March 2011 might be snowless for NYC

[nzucker]

I would say this 3/24 system is a legit chance for accumulating snow in NYC. The only concern is that if the GFS is overdoing how fast the rex block drops in from west Canada, then the storm will end up further north. A block coming in from this position isn't quite the same as our NAO blocks in keeping the systems more suppressed. One timing issue and this ends up another inland runner.

0z GFS smokes the PHL-NYC corridor with heavy snows. Snowless March in danger?

[A-L-E-X]

I would say this 3/24 system is a legit chance for accumulating snow in NYC. The only concern is that if the GFS is overdoing how fast the rex block drops in from west Canada, then the storm will end up further north. A block coming in from this position isn't quite the same as our NAO blocks in keeping the systems more suppressed. One timing issue and this ends up another inland runner.

HM.... is this the storm you were talking about, or do you think the pattern may sustain itself for a couple weeks and there could actually be a few legit threats between 3/20 and 4/10? One thing that I saw mentioned earlier was that the last few storms have been trending S/E.

[HM]

HM.... is this the storm you were talking about, or do you think the pattern may sustain itself for a couple weeks and there could actually be a few legit threats between 3/20 and 4/10? One thing that I saw mentioned earlier was that the last few storms have been trending S/E.

No, this isn't the storm signal. But accumulating snow is certainly possible during this entire stretch.

Keep in mind, the last system was once modeled well offshore only to trend well inland, bringing a solid rainstorm a few days ago. Now granted, that was a cutoff low that ultimately phased with a quick moving s/w from the northern Plains. The 50-50 low will likely halt that model trend this go-around.

[HM]

0z GFS smokes the PHL-NYC corridor with heavy snows. Snowless March in danger?

With the development of these poleward ridges/blocks and 50-50 low, I would say the idea of no snow through 4/10 is in trouble. Now should this whole idea break down, then yes...game over. But that is looking increasingly unlikely.

[HM]

By the way Alex, putting all this fantasy long range storm talk aside for a minute...the real storm will be when the -NAO block retrogrades into the mean flow and the final s/w digs into the Northeast (Heather signal). Now this all rests on the idea that 1. the 50-50 low/NAO block are legit and 2. the block retrogrades west. I said April 5-10, but it could just as easily be April 1-5 according to the 00z GFS.

[A-L-E-X]

By the way Alex, putting all this fantasy long range storm talk aside for a minute...the real storm will be when the -NAO block retrogrades into the mean flow and the final s/w digs into the Northeast (Heather signal). Now this all rests on the idea that 1. the 50-50 low/NAO block are legit and 2. the block retrogrades west. I said April 5-10, but it could just as easily be April 1-5 according to the 00z GFS.

HM, do you know what this pattern reminds me of ? What happened in late March - early April 1996. I remember there was a mild stretch in the middle of March that year also and then we went colder/stormier towards the end of the month. There was a storm about a week or so before the big one on April 9-10, 1996 that was a rain changing to snow scenario. That storm actually had an interesting gradient in that while it rained in the immediate area, cold air swept in from both the west and the east (MTP had like 5 inches I believe) with heavier rates and finally ended as a period of light snow-- it was just an appetizer to the big one on April 9-10, 1996. Now if we put everything back by let's say 7 days..... that first storm which was rain changing to snow would have been close to the date for the storm next week and the April 9-10, 1996 storm would be displaced to the April 1-5 period you mentioned. Would that long range forecasting were that easy lol.

[earthlight]

0z GFS smokes the PHL-NYC corridor with heavy snows. Snowless March in danger?

Has nothing to do with the threat itself, but I believe that was yesterdays 00z GFS.

[earthlight]

By the way Alex, putting all this fantasy long range storm talk aside for a minute...the real storm will be when the -NAO block retrogrades into the mean flow and the final s/w digs into the Northeast (Heather signal). Now this all rests on the idea that 1. the 50-50 low/NAO block are legit and 2. the block retrogrades west. I said April 5-10, but it could just as easily be April 1-5 according to the 00z GFS.

I have to say, I've been pretty impressed with the upper air anomaly developments on the global ensembles in the medium range. These were looking absolutely atrocious as recently as a few days ago. About a month or more ago, after the Feb 10 event, there was a discussion ongoing about how the pattern would almost certainly flip back after the warm up. My argument then was that it was really late in the game, a good analogy would be with around 2:00 left on the clock, and that I wasn't too sold on the pattern flipping back in time. The window for late season snow is certainly getting smaller by the day, but should the pattern verify as advertised on the global ensemble means, we could have a shot. That's an impressive Central Canadian ridge which is working in tandem with a blocking regime over Greenland and the North Atlantic.

[A-L-E-X]

With the development of these poleward ridges/blocks and 50-50 low, I would say the idea of no snow through 4/10 is in trouble. Now should this whole idea break down, then yes...game over. But that is looking increasingly unlikely.

