2021 Mid-Atlantic Severe Weather - General Discussion

[Baltimorewx]

1 hour ago, Kmlwx said:

Looking like the immediate DC-Balt corridor may be out of the game completely at this point. Thinking east of the Bay is where it's at. Oh well. We keep waiting for severe season! 

Agree but I think some gusty wind showers might still be possible with this strong front right around 1 or so

[Scraff]

7 minutes ago, Baltimorewx said:

Agree but I think some gusty wind showers might still be possible with this strong front right around 1 or so

Not a drop of water on radar at the moment.  Hopefully something pops.

[Baltimorewx]

2 minutes ago, Scraff said:

Not a drop of water on radar at the moment.  Hopefully something pops.

Yeah, verbatim the HRRR has some showers literally popping right over I95 at like 1-2pm..not impressive looking but with the front I could see a quick burst of rain and wind happening maybe

[high risk]

Several of the CAMs this morning do break out some showers on the east side of town in the 1-2pm hour, although it appears that they are actually just behind the front.     This lessens a threat of big wind, although it may still be sufficiently mixed to bring some decent gusts to the surface.    The question is still whether something can form just ahead of the front around noon.    Only the HiResW ARW2 suggests this scenario.

[mappy]

Breeze has picked up, up here. Guess it will only get windier as the day goes on.

[weatherCCB]

Looks like some showers firing up just west of here. Might bode well for east of 95

[r3w]

Looking better than expected so far.

[wawarriors4]

A few lightning flashes and rumbles of Thunder in Spotsy at work. Radar looks ok.

[high risk]

radar looks good along I-95 in VA for sure, although I think that this activity (except perhaps for the cells moving into Calvert County) is just behind the front which has now cleared IAD and DCA.

[wawarriors4]

Solid Thunderstorm on-going right now here in Spotsy!

[vastateofmind]

2 minutes ago, wawarriors4 said:

Solid Thunderstorm on-going right now here in Spotsy!

Yep...I've seen at least one flash to the south, and have been hearing the thunder from your Spotsy storm for the past 10 minutes.

[r3w]

26 minutes ago, high risk said:

radar looks good along I-95 in VA for sure, although I think that this activity (except perhaps for the cells moving into Calvert County) is just behind the front which has now cleared IAD and DCA.

Looks like there's some hail in that bigger cell over Spotsy, it's 72/54F around the Calvert area right now, I'll be satisfied just hearing some thunder honestly.

[wawarriors4]

13 minutes ago, r3w said:

Looks like there's some hail in that bigger cell over Spotsy, it's 72/54F around the Calvert area right now, I'll be satisfied just hearing some thunder honestly.

Lots of thunder and lightning as the storm moved through, poured rain for about 15 minutes and wind gusted above 40mph. Nothing crazy, but a solid storm, was nice to hear the thunder and see lightning.

[Rhino16]

Was some pea sized, maybe slightly bigger hail here. Pretty brief.

[Kmlwx]

Big wind here now. But with the precip side of things - I got like 15 rain drops earlier (Colesville, MD today)

[yoda]

Looks like a damage report out of St. Mary's county from the severe weather

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
229 PM EDT WED APR 21 2021

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0118 PM     TSTM WND DMG     1 E CLEMENTS            38.32N  76.70W
04/21/2021                   ST. MARYS          MD   EMERGENCY MNGR

            TREE SNAPPED AND ONE END OF BARN TIN ROOF RIPPED OFF
            AND THROWN DOWNWIND NEAR THE INTERSECTION OF PIN CUSHION
            ROAD AND ROUTE 243.

[r3w]

Welp...didn't get the lightning I'd hoped for...lol but some nasty winds on that southern-most cell tore through St. Marys & Calvert though, just got power back on here. Had a tree come down on the substation apparently.

[Eskimo Joe]

1 hour ago, r3w said:

Welp...didn't get the lightning I'd hoped for...lol but some nasty winds on that southern-most cell tore through St. Marys & Calvert though, just got power back on here. Had a tree come down on the substation apparently.

Looks like there was a decent microburst in St. Mary's County today...a linear series of wind reports that would make me believe it's straight line winds.

[vastateofmind]

13 hours ago, Eskimo Joe said:

Looks like there was a decent microburst in St. Mary's County today...a linear series of wind reports that would make me believe it's straight line winds.

On radar yesterday at lunchtime, it looked like the line really got its act together right at I-95...I'm about two miles east of the interstate, and it seemed to "bloom" overhead pretty quickly (in terms of lightning, wind and rain), and intensify as it moved east to cross the Potomac into MD.

For you mets and other smarter-than-me wx people -- is there something about our geography, or topology, or climate (or, or, or?) that causes lines of thunderstorms to strengthen between I-95 and the Potomac River, and pick up even more steam in southern MD? Is the Potomac playing a role in that? I can't tell you how many times I've noticed this phenomenon in the past 20 years -- a storm will approach us here in southeastern FfxCo in spring/summer, be "standard strength" while crossing overhead, but when checking radar and stepping outside to see the "backside" of the storm, you could literally hear/see it getting worse and building in strength as it moved toward the river...often producing warned storms in southern MD.

