yoda Posted July 21, 2017 Share Posted July 21, 2017 28 minutes ago, mappy said: Yoda: King of Copy and Paste with no explanation. Well if more people would say something... like mattie g did in the banter thread and then I linked him to where he could learn more about that Skew-T's... I mean most should know about the sup composite maps... not trying to toss you under the bus mappy, but no one really comes out and says explain this or I don't understand this so I (and I would assume others as well) just post images and go Link to comment Share on other sites More sharing options...
yoda Posted July 21, 2017 Share Posted July 21, 2017 Thats an early afternoon AFD from LWX... Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 159 PM EDT Fri Jul 21 2017 .SYNOPSIS...Weak upper level disturbances will be possible tonight through Sunday. An upper level trough of low pressure will move over the northeastern US early in the new week. && .NEAR TERM /THROUGH TONIGHT/... Showers and thunderstorms moving across the Appalachians will likely hold together as they move across the southern half of the fcst area. Thermodynamic profiles are very warm aloft (-3C @500 mb) and no svr warnings have been issued by offices to the west. T-storms will likely dissipate during the early evening. Otherwise, another very warm and muggy night similar to last night but with more cloud cover. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...Global and hi-res models continue to show an MCS forming over southern Wisconsin late tonight and moving across Chicago and eastern OH and wrn PA by Sat morning. While this complex is expected to weaken toward daybreak, redevelopment is expected during the afternoon across the local area. 0-6km shear increases somewhat supporting organized convection. CAPE is also on the increase given hotter temperatures and plenty of moisture (850 mb dewpoints of 15C). Some severe wx is possible, but ensemble guidance shows a large spread in CAPE values with some members showing only weak CAPE. Sunday appears to be shaping up a potentially more significant severe convective day. Models progged a stronger upper level disturbance with significant height falls for summertime standards. Shear is also on the increase and many ensemble members show moderate CAPE and some even high CAPE values over 3500 J/kg. Expect clusters of storms to move across the area some with damaging winds. Link to comment Share on other sites More sharing options...
high risk Posted July 22, 2017 Share Posted July 22, 2017 00z NAM nest is continuing the idea of later Saturday and later Sunday to both be pretty active in the mid-Atlantic. The lack of decent low-level flow should keep supercell chances fairly low, but the deep-layer shear will likely be sufficient for more than just isolated SVR. I think we'll likely get ENH on at least one of the two days. Link to comment Share on other sites More sharing options...
yoda Posted July 22, 2017 Share Posted July 22, 2017 23 minutes ago, high risk said: 00z NAM nest is continuing the idea of later Saturday and later Sunday to both be pretty in the mid-Atlantic. The lack of decent low-level flow should keep supercell chances fairly low, but the deep-layer shear will likely be sufficient for more than just isolated SVR. I think we'll likely get ENH on at least one of the two days. Def agree. 3km NAM tries to crush the area hard late Sunday in its sim radar... huge bow echo appears in W VA at 00z Link to comment Share on other sites More sharing options...
Kmlwx Posted July 22, 2017 Share Posted July 22, 2017 I'm starting to get a little excited about both days. That bow echo on sim radar for Sunday looks awesome but it's also the 3km NAM at a decent range. Let's see how tomorrow shakes out before moving to Sunday. The regular NAM still is a bit more mundane as somebody mentioned earlier which is interesting. I'm more intrigued by these two days than I have been in a while. But I've been burned many times so...we'll see. Link to comment Share on other sites More sharing options...
Kmlwx Posted July 22, 2017 Share Posted July 22, 2017 06z NAM is a lot less impressive on parameters for whatever reason - I have not looked closely yet. Link to comment Share on other sites More sharing options...
