ChescoWx Posted December 19, 2017 Share Posted December 19, 2017 12z GFS again coming in colder - now has snow for at least some of the area on Christmas Day....of course Euro not biting but it has begun to trend the way of the GFS. Expect another move toward the GFS with today's 12z Euro run Link to comment Share on other sites More sharing options...
RedSky Posted December 19, 2017 Share Posted December 19, 2017 Tremendous turn of Fortune the last 24 hours for some white on Christmas or at least being a cold day. December just wants to rock. Link to comment Share on other sites More sharing options...
ChescoWx Posted December 19, 2017 Author Share Posted December 19, 2017 Of course it might be too much of a good thing as although it may snow if you take the GFS verbatim....it likely would not be much - may want to root on a bit more SE ridge if this trend continues Link to comment Share on other sites More sharing options...
ChescoWx Posted December 19, 2017 Author Share Posted December 19, 2017 12z Euro as expected came in colder now gets an inch or two of snow just about right to I95 on Christmas Day Link to comment Share on other sites More sharing options...
ChescoWx Posted December 20, 2017 Author Share Posted December 20, 2017 18z GFS - not surprisingly loses the storm - call me stunned...not! I would be surprised if with the baroclinic zone nearby that this does not have a few more surprises in store over the next few days. Now, I am not saying all frozen by any means....but more L.E. - yes. Link to comment Share on other sites More sharing options...
Ralph Wiggum Posted December 20, 2017 Share Posted December 20, 2017 Im actually more optimistic for some sort of snowfall on Christmas Day than I am for the end of the Christmas week threat some are buzzing about, though either will fit that date range of opportunity which I highlighted the other day (Dec 25-Dec 30). Im also a firm believer of one threat at a time. Too often I see folks overlook a good medium range threat which models struggle with in anticipation of something fantasy in the long range. This is not to say the signal that guidance is showing towards second half of Christmas week is worth ignoring.....not suggesting that in the least. But based on the short term rapid changes we are seeing this year, I prefer the one threat at a time mentality. With that said, I really think we are now in a decent spot if you want to see flakes on Christmas Day. Without diving too into detail, I will sum up with the ens means surface plots (will start looking at ops 12z Wednesday but more likely 0z Thursday):EPS has a surface low tucked into the coast.....temps too warm for frozen to start but looks to transition to wet flakes on Monday as system moves NNE. GEPS mean has slp in a good spot S and E off the coast. Precip looks frozen or really close in SE PA....mean precip over .5" liquid Monday so looks like wettest mean as well. GEFS ticked E with slp and while a little farther S and E of the others is exactly where we want to see the lp area at this range.....gives us some wiggle room as I suspect EPS will continue to move towards the GEFS and vice versa, potentially settling on a near-perfect track (close to GEPS?). Temps may still be an issue to start but Im not stressing out at 6 days lead time. This doesnt look like a major event for our area right now imo.....potential SECS at best under perfect trends/conditions. However, the EPS now has a -NAO showing up on Christmas Eve and the GEFS tries to extend the ridge bridge from the epo over the N Pole into the NAO region, so this is a new look. Certainly looks to get colder next week, maybe a few of our coldest days of the season thus far mid to late week. Link to comment Share on other sites More sharing options...
ChescoWx Posted December 20, 2017 Author Share Posted December 20, 2017 Per JB at WB "I like the track to Cape Cod, rain ending as snow in the big cities with a coating to an inch or 2 but larger amounts west and north. I am not getting into any backyard brawls here the fact is the chance is there for the Christmas even snow from the Ohio Valley into the northeast and it's far more likely that people are not 50 degrees with a southerly rains storm on the east coast Christmas day. I do think the Euro will likely correct a bit east from the hugger it has. Look at it this way. Given sentiment a few days ago, a lot more folks have a shot and snow Christmas eve into Christmas day than before, right? And its a pattern that is about as good as it can get for this time of the year. So for me, I have an attitude of gratitude at all the cold showing up and the chance for a lot of people now, from the plains east, if you don't get one, you have a shot at another" Link to comment Share on other sites More sharing options...
