Ralph Wiggum Posted December 13, 2020 Share Posted December 13, 2020 5 minutes ago, Animal said: Yea curious if dry slotted or caught between snow bands. Dry slot as system briefly closes off and starts occluding. Not sure if that trend is correct or not yet. At work not much time to digest everything. Link to comment Share on other sites More sharing options...
Birds~69 Posted December 13, 2020 Share Posted December 13, 2020 1 minute ago, Ralph Wiggum said: Yep, surprised nobody mentioned the closing off at h5 and the comma head opening up pushing the dry slot up into SE PA. I think it's because it's still too early for specifics? I'm happy where we are.... Link to comment Share on other sites More sharing options...
RedSky Posted December 13, 2020 Share Posted December 13, 2020 1 minute ago, Ralph Wiggum said: Yep, surprised nobody mentioned the closing off at h5 and the comma head opening up pushing the dry slot up into SE PA. We excel at dry slots, wear them like old scars. 2 1 Link to comment Share on other sites More sharing options...
Moderately Unstable Posted December 13, 2020 Share Posted December 13, 2020 Ok, euro brings me back from the brink lol. I've been writing up an analysis (see below), but I'm taking a break now to go exercise, so this is incomplete. Also, I was mainly writing this for myself so it may be full of errors. On the off chance I say something helpful, posting below. /////////// Current Analysis (please take with giant grain of salt): Setup: Miller B type-ish cyclogenesis under a negative NAO, weak La Nina, PNA approximately neutral, may be trending slightly negative. A low currently over the eastern pacific ocean will traverse and be disrupted by the rockies, progressing into a trough over the southern and central US. Canadian high pressure builds over Quebec. Cold air damming occurs as cP air mass moves SE...Canadian high pushes and traps cold air against the apps. Trough/sw amplifies and move NE along the NE coast becoming a closed sfc low. Recent trends focus more on a developing low east of FL to phase with the low ejecting from the rockies which is more akin to miller A than B. Vertical Velocity Position and causes: S of Philadelphia primarily...NAM disagrees and thinks omega is higher further N, reasoning: 700mb low position (eh), 850 mb position, jet streak (UL divergence), LL convergence. Strength of WAA/CAA f(wind S, wind Dir, T gradient)....solenoids: ##todo Positioning of the low/rain-snow line: SE along a line between 20 miles SSE of Philadelphia to 5 NNW of Philadelphia depending on model run specifics. All runs indicate sfc temps sub freezing due to either precip rate or myriad other factors. Precip components: Overrunning Y/N--> Yes Central Y/N--->Yes Wrap-Around Y/N---> Unclear. Dry slot vs deformation banding. Model comparison: (to finish) GFS--> 12z Sun run weaker. At 06z Thurs, has the low up by 6mb vs previous run, and slower. Compared to runs over the past day, the 06z run low position appears to be an outlier, most of the runs keep the storm closer to the coast, and differ with strength and direction from there. The decrease in QPF seen in the 12z run (and thus, total potential snow) appears to be a function of less 6 hr QPF forecast at 00z Thursday vs earlier runs, which is itself due to the low being further south of the Philly metro at that timestamp. Despite these changes, the rain/snow line has been quite consistent since the 00z run. 00z, 06z, and 12z, all depict a virtually identical rain/snow line at 00z Thurs. This is not as true at 06z Thurs--earlier runs, including 00z Sun, had heavy snow reach further into NJ due to extreme dynamical cooling and FGEN effects, however, the 12z and 06z run are in fair agreement with a rain/snow line towards coastal NJ and DE. ECMWF-->Has the best positioning right now of the 700mb low in terms of maximal snow potential. 06z Euro brings storm further north than 00z, poss ptype implications. UKMET--> 00z run splits the difference in terms of southeast ridging between the 12z GFS solution and the 06z ECMWF solution with respect to possible temps during the storm's projected peak (around 21z Wed-09z Thurs). 12z run warmer, lowers snowfall totals in PHL from 13 to 8 or sig less (to finish). NAM--> Brings the low further north and closer to DE at 84 hours vs other models due to positioning the Canadian high further NE. Has the closest SFC low approach to Philly of any current or recent model run across models. As a result, projects much more of a mix than other models--the 12z run would bring a mostly freezing rain type event to the Philly metro, with up to 0.5" of freezing rain forecast to potentially fall by 00z Thurs. Pulling up a sounding, this is due to WAA between 850 and 700mb. In fact, the NAM actually suggests that the surface temps will be colder than other models suggest--but is so aggressive with the mid-level conveyor belt WAA that it makes much of the event FZRA. I agree with earlier analysis suggesting the NAM is too amplified. EPS vs GEFS--> EPS slightly closer to coast. Edit: NAM time stamp. 2 1 Link to comment Share on other sites More sharing options...
JTA66 Posted December 13, 2020 Share Posted December 13, 2020 I just realized why I feel confident of a MECS on Wed... I'm dropping the cat off to be neutered at 7am and taking my mom to the cardiologist at 11am. So yeah, one the the few days I have to get in the car since March. 1 Link to comment Share on other sites More sharing options...