MN Transplant Posted July 22, 2017 Share Posted July 22, 2017 I like the evolution of the 9z HRRR. Link to comment Share on other sites More sharing options...
high risk Posted July 22, 2017 Share Posted July 22, 2017 While the details differ, every hi-res run brings a round of convection through much of the area during the late afternoon hours, with a second round possible after dark. This certainly fits what's implied by the morning map with a primary MCS now moving across eastern OH and another in IL/IN. The lead MCS should send an outflow boundary down into northern MD/VA and serve as the focus of storms later. Low-level shear looks to be weak, but deep-layer shear should be sufficient for at least some wind and maybe a few hail reports with the decent instability. The likelihood of storms is reflected in the 00z parallel HREF (high-resolution ensemble forecast system) which basically takes the most recent run of the NAM nest, each Hi-Res Window, and the NSSL WRF as well as a time-lagged run of each and generates probability and mean fields. This plot shows the probability of 1 km reflectivity exceeding 40 dbz between 21 and 22z today within 40 miles of a point. Link to comment Share on other sites More sharing options...
showmethesnow Posted July 22, 2017 Share Posted July 22, 2017 1 hour ago, high risk said: While the details differ, every hi-res run brings a round of convection through much of the area during the late afternoon hours, with a second round possible after dark. This certainly fits what's implied by the morning map with a primary MCS now moving across eastern OH and another in IL/IN. The lead MCS should send an outflow boundary down into northern MD/VA and serve as the focus of storms later. Low-level shear looks to be weak, but deep-layer shear should be sufficient for at least some wind and maybe a few hail reports with the decent instability. The likelihood of storms is reflected in the 00z parallel HREF (high-resolution ensemble forecast system) which basically takes the most recent run of the NAM nest, each Hi-Res Window, and the NSSL WRF as well as a time-lagged run of each and generates probability and mean fields. This plot shows the probability of 1 km reflectivity exceeding 40 dbz between 21 and 22z today within 40 miles of a point. Interesting the hole of lower probabilities showing up in Western MD/WV/SW PA. Is that topographically induced or is that more about timing? Link to comment Share on other sites More sharing options...
high risk Posted July 22, 2017 Share Posted July 22, 2017 31 minutes ago, showmethesnow said: Interesting the hole of lower probabilities showing up in Western MD/WV/SW PA. Is that topographically induced or is that more about timing? it's more about timing, as all of the models being used to generate the probs have ~3km resolution. It only covers a 1-hr period, so there is a signal here that the area in question might be in between lines, but the probs in that minimum area aren't that low either. Link to comment Share on other sites More sharing options...
showmethesnow Posted July 22, 2017 Share Posted July 22, 2017 18 minutes ago, high risk said: it's more about timing, as all of the models being used to generate the probs have ~3km resolution. It only covers a 1-hr period, so there is a signal here that the area in question might be in between lines, but the probs in that minimum area aren't that low either. Gotcha, thanks for the explanation. Link to comment Share on other sites More sharing options...
Kmlwx Posted July 22, 2017 Share Posted July 22, 2017 DCAPE is presently lacking pretty heavily - that could easily change with time. Instability is building nicely. I'm mostly in for today - TBD for tomorrow. Link to comment Share on other sites More sharing options...
Eskimo Joe Posted July 22, 2017 Share Posted July 22, 2017 The 2012 derecho featured a morning MCS in PA that shoved a boundary to its south like High Risk alluded to. That served as the focus for the real event in the evening which was evident on the radar loop once the storm got to Garrett County....storm light up along Mason-Dixon and Frederick County before the main event rolled through. It will be interesting to see if this MCS sucks all of the sting out of the atmosphere and shoves the boundary for the second event well south of DC towards CHO or something. Link to comment Share on other sites More sharing options...
MN Transplant Posted July 22, 2017 Share Posted July 22, 2017 The HRRR really likes multiple rounds of precip, even if it isn't necessarily big time severe. Many of us would take that. Link to comment Share on other sites More sharing options...
BTRWx Posted July 22, 2017 Share Posted July 22, 2017 23 hours ago, yoda said: Well if more people would say something... like mattie g did in the banter thread and then I linked him to where he could learn more about that Skew-T's... I mean most should know about the sup composite maps... not trying to toss you under the bus mappy, but no one really comes out and says explain this or I don't understand this so I (and I would assume others as well) just post images and go You were saying... Link to comment Share on other sites More sharing options...
Kmlwx Posted July 22, 2017 Share Posted July 22, 2017 Looks like Winchester had a 45mph gust. Link to comment Share on other sites More sharing options...