ChescoWx Posted December 21, 2017 Author Share Posted December 21, 2017 Per JB at WB this evening "This is a borderline situation in the big cities. Its a fast moving feature and likely to dump 6-`12 over interior New England, 3-6 from WVa to Central pa with the increase further northeast. In the coastal cities, the toss up argues for 1-2 inches of snow out of the precip. Its the storm type I am looking at, some snow but not the core of the snow." Link to comment Share on other sites More sharing options...
Ralph Wiggum Posted December 21, 2017 Share Posted December 21, 2017 For now I tend to agree with JB....likely not a big ticket event in Philly proper and Ive said this from the get-go. Looks like a possible SECS farther N and E. These cold chasing precip storms rarely work out and Im not even sure his 1-2" call works out based on *current* data, but I would be surprised if we didnt see some flakes on Monday whether from the coastal developing or from snow showers behind the front. We'll see....5 days to adjust and fine-tune. Link to comment Share on other sites More sharing options...
Ralph Wiggum Posted December 21, 2017 Share Posted December 21, 2017 NAVGEM attempting to lead the way with Christmas Day event at the same exact lead time as it did with our Dec 9 snow. If u remember, Dec 9 had our boundary on most guidance forecast to be well S and E off the coast. At around 4 days out, the NAVGEM (generally regarded as the most progressive model) suddenly showed the boundary being much farther N and W moreso than any other model at that time which sent off a red flag when I saw it suggesting other models may be too far off the coast. Then other guidance began coming around to the NAVGEM. Something similar just happened on the 0Z run and now the NAVGEM is farther N and W and provides light snow over SE PA the entire day Monday. Is it right? Probably not verbatim as depicted but certainly has good support from the EPS (warmish?) and CMC (drier?). NAVGEM depiction, at the very least, has at least raised a flag for me suggesting the GFS may be out to lunch. Link to comment Share on other sites More sharing options...
Ralph Wiggum Posted December 21, 2017 Share Posted December 21, 2017 Big enough changes on 6z gfs to warrant a followup post.....trended towards NAVGEM. GFS is a White Christmas for DC - PHL - NYC. More amplified and not far off from being even juicier. Dream a little dream..... Link to comment Share on other sites More sharing options...
ChescoWx Posted December 21, 2017 Author Share Posted December 21, 2017 a little off topic but the 6z GFS has 28" of snow on the ground in Chester County by the 30th....of course we don't shovel model output...it will change Link to comment Share on other sites More sharing options...
Ralph Wiggum Posted December 21, 2017 Share Posted December 21, 2017 12 minutes ago, ChescoPaWxman said: a little off topic but the 6z GFS has 28" of snow on the ground in Chester County by the 30th....of course we don't shovel model output...it will change Not off-topic. I just created a dedicated threat. Normally I wouldnt make one this early, but when almost all guidance has the potential for *something*, chances are better than not that they are sniffing something out. Link to comment Share on other sites More sharing options...
hazwoper Posted December 21, 2017 Share Posted December 21, 2017 OH BOY! The 90 hr panel for the 12Z GFS looks nice! Is that an inverted trough I see? Link to comment Share on other sites More sharing options...
Ralph Wiggum Posted December 21, 2017 Share Posted December 21, 2017 12z gfs RedSky near-bullseye on Christmas morning....3-4" white gold for his area a general 1-3" elsewhere in PA. The good trend continues. Link to comment Share on other sites More sharing options...
Ralph Wiggum Posted December 21, 2017 Share Posted December 21, 2017 Fwiw, NAM has nada and CMC is closer looking to GFS but barely a coating for most. Link to comment Share on other sites More sharing options...
hazwoper Posted December 21, 2017 Share Posted December 21, 2017 18Z GFS backing off on Xmas snows a bit. Just a few mood flakes for most with the low farther out to sea. Still several runs to go Link to comment Share on other sites More sharing options...
