Voyager Posted January 25, 2011 Share Posted January 25, 2011 The quicker it can close the better because it slows down and also is more likely to shrink the 850/700mb low centers and pull the colder air in from the NW. What does this do to inland areas? Expand or contract the precip shield? Link to comment Share on other sites More sharing options...
SnowGoose69 Posted January 25, 2011 Share Posted January 25, 2011 I think this event could be wetter AND colder. Or various mixed combinations like much wetter and a little warmer or a little drier and much colder. And a few of the next several models runs will likely show one of these possibilities. But I'd take the under on 10" of snow for NYC at this point. The 18z GFS is probably one of the better scenarios. 3-6 is safe....4-8 or 5-10 I'd be more confident if I knew when that mid-level warm nose was getting out....its the type of event where LGA could snow much earlier than JFK Link to comment Share on other sites More sharing options...
A-L-E-X Posted January 25, 2011 Share Posted January 25, 2011 3-6 is safe....4-8 or 5-10 I'd be more confident if I knew when that mid-level warm nose was getting out....its the type of event where LGA could snow much earlier than JFK Im thinking a changeover for JFK by midnight, hopefully sooner, but that's what Im prepared for. Link to comment Share on other sites More sharing options...
NortheastPAWx Posted January 25, 2011 Share Posted January 25, 2011 What does this do to inland areas? Expand or contract the precip shield? Well if it's shrinking the low center it sounds to me like it would contract the shield -- but SG would know better. Link to comment Share on other sites More sharing options...
SnowGoose69 Posted January 25, 2011 Share Posted January 25, 2011 Haha that reminds me of something I saw back in the early 90s. Bob Harris on WPIX was talking about a cold front that was supposed to move through the area with light rain changing to flurries and he said that there was like a 1 in 20 chance a low could form along it and stall out and give us hours of snow. He said that kind of thing he was talking about probably only happens once every couple of decades, and guess what happened the next day. SG do you remember this storm? The temps were marginal during the day so it was a wet snow but it got heavier as the temps dropped near the evening. We ended up with 8 inches of a very heavy wet snow that lasted for like 18 hours, although it only accumulated for the last 8 hours or so. The accumulating snowfall was confined to EWR and points east. I don't remember that one....it sounds alot like 3/20/92 but the setup was more a typical low off the Delmarva. Link to comment Share on other sites More sharing options...
hudsonvalley21 Posted January 25, 2011 Share Posted January 25, 2011 I think upton is being very smart. It's a highly changeable situation; rain to snow scenarios rarely work out well for the city, with some noteable exceptions; and we're still 48 hours away from the main event. If 0z models come in strong, they will change their tune with 4am update. Agree, this could bust either way. As of now, they are putting out the word that we are all going to get something in their HWO's. They are saying to keep an eye out for this one. Smart move. Link to comment Share on other sites More sharing options...
SnowGoose69 Posted January 25, 2011 Share Posted January 25, 2011 Well if it's shrinking the low center it sounds to me like it would contract the shield -- but SG would know better. Yeah that would tend to result in it being closer to the low center...the 12/26 event was a good example...if that low was 10-12mb weakeer NW NJ sees more snow likely but the combination of a stronger storm pulling everything more in and the mesoband screwed NW areas...thats another reason inland areas can get shafted in a deep low center, meso bands are more likely to their east. Link to comment Share on other sites More sharing options...
eduggs Posted January 25, 2011 Share Posted January 25, 2011 I meant in terms of affects for our area with the first low. It seems like, from latest guidance that the 1st low and precip is really nothing. We are waiting for the ull to get entrenched into the system when things go kaboom. Obviously you need a surface low with the h5 low. But the location of that h5 ull is going to be key. I don't see two surface lows affecting our area. Sure maybe two pronounced areas of lift, but it's not the surface low that causes precipitation anyway. Just like a high pressure center doesn't impact the movement of a SLP. They are effects instead of causes. But yeah, totally agree. If the mid-level has a pronounced and early tilt, h7 moisture wraps up the coast into our area just as the 850mb low tucks beneath us and the surface low begins to slow before stacking. That's a perfect evolution for us. h5 is almost always key. Link to comment Share on other sites More sharing options...
A-L-E-X Posted January 25, 2011 Share Posted January 25, 2011 I don't remember that one....it sounds alot like 3/20/92 but the setup was more a typical low off the Delmarva. I wish I remembered when this happened..... all I can say is somewhere between 89 and 92 and it was a December storm (I think). EWR and NYC got 4 inches or so, but JFK had like 8, LGA might have had even more, maybe 10. It snowed from the changeover at 7 AM to about 1 AM, but most of the snow during the day didnt accumulate because the temps were 33-34, but it started accumulating just before sunset and snowed heavily at night until it ended around 1 AM. The low developed along the front and stalled just south of the Hamptons for 18 hours! No snow in Philly or Boston and a very narrow band of heavy snow from EWR to Long Island. Link to comment Share on other sites More sharing options...
eduggs Posted January 25, 2011 Share Posted January 25, 2011 3-6 is safe....4-8 or 5-10 I'd be more confident if I knew when that mid-level warm nose was getting out....its the type of event where LGA could snow much earlier than JFK That sounds perfect at this point. I'd cosign the median 4-8. Link to comment Share on other sites More sharing options...
