high risk

Storms are starting to intensify as they move east of I-81, and they're about to move into an environment with moderate CAPE values and 50 kt of deep layer shear.     It likely won't be a higher-end or widespread SVR event, but there will definitely be severe reports in northern VA and central and eastern MD later this afternoon.

3 minutes ago, Kmlwx said:

 

Well - here we go into the clearing. It's not quite to me in Colesville yet...but it's right on the doorstep. Should be solid for a decent amount of clearing. Temperatures elevated pretty quick in the clearing (seeing 76 degrees near Culpeper). Probably going to be a "garden variety+" severe day here. Perhaps a bit more widespread and intense than our true "meh" days but also not any sort of higher end/memorable event. 

          That's a very reasonable take.     I will note that the longer we have to wait for any threat to materialize, the better the shear gets.

12 minutes ago, osfan24 said:

Sure, there is a chance for a severe thunderstorm or two. That isn't a reason to dismiss schools early.

        Oh, I'm with you all the way.      I'm curious how they reached the decision.     

7 minutes ago, Kmlwx said:

The 45% wind probs were removed at the 1630z outlook. The 5% tor probs were also removed. Adding those seemed iffy with the uncertainties. Let's see how the next hour or two plays out in terms of destabilization. The ENH as a whole was trimmed a bit in terms of areal coverage. 

       Those TOR and WIND probs were definitely set too high.    But I agree with you that we shouldn't completely swing the pendulum all the way to the other side and go total 'meh' - there is still some SVR threat, especially for those along and east of I-95.

CAMs are all over the place for this afternoon, and none of them really have a good handle on this lead convection.    The HRRR is now at least starting to initialize the ongoing storms, and it still ramps up a line right along the I-95 corridor during the mid-late afternoon hours.     But the ongoing storms are stronger and in greater coverage than the HRRR has, so I'm still not convinced that it will capture the evolution.

I'm actually rooting for SVR, given that Howard County is releasing schools early.    I would hate for their decision to be ridiculed, leading them to not dismiss early on a future day where it was really needed.

3 hours ago, Kmlwx said:

Wish the models would be a little more enthused. HRDRPS looked decent, but a lot of the models are kind of anemic with activity tomorrow - at least compared to our higher end days. Not that I'm expected an outbreak...but for a day 2 enhanced - and one that @Eskimo Joe uttered the mod possible phrase...I'd expect more. 

I'm cautiously optimistic that I'm just reading too much into sim reflectivity and parameters - but the oranges and reds on supercell composite parameter just aren't there on the guidance that I'm looking at. 

No doubt that the area sees storm activity tomorrow afternoon...but I'm having some doubts as to whether it will be an ENH or MOD day. My mental storm prediction level is at a slight right now. 

      If you're looking for significant supercell potential, prepare to be very disappointed.    I know that SPC has us in the 5 TOR, but I've always thought of tomorrow as a wind day.     There is deep layer shear to support SVR, but the low-level shear to ramp up the TOR potential is pretty marginal at best.     That's especially true if it ends up as an early show.    The NAM Nest has gone back to a single beefy squall line later in the day, but other CAMs seem to prefer an earlier, broken line.     Among those, there is disagreement as to whether a second line will roll through later in the day;  a second line might have better wind fields to work with.   I still line the overall wind threat tomorrow, although unless the 00Z NAM Nest idea is right, it's probably more of a SLGT than an ENH.

1 hour ago, George BM said:

... And shear actually looks quite decent (EBWD >= 40kts). Could certainly be some decent storms in spots if we manage > 1000J/kg mlcape to go along with the shear. The later the front moves through the better.

          Agreed.   NAM Nest for Monday afternoon looks impressive, both in terms of forecast soundings and simulated reflectivity.   

On 5/12/2022 at 6:24 PM, Eskimo Joe said:

The PDS Blue Box in the midwest is insane. 2012 Derecho on steroids. For @yoda yea that's the only thing I can think of...storms bubbling up along the edge of a high...IIRC the 2012 Derecho was an impulse riding the edge of a pretty big high pressure system and since it wasn't an airmass change it kept temps from cooling off post event.

       Sorry, @yoda.    Didn't see your question earlier, but this explanation is correct.      You typically get stronger flow around the edges of a ridge, and there is a typically a "quality" air mass in place beneath.   Add a few disturbances moving through that faster flow, and you're in business.   