ChescoWx Posted December 21, 2017 Author Share Posted December 21, 2017 34 minutes ago, hazwoper said: 18Z GFS backing off on Xmas snows a bit. Just a few mood flakes for most with the low farther out to sea. Still several runs to go Always a good idea to take any 18z or 6z model with a grain of salt..... Link to comment Share on other sites More sharing options...
The Plowsman Posted December 21, 2017 Share Posted December 21, 2017 a little off topic but the 6z GFS has 28" of snow on the ground in Chester County by the 30th....of course we don't shovel model output...it will changeYeah n 55" for SW Pa lol! 🤣 Link to comment Share on other sites More sharing options...
RedSky Posted December 22, 2017 Share Posted December 22, 2017 GFS with 1-2" in SEPA for Christmas morning, better looking little wave. Link to comment Share on other sites More sharing options...
Birds~69 Posted December 22, 2017 Share Posted December 22, 2017 4 minutes ago, RedSky said: GFS with 1-2" in SEPA for Christmas morning, better looking little wave. Hell, lock it in...I'll take it. Link to comment Share on other sites More sharing options...
RedSky Posted December 22, 2017 Share Posted December 22, 2017 Just now, Birds~69 said: Hell, lock it in...I'll take it. If this happens and if there is a big winter weather system next week and they are big if's we could be living the best damn winter December of our lifetime. Link to comment Share on other sites More sharing options...
Birds~69 Posted December 22, 2017 Share Posted December 22, 2017 2 minutes ago, RedSky said: If this happens and if there is a big winter weather system next week and they are big if's we could be living the best damn winter December of our lifetime. For sure...and everything is over-acheiving and good timing. Let's keep it going... Link to comment Share on other sites More sharing options...
Ralph Wiggum Posted December 22, 2017 Share Posted December 22, 2017 12z NAM is showing how it would take a true miracle for a white Christmas to pan out for extreme SE PA, even if just a coating or an inch or so. Has the sw energy with a slightly diggier look which allows lp to develop a little sooner and farther W by a hair vs 6z. However, that's all well and good to try and get precip in sooner but now you are looking a cold chasing precip in extreme SE PA as it starts as rain or a mix even back thru central Bucks, Montco, etc. 2m temps do appear a degree or so cooler as lp tries to strengthen but extreme SE PA really is a challenge verbatim on the NAM to try and get accums before precip pulls NE regardless of what the snow maps may say. 850 temps look great (somehow) yet the 850 low is in the G Lakes and flow is coming from the South at that level. Couple this with an Easterly fetch at 10m just about the surface as the lp is in its infancy before winds veer to a N component and 2m temps at 33-35 and you can see without even taking the NAM verbatim (just using its hi res to see what is happening in general aloft) that extreme SE PA is really walking the tightrope here. Not saying it wont work out, but there is alot still going against it right now. Good thing is we have 3 days to adjust for the better (or worse?). If ever there was going to be a possible last minute miracle for a white Christmas in extreme SE PA, this is probably it. LV, you look good. Link to comment Share on other sites More sharing options...
