cbelke Posted May 20, 2022 Report Share Posted May 20, 2022 Could be interesting this afternoon if this drops further South. Most models seem to have it further North. 3 Quote Link to comment Share on other sites More sharing options...
Parsley Posted May 20, 2022 Report Share Posted May 20, 2022 Ohio storms could threaten eastern PA later today. Models not 100% sure with exact placement as it traverses east toward us today. Lehigh Valley, Poconos, NNJ in crosshairs perhaps? 1 Quote Link to comment Share on other sites More sharing options...
Allsnow Posted May 20, 2022 Report Share Posted May 20, 2022 Going to get slammed later!!!! Go Niña!! Quote Link to comment Share on other sites More sharing options...
Parsley Posted May 20, 2022 Report Share Posted May 20, 2022 NWS PHI: Late this morning/ early this afternoon the warm front will pull northward in response to the MCV to about/ or just north of I-195 in NJ. The MCV will then turn more easterly and track along the warm front. In the warm sector, destabilization is forecast to occur with MLCAPE values of 1500 to 2500 J/kg. The main possible failure mode for convection this afternoon will be the rapidly warming low level thermal profiles. The latest forecast soundings off of the NAM and GFS all show some version of capping in place across the area. The overall strength of the CAP looks like it can be overcome given the strength of the forcing for ascent. The most likely scenario at this point appears to be convection maintaining itself across central PA early this afternoon and quickly going linear as anvil-level storm- relative flow vectors point southwest. The convection is then forecast to turn more easterly, or into the instability and down the warm front. Bulk shear vectors with the convection are perpendicular to the orientation of the convection at about 40 kts which makes damaging winds the primary threat. An isolated tornado embedded in the line of convection is also possible given the proximity of the warm front. The convection looks like it will approach the Lehigh Valley around 2 - 4 PM and quickly head east towards the NJ coast. As the convection heads east it will encounter an increasingly capped environment and begin to decay. The main question here is how quickly will the convection weaken. In these type of setups, convection usually weakens but doesn`t immediately collapse. Towards MD and DE, mostly dry weather is expected as the forcing from the MCV will be just to the north. Expect high temperatures mostly in the mid 80s today. 2 Quote Link to comment Share on other sites More sharing options...
irishbri74 Posted May 20, 2022 Report Share Posted May 20, 2022 Great write up from Mt. Holly. Bravo. we’ll see how this plays out I guess. Latest run of HRRR is a bit messy: Quote Link to comment Share on other sites More sharing options...
Rainshadow Posted May 20, 2022 Report Share Posted May 20, 2022 1 hour ago, irishbri74 said: Great write up from Mt. Holly. Bravo. we’ll see how this plays out I guess. Latest run of HRRR is a bit messy: Yes excellent discussion. Quote Link to comment Share on other sites More sharing options...
susqushawn Posted May 20, 2022 Report Share Posted May 20, 2022 sneaky severe threat today especially whoever gets the MCV bow echo. shear is low probably due to weak upper air flow 500 and above, but that may be offset pretty strong winds near 700 which the storms might be able to tap into. Surface flow is weak but completely backed 180 to the upper level flow above it, look at the surface wind barb below. Hodograph as a result is curved. Some capping in place but it appears weak here. I'd think if a MCV bow echo is bearing down, it will overcome weak capping with ease until getting closer to coast maybe. Hi res guidance except HRRR keeps MCV up north towards Poconos/Lehigh Valley. HRRR blasts it through SE PA after turning SE from central PA. Upper air flow is more west to east, so it must be something on a mesoscale level that turns it SE against the flow a bit. not sure... Quote Link to comment Share on other sites More sharing options...
susqushawn Posted May 20, 2022 Report Share Posted May 20, 2022 12z update, hi res nam in NE PA w/ MCV, ARW goes derecho like: Quote Link to comment Share on other sites More sharing options...
susqushawn Posted May 20, 2022 Report Share Posted May 20, 2022 from the little I've seen, I wouldn't be surprised to see an elevated risk level from the SPC, or at least a meso discussion to further highlight the risk of a fast moving bow echo Quote Link to comment Share on other sites More sharing options...
susqushawn Posted May 20, 2022 Report Share Posted May 20, 2022 Probability of Watch Issuance...80 percent SUMMARY...The severe threat is increasing across portions of central PA into MD. Damaging gusts and perhaps a few tornadoes may accompany the strongest, longer lived storms. A WW issuance will be needed within the next couple of hours. DISCUSSION...A remnant mid-level MCV (evident via water vapor imagery and 700-500 mb objective analysis fields) is currently located just west of the OH/PA border and continues to track eastward towards central PA, and is expected to support more robust convective initiation in the next few hours. Immediately ahead of the MCV center lies a highly sheared low-level environment, with recent PBZ VAD data showing relatively long, curved low-level hodographs and over 300 m2/s2 of associated 0-1km SRH. At the moment, buoyancy remains scant across portions of western into central PA. However, modest breaks in the clouds are contributing to modest surface heating, with mid 60s F surface temperatures already noted across central PA, with low 70s F along the PA/MD border. With surface dewpoints around 60F across several locales, RAP forecast soundings suggest temperatures need to warm into the lower 70s for appreciable buoyancy to develop given the presence of relatively poor (5.5-6.5 C/km) low and mid-level lapse rates. While buoyancy is expected to initially be marginal (i.e. at or below 1000 J/kg MLCAPE), localized deep-layer ascent and strong low-level shear associated with the approaching MCV should support at least a few strong to severe storms developing early this afternoon. Damaging gusts and perhaps a few tornadoes will be the primary concerns, though a brief instance or two of marginally severe hail cannot be completely ruled out with the longer-lived, persistent rotating updrafts. A WW issuance will be needed within the next couple of hours to address the severe threat. Quote Link to comment Share on other sites More sharing options...
susqushawn Posted May 20, 2022 Report Share Posted May 20, 2022 storms firing over northern WV, farther south than all 12z hi res guidance 1 Quote Link to comment Share on other sites More sharing options...
el_nino Posted May 20, 2022 Report Share Posted May 20, 2022 1 Quote Link to comment Share on other sites More sharing options...
