WxUSAF Posted October 28, 2011 Share Posted October 28, 2011 ...simply put, rain for most in the morning and then flakes mixing in around or after noon and then all snow around 4 pm but not accummulating until sunset and then the precip. shuts off by about 10 pm. If the GFS is 100% accurate, precip would end a lot sooner than that for those of us west of the Bay. Because the 850mb low and vort track a bit farther north, we would dryslot and probably most precip would end by 6pm. We need to be in the deform band to have sufficient time with 1. a cold temperature profile and 2. moderate-to-heavy precip to get any accumulation. Link to comment Share on other sites More sharing options...
MD Snow Posted October 28, 2011 Share Posted October 28, 2011 DC/Balt doesn't see a flake according to the GFS. Does anyone remember last winter? It was like normal winters...it's all west of I95 period For the Balto/DC metro area: Nothing more than a non-event until after 3 pm Saturday when... The 21Z GFS shows the 0C line at 850 reaching the western Chesapeake Bay and when that happens, the changeover will be nearly complete... ...simply put, rain for most in the morning and then flakes mixing in around or after noon and then all snow around 4 pm but not accummulating until sunset and then the precip. shuts off by about 10 pm. So...about three accummulating hours except for outlying north and west. Climo tells us the mid-level moisture shuts off as the entire column cools this early in the season. Link to comment Share on other sites More sharing options...
BristowWx Posted October 28, 2011 Share Posted October 28, 2011 For the Balto/DC metro area: Nothing more than a non-event until after 3 pm Saturday when... The 21Z GFS shows the 0C line at 850 reaching the western Chesapeake Bay and when that happens, the changeover will be nearly complete... ...simply put, rain for most in the morning and then flakes mixing in around or after noon and then all snow around 4 pm but not accummulating until sunset and then the precip. shuts off by about 10 pm. So...about three accummulating hours except for outlying north and west. Climo tells us the mid-level moisture shuts off as the entire column cools this early in the season. And that sure beats a normal last weekend of Oct around here which would be around 60F and partly cloudy...thinking of what could have been will drive you crazy! Link to comment Share on other sites More sharing options...
WxUSAF Posted October 28, 2011 Share Posted October 28, 2011 It actually looks more drizzly than snowy as it looks dry above minus 8C. That may be too warm to activate any nuclei Good point. We had a similar issue last year during the PSU Hoffman storm. Had that burst of snow in the morning and then had drizzle most of the daytime with a similar temp profile. Once the upper levels resaturated in the evening, it turned back over to snow. Link to comment Share on other sites More sharing options...
Ian Posted October 28, 2011 Share Posted October 28, 2011 For the Balto/DC metro area: Nothing more than a non-event until after 3 pm Saturday when... The 21Z GFS shows the 0C line at 850 reaching the western Chesapeake Bay and when that happens, the changeover will be nearly complete... ...simply put, rain for most in the morning and then flakes mixing in around or after noon and then all snow around 4 pm but not accummulating until sunset and then the precip. shuts off by about 10 pm. So...about three accummulating hours except for outlying north and west. Climo tells us the mid-level moisture shuts off as the entire column cools this early in the season. i think more often than not these storms depart quicker than modeled too. im not holding out much hope for a very late changeover followed by wraparound accum, that's for sure. flakes in the air is probably still a good general goal right around here. Link to comment Share on other sites More sharing options...
WxUSAF Posted October 28, 2011 Share Posted October 28, 2011 For those who care, RGEM shows us little love if you're east of the Catoctins and Blue Ridge. For people north of DC, it changes over to snow 1-2hr before precip ends. http://collaboration.cmc.ec.gc.ca/cmc/cmdn/pcpn_type/pcpn_type_gem_reg.html Link to comment Share on other sites More sharing options...
H2O Posted October 28, 2011 Share Posted October 28, 2011 where you live you should have never been invested one way or the other, other than hoping for the real possibility of seeing some flakes....and that may still happen....this was never an IMBY storm.....this was a storm to follow out of interest in weather if you live in somewhat close in burbs below say 600' I think the historic angle of this storm had added to things. The fact that we were talking snow(measurable one can argue) in Oct can make one not want to leave open the idea that this could go the other direction as it appears to be doing. Link to comment Share on other sites More sharing options...
usedtobe Posted October 28, 2011 Share Posted October 28, 2011 no argument there. super rare events that never happen are super rare for a reason. i still have no real clue what will happen but im generally planning on wet ground as i have been imby at least. Based on the 500h track of the NAM, I kind of like the idea of the 850 low tracking almost over us like the GFS does, that said, I really don't have a clue of what will happen except that DCA is unlikely to get an accumulation and that there, the bulk of the precp will probably be rain. For people out west this is a nightmare as it could be a non even or could be one that might cause lots of tree damage. Link to comment Share on other sites More sharing options...