I keep waiting for a "real" severe threat to develop here, and by that I mean something with a legitimate amount of instability, and not those cool season low CAPE - high shear events.    Climo generally says that we have to wait until mid May or so, and right on schedule, it looks like Monday may have some modest potential.

36 minutes ago, high risk said:

   Seems like there is a good chance of embedded thunder during the evening hours.     While it's a bit uncertain how far north the warm front will get, I agree with SPC that any cells in the warm sector or especially ones that interact with the boundary have potential to spin.     For DC and points north (and probably even a bit further south than that, as I have doubts how far north the warm front will make it before retreating), any storms will be elevated, eliminating the severe potential but allowing for some hopefully nice lightning and thunder.  

       I think I should have said "this afternoon and evening".     Radar shows very much a rapidly increasingly convective nature to the precipitation across our area.

   Seems like there is a good chance of embedded thunder during the evening hours.     While it's a bit uncertain how far north the warm front will get, I agree with SPC that any cells in the warm sector or especially ones that interact with the boundary have potential to spin.     For DC and points north (and probably even a bit further south than that, as I have doubts how far north the warm front will make it before retreating), any storms will be elevated, eliminating the severe potential but allowing for some hopefully nice lightning and thunder.  

1 hour ago, WxUSAF said:

CMC went to keeping rain through Sunday which sucks.

      Two days of wet and upper 40s during a May weekend is as ugly as it gets.

6 minutes ago, WxUSAF said:

I’m starting to wonder if this is one of those spring days where the wedge holds all day. Seems like we’re due for one of those.

    I think so.   NAM Nest has been adamant that we'll stay in the mid to upper 50s, at least on the northeast side of town.    HRRR seems to be coming around to the same idea.

2 hours ago, WxUSAF said:

I thought I heard a few at that time as well, but it was pouring, so I didn’t venture out to confirm.

         I can confirm that there were pingers here a few miles south of you this morning.

12 minutes ago, high risk said:

Thunder in Howard County. 

And now a few small hailstones. 

Thunder in Howard County. 

3 hours ago, Eskimo Joe said:

12z RAOB has decent mid level lapse rates. Could definitely be a conditional wind threat. Wouldn't shock me to see the 15% wind get nudges back further SW.

      good call!

54 minutes ago, Eskimo Joe said:

12z RAOB has decent mid level lapse rates. Could definitely be a conditional wind threat. Wouldn't shock me to see the 15% wind get nudges back further SW.

       Agreed.    Ultimately, I think it's going to come down to the surface dew points.    The NAM Nest and ARW2 keep dew points around 60 ahead of the line, and both have impressive reflectivity signatures.    Other CAMs (including the HRRR) mix out the low-level moisture and end up with mid 50s dew points, and their simulated radars look very meh.

Really not sure what to make of the SVR chances this afternoon.    Pretty much every CAM brings some sort of line or broken line through the area (with perhaps a few stronger cells immediately behind), but there is no agreement on intensity.    Overall, based on simulated reflectivity, it's tough to expect more than a few SVR reports, but if we can maximize surface heating without mixing out the low-level moisture, perhaps we can have a modestly more interesting event.

Wednesday has some sneaky supercell potential for the northwest areas, perhaps HGR and points west and north of there.  CAMs suggest that the greatest threat for a few cells is in PA, but there is a signal for northwest and western MD     The wind profiles might not support TORs, but they would support storm rotation.

NAM Nest and hi-res FV3 both show a narrow line ahead of the front Thursday afternoon.   There are questions about the amount of instability, and some of the wind profiles look “weird”, but this could eventually end up as a SLGT day. 

some lightning in the cell by Bowie

Thinking that there is some potential for lightning and small hail this evening and again Saturday afternoon.     Good forcing during both periods with a little bit of instability and very low freezing levels - some healthy reflectivity signatures in the CAMs.

2 minutes ago, WxUSAF said:

Thunder!

       Yeah, the only strike in the entire area was in Howard County.      #winning

25 minutes ago, IronTy said:

It's blasphemy 

       It's also from a single deterministic GFS run that is inconsistent with its previous cycles and doesn't match what all of the ensembles are showing.

consistently with the previous posts, there seems to be some very, very good agreement across the various models (and their ensembles) for next week being very warm