Newman Posted December 13, 2020 Share Posted December 13, 2020 Winter Weather Advisories issued by State College in central PA for much of the southern tier of the state for tomorrow's system. I expect Mt. Holly to do the same within the next few hours. 1 Link to comment Share on other sites More sharing options...
Ralph Wiggum Posted December 13, 2020 Share Posted December 13, 2020 Again, not saying we will continue to see the slp tick farther N before moving East BUT you need only look at the most recent example on our doorstep for tomorrow. That system was progged well to the South just 36 hours or so ago then began ticking N and amping more each run. Now this should help the system for Wednesday, but it needs to be watched as this is the 3rd system this month already to come farther N. Not my final call at all, just saying it shouldn't come as a shock to anyone if we continue seeing the trend. The saving grace for Wednesday is CAD....confluence, a 50/50, and some blocking up top. 3 Link to comment Share on other sites More sharing options...
ChescoWx Posted December 13, 2020 Share Posted December 13, 2020 WXSIM much more enthused about tomorrow's initial event than my NWS point and click is.....WXSIM sees a mix of rain and snow becoming all snow and briefly heavy after 230pm with 2" to maybe 3" accumulating. It has "backed off" a bit on the Wed event starting around 2pm with 19.4" of snow accumulating.... Link to comment Share on other sites More sharing options...
MPotter_WX Posted December 13, 2020 Share Posted December 13, 2020 Definitely getting excited here in the LV! Looking like at lock of at least 12”+; however, I am a little wary of mixing with sleet should enough warm air filter in aloft if those trends N occur. The strength of the confluence/1038-mb high is a saving grace for this event. The position of the coastal low will ultimately decide the fate of you guys to the south, so keep the faith. As is typical of all of these systems, once we get a good sampling of this system once it makes it to the west coast (12z Monday), we should have a good handling of its position. Link to comment Share on other sites More sharing options...
Moderately Unstable Posted December 13, 2020 Share Posted December 13, 2020 9 minutes ago, ChescoWx said: WXSIM much more enthused about tomorrow's initial event than my NWS point and click is.....WXSIM sees a mix of rain and snow becoming all snow and briefly heavy after 230pm with 2" to maybe 3" accumulating. It has "backed off" a bit on the Wed event starting around 2pm with 19.4" of snow accumulating.... Double check to make sure it's actually accumulating (if it is, that is indeed interesting). For example, tomorrow, the NAM says 2-3" of snow could fall (snow accumulation graphic), but precisely 0 of that will accumulate (change in snow depth graphic). Also, remember that unless otherwise noted, rain:snow ratios are 1:10...since temps here are so close to freezing, ratios won't be 1:10, they'll be 1:7, 1:8...which is why Kuchara totals are lower than the non-kuch totals. Machine learning models are great, sometimes they don't pick up on big changes quick enough. Link to comment Share on other sites More sharing options...
Birds~69 Posted December 13, 2020 Share Posted December 13, 2020 7 minutes ago, Moderately Unstable said: Double check to make sure it's actually accumulating. For example, tomorrow, the NAM says 2-3" of snow could fall, but precisely 0 of that will accumulate. Also, remember that unless otherwise noted, rain:snow ratios are 1:10...since temps here are so close to freezing, ratios won't be 1:10, they'll be 1:7, 1:8...which is why Kuchara totals are lower than the non-kuch totals. True. Maybe some on grass tops, sloppy and pointless. Always thought the WXSIM algorithm was screwed up....always on the high end. Doesn't take many factors into account... Link to comment Share on other sites More sharing options...
Animal Posted December 13, 2020 Share Posted December 13, 2020 Mt Holly afternoon afd going with a switch to rain and sleet to the i 95 corridor! Noted the nam model which is a train wreck. mostly all snow event further out in the burbs up through the poconos! Link to comment Share on other sites More sharing options...
CoolHandMike Posted December 13, 2020 Share Posted December 13, 2020 So I got one of the snow blowers working. I had to kludge together a linkage for engaging the auger, which then immediately broke. The only thing I could find last minute was a lawnmower throttle cable, but the actual lever is made of the cheapest plastic known to man and almost immediately shattered under load. Oh well. Ordered some correct replacement parts, and with any luck they'll be here on Tuesday... We shall see. But I was really happy to get it running after sitting neglected for who know how long. It's a 1996 Craftsman, FWIW. 2 1 Link to comment Share on other sites More sharing options...
RedSky Posted December 13, 2020 Share Posted December 13, 2020 RGEM is good for everyone. Link to comment Share on other sites More sharing options...
RedSky Posted December 13, 2020 Share Posted December 13, 2020 GFS cold and good, NW trend abated 2 1 Link to comment Share on other sites More sharing options...
Birds~69 Posted December 13, 2020 Share Posted December 13, 2020 2 minutes ago, RedSky said: RGEM is good for everyone. Not too far N/W Philly has been 12"+ throughout for the most part of these runs. The gift that keeps on giving.... 1 Link to comment Share on other sites More sharing options...