The question then becomes how much accumulating snow (if any)-- which it's way too soon to say anything about of course-- but we've had accumulating snow in early April 1/3 years, warning criteria snow 3/30 or 1/10 on average.

[earthlight]

Also, it should be noted that even afterwards, the global ensemble mean height anomalies have a signal for a PNA spike...which would help us tremendously. There were -9 to -12 dm height anomalies over the Northeast on the GFS ensembles today in as late as 3/31.

[A-L-E-X]

John, it seems like when we have the thaw in January it's actually a stronger signal for a late season cold outbreak or snowy end to the season..... it seems like when winter, for lack of a better term, blows its load later, that it usually doesnt have enough time to recover and reload.

[earthlight]

John, it seems like when we have the thaw in January it's actually a stronger signal for a late season cold outbreak or snowy end to the season..... it seems like when winter, for lack of a better term, blows its load later, that it doesnt have enough time to recover and reload.

Yes, exactly what I was trying to get at. There was a whole crew of people who were on the train for late season snow and cold...but I had a serious feeling it was going to be a buzzer-beater type deal. When you flip the pattern so terribly as late as Mid-Feb like we did, these things don't just turn around and do a 180. We're still recovering, and barely. The signals are good though. We will see where this goes.

[earthlight]

The worst will be if we get a synoptically nice setup that occurs during the day, this way we get the chance to watch all our snow fall moderately and melt. I'm sure that will be an awesome OBS thread.

[A-L-E-X]

The worst will be if we get a synoptically nice setup that occurs during the day, this way we get the chance to watch all our snow fall moderately and melt. I'm sure that will be an awesome OBS thread.

Yes, if Nate brags about skiing down his 400 foot hill again.... well he should be glad the GTG isnt after the event

[nzucker]

Also, it should be noted that even afterwards, the global ensemble mean height anomalies have a signal for a PNA spike...which would help us tremendously. There were -9 to -12 dm height anomalies over the Northeast on the GFS ensembles today in as late as 3/31.

I'm thinking we might get 2-3 threats out of this period. First, we have the overrunning wave on 3/23-24 that should be watched. Then, there is the PNA spike right at the end of the month. Finally, we have HM talking about an Archembault type storm in the April 5-10 timeframe as the impressive NAO blocking finally dissipates. It could be interesting if we saw a couple of accumulating snows this late in the season, maybe an attempt to challenge Central Park's 95-96 record after all.

The worst will be if we get a synoptically nice setup that occurs during the day, this way we get the chance to watch all our snow fall moderately and melt. I'm sure that will be an awesome OBS thread.

I think you are attributing too much power to the March sun angle; sure it's a factor, but if it's cloudy and in the 30s, not that much snow is going to melt. Snow falling moderately will certainly stick to the grassy surfaces in late March if the temperature is upper 20s/low 30s as many of these models are showing with 850s dropping to -8C by the end of the snowfall. The April 1982 blizzard, which dumped 10" in Central Park, stayed on the ground for almost an entire week. That storm was two weeks later than the 3/24 threat that is now being discussed. Dobbs Ferry also had around 14 days of snow cover in March 1958, so it's not impossible to have long periods of snow cover at this time of the year, just difficult. We should see an impressive airmass with the block over Central Canada teaming up with the -NAO to provide a dual blocking scenario.

[A-L-E-X]

Nate, so you're thinking we might have a late March - early April 1996 type pattern also?

[nzucker]

Nate, so you're thinking we might have a late March - early April 1996 type pattern also?

I'm starting to think so, as the models are really locking in on an impressive -NAO with 570dm heights over the North Atlantic in the timeframe of the first storm at Day 6/7. This block should last a while, and then we have the PNA spiking towards the end of the month, which may give us the chance for another snowfall before we finally move into spring weather. 0z GFS completely lost the warm look in the long range and now has snow threats at 162, 216, 300, and 348 hours, several of which would accumulate in NYC. 850s approach -8C after the Day 7 storm with the 50/50 low and -NAO locked into place and higher heights moving into the West as a result of the shorter wavelengths causing the East Pacific trough to become an asset in creating a ridge over the Mountain West. We should see plenty of days with highs in the upper 30s/low 40s, especially if the overrunning results in a large coastal.

Many people forget the April 1982 snowfall occurred with temperatures in the 20s and stayed on the ground for a week. Satellite analysis shows that Canada was well below average in February for temperatures, and this trend of an amplified Aleutian/Bering Strait block pouring cold air into Canada has continued into March. We definitely have a great cold pool to our north with above average snowpack over New England and Quebec, a positive at this time of year. If we get a long period of north winds and a favorable storm track just to our south in the baroclinic zone between a SE ridge and the Eastern Canada vortex, we could be in great shape, Alex.

