yoda Posted October 30, 2019 Share Posted October 30, 2019 4 hours ago, Kmlwx said: 3k NAM gets MLCAPE to 500+ into the area. Not bad. If we do get any severe, looks like it would be in the form of damaging winds... don't think there is a tornado threat, but I could be wrong on that Link to comment Share on other sites More sharing options...
yoda Posted October 30, 2019 Share Posted October 30, 2019 Well well surprise surprise @Kmlwx @high risk Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1249 AM CDT Wed Oct 30 2019 Valid 311200Z - 011200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE MID-ATLANTIC STATES... ...SUMMARY... Severe thunderstorms capable of strong wind gusts are possible from the Upper Ohio Valley into portions of the Mid-Atlantic States and Southeast on Thursday. ...Synopsis... A strong shortwave trough is expected to mature into a vertically stacked mid-latitude cyclone as it moves through the mid MS and OH Valleys and into eastern Ontario and the Northeast States. Very strong mid/upper-level flow will accompany this system, with a 100+ kt 500-mb jet streak moving throughout its eastern periphery across the TN/OH Valleys and into the Northeast. Surface low associated with this system will likely be centered over the IN/OH border early Thursday with an attendant cold front extending south-southwestward through middle TN and central AL and off the central Gulf Coast. This low will occlude as it moves north-northeastward throughout the day. The attendant cold front will sweep eastward across the eastern CONUS, moving off the East Coast of the CONUS late Thursday night. Thunderstorms are anticipated along the length of this front, some which could be severe. ...Southeast into Mid-Atlantic States... Showers and isolated thunderstorms will likely be ongoing within the broad pre-frontal warm sector from the Southeast into the northern Mid-Atlantic. Moisture advection ahead of the front will likely result in low 70s dewpoints across the Southeast, upper 60s/low 70s across much of the Mid-Atlantic, and mid 60s as far north as PA and NJ. Diurnal heating will be tempered by abundant cloud cover and antecedent precipitation but ample low-level will still result in modest instability (i.e. MLCAPE 500-1000 J/kg) ahead of the front. Pre-frontal showers and thunderstorms are anticipated through the mid to late afternoon. Thereafter, the fast-moving cold front will likely catch up to these pre-frontal storms, leading to a consolidation of all the deep convection along the front. The strong southwesterly flow aloft will extend across the entire region and a few of the pre-frontal storms may be able to organize enough to produce damaging wind gusts and perhaps a brief tornado. Once storms consolidate along the front, strong forcing for ascent attendant to the shortwave trough coupled with vertically veering wind profiles will likely lead to a narrow but well-organized convective line. Strong wind gusts will be the main threat within the line and the highest coverage of severe storms is currently expected across the Mid-Atlantic states, from central PA through western SC. A few tornadoes are possible within the line, particularly across the northern Mid-Atlantic where low-level flow will be strongest. Current HREF guidance suggests the probability of any pre-frontal supercells across central VA and the central Carolinas is low. However, the environmental conditions ahead of the front during the late afternoon support supercell development with any persistent deep convection. ...MAXIMUM RISK BY HAZARD... Tornado: 5% - Slight Wind: 15% - Slight Hail: 5% - Marginal ..Mosier.. 10/30/2019 1 Link to comment Share on other sites More sharing options...
Eskimo Joe Posted October 30, 2019 Share Posted October 30, 2019 IMO, tomorrow is a QLCS tornado kind of day. Wouldn't surprise me to see a D1 ENH and a red box or two go out. Link to comment Share on other sites More sharing options...
high risk Posted October 30, 2019 Share Posted October 30, 2019 6 hours ago, yoda said: Well well surprise surprise @Kmlwx @high risk not totally surprised given that last night's runs added in a little bit of sfc-based cape. As I mentioned yesterday, if the guidance is correct about a long break between the final round of showers (early afternoon) and this squall line (late evening), we can actually achieve some (modest) low-level lapse rates and have a shot to mix some of the impressive winds just above the ground to the surface. And as noted by @Eskimo Joe, while these low instability/intense shear QLCS setups rarely work around here, I agree with him at least a little bit that the threat of a few TORs within the line is non-zero, especially further south. Link to comment Share on other sites More sharing options...