aldie 22 Posted October 28, 2011 Share Posted October 28, 2011 WUSA goes more aggressive in the face of the GFS Link to comment Share on other sites More sharing options...
winterymix Posted October 28, 2011 Share Posted October 28, 2011 If the GFS is 100% accurate, precip would end a lot sooner than that for those of us west of the Bay. Because the 850mb low and vort track a bit farther north, we would dryslot and probably most precip would end by 6pm. We need to be in the deform band to have sufficient time with 1. a cold temperature profile and 2. moderate-to-heavy precip to get any accumulation. I'm using deep moisture at 700 mb at the cutoff. GFS shuts off precip around 4Z Link to comment Share on other sites More sharing options...
usedtobe Posted October 28, 2011 Share Posted October 28, 2011 my quote that was used for CWG. Despite issuing a snow accumulation map for the area, there still is an incredible amount of uncertainty inherent in the forecast. The one thing we are pretty sure of is that the approaching system will produce lots of precipitation. Beyond that simple fact the outcome becomes muddled. One model (the GFS) has really trended warmer while the other (The NAM) switched to colder last night but now while still forecasting plenty of snow has waffled back to a slightly warmer look. The differences in the two models are largely due to the track of the circulation at around 5000 ft, the GFS track takes it right over us which assures the area of being too warm for snow if it is correct. The European model still remains a cold enough run to produce snow especially to the western suburbs but it’s upper level pattern does not look quite as good as yesterday. Given the time of year and that it often has a little better forecast of the mid level features than the NAM, right now I lean slightly more towards the GFS solution. and Jason's article http://www.washingtonpost.com/blogs/capital-weather-gang/post/rare-october-snow-likely-for-dcs-north-and-west-suburbs/2011/10/28/gIQAyqHZPM_blog.html#pagebreak Link to comment Share on other sites More sharing options...
BaltimoreWxGuy Posted October 28, 2011 Share Posted October 28, 2011 WUSA goes more aggressive in the face of the GFS Howard didnt see the GFS before he made this...just FYI Link to comment Share on other sites More sharing options...
stormtracker Posted October 28, 2011 Author Share Posted October 28, 2011 lol...It is a better model and the runs have made more sense.... Vs. The euro (which the NAM matched up pretty well). I know what the model standings are. I think we all should have known the NAM was overdone. Link to comment Share on other sites More sharing options...
MD Snow Posted October 28, 2011 Share Posted October 28, 2011 Remember this is shaping up to be a sharp cutoff storm. And there will be an area where it snows but doesn't accumulate at all...so I would go west of Frederick and Leesburg etc with any accumulating snow...just my opinion Link to comment Share on other sites More sharing options...
TalcottWx Posted October 28, 2011 Share Posted October 28, 2011 That is pretty obvious because your ignorance is glaring This area is sometimes far departed and sometimes largely unrelated for storms to where I lived in the past. Not apologizing for not following aspects of DC weather until now. It wasn't even INMR (In my region, lol). Link to comment Share on other sites More sharing options...
Deck Pic Posted October 28, 2011 Share Posted October 28, 2011 Remember this is shaping up to be a sharp cutoff storm. And there will be an area where it snows but doesn't accumulate at all...so I would go west of Frederick and Leesburg etc with any accumulating snow...just my opinion yes....this was never an IMBY storm...If you want to be assured of snow, then travel Link to comment Share on other sites More sharing options...
WVclimo Posted October 28, 2011 Share Posted October 28, 2011 15z for me LWX text forecast for me upped from 1-2" at 5 am to 4-6" now. unbelievable. Trixie, Do you have the sounding for our area on the 12Z GFS ? I'm at work and don't have my links, but it seems like we are still in the game with the GFS run. Thanks. Link to comment Share on other sites More sharing options...
Deck Pic Posted October 28, 2011 Share Posted October 28, 2011 Vs. The euro (which the NAM matched up pretty well). I know what the model standings are. I think we all should have known the NAM was overdone. I don't have thermal profiles for the euro but I am pretty sure it never dumped inches of convective snow on DC and points east Link to comment Share on other sites More sharing options...
mitchnick Posted October 28, 2011 Share Posted October 28, 2011 slipping away, or so it seems no matter if it does, better 10/29 than 12/29 Link to comment Share on other sites More sharing options...
usedtobe Posted October 28, 2011 Share Posted October 28, 2011 12z GFS at 12 UTC: 12z GFS at 15UTC: Looks like you still may do OK. Link to comment Share on other sites More sharing options...