[A-L-E-X]

I'm starting to think so, as the models are really locking in on an impressive -NAO with 570dm heights over the North Atlantic in the timeframe of the first storm at Day 6/7. This block should last a while, and then we have the PNA spiking towards the end of the month, which may give us the chance for another snowfall before we finally move into spring weather. 0z GFS completely lost the warm look in the long range and now has snow threats at 162, 216, 300, and 348 hours, several of which would accumulate in NYC. 850s approach -8C after the Day 7 storm with the 50/50 low and -NAO locked into place and higher heights moving into the West as a result of the shorter wavelengths causing the East Pacific trough to become an asset in creating a ridge over the Mountain West. We should see plenty of days with highs in the upper 30s/low 40s, especially if the overrunning results in a large coastal.

Many people forget the April 1982 snowfall occurred with temperatures in the 20s and stayed on the ground for a week. Satellite analysis shows that Canada was well below average in February for temperatures, and this trend of an amplified Aleutian/Bering Strait block pouring cold air into Canada has continued into March. We definitely have a great cold pool to our north with above average snowpack over New England and Quebec, a positive at this time of year. If we get a long period of north winds and a favorable storm track just to our south in the baroclinic zone between a SE ridge and the Eastern Canada vortex, we could be in great shape, Alex.

We also got a second snowfall after the big blizzard... granted it was just an inch but it was two snowstorms, and both were during the day.

[CooL]

Im loving this thread right now, the "big 3" are all barking now about late season snowstorm (s)

[nzucker]

We also got a second snowfall after the big blizzard... granted it was just an inch but it was two snowstorms, and both were during the day.

Yeah people overestimate the effect of the sun angle during late-season snowfalls; sure, a clear day devastates a snowpack fairly quickly in March/April, but when it's actually snowing it doesn't matter too much as long as 850s are cold enough. At 162, the GFS has a band of moderate snow over Northern Virginia; although it shows 2m temperatures to be quite warm, 850s are -5C so I'd assume anyone under decent banding would receive snow, and it would definitely be snow for those in the Appalachians or foothills. On the 0z GFS, NYC metro receives a light snowfall of 1-2" at 228 hours; surface temperatures are 32F with 850s around -5C. None of these is really a marginal event, the upper atmosphere is plenty cold because the -30C 850s currently over Greenland are being released to the south in moderated form due to the NAO blocking, and the SE ridge has retreated some to allow these storms to pass south of us, allowing for some evaporational/dynamic cooling. Sticking might be an issue for Manhattan but not for those in suburban areas.

April 2006, much of April 1997, and the two April 1982 events were all during the day, which goes to show that a good pattern beats the sun angle at this point of the year. April 1982 had a very impressive -EPO/-NAO pattern early in the month which allowed for the dual late-season snows. Last year, I witnessed a 3.5" snowfall at Middlebury on April 27th, the latest snow I'd seen since I was in the Poconos for the May 2002 storm. Even with a late April sun angle, we had no problem accumulating on campus, a weird sight against the green grass and partially leafed out trees and blooming tulips, a product of the early April heat wave which pushed central Vermont into the low 80s. The snow fell heavily and stuck to all grass surfaces and even coated the roads, but of course it was gone in two days. I went to the Green Mountains on April 28th, reaching an elevation of 2100'; it was about 20F with 30mph north winds and 2' of snow on the ground, quite a scene for that late in the season.

[earthlight]

Yeah people overestimate the effect of the sun angle during late-season snowfalls; sure, a clear day devastates a snowpack fairly quickly in March/April, but when it's actually snowing it doesn't matter too much as long as 850s are cold enough.

It also has a good bit to do with the weather over the previous few weeks. That being said, I can't really argue that we've had a ton of warmth so that the ground temperature is warmer. Tomorrow certainly won't help, but we've got a week or so until this threat so I don't think it will be an issue.

[CooL]

The euro is flirting with a major hit for the area tonight

[earthlight]

0z GFS completely lost the warm look in the long range and now has snow threats at 162, 216, 300, and 348 hours, several of which would accumulate in NYC.

Not trying to be a d***, seriously, but the 162 threat on the GFS is hundreds of miles to our south, the 216 hour threat has a very marginal temperature setup (not using the 2m temps at this range verbatim, but the lack of a supportive cold air source and the resulting crappy thermal profiles), the 288 hour threat is too far north and again has no cold air source, and the 348 hour threat...which is into Mr. Rogers fantasy land is probably the best of the setups. This is taking the 00z GFS verbatim..but I think you used this run to advertise the snowy potential which it does not. Again, verbatim.