Kmlwx Posted October 30, 2019 Share Posted October 30, 2019 25 minutes ago, Eskimo Joe said: IMO, tomorrow is a QLCS tornado kind of day. Wouldn't surprise me to see a D1 ENH and a red box or two go out. Whoa...who are you? 1 1 Link to comment Share on other sites More sharing options...
Eskimo Joe Posted October 30, 2019 Share Posted October 30, 2019 16 minutes ago, high risk said: not totally surprised given that last night's runs added in a little bit of sfc-based cape. As I mentioned yesterday, if the guidance is correct about a long break between the final round of showers (early afternoon) and this squall line (late evening), we can actually achieve some (modest) low-level lapse rates and have a shot to mix some of the impressive winds just above the ground to the surface. And as noted by @Eskimo Joe, while these low instability/intense shear QLCS setups rarely work around here, I agree with him at least a little bit that the threat of a few TORs within the line is non-zero, especially further south. 00z CAMS yield Significant Tornado Parameter (STP) of 2 - 5 in advance of the line and generally clear us out of junk precip. In fact, the CAMS try to really clear us out and get some quick sun in from 3 - 5 pm. It's going to be an active weather day tomorrow for sure. Link to comment Share on other sites More sharing options...
caviman2201 Posted October 30, 2019 Share Posted October 30, 2019 That is a serious cold front... look at the temp gradient. 70 at Andrews and 49 at College Park? 1 Link to comment Share on other sites More sharing options...
George BM Posted October 30, 2019 Author Share Posted October 30, 2019 HRRR at range of course but the 12z says sorry trick or treaters west of I-95. Link to comment Share on other sites More sharing options...
Eskimo Joe Posted October 30, 2019 Share Posted October 30, 2019 Just now, George BM said: HRRR at range of course but the 12z says sorry trick or treaters west of I-95. It's going to be very close. Best option is either a 2 hours delay or have this thing blast through at 4 or 5 pm Link to comment Share on other sites More sharing options...
George BM Posted October 30, 2019 Author Share Posted October 30, 2019 3 minutes ago, Eskimo Joe said: It's going to be very close. Best option is either a 2 hours delay or have this thing blast through at 4 or 5 pm With preference for the latter of course for the best heating. Link to comment Share on other sites More sharing options...
yoda Posted October 30, 2019 Share Posted October 30, 2019 12z NAM waits too long... has the line coming through the i81 corridor at 00z Halloween night Link to comment Share on other sites More sharing options...
Eskimo Joe Posted October 30, 2019 Share Posted October 30, 2019 Just now, yoda said: 12z NAM waits too long... has the line coming through the i81 corridor at 00z Halloween night It appears the NAM and Euro have been showing the line working east of I-81 after 00z for several consecutive runs. Link to comment Share on other sites More sharing options...
Stormfly Posted October 30, 2019 Share Posted October 30, 2019 36 minutes ago, caviman2201 said: That is a serious cold front... look at the temp gradient. 70 at Andrews and 49 at College Park? Nov 11, 1995? That one was crazy. 70mph gusts and rain to sleet and wet snow. I was in Towson and remember the green flashes from power lines arcing well. Link to comment Share on other sites More sharing options...
yoda Posted October 30, 2019 Share Posted October 30, 2019 1 minute ago, Eskimo Joe said: It appears the NAM and Euro have been showing the line working east of I-81 after 00z for several consecutive runs. Line still looks nice as it crosses the i95 corridor at 03z... snow showers ongoing in the far western part of the LWX CWA Link to comment Share on other sites More sharing options...