Parsley Posted May 20, 2022 Report Share Posted May 20, 2022 Already pouring up here. Sigh….. Quote Link to comment Share on other sites More sharing options...
Parsley Posted May 20, 2022 Report Share Posted May 20, 2022 47 minutes ago, susqushawn said: storms firing over northern WV, farther south than all 12z hi res guidance Yeah, you knew the models would struggle with placement. Seemed that way earlier (in Ohio) as well. Quote Link to comment Share on other sites More sharing options...
Seanvolz98 Posted May 20, 2022 Report Share Posted May 20, 2022 5 minutes ago, Parsley said: Already pouring up here. Sigh….. Must mean the weekend has started lol 3 Quote Link to comment Share on other sites More sharing options...
susqushawn Posted May 20, 2022 Report Share Posted May 20, 2022 Quote Link to comment Share on other sites More sharing options...
mweav067 Posted May 20, 2022 Report Share Posted May 20, 2022 It seems odd to me to have a Tornado Watch up but without a Severe Thunderstorm Watch coupled with it. I'm guessing the criteria, lead time, etc. are different between them? Quote Link to comment Share on other sites More sharing options...
susqushawn Posted May 20, 2022 Report Share Posted May 20, 2022 6 minutes ago, mweav067 said: It seems odd to me to have a Tornado Watch up but without a Severe Thunderstorm Watch coupled with it. I'm guessing the criteria, lead time, etc. are different between them? I've never seen both simultaneously issued, I suspect that the Tornado Watch inherently assumes that severe thunderstorms are possible and when the setup is conducive for tornadoes (or is it tornados?) a tornado watch is specified vs svr thunderstorm. Here's a NWS definition: Tornado Watch A Tornado Watch is issued when severe thunderstorms and tornadoes are possible in and near the watch area. It does not mean that they will occur. It only means they are possible. Severe thunderstorms are defined as follows: 1) Winds of 58 mph or higher AND/OR 2) Hail 1 inch in diameter or larger. 1 Quote Link to comment Share on other sites More sharing options...
ACwx Posted May 20, 2022 Report Share Posted May 20, 2022 2 observations from my end: Much of the NWS discussion today had predicted the line to eventually stop moving NE and eventually move more eastward. Considering it is already centered around the PA/MD border, I think Philly and south Jersey may be in position to get the brunt of this if it holds together. The HRRR has not initialized anywhere near that level of intensity over its last few runs, so I think we may have to be in nowcasting mode for the rest of the day. 1 Quote Link to comment Share on other sites More sharing options...
ACwx Posted May 20, 2022 Report Share Posted May 20, 2022 On a separate note, if this end up producing SVR warnings all the way into NJ, wouldn't that meet the criteria for a derecho from a distance perspective? Quote Link to comment Share on other sites More sharing options...
susqushawn Posted May 20, 2022 Report Share Posted May 20, 2022 ...Mid Atlantic Region... A well-defined MCV is noted on satellite imagery over southwest PA. This feature will track eastward today across PA, northern MD, and into NJ, fostering the development of severe thunderstorms. Destabilization ahead of the MCV, combined with strong low and mid-level wind fields near the circulation will promote the development of supercell and bowing structures capable of damaging winds, large hail, and a few tornadoes. Given the rapid eastward motion of the activity, it should move off the NJ coast well before dark, ending the severe threat. 2 Quote Link to comment Share on other sites More sharing options...
susqushawn Posted May 20, 2022 Report Share Posted May 20, 2022 who knows how to zoom the SPC map into our region? Quote Link to comment Share on other sites More sharing options...
irishbri74 Posted May 20, 2022 Report Share Posted May 20, 2022 2 minutes ago, susqushawn said: who knows how to zoom the SPC map into our region? Take your 2 fingers and start with pull a reverse “pinching” motion on your screen 🫡 jk jk , I know there’s a way to use google overlay somehow. 1 Quote Link to comment Share on other sites More sharing options...
Allsnow Posted May 20, 2022 Report Share Posted May 20, 2022 7 minutes ago, susqushawn said: ...Mid Atlantic Region... A well-defined MCV is noted on satellite imagery over southwest PA. This feature will track eastward today across PA, northern MD, and into NJ, fostering the development of severe thunderstorms. Destabilization ahead of the MCV, combined with strong low and mid-level wind fields near the circulation will promote the development of supercell and bowing structures capable of damaging winds, large hail, and a few tornadoes. Given the rapid eastward motion of the activity, it should move off the NJ coast well before dark, ending the severe threat. Wow Quote Link to comment Share on other sites More sharing options...
Parsley Posted May 20, 2022 Report Share Posted May 20, 2022 1 hour ago, Seanvolz98 said: Must mean the weekend has started lol Lol. Looking forward to swampy yard and swampy ass mowing tomorrow. Quote Link to comment Share on other sites More sharing options...
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