I will never forget watching the "backside" of the thunderstorm that produced the 2002 La Plata tornado move east away from us -- the sun started returning pretty quickly after its passage here, and the "backside" of that storm was lit up, clouds churning and building so high to make it look like the coming (or departure, in my case) of the Four Horsemen of the Apocalypse.   

[George BM]

2 minutes ago, vastateofmind said:

On radar yesterday at lunchtime, it looked like the line really got its act together right at I-95...I'm about two miles east of the interstate, and it seemed to "bloom" overhead pretty quickly (in terms of lightning, wind and rain), and intensify as it moved east to cross the Potomac into MD.

For you mets and other smarter-than-me wx people -- is there something about our geography, or topology, or climate (or, or, or?) that causes lines of thunderstorms to strengthen between I-95 and the Potomac River, and pick up even more steam in southern MD? Is the Potomac playing a role in that? I can't tell you how many times I've noticed this phenomenon in the past 20 years -- a storm will approach us here in southeastern FfxCo in spring/summer, be "standard strength" while crossing overhead, but when checking radar and stepping outside to see the "backside" of the storm, you could literally hear/see it getting worse and building in strength as it moved toward the river...often producing warned storms in southern MD.

I will never forget watching the "backside" of the thunderstorm that produced the 2002 La Plata tornado move east away from us -- the sun started returning pretty quickly after its passage here, and the "backside" of that storm was lit up, clouds churning and building so high to make it look like the coming (or departure, in my case) of the Four Horsemen of the Apocalypse.   

I'm no expert but I would guess that this would have to do with the higher dewpoints that often reside closer to the bay, especially as the bay surface water temps rise late in the spring and during the summer. @JakkelWx always talked about the cornfields in his area near Easton, MD before he moved. They often allowed dewpoints to get into the low 80'sF there while areas near the bay in general had dews in the upper 70's while the rest of us experienced the more typical 70-75F dewpoint range. Higher dewpoints result in higher instability. Lets say that the temperature/dewpoint one day is 90/70 respectively. Raising the dewpoint temperature 5F (90/75) will result in higher instability than raising the temperature 5F (95/70). It's easier to see why on a skew-t diagram. But I'll let someone more knowledgeable than me explain that. 

[r3w]

4 hours ago, vastateofmind said:

On radar yesterday at lunchtime, it looked like the line really got its act together right at I-95...I'm about two miles east of the interstate, and it seemed to "bloom" overhead pretty quickly (in terms of lightning, wind and rain), and intensify as it moved east to cross the Potomac into MD.

For you mets and other smarter-than-me wx people -- is there something about our geography, or topology, or climate (or, or, or?) that causes lines of thunderstorms to strengthen between I-95 and the Potomac River, and pick up even more steam in southern MD? Is the Potomac playing a role in that? I can't tell you how many times I've noticed this phenomenon in the past 20 years -- a storm will approach us here in southeastern FfxCo in spring/summer, be "standard strength" while crossing overhead, but when checking radar and stepping outside to see the "backside" of the storm, you could literally hear/see it getting worse and building in strength as it moved toward the river...often producing warned storms in southern MD.

I will never forget watching the "backside" of the thunderstorm that produced the 2002 La Plata tornado move east away from us -- the sun started returning pretty quickly after its passage here, and the "backside" of that storm was lit up, clouds churning and building so high to make it look like the coming (or departure, in my case) of the Four Horsemen of the Apocalypse.   

I'm not an expert either but I've noticed it watching storms over the years as well, the Potomac seems to either inhibit or enhance the storms we get, I'm sure there's also the usual "sea breeze" attributes at play. I was too young during the La Plata 2002 event to understand it, but I've read that it intensified substantially over the water before hitting La Plata.

That storm packed a punch yesterday, I saw that most of it ended up around St. Leonard but there was some decent velocities on radar on the Southern end that ended up over Calvert, little to no precip, seemed like a dry microburst. Sky looked pretty wild too.

[Kmlwx]

The 168hr CIPS time slot from the 0z suite does have some severe potential over us. Nothing big, though. 

[high risk]

On 4/23/2021 at 3:24 PM, Kmlwx said:

The 168hr CIPS time slot from the 0z suite does have some severe potential over us. Nothing big, though. 

      As it looks now, the early Friday period does have some very limited SVR potential, with a strong front pushing through amidst some fairly impressive wind fields.   Ultimately, though, the poor timing of the front and limited moisture will likely eliminate any threat without some significant modification to the evolution.    The GFS idea of a phased trough, instead of the northern stream system shown by most other guidance, would help.