high risk Posted October 30, 2019 Share Posted October 30, 2019 11 minutes ago, George BM said: With preference for the latter of course for the best heating. Timing isn't really relevant for SVR chances. Most guidance shows temperatures remaining steady right up until FROPA due to clouds and strong warm advection. 1 Link to comment Share on other sites More sharing options...
high risk Posted October 30, 2019 Share Posted October 30, 2019 3 minutes ago, Eskimo Joe said: It appears the NAM and Euro have been showing the line working east of I-81 after 00z for several consecutive runs. and all 3 of the Hi-Res Windows also show a 2-3z arrival in DC Metro too. That HRRR run showing an earlier arrival is an outlier.....at least for now. 1 Link to comment Share on other sites More sharing options...
yoda Posted October 30, 2019 Share Posted October 30, 2019 28 minutes ago, high risk said: Timing isn't really relevant for SVR chances. Most guidance shows temperatures remaining steady right up until FROPA due to clouds and strong warm advection. Agreed. 12z NAM at 00z THURS says DCA is in the mid 70s.... and then mid 40s with upper 30s back in the i81 corridor at 06z THURS... ETA: 12z 3km NAM does the same as the 12z NAM re temps... DCA is still in the mid 70s at 01z THUR as the line comes in Link to comment Share on other sites More sharing options...
Kmlwx Posted October 30, 2019 Share Posted October 30, 2019 In practice - I feel like these lines tend to speed up even if just by a bit with time. Link to comment Share on other sites More sharing options...
Kmlwx Posted October 30, 2019 Share Posted October 30, 2019 Lol...from the 12z HRRR. Link to comment Share on other sites More sharing options...
Kmlwx Posted October 30, 2019 Share Posted October 30, 2019 The trend definitely seems to have been to bump CAPE values up a bit. I'm seeing numbers of 500 to almost 1000 in some soundings. I might be in - depending on model runs today. Link to comment Share on other sites More sharing options...
mappy Posted October 30, 2019 Share Posted October 30, 2019 QLCS tornadoes are no joke, those suckers spin up real quick, so hopefully people will be paying attention. But in terms of heading out with kids -- mine is set to a wear a fake furry monster costume, so here's hoping the line comes in early (before 6pm) or after 8pm. Fingers crossed. Link to comment Share on other sites More sharing options...
George BM Posted October 30, 2019 Author Share Posted October 30, 2019 2 hours ago, high risk said: Timing isn't really relevant for SVR chances. Most guidance shows temperatures remaining steady right up until FROPA due to clouds and strong warm advection. Yeah that's true. I also prefer the daytime to be able to see the action clearly... whatever action there may be. That's just me personally though. Link to comment Share on other sites More sharing options...
WxUSAF Posted October 30, 2019 Share Posted October 30, 2019 Looks like the 6-8pm window should be good in HoCo. Assuming no major changes. NAM is very chilly for Friday. Caveat that it usually runs too cold. Link to comment Share on other sites More sharing options...
mappy Posted October 30, 2019 Share Posted October 30, 2019 6 minutes ago, losetoa6 said: Hope trick o treatin stays dry for the little ones. A 2 hour window isn't much time to begin with . Things have really changed on that front . In Northeast Baltimore back in the day we started at 3:30 after school and didn't stop till 11pm . i hope it does too! Link to comment Share on other sites More sharing options...
Kmlwx Posted October 30, 2019 Share Posted October 30, 2019 I miss the locally run LWX models for the weenie factor. We had like 3 extra models to look at for severe. Link to comment Share on other sites More sharing options...
Eskimo Joe Posted October 30, 2019 Share Posted October 30, 2019 1 minute ago, Kmlwx said: I miss the locally run LWX models for the weenie factor. We had like 3 extra models to look at for severe. Millersville University runs their tweaked in house WRF and it's a nice alternative for us here http://www.atmos.millersville.edu/~wrf/wrf.php 1 1 Link to comment Share on other sites More sharing options...
yoda Posted October 30, 2019 Share Posted October 30, 2019 ENH ISSUED ON 1730 OTLK Link to comment Share on other sites More sharing options...
