tmagan Posted March 23, 2011 Share Posted March 23, 2011 That event much like 3/14/99 there was a glaring QPF gradient between NYC and Nassau county, the heavier echoes in both never really made it much west of Queens and that more than anything caused the big difference in amounts from west to east. I remember heavy rain being reported in Manhattan in the 1996 storm. Link to comment Share on other sites More sharing options...
Wxoutlooksblog Posted March 23, 2011 Share Posted March 23, 2011 The NAM does show .25" QPF between 18-24 hours and ~.35" QPF between 24-30, so that's not exactly flurries. 18-24 is daylight. Even though we will be getting precipitation, probably mostly wet snow, it should be a very wet snow with some sleet at times. The sun above the clouds still does more a job at this time of year even though it is totally obscured and wet snow is falling. I do expect we will see some accumulations between 24-36 hours though it may be only or primarily on grassy surfaces. But I wouldn't get too excited about this because alot of the ingredients for a major spring snowstorm are actually missing--one of those being vertical velocity. If we are to get another major snowstorm this season, I think the better opportunity would still be toward the end of this month or the beginning of April with more of +PNA and a resulting more important coastal storm. WX/PT Link to comment Share on other sites More sharing options...
nzucker Posted March 23, 2011 Share Posted March 23, 2011 Upton just changed NYC back to mostly snow with some sleet and rain mixing in. Link to comment Share on other sites More sharing options...
supermeh Posted March 23, 2011 Share Posted March 23, 2011 Upton just changed NYC back to mostly snow with some sleet and rain mixing in. talk about bipolar. Maybe they received the memo. Link to comment Share on other sites More sharing options...
tmagan Posted March 23, 2011 Share Posted March 23, 2011 Upton just changed NYC back to mostly snow with some sleet and rain mixing in. I would pay attention only to those text products. Link to comment Share on other sites More sharing options...
eduggs Posted March 23, 2011 Share Posted March 23, 2011 I would pay attention only to those text products. Yeah, I thought the 10:40pm forecast discussion was very good. Link to comment Share on other sites More sharing options...
Isotherm Posted March 23, 2011 Share Posted March 23, 2011 00z NAM was a definite step in the direction of the GFS, with the 850mb 0c line about 30 miles further north. In addition, the simulated radar is much less impressive than the NAM had progged only 24 hours ago. Certainly over the past couple days, the GFS has been very consistent with its northern solution while the NAM, initially stubborn, seems to be moving north now (in line with other model guidance). However, the disappearance of heavier precipitation is an important point, as that was likely to make or break the event for coastal folks. Disorganized precip with occasional bursts of moderate snow isn't going to do it with surface temps around 33-34 degrees. My guess on snowfall at this point would be 1" or less on grassy surfaces from NYC southward through CNJ and PHL. 1-3" just outside of NYC to the NW, 3-6" in NW NJ up through Orange County, and 5-10" for the higher elevations of the Poconos and SW NY. Still think the more interesting event for us comes next week, strong archambault signal for a hvy pcpn event on the east coast. Link to comment Share on other sites More sharing options...
SBUWX23 Posted March 23, 2011 Share Posted March 23, 2011 Yeah, I thought the 10:40pm forecast discussion was very good. The 10:40 pm near and short term discussion have not changed since this afternoon. Link to comment Share on other sites More sharing options...
ag3 Posted March 23, 2011 Share Posted March 23, 2011 00z NAM was a definite step in the direction of the GFS, with the 850mb 0c line about 30 miles further north. In addition, the simulated radar is much less impressive than the NAM had progged only 24 hours ago. Certainly over the past couple days, the GFS has been very consistent with its northern solution while the NAM, initially stubborn, seems to be moving north now (in line with other model guidance). However, the disappearance of heavier precipitation is an important point, as that was likely to make or break the event for coastal folks. Disorganized precip with occasional bursts of moderate snow isn't going to do it with surface temps around 33-34 degrees. My guess on snowfall at this point would be 1" or less on grassy surfaces from NYC southward through CNJ and PHL. 1-3" just outside of NYC to the NW, 3-6" in NW NJ up through Orange County, and 5-10" for the higher elevations of the Poconos and SW NY. Still think the more interesting event for us comes next week, strong archambault signal for a hvy pcpn event on the east coast. Nice discussion but all nam did was come in a nearly exact agreement with euro, Ggem, UKIE and Srefs. I wouldn't say it trended towards GFS which is way north. GFS at 18z bumped south and 18z Gefs is almost exact to nam and euro. I expect GFS to bump south and come in line with the overwhelming model consensus. Link to comment Share on other sites More sharing options...