[yoda]

LWX says maybe next week in their afternoon AFD

.LONG TERM /SATURDAY THROUGH TUESDAY/...
Guidance continues to depict a split flow regime across the CONUS
with a deep trough exiting New England Saturday. A somewhat deeper
trend has been noted with this trough over the last few model
cycles. There is some lingering uncertainty with the fate of an
upper low in the southern stream and its ejection across the lower
MS Valley late in the weekend into early next week, but locally most
sensible weather will be reliant on the more closely positioned
northern stream this weekend.

Noticeably cooler temperatures and blustery conditions are forecast
Saturday in the wake of a surface cold front attendant to the
aforementioned upper trough exiting New England. A warming trend is
anticipated Sunday into Monday as high pressure building in behind
the front shifts offshore.

By early next week, the upper low moving across the lower MS Valley
begins to drift back into phase with the northern stream. At the
surface, a sprawling frontal zone will likely arc from the Northeast
across the Midwest and into the Plains. As the front slowly presses
southeastward, multiple waves riding along it will spark shower and
thunderstorm chances. Given increasing heat, humidity, and shear
overlaying the approaching frontal zone, thunderstorms that develop
could become severe, especially if the waves forcing the storms
cross around peak heating. Uncertainty remains, though, given at
least part of this setup will be reliant on the ejection of an upper
low, something that models often struggle with in the medium
range.

[high risk]

We have a MRGL today for areas generally north of the Capital Beltway in MD and Rt 7 in VA.     CAMs suggest that the small window of opportunity for a few small clusters of northeast-moving cells with modest wind potential exists around dinner time, and the best chances *may* be in north-central and/or northern MD.    A decent line on the cold front will approach the far northwest sections by early evening, but due to winds veering in the DC-Baltimore area behind the lead surface trough, limited convergence will likely cause the line to weaken or entirely fall apart.     I'll be happy with some rain and a few rumbles of thunder (neither of which is a certainty).

[yoda]

4 minutes ago, high risk said:

We have a MRGL today for areas generally north of the Capital Beltway in MD and Rt 7 in VA.     CAMs suggest that the small window of opportunity for a few small clusters of northeast-moving cells with modest wind potential exists around dinner time, and the best chances *may* be in north-central and/or northern MD.    A decent line on the cold front will approach the far northwest sections by early evening, but due to winds veering in the DC-Baltimore area behind the lead surface trough, limited convergence will likely cause the line to weaken or entirely fall apart.     I'll be happy with some rain and a few rumbles of thunder (neither of which is a certainty).

Same.  I'm looking towards next week (Tuesday in particular)... morning AFD discussed GEFS members showing 1000-2500 CAPE with some decent heat and humidity.  Monday looks like a high shear/low instability event... though both EURO and GFS show 40-50 kts 0-6km shear, which isn't high shear, its more like optimal around here

[high risk]

5 hours ago, yoda said:

Same.  I'm looking towards next week (Tuesday in particular)... morning AFD discussed GEFS members showing 1000-2500 CAPE with some decent heat and humidity.  Monday looks like a high shear/low instability event... though both EURO and GFS show 40-50 kts 0-6km shear, which isn't high shear, its more like optimal around here

          Yeah, Monday and either Tuesday or Wednesday (per the Euro) seem to have at least some potential next week.

[midatlanticweather]

https://www.spc.noaa.gov/products/md/md0468.html

 

[yoda]

Maybe on Tuesday and Wed per SPC?

Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0400 AM CDT Fri Apr 30 2021

   Valid 031200Z - 081200Z

   ...DISCUSSION...
   Models suggest that a southern branch of split mid-latitude
   westerlies may gradually become less prominent next week.  It
   appears that a couple of perturbations emanating from the northern
   mid-latitude Pacific, and at least another pivoting south/southeast
   of the Hudson Bay vicinity, may eventually contribute to mid/upper
   trough amplification east of the Mississippi Valley by late next
   week, as upstream flow in the western U.S. becomes more zonal.  

   Before this proceeds, it appears that one significant perturbation
   may emerge from initially amplified troughing across the Four
   Corners states early next week, and contribute to an organized
   severe weather risk across parts of the southern Great Plains into
   Ozark Plateau on Monday.  This now seems most likely to become
   focused across central/eastern Oklahoma into southwestern
   Missouri/northwestern Arkansas, where forcing for ascent ahead of a
   developing surface low may contribute to the evolution of an
   organized convective system in the presence of moderate to strong
   instability by Monday evening.

   Thereafter, model spread and the uncertain influence of prior
   convection result in more uncertainty, but there appears at least
   some potential that an organized severe weather threat could develop
   eastward with the mid/upper impulse, across the Mid South and
   Tennessee Valley into the Mid Atlantic region Tuesday into
   Wednesday.

   ..Kerr.. 04/30/2021

[Kmlwx]

CIPS for the super long range is really lighting up for huge swaths of the US.