Eskimo Joe Posted October 30, 2019 Share Posted October 30, 2019 5 hours ago, Eskimo Joe said: IMO, tomorrow is a QLCS tornado kind of day. Wouldn't surprise me to see a D1 ENH and a red box or two go out. I win the computer game. 1 Link to comment Share on other sites More sharing options...
yoda Posted October 30, 2019 Share Posted October 30, 2019 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1224 PM CDT Wed Oct 30 2019 Valid 311200Z - 011200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF SOUTHERN PENNSYLVANIA SOUTHWARD INTO NORTHERN NORTH CAROLINA... ...SUMMARY... Severe thunderstorms capable of strong wind gusts are expected across much of the eastern U.S. Thursday -- particularly from areas along and east of the central and southern Appalachians to the mid Atlantic and Carolinas coastal areas. ...Synopsis... An upper trough crossing the central U.S. at the start of the period will evolve into a deepening closed low with time, as the system shifts quickly east-northeastward across the Midwest, and then into the Northeast overnight. As this occurs, the broader trough surrounding the low will gradually take on a more neutral to slightly negative tilt, through the end of the period. As this occurs, a cold front -- initially trailing from a low near the KY vicinity southward across Alabama to near the mouth of the Mississippi River -- will advance steadily eastward during the day. The front should cross the Appalachian crest by afternoon, as the parent low rapidly deepens and eventually occludes over the Lower Great Lakes area, reaching the Atlantic coast after midnight. This front will focus a band of showers and thunderstorms -- and attendant risk for severe weather primarily along and east of the mountains. ...Portions of the PA/NY vicinity southward/southwestward to the southern Appalachians... A zone of showers and thunderstorms should be ongoing at the start of the period from the mid Ohio Valley/Mid South region south-southwestward to the western Gulf of Mexico, in the vicinity of an advancing surface cold front. A secondary area of showers -- perhaps with some embedded lightning -- will be shifting quickly northeastward across the Carolinas/Virginia vicinity. Only minimal severe risk -- mainly in the form of gusty winds or a brief tornado -- is apparent at this time within either of these areas of convection through the first several hours of the period. With time, the advance of the cold front across the southern, and then the central, Appalachians during the afternoon in conjunction with the strengthening upper system will result in gradual organization of a band of frontal convection. Very strong flow aloft will aid in the convective organization, with upscale evolution toward a semi-continuous band of storms expected. By late afternoon/early evening, storms will likely have become fairly well-organized, crossing south-central and southeastern PA, MD, VA, and the Carolinas along with attendant risk for strong/damaging wind gusts. Low-level wind profiles will become supportive of supercells during the afternoon across the pre-frontal warm sector. While suggestive of some tornado potential, pre-frontal warm-sector storms are largely not anticipated. Still, a few mainly QLCS-type tornadoes will be possible, given the overall dynamic/kinematic set-up -- particularly from late afternoon through mid evening. As storms near the coast overnight, gradual weakening of the convection -- and associated diminishing of the severe risk -- is expected, though limited wind risk will likely extend to near the mid Atlantic/Carolina coasts overnight. ...MAXIMUM RISK BY HAZARD... Tornado: 5% - Slight Wind: 30% - Enhanced Hail: 5% - Marginal ..Goss.. 10/30/2019 Link to comment Share on other sites More sharing options...
Kmlwx Posted October 30, 2019 Share Posted October 30, 2019 21 minutes ago, Eskimo Joe said: Millersville University runs their tweaked in house WRF and it's a nice alternative for us here http://www.atmos.millersville.edu/~wrf/wrf.php Sweet! Thanks! Not sure how I had no idea about this. Link to comment Share on other sites More sharing options...
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