.edu/~fxg1/ENSPRSNE_18z/ensprsloopmref.html

[MJO812]

21z SREF ( FWIW )

 

http://i50.tinypic.com/hx9qhw.gif

[WeatherX]

Sorry if this has been posted, but how about the NAEFS?

 

[earthlight]

It makes plenty of sense as modeled. The models are showing a very strong confluent flow over much of the Northeast just before the shortwave begins to shift towards the TN Valley which is pretty much game time for us as far as advecting in the moisture and getting the best lift into the area. The jet dynamics wont support the northwest expansion of the precipitation shield because the upper level height field is not just collapsing but being forced eastward as well. You can see the sharp pressure gradient to the northwest of the surface low..and look aloft at how the mid level height field is shunting the vort max to the south and east instead of allowing it to come up the coast. 

 

This is a perfect situation for a sharp cutoff on the north-northwest side of the precipitation shield. The good thing for our area is that we are still on the fringes on most of the medium range model guidance, and the trend has been (albeit a slow one) to orient the upper level low to our north in a more favorable position. Once this occurs there is a window for the secondary surface low to track farther northwest tucked in a bit more towards the coast. We aren't very far away from seeing robust solutions on the GFS and NAM but as it stands now this is a Central NJ gradient as the surface low doesn't have room to get past Ocean City Maryland when it's within striking distance of the coast.

 

The mesoscale models are really going to struggle with the height falls and adjustment of the mid level height field with this shortwave moving northeast. The vort lobe over New England that drops southward from the upper level low acting as confluence is likely to be handled differently by each model as we move forward. There has been a trend (not very noticeable unless you really analyze the vorticity and height field) to weaken this feature. Generally the upper level low has been trending more favorable as well on most medium range model guidance...the Euro had been ticking that way as well. 

 

The more amplified models have this vorticity either weaker all together or farther northwest over the Great Lakes. This is very similar to not only Feb 6 2010 but the earlier March event where we were hoping that a piece of the upper level low would retrograde to the Great Lakes. This opens up a window for more favorable jet dynamics and the surface low can tuck in closer to the coast. We can see this on the 00z ARW which has a significant snowstorm for the entire area. The height field is more more favorably oriented and the surface low can tuck in closer to the coast as a result.

 

You then get reformed mid level centers at H85 and H7 and we're off to the races.

 

http://www.meteo.psu.edu/~fxg1/RSMEAST_0z/f87.gif