SN_Lover Posted October 28, 2011 Share Posted October 28, 2011 I don't know. If anyone has posted this. but here is a statement the HPC posted at 11:00AM EST. Here are some excerpts: "WITH RAIN SPREADING ACROSS MOST OF THE MID-ATLANTIC AND SNOW DEVELOPING ACROSS MUCH OF THE HIGHER TERRAIN OF THE CENTRAL APPALACHIANS. BY SATURDAY MORNING...AS COLDER AIR WORKS INTO THE REGION...THE SNOW WILL SPREAD TO LOWER ELEVATIONS" "ISOLATED AMOUNTS IN EXCESS OF A FOOT AREPOSSIBLE OVER THE HIGHER ELEVATIONS OF EASTERN PENNSYLVANIA.LIGHTER SNOW ACCUMULATIONS ARE POSSIBLE FOR THE MAJOR CITIES OFTHE MID-ATLANTIC AND NORTHEAST...INCLUDING WASHINGTOND.C...BALTIMORE...PHILADELPHIA...NEW YORK CITY...AND BOSTON." "UNCERTAINTY REMAINS AS TO THE EXACT TRACK OF THE SURFACELOW...WHICH WILL DETERMINE EXACTLY WHERE THE HEAVIEST SNOW FALLS." http://www.hpc.ncep....ns/nfdscc2.html Also keep in mind ground temperatures are still relatively warm, so a couple of inches could be lost to melting. Ground temperatures: Link to comment Share on other sites More sharing options...
yoda Posted October 28, 2011 Share Posted October 28, 2011 12z UKIE at 24 hrs (12z SAT) White lines 850 temps. 850 0C line goes right through DC at 12z SAT. Color fill is QPF Link to comment Share on other sites More sharing options...
WxUSAF Posted October 28, 2011 Share Posted October 28, 2011 Also keep in mind ground temperatures are still relatively warm, so a couple of inches could be lost to melting. No, no, no, no...people need to understand how this works. If the snow was falling lightly all day then yes, this could happen. That's not the case in this scenario. If/where it snows, it will likely come down moderately or heavily. That will quickly cool the surface down and snow can accumulate on the surface. Even on the streets, particularly if there is very thick cloud cover, as we are expecting. Link to comment Share on other sites More sharing options...
Bob Chill Posted October 28, 2011 Share Posted October 28, 2011 Watching the water vapor loop and the most recent track from the gfs and nam does raise some flags for sure. The 2 things I was hoping wouldn't happen appear possible to likely. Track too close and vort amping up to much. You can see the dryslot forming already. Stating the obvious here but it is starting to look like we end up too warm at the beginning and in the dryslot or fringe once 850's crash. I'm planning on taking a trip to the cunningham falls area of the catoctins and take a nice hike above 1,500'. Link to comment Share on other sites More sharing options...
yoda Posted October 28, 2011 Share Posted October 28, 2011 12z UKMET at 36 hrs (00z SUN) Again, white line is 850 temps... color fill is QPF Link to comment Share on other sites More sharing options...
stormtracker Posted October 28, 2011 Author Share Posted October 28, 2011 I don't have thermal profiles for the euro but I am pretty sure it never dumped inches of convective snow on DC and points east Not convective no. And I was talking about thermal profiles in that post. Link to comment Share on other sites More sharing options...
usedtobe Posted October 28, 2011 Share Posted October 28, 2011 No, no, no, no...people need to understand how this works. If the snow was falling lightly all day then yes, this could happen. That's not the case in this scenario. If/where it snows, it will likely come down moderately or heavily. That will quickly cool the surface down and snow can accumulate on the surface. Even on the streets, particularly if there is very thick cloud cover, as we are expecting. People forget that melting while not as efficient a cooling mechanism as evaporation, does provide cooling of any surface. That's why you put rock salt in the ice around the old time ice cream makers. Link to comment Share on other sites More sharing options...
WVclimo Posted October 28, 2011 Share Posted October 28, 2011 12z GFS at 12 UTC: 12z GFS at 15UTC: Thanks very much. Looks like we still have a shot at some snow. Link to comment Share on other sites More sharing options...
WxUSAF Posted October 28, 2011 Share Posted October 28, 2011 UKMET takes the vort overhead. Seems to be sub-freezing aloft (850 and 700) for folks along and N/W of I-95 through the storm, however. Surface temps look really warm, however. Not sure if Ukie is good at such things or not. Link to comment Share on other sites More sharing options...
SN_Lover Posted October 28, 2011 Share Posted October 28, 2011 People forget that melting while not as efficient a cooling mechanism as evaporation, does provide cooling of any surface. That's why you put rock salt in the ice around the old time ice cream makers. "No, no, no, no...people need to understand how this works. If the snow was falling lightly all day then yes, this could happen. That's not the case in this scenario. If/where it snows, it will likely come down moderately or heavily. That will quickly cool the surface down and snow can accumulate on the surface. Even on the streets, particularly if there is very thick cloud cover, as we are expecting. " True, but it will take a unknown amount of snow to cool the ground. Whereas if you have ground temperatures at or below 32F and get instant accumulation. Link to comment Share on other sites More sharing options...
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