[A-L-E-X]

Yeah people overestimate the effect of the sun angle during late-season snowfalls; sure, a clear day devastates a snowpack fairly quickly in March/April, but when it's actually snowing it doesn't matter too much as long as 850s are cold enough. At 162, the GFS has a band of moderate snow over Northern Virginia; although it shows 2m temperatures to be quite warm, 850s are -5C so I'd assume anyone under decent banding would receive snow, and it would definitely be snow for those in the Appalachians or foothills. On the 0z GFS, NYC metro receives a light snowfall of 1-2" at 228 hours; surface temperatures are 32F with 850s around -5C. None of these is really a marginal event, the upper atmosphere is plenty cold because the -30C 850s currently over Greenland are being released to the south in moderated form due to the NAO blocking, and the SE ridge has retreated some to allow these storms to pass south of us, allowing for some evaporational/dynamic cooling. Sticking might be an issue for Manhattan but not for those in suburban areas.

April 2006, much of April 1997, and the two April 1982 events were all during the day, which goes to show that a good pattern beats the sun angle at this point of the year. April 1982 had a very impressive -EPO/-NAO pattern early in the month which allowed for the dual late-season snows. Last year, I witnessed a 3.5" snowfall at Middlebury on April 27th, the latest snow I'd seen since I was in the Poconos for the May 2002 storm. Even with a late April sun angle, we had no problem accumulating on campus, a weird sight against the green grass and partially leafed out trees and blooming tulips, a product of the early April heat wave which pushed central Vermont into the low 80s. The snow fell heavily and stuck to all grass surfaces and even coated the roads, but of course it was gone in two days. I went to the Green Mountains on April 28th, reaching an elevation of 2100'; it was about 20F with 30mph north winds and 2' of snow on the ground, quite a scene for that late in the season.

and April 2003 was during the day also. LOL we're in midseason form with the late night discussions. Any word on the Euro?

[A-L-E-X]

The euro is flirting with a major hit for the area tonight

How close?

[earthlight]

The euro is flirting with a major hit for the area tonight

Oh man that is close...but that has the look of the type of system which has very little cold sector precipitation. Check out the thermal gradient. It's 40 F just south of DC and the heavy precipitation is right along that gradient. Further to the north where you have the colder temps as a result of the confluent flow pressing on the pattern, you don't have enough moisture for precipitation.

[earthlight]

How close?

Just a weenie's length away

[A-L-E-X]

Yeah people overestimate the effect of the sun angle during late-season snowfalls; sure, a clear day devastates a snowpack fairly quickly in March/April, but when it's actually snowing it doesn't matter too much as long as 850s are cold enough. At 162, the GFS has a band of moderate snow over Northern Virginia; although it shows 2m temperatures to be quite warm, 850s are -5C so I'd assume anyone under decent banding would receive snow, and it would definitely be snow for those in the Appalachians or foothills. On the 0z GFS, NYC metro receives a light snowfall of 1-2" at 228 hours; surface temperatures are 32F with 850s around -5C. None of these is really a marginal event, the upper atmosphere is plenty cold because the -30C 850s currently over Greenland are being released to the south in moderated form due to the NAO blocking, and the SE ridge has retreated some to allow these storms to pass south of us, allowing for some evaporational/dynamic cooling. Sticking might be an issue for Manhattan but not for those in suburban areas.

April 2006, much of April 1997, and the two April 1982 events were all during the day, which goes to show that a good pattern beats the sun angle at this point of the year. April 1982 had a very impressive -EPO/-NAO pattern early in the month which allowed for the dual late-season snows. Last year, I witnessed a 3.5" snowfall at Middlebury on April 27th, the latest snow I'd seen since I was in the Poconos for the May 2002 storm. Even with a late April sun angle, we had no problem accumulating on campus, a weird sight against the green grass and partially leafed out trees and blooming tulips, a product of the early April heat wave which pushed central Vermont into the low 80s. The snow fell heavily and stuck to all grass surfaces and even coated the roads, but of course it was gone in two days. I went to the Green Mountains on April 28th, reaching an elevation of 2100'; it was about 20F with 30mph north winds and 2' of snow on the ground, quite a scene for that late in the season.

You had snow in May 2002? Wow... I remember we had a three day heatwave in April that year when it topped out at 96. It almost was a four day heatwave as the fourth day it made it to 89.

[A-L-E-X]

Oh man that is close...but that has the look of the type of system which has very little cold sector precipitation. Check out the thermal gradient. It's 40 F just south of DC and the heavy precipitation is right along that gradient. Further to the north where you have the colder temps as a result of the confluent flow pressing on the pattern, you don't have enough moisture for precipitation.

Hopefully being this late in the season it will trend north with the precip but keep us in the cold

[CooL]

Just a weenie's length away

yeah and the coastal (sub 992) almost gets tugged up the coast, if the 50/50 low wasnt so far south the heights probly wouldve risen faster and forced the storm over the BM instead of east of it.

and it looks like it cools down pretty good after the storm as well