Kmlwx Posted July 22, 2017 Share Posted July 22, 2017 Core of winds is heading in my general direction. Looks like mostly 40-50mph range. Non-severe but could change. Link to comment Share on other sites More sharing options...
Kmlwx Posted July 22, 2017 Share Posted July 22, 2017 Very nice gust here - but below severe levels it seems. Link to comment Share on other sites More sharing options...
BTRWx Posted July 22, 2017 Share Posted July 22, 2017 The District is about to get smoked! Link to comment Share on other sites More sharing options...
Kmlwx Posted July 22, 2017 Share Posted July 22, 2017 Respectable line. Certainly nothing derecho-like but very decent wind gusts came through here in a few waves. Much needed rain as well. Looks like more to the west but we are probably overturned now. Maybe if the sun pops out between lines we can refuel just a touch. Link to comment Share on other sites More sharing options...
yoda Posted July 22, 2017 Share Posted July 22, 2017 Trees and powerlines down in Montgomery County Link to comment Share on other sites More sharing options...
yoda Posted July 22, 2017 Share Posted July 22, 2017 PRELIMINARY LOCAL STORM REPORT NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 300 PM EDT SAT JUL 22 2017 ..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON... ..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE.... ..REMARKS.. 0222 PM TSTM WND DMG 1 SW CHILLUM 38.95N 77.00W 07/22/2017 DISTRICT OF COLUMB DC TRAINED SPOTTER ROOF SHINGLES PEELED BACK BY THUNDERSTORM WINDS. Link to comment Share on other sites More sharing options...
ThePhotoGuy Posted July 22, 2017 Share Posted July 22, 2017 Pretty meh up here. Some thunder. Reported Overturned Boat in Edgewater. Link to comment Share on other sites More sharing options...
yoda Posted July 22, 2017 Share Posted July 22, 2017 Hmmmm... I say hmmm http://www.spc.noaa.gov/products/md/2017/md1395.html Link to comment Share on other sites More sharing options...
southmdwatcher Posted July 22, 2017 Share Posted July 22, 2017 1 minute ago, yoda said: Hmmmm... I say hmmm http://www.spc.noaa.gov/products/md/2017/md1395.html Those of us south of DC can say....Hmmmmm. But that convection would be well past midnight getting east of the mountains and would likely propagate southeastward. Link to comment Share on other sites More sharing options...
Kmlwx Posted July 22, 2017 Share Posted July 22, 2017 2 minutes ago, yoda said: Hmmmm... I say hmmm http://www.spc.noaa.gov/products/md/2017/md1395.html Impact to our area from anything over that way would likely be largely dependent on airmass recovery. I wouldn't anticipate any follow-up lines to be more intense than the first one - perhaps that could be the case in areas not impacted by the line that just went through. Would temper your expectations to general to iso strong storms with any follow-up lines. Link to comment Share on other sites More sharing options...
yoda Posted July 22, 2017 Share Posted July 22, 2017 If you want to believe SPC meso... it gets mighty interesting with some of the future forecasts... like the sup composite and eff shear Link to comment Share on other sites More sharing options...
Kmlwx Posted July 22, 2017 Share Posted July 22, 2017 That RAP forecast that the mesoanalysis uses on that website cannot generally be trusted. Can sometimes pull a coup but it often underestimates and overestimates stuff or the frames are out of order sometimes. Not a great system to rely on. I'll stick with my knowledge of climo around here - hard for us to do consecutive rounds in same areas twice in one day. Link to comment Share on other sites More sharing options...
yoda Posted July 22, 2017 Share Posted July 22, 2017 Just now, Kmlwx said: That RAP forecast that the mesoanalysis uses on that website cannot generally be trusted. Why is that? Besides it changes every hour when it updates Link to comment Share on other sites More sharing options...
Kmlwx Posted July 22, 2017 Share Posted July 22, 2017 1 minute ago, yoda said: Why is that? Besides it changes every hour when it updates See my updated post - large overestimations or underestimations. - Frames get out of order sometimes which can be misleading (you and I have discussed this before). It's another tool - but I'm not convinced it's a great one at all. Link to comment Share on other sites More sharing options...
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