Voyager Posted January 25, 2011 Share Posted January 25, 2011 Yeah that would tend to result in it being closer to the low center...the 12/26 event was a good example...if that low was 10-12mb weakeer NW NJ sees more snow likely but the combination of a stronger storm pulling everything more in and the mesoband screwed NW areas...thats another reason inland areas can get shafted in a deep low center, meso bands are more likely to their east. That's what I thought, but I wanted a pro's opinion. Thanks. Link to comment Share on other sites More sharing options...
Noreaster07 Posted January 25, 2011 Share Posted January 25, 2011 someone asked about the ratio system for WXcaster clown snowfall plots, goes as follows The snowfall accumulation algorithm used on these charts is as follows:1) Find the maximum temperature in the lowest 500 hPa in degrees K (MAXTMP)2) If MAXTMP is greater than 271.16K, then the liquid equivalent ratio (RATIO) is 12.0 + 2.0*(271.16-MAXTMP)3) If MAXTMP is less than 271.16K, then the liquid equivalent ratio (RATIO) is 12.0 + (271.16-MAXTMP)The 3-hourly snowfall (SNOW) is RATIO multiplied by the three hour liquid precipitation total. The accumulated snowfall (ACCUM_SNOW) is the sum of all the SNOW values up to that projection time. Link to comment Share on other sites More sharing options...
chubbs Posted January 25, 2011 Share Posted January 25, 2011 I meant in terms of affects for our area with the first low. It seems like, from latest guidance that the 1st low and precip is really nothing. We are waiting for the ull to get entrenched into the system when things go kaboom. Obviously you need a surface low with the h5 low. But the location of that h5 ull is going to be key. The 500 mb plot you posted is great for this area. It ends up that way due to the way the storm develops on the gulf coast. The 18Z had a stronger and better organized gulf low. Note how 500mb was already closed off in the deep south. This results in a stronger and further north mid and upper system. The 18z GFS is trending to the Euro and UKMET.. The 12 z UKMET at 60 is a little stronger version of the 18z GFS map you posted Link to comment Share on other sites More sharing options...
hudsonvalley21 Posted January 25, 2011 Share Posted January 25, 2011 Yeah I heard that too lol-- they were the last to "cave in" but even they have started to talk about a rain to snow scenario. Nick Gregory mentioned the chance for significant accumulations in NYC but wont give out an accumulation forecast until tomorrow night. Craig Allen on 880am in NYC, did not get specific in his forecast too. Link to comment Share on other sites More sharing options...
A-L-E-X Posted January 25, 2011 Share Posted January 25, 2011 Yeah that would tend to result in it being closer to the low center...the 12/26 event was a good example...if that low was 10-12mb weakeer NW NJ sees more snow likely but the combination of a stronger storm pulling everything more in and the mesoband screwed NW areas...thats another reason inland areas can get shafted in a deep low center, meso bands are more likely to their east. Less banding would probably have meant more snow for Long Island also. Link to comment Share on other sites More sharing options...
Zelocita Weather Posted January 25, 2011 Share Posted January 25, 2011 Most important run of the NAM ever coming up. Just looked at the 6 hr. EURO Temp/Precip Maps, literally the GFS & EURO could not be any closer at this point. 850 line at the same times are probably within 5-10 miles of each other, and precip during the same times are within .1 of each other aronnd the NYC Metro (except for Long Island)... Link to comment Share on other sites More sharing options...
NortheastPAWx Posted January 25, 2011 Share Posted January 25, 2011 12z models tomorrow look to be the most important with that NOAA recon data. Link to comment Share on other sites More sharing options...
benfica356 Posted January 25, 2011 Share Posted January 25, 2011 http://www.erh.noaa.gov/okx/WxBriefing_FB.pdf Nice presentation by Upton today Link to comment Share on other sites More sharing options...
_AR_ Posted January 25, 2011 Share Posted January 25, 2011 http://www.erh.noaa....Briefing_FB.pdf Nice presentation by Upton today Here is Mt Holly's current briefing as well: http://www.erh.noaa.gov/phi/briefing/packages/current_briefing.pdf Link to comment Share on other sites More sharing options...
Hailstorm Posted January 25, 2011 Share Posted January 25, 2011 Yeah I heard that too lol-- they were the last to "cave in" but even they have started to talk about a rain to snow scenario. Nick Gregory mentioned the chance for significant accumulations in NYC but wont give out an accumulation forecast until tomorrow night. Meanwhile, Elise Finch on CBS 2 thinks that mainly rain will fall for NYC metro since it seems to her that surface temps with be near 40* F during most of the event. Link to comment Share on other sites More sharing options...