Animal Posted December 13, 2020 Share Posted December 13, 2020 4 minutes ago, RedSky said: GFS cold and good, NW trend abated Yea it’s been consistent. just printed out 12-20 philly metro 1 1 Link to comment Share on other sites More sharing options...
Animal Posted December 13, 2020 Share Posted December 13, 2020 4 minutes ago, Birds~69 said: Not too far N/W Philly has been 12"+ throughout for the most part of these runs. The gift that keeps on giving.... rgem drops 14 center city 1 Link to comment Share on other sites More sharing options...
Birds~69 Posted December 13, 2020 Share Posted December 13, 2020 I don't expect this but it's nice to look at... 1 1 Link to comment Share on other sites More sharing options...
Moderately Unstable Posted December 13, 2020 Share Posted December 13, 2020 ^^agreed. It is nice to look at. The bulk of the guidance is not on the GFS amounts train, though I don't think it's out to lunch per se. I think a lot of the gfs's progging relates to thinking super heavy precip rates will overcome all else. For Philly CC, my gut instinct at this point for a first call is, 5-8 if we see a snow-mix/rain-snow, 8-12 if mostly snow, 12-16 if phl stays mostly snow, and everything aligns just right. I'm a bit concerned about the dry slot timing on the backend. That's screwed the region in the past and is showing more of an issue in recent runs. Thus if I had to choose a single range, I'd go 8-12, with the (*) that more is possible. 1 Link to comment Share on other sites More sharing options...
Newman Posted December 13, 2020 Share Posted December 13, 2020 @tombo82685 Thoughts? 1 1 Link to comment Share on other sites More sharing options...
Ralph Wiggum Posted December 13, 2020 Share Posted December 13, 2020 New thread started. I'll take the heat if its jinxed. Link to comment Share on other sites More sharing options...
wkd Posted December 14, 2020 Share Posted December 14, 2020 Light snow/sleet mix. 38/34 Link to comment Share on other sites More sharing options...
Rockem_sockem_connection Posted December 14, 2020 Share Posted December 14, 2020 20 hours ago, Birds~69 said: You're in SJ, no shit. I live like right across the way from Philly, which was in the 18" range days ago when the weenie fest was full blown. As literally always, looks like rain now which works for me. This was an easy one to get right since it literally goes down this way every single time lol Link to comment Share on other sites More sharing options...
ChasingFlakes Posted December 14, 2020 Share Posted December 14, 2020 Went outside last night around 1am and immediately saw 2 shooting stars as I was closing the door. Thought it would be cloudy, but it had cleared up above me for 15 minutes and I sat and saw about 8-10 meteors in that time. Really good rates, better than the perseids in August, although those tend to have cooler trails and more fireballs than the gemenids. Link to comment Share on other sites More sharing options...
Ralph Wiggum Posted December 14, 2020 Share Posted December 14, 2020 12z NAM stopped the trend and came in colder....so thats refreshing for anyone who put stock in the NAM at range last day or so. Eta: upon farther inspection actually took a sizeable move to the rgem wrt track and intensity Link to comment Share on other sites More sharing options...
The Iceman Posted December 14, 2020 Share Posted December 14, 2020 17 minutes ago, Ralph Wiggum said: 12z NAM stopped the trend and came in colder....so thats refreshing for anyone who put stock in the NAM at range last day or so. Eta: upon farther inspection actually took a sizeable move to the rgem wrt track and intensity Yeah definitely buckdd the NW trend and way less amped. Mix line touches 95(still frozen) but sinks back down. It isn't the rgem but it's actually more in line what I'm thinking. Warning level event 6-10" for 95 with a period of sleet. 10-15" with lolli's in the 20s N and W of 95 toward Lehigh Valley. Sharp cut off south of 95 though(sorry s. Jersey). 1 Link to comment Share on other sites More sharing options...
Ralph Wiggum Posted December 14, 2020 Share Posted December 14, 2020 3 minutes ago, The Iceman said: Yeah definitely buckdd the NW trend and way less amped. Mix line touches 95(still frozen) but sinks back down. It isn't the rgem but it's actually more in line what I'm thinking. Warning level event 6-10" for 95 with a period of sleet. 10-15" with lolli's in the 20s N and W of 95 toward Lehigh Valley. Sharp cut off south of 95 though(sorry s. Jersey). Agreed. Just good to see that trend stop and even reverse. Maybe windshield wiper effect or maybe going to continue. Up next....rgem. Link to comment Share on other sites More sharing options...
Birds~69 Posted December 14, 2020 Share Posted December 14, 2020 Snowing nicely in Allentown... https://www.fox29.com/allentown-webcam Link to comment Share on other sites More sharing options...
LVblizzard Posted December 14, 2020 Share Posted December 14, 2020 18 minutes ago, Birds~69 said: Snowing nicely in Allentown... https://www.fox29.com/allentown-webcam Just changed over an hour ago. Coating on the ground. Expecting an inch or two before it ends. Link to comment Share on other sites More sharing options...
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