hazwoper Posted December 22, 2017 Share Posted December 22, 2017 11 minutes ago, Ralph Wiggum said: 12z NAM is showing how it would take a true miracle for a white Christmas to pan out for extreme SE PA, even if just a coating or an inch or so. Has the sw energy with a slightly diggier look which allows lp to develop a little sooner and farther W by a hair vs 6z. However, that's all well and good to try and get precip in sooner but now you are looking a cold chasing precip in extreme SE PA as it starts as rain or a mix even back thru central Bucks, Montco, etc. 2m temps do appear a degree or so cooler as lp tries to strengthen but extreme SE PA really is a challenge verbatim on the NAM to try and get accums before precip pulls NE regardless of what the snow maps may say. 850 temps look great (somehow) yet the 850 low is in the G Lakes and flow is coming from the South at that level. Couple this with an Easterly fetch at 10m just about the surface as the lp is in its infancy before winds veer to a N component and 2m temps at 33-35 and you can see without even taking the NAM verbatim (just using its hi res to see what is happening in general aloft) that extreme SE PA is really walking the tightrope here. Not saying it wont work out, but there is alot still going against it right now. Good thing is we have 3 days to adjust for the better (or worse?). If ever there was going to be a possible last minute miracle for a white Christmas in extreme SE PA, this is probably it. LV, you look good. If the 850 temps work out, I can see accumulations (especially seeing this will be an overnight event). The NAM is still outside of its range, and with its awful low depiction from 69-72 (feedback?) I am not buying into the rain snow line especially with a deepening low offshore. Link to comment Share on other sites More sharing options...
hazwoper Posted December 22, 2017 Share Posted December 22, 2017 12Z GFS seems pretty close to the NAM, so not great. Not liking the stronger low to the west on the last couple runs Link to comment Share on other sites More sharing options...
Ralph Wiggum Posted December 22, 2017 Share Posted December 22, 2017 Rgem (another hi-res model) right in line with the tightrope walk for extreme SE PA. Verbatim gets a decent burst of accum snow into all of Eastern PA except right along the Delaware River. Nice look to it. Would love to see this hold for 72 hours.....I dont need a SECS, this will do just fine. Holding out for early seasonal trend to make this happen. Link to comment Share on other sites More sharing options...
Ralph Wiggum Posted December 22, 2017 Share Posted December 22, 2017 If the 850 temps work out, I can see accumulations (especially seeing this will be an overnight event). The NAM is still outside of its range, and with its awful low depiction from 69-72 (feedback?) I am not buying into the rain snow line especially with a deepening low offshore.Low doesnt deepen as much as we need until it is past us....was never progged to be the source for the cold air with this. Dont follow NAM verbatim with lp location. Moral of story is for our area this is about bl temps and caa working for us prior to precip moving in.....cold chasing precip for i78 Southward and that has not changed. Link to comment Share on other sites More sharing options...
Ralph Wiggum Posted December 22, 2017 Share Posted December 22, 2017 18z NAM slightly colder at the surface.....has my area barely dropping to 32F at 2m but the real killer still looks to be those S/SW winds at 850mb and not necessarily the positioning of the slp. 850s are getting progressively toastier with each run. Would need surface low off coast to deepen rapidly and have the 850 low jump the coast which happens once the low is well N of our latitude. Fragile setup for some of the NW burbs but again, LV looks good. Will take something short of a miracle to buck the trend for us in extreme SE PA. Who knows.....maybe we awaken on the 25th to a surprise. Not digging the BL fragility and trends tho. Link to comment Share on other sites More sharing options...
hazwoper Posted December 22, 2017 Share Posted December 22, 2017 8 minutes ago, Ralph Wiggum said: 18z NAM slightly colder at the surface.....has my area barely dropping to 32F at 2m but the real killer still looks to be those S/SW winds at 850mb and not necessarily the positioning of the slp. 850s are getting progressively toastier with each run. Would need surface low off coast to deepen rapidly and have the 850 low jump the coast which happens once the low is well N of our latitude. Fragile setup for some of the NW burbs but again, LV looks good. Will take something short of a miracle to buck the trend for us in extreme SE PA. Who knows.....maybe we awaken on the 25th to a surprise. Not digging the BL fragility and trends tho. Im still not buying into (yet) the stronger further north western piece of energy. Heck, it even continues to deepen as the coastal deepens off shore. Once we are within 48 hrs of precip onset, if this either holds pat or continues to warm, I'll jump. Link to comment Share on other sites More sharing options...
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