Sundog Posted March 23, 2011 Share Posted March 23, 2011 00z NAM was a definite step in the direction of the GFS, with the 850mb 0c line about 30 miles further north. In addition, the simulated radar is much less impressive than the NAM had progged only 24 hours ago. Certainly over the past couple days, the GFS has been very consistent with its northern solution while the NAM, initially stubborn, seems to be moving north now (in line with other model guidance). However, the disappearance of heavier precipitation is an important point, as that was likely to make or break the event for coastal folks. Disorganized precip with occasional bursts of moderate snow isn't going to do it with surface temps around 33-34 degrees. My guess on snowfall at this point would be 1" or less on grassy surfaces from NYC southward through CNJ and PHL. 1-3" just outside of NYC to the NW, 3-6" in NW NJ up through Orange County, and 5-10" for the higher elevations of the Poconos and SW NY. Still think the more interesting event for us comes next week, strong archambault signal for a hvy pcpn event on the east coast. The NAM is almost exactly the same temp wise with its 18z run except for hour 27 where the 850 line is about 25 miles farther north cutting through the southern parts of the city. Every other frame is the same. The 18z GFS at hour 33 had the 850 line cutting north of Sussex county, NJ and through southern CT, not to mention how it was much warmer prior to and after that time frame. The GFS is basically the only model that shows that much warmth right now. I wouldn't say it trended toward the GFS at all. Link to comment Share on other sites More sharing options...
ag3 Posted March 23, 2011 Share Posted March 23, 2011 The NAM is almost exactly the same temp wise with its 18z run except for hour 27 where the 850 line is about 25 miles farther north cutting through the southern parts of the city. Every other frame is the same. The 18z GFS at hour 33 had the 850 line cutting north of Sussex county, NJ and through southern CT, not to mention how it was much warmer prior to and after that time frame. The GFS is basically the only model that shows that much warmth right now. I wouldn't say it trended toward the GFS at all. Exactly. All NAM did was move in line with the major model concensus. It was far southern outlier. GFS is a major north outlier right now with the new Srefs coming south now. Link to comment Share on other sites More sharing options...
eduggs Posted March 23, 2011 Share Posted March 23, 2011 The 10:40 pm near and short term discussion have not changed since this afternoon. Thanks. I was just referencing the most recent timestamp. I recognized the bulk of the discussion from earlier. I didn't mean to highlight it as something new, rather, I was seconding the notion that the text products are more useful than point & click, and specifically that the discussion was thorough and reasonable. Link to comment Share on other sites More sharing options...
Isotherm Posted March 23, 2011 Share Posted March 23, 2011 Exactly. All NAM did was move in line with the major model concensus. It was far southern outlier. GFS is a major north outlier right now with the new Srefs coming south now. True, but recall how cold the NAM was at 850mb just a couple days ago, along with most mesoscale modelling, whereas the GFS has pretty much been steady w/ the idea of warmer 850-sfc layer. No doubt the NAM has made more changes over the past 48 hous than the GFS has. And that's my concern - now that the NAM is in sync w/ most guidance, will the end result be a compromise between the current GFS and other models? If this is the case, the > 0c 850mb warming would likely bisect NYC making it even more difficult to accumulate snow. I'm interested to see what the 00z GFS says.. Link to comment Share on other sites More sharing options...
tmagan Posted March 23, 2011 Share Posted March 23, 2011 The 00Z RGEM looks warmer than its previous runs, yet by 00Z Thursday has the rain/snow line just south of NYC. Link to comment Share on other sites More sharing options...
LocoAko Posted March 23, 2011 Share Posted March 23, 2011 Guys, keep in mind that on the model soundings the warmest push of air is occurring at around 750hPa, not at 850hPa. I looked through the soundings for KEWR on the 00Z NAM and they barely stay below 0C through the column (with the surface slightly above 0C) but even the 27-hour forecast has a layer between 750-825hPa above freezing (this is at 03Z, which seems to be our best chance for accumulation as others have stated). This may be able to be overcome through heavy precipitation, but it is just a reminder not to look solely at 850hPa temperatures... Link to comment Share on other sites More sharing options...
TheTrials Posted March 23, 2011 Share Posted March 23, 2011 The 00Z RGEM looks warmer than its previous runs, yet by 00Z Thursday has the rain/snow line just south of NYC. Respectfully disagree, the precip type maps on the canadian site seem to be snowier, but a lot happens between 24 and 36 we can't see yet Link to comment Share on other sites More sharing options...
Allsnow Posted March 23, 2011 Share Posted March 23, 2011 Guys, keep in mind that on the model soundings the warmest push of air is occurring at around 750hPa, not at 850hPa. I looked through the soundings for KEWR on the 00Z NAM and they barely stay below 0C through the column (with the surface slightly above 0C) but even the 27-hour forecast has a layer between 750-825hPa above freezing (this is at 03Z, which seems to be our best chance for accumulation as others have stated). This may be able to be overcome through heavy precipitation, but it is just a reminder not to look solely at 850hPa temperatures... I expect all rain imby......my eyes have turn to sunday and next week....but how dare i dont get snowflakes in my local forcast for tomorrow....... Link to comment Share on other sites More sharing options...
tmagan Posted March 23, 2011 Share Posted March 23, 2011 Wrong but nice to look at. Link to comment Share on other sites More sharing options...
Ericjcrash Posted March 23, 2011 Share Posted March 23, 2011 Wrong but nice to look at. How could you say its wrong? Link to comment Share on other sites More sharing options...