Stormlover74 Posted January 25, 2011 Share Posted January 25, 2011 Heard him on the radio, he gave the vague "everyone changes to snow before ending" Said N&W mostly snow mixing with sleet Craig Allen on 880am in NYC, did not get specific in his forecast too. Link to comment Share on other sites More sharing options...
Hailstorm Posted January 25, 2011 Share Posted January 25, 2011 upton is being conservative as usual and you're right about these rain to snow situations rarely working out in the city. But there are many people who live to the north and west of the city in OKX's forecasting zones. Word for word, upton said low chance of ANYONE seeing warning criteria snow, and that is why I believe they are not approaching this situation correctly. City on east I agree. West and north? completely disagree It's kind of surprising Upton would still be conservative with warning-level snow based off these bullish maps from HPC just issued prior to the 18z GFS and NAM runs: Probability of at least 4 inches: Probability of at least 6 inches: Probability of at least 0.10" of ice: Link to comment Share on other sites More sharing options...
gkrangers Posted January 25, 2011 Share Posted January 25, 2011 It's kind of surprising Upton would still be conservative with warning-level snow based off these bullish maps from HPC just issued prior to the 18z GFS and NAM runs: Probability of at least 4 inches: Probability of at least 6 inches: I don't think they have anything to gain by being bullish now. Wait for 00z, see how it goes, then start getting more serious in the morning if models look good. Link to comment Share on other sites More sharing options...
hudsonvalley21 Posted January 25, 2011 Share Posted January 25, 2011 I don't think they have anything to gain by being bullish now. Wait for 00z, see how it goes, then start getting more serious in the morning if models look good. I'm thinking they might put a Watch up for sections n&w in the overnight pakage. Link to comment Share on other sites More sharing options...
Quakertown needs snow Posted January 25, 2011 Share Posted January 25, 2011 gathering moisture! Link to comment Share on other sites More sharing options...
dryslotted Posted January 25, 2011 Share Posted January 25, 2011 In their briefing, Mt Holly says, "Mainly rain is expected from Philadelphia south, but could change to snow near the end of the event.". I know full well these 'battleground' systems often don't work out well for us S&E of the Delaware, but I've seen it go the other way too and the mention of 2/2001 earlier brought back some funny (retrospectively) memories of the commute that day. Its very difficult, and understandably so, for schools/businesses to close with no flakes flying and no snow on the roads, so it could wind up being one of those days... Link to comment Share on other sites More sharing options...
winterwarlock Posted January 25, 2011 Share Posted January 25, 2011 how does this one compare to the snowstorm in March 14 or 15? of 1999 that was rain during the day but turned to heavy wet snow by early evening and dumped 4-6 inches Link to comment Share on other sites More sharing options...
Hailstorm Posted January 25, 2011 Share Posted January 25, 2011 Mean SLP on 21z looks to be in the same spot as in 15z. Link to comment Share on other sites More sharing options...
jimmosk Posted January 25, 2011 Share Posted January 25, 2011 Mt. Holly has a new forecast discussion out as of 8:13PM: ***Winter storm likely from 10z Wednesday to 10z thursday*** 12z GFS UKMET rgem ggem model guidance confirms the past several days of gefs and more recently the sref trends for a substantial winter weather event. Please reference the NCEP discussions on model choice...winter weather and quantitative precipitation forecast. Essentially... we will be in the developing comma head of a Gulf Coast intensifying short wave that lifts NE into a compact closed low through the middle Atlantic coast that has deformation zone banding on the southeast edge of the deeper relative humidity ..looks unstable aloft in that region per GFS.. for late Wednesday aftn/evening. That could mean decent snowfall rates of an inch or so an hour in an area that will have less than 1 inch of frozen water equivalent quantitative precipitation forecast. The i95 region looks like a mess with rain/sleet and some snow changing to all snow as the low pulls away in the evening. Looks like all snow /possibly a prd of sleet mix/ from somewhere near kukt north and west....certainly Allentown north and west. Southeast New Jersey and southeast 2/3rds del should be mostly rain with maybe a little ice at the start near dawn Wednesday and maybe a 0.5 to 3 inch event snow event in the backlash comma head rotating south behind the departing low Wednesday evening. Link to comment Share on other sites More sharing options...
winterwarlock Posted January 25, 2011 Share Posted January 25, 2011 not sure why everyone is bashing Upton or CBS mets because they are conservative right now. 18z was one model run. The 0z run of the NAM/GFS/Euro are huge tonight. Thats where first forecasts will be based upon plus tomorrow 12z runs. Why go bullish right now and then have to backtrack if the 0z runs have pulled back. Mets are right now to flip flop with every model run Link to comment Share on other sites More sharing options...
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