TheTrials Posted March 23, 2011 Share Posted March 23, 2011 HRRR has been very very solid this winter Link to comment Share on other sites More sharing options...
nzucker Posted March 23, 2011 Share Posted March 23, 2011 0z NAM soundings do show mostly snow for NYC, might mix around 27 hours but 24 and 30 look good: HPN Westchester County Airport) looks like solid snow: Link to comment Share on other sites More sharing options...
tmagan Posted March 23, 2011 Share Posted March 23, 2011 How could you say its wrong? There is no way Nassau will have an inch of snow by 15Z. Link to comment Share on other sites More sharing options...
LocoAko Posted March 23, 2011 Share Posted March 23, 2011 Case in point: For New Brunswick, NJ tomorrow: 850hPa temperature of ~-3C, but a 750hPa temperature of ~2C. And a surface temperature of around 2C as well. Now I know Central NJ was never the jackpot zone, but it illustrates the point of not just looking at 850hPa temperatures. Also, while we all know the danger of using thicknesses to forecast these situations, the 1000-850hPa forecast thicknesses have the 1320dam line well south of the area (the "critical" thickness for that layer) but the 850-700hPa layer shows where the issue lies: Link to comment Share on other sites More sharing options...
Isotherm Posted March 23, 2011 Share Posted March 23, 2011 Also note the NAM's H7 vertical velocity charts through Thursday morning; much less impressive than early runs. Now depicts only a short window late afternoon-early evening for mod-hvy precip before lightening up, in which time NYC could reach a slushy 1" if they're lucky. Lack of dynamics at this time of year is a red flag IMO, and we've got marginal temps throughout the boundary layer in addition to this lack of strong frontogenesis. Link to comment Share on other sites More sharing options...
ORH_wxman Posted March 23, 2011 Share Posted March 23, 2011 Case in point: For New Brunswick, NJ tomorrow: 850hPa temperature of ~-3C, but a 750hPa temperature of ~2C. And a surface temperature of around 2C as well. Now I know Central NJ was never the jackpot zone, but it illustrates the point of not just looking at 850hPa temperatures. Also, while we all know the danger of using thicknesses to forecast these situations, the 1000-850hPa forecast thicknesses have the 1320dam line well south of the area (the "critical" thickness for that layer) but the 850-700hPa layer shows where the issue lies: Jake, the critical thickness for 1000-850mb is 1300m...almost impossible to snow at 1320m. Just a minor correction that doesn't change the main point of your post. Link to comment Share on other sites More sharing options...
LocoAko Posted March 23, 2011 Share Posted March 23, 2011 Jake, the critical thickness for 1000-850mb is 1300m...almost impossible to snow at 1320m. Just a minor correction that doesn't change the main point of your post. Oh, thanks! I saw that 132dam was the first blue line and assumed it was the critical thickness. Good to know. Edit: And oh, I guess it would be hard to snow at 1320 dam too. Link to comment Share on other sites More sharing options...
Rjay Posted March 23, 2011 Share Posted March 23, 2011 Also note the NAM's H7 vertical velocity charts through Thursday morning; much less impressive than early runs. Now depicts only a short window late afternoon-early evening for mod-hvy precip before lightening up, in which time NYC could reach a slushy 1" if they're lucky. Lack of dynamics at this time of year is a red flag IMO, and we've got marginal temps throughout the boundary layer in addition to this lack of strong frontogenesis. http://68.226.77.253/text/NAMSFC/NAM_Knyc.txt Link to comment Share on other sites More sharing options...
nzucker Posted March 23, 2011 Share Posted March 23, 2011 Also note the NAM's H7 vertical velocity charts through Thursday morning; much less impressive than early runs. Now depicts only a short window late afternoon-early evening for mod-hvy precip before lightening up, in which time NYC could reach a slushy 1" if they're lucky. Lack of dynamics at this time of year is a red flag IMO, and we've got marginal temps throughout the boundary layer in addition to this lack of strong frontogenesis. We're saturated here at HPN up to like 600mb, so that's not a bad sounding, look at 24 on the 0z NAM. Temps are great, well below freezing at all levels. I mean, Tom, models aren't showing 1" of QPF for nothing: this storm is obviously going to have some decent bands. I mean look at what's going on out west, no lack of dynamics there with thundersnow, tornado warnings, blizzard conditions, etc. Also, I think that New Brunswick sounding might be snow, Jake. We had crazy heavy snow here Monday morning with one of the worst set-ups and warmest temp profiles I've seen. Surface was 39F with 850s of like -.2C and yet it stayed all snow when it increased in intensity. I think a small area of above freezing temperatures could be overcome by decent precipitation rates at the height of the storm. Link to comment Share on other sites More sharing options...
tornadojay Posted March 23, 2011 Share Posted March 23, 2011 GFS has a pretty healthy dose of QPF.. 850 strattles NYC a good part of the time Link to comment Share on other sites More sharing options...
tornadojay Posted March 23, 2011 Share Posted March 23, 2011 It actually has over an inch in fact Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.