high risk

Sunday looks like a really rotten day - still not clear whether we'll have periods of rain or just some occasional drizzle, but low clouds with temps stuck in the 40s seems fairly likely.

20 hours ago, WxUSAF said:

18z 3k nam has Delta hit 899mb in the Gulf. #seemslegit

    FWIW, when the final NAM upgrade was in the final stages of validation, the developers realized that changes made to improve forecasts of the marine stratus layer along the west coast were causing crazy intensification of TCs.      Since the NAM is used way more for forecasting ceiling and visibility than it is for TCs, and since there was little wiggle room on the schedule for further development, it was decided to leave the model configuration as is.       Certainly makes for some fascinating tropical forecasts.......

getting some huge drops that sound like small hail when hitting the ground with the southern Howard County cell

22 hours ago, Kmlwx said:

I'm having a hard time remembering what the cloud cover/precip situation was just ahead of the Sept 2012 event. Based on the SPC events page, it looks like that might have been an event that started earlier in the day. We had mesoscale discussions by mid morning it seems. 

       I do remember that event - another classic low cape, high shear fall event here, although this one had dew points into the low 70s.      I don't think that there was much precip out ahead of the line, but it was definitely cloudy.   The reports map looks way better than the event was - I remember being very surprised by the upgrade to MDT and very unimpressed by the line.    Most of the reports in our area were of single trees being knocked down.

yeah, the shear profiles for later Tuesday have so much potential, but over the years, I've seen a ton of great fall setups fail here due to terrible lapse rates and instability.   Any system at this time of year that is strong enough to have great accompanying wind fields usually generates a lot of cloud cover and showers well out ahead of the front.

         I can actually say that I saw the 2001 tornado as it moved through Laurel.      No one had cell phone cameras back then, so I have no pictures, but my view was very similar to this one:

             I'm definitely intrigued by the Tuesday potential, although fall events here are so tough to pull off due to limited instability.

7 hours ago, yoda said:

Why then do the stories only mention 2 deaths, the 2 sisters on UMD campus and not him?  Unless its a different tornado then talked about below in the links?

https://www.tornadotalk.com/college-park-md-f3-tornado-september-24-2001/

https://www.baltimoresun.com/bal-te.md.storm25sep25-story.html

https://en.wikipedia.org/wiki/Tornado_outbreak_of_September_24,_2001

     He assisted at the cleanup at the Maryland Fire and Rescue Institute which was heavily damaged and suffered a heart attack while driving home that evening.     Who knows if he would have suffered the cardiac episode had he not been at the scene.....

I'd love to see what the models actually look like today, as WPC has some big totals for our area in the next 24 hours and a SLGT risk for flash flooding overnight.

1 hour ago, JakkelWx said:

Surprise!

 

        yeah, CAMs have a good signal for storms later this afternoon, mainly for DC and points south.    As SPC notes, instability is weak, but shear is fairly good, and the forecast soundings show some good DCAPE,  so I guess I agree that some gusty winds are possible.

Hello, SPC?    Hello?     Time to get that box issued.

31 minutes ago, mappy said:

any more "mappyland" thoughts? 

      I think you're in as good of a location as any.    I'm very bullish on the SVR threat today, just more bearish than most on the tornado threat (although I think that a TOR watch will be and should be issued).    The 18z LWX sounding should be a big help in understanding the magnitude of the threat.

1 minute ago, WxWatcher007 said:

The system is probably due for an update but if it’s a big enough threat I’ll see the smoke signal on Twitter. It really is amazing how accurate the system is though. Other than The Panic Room this might be my best work.  

   it really is, although kmlwx and I are not quite in lock step today.....

4 minutes ago, Kmlwx said:

When in doubt... Always go with the QLCS mode in this area. More often than not you will win. Doesn't mean a rogue cell can't get it done, and also doesn't rule out QLCS tornadoes, gustnadoes or bookend circulation type things. 

             I agree that QLCS tornadoes are the bigger (although still not a huge) threat.     There is enough shear to get rotation today, but the low-level shear still looks pretty marginal to me.    We need the low-level flow to strengthen and back to have a larger threat, and that's not progged on a large scale, so we'll have to look for mesoscale areas that get their low-level winds modified by nearby ongoing convection.

Many things to like about Thursday afternoon, but I'd sure like to see some stronger 10m wind speeds.     There will be mesos for sure, but we need some better speeds at the sfc to really get a legit TOR event.      

1 hour ago, Eskimo Joe said:

 

Nothing on CAD or our DOT feed. Really surprised. It came through Reisterstown as nothing but heavy rain. Radar looked a lot better than ground truth.

     I don't really understand why the line was so meh.    The 00z IAD sounding isn't bad.     Maybe the CAPE is a bit tall and skinny, and deep layer shear is marginal, but I would have expected an organized line like that to have a lot more wind.

So the box is out...... but it's BLUE.     I guess I'm not surprised (that it's not a red box)  given the linear evolution, but the shear parameters argue that a few embedded mesos are quite possible.

10 minutes ago, Kmlwx said:

There's probably enough moisture to support a threat for storms (some strong maybe) past sunset. For the superstitious/non-scientific side of us - this could bode well for our odds to see stronger storms tomorrow. We just can't seem to string multiple days together - the area of focus always shifts a little bit day to day - even when it seems like we'll be bullseyed for days on days. 

I personally thought that earlier mesoscale discussion was VERY high probs for something that had not even developed yet - and didn't look insanely good on modeling. 

      SPC Mesoanalysis shows the supercell composite here increasing to 8 here over the next couple of hours.     Given that and most of the CAMs showing convection developing by now, I'm assuming that's why they went with such high watch probs.      I'd think that the convection to the west should do better as it moves east into the better environment, but we'll see.

3 minutes ago, Kmlwx said:

Today is looking super lame at least at the current moment. More eggs into the tomorrow basket perhaps. 

     Yeah, I'm a bit surprised, and I think that SPC is too.    Latest HRRR still suggests that the convection firing near the I-81 corridor will still become a bigger deal further east in a few hours.

I only had to whine for 23 hours before SPC finally put us in the SLGT risk we warranted.

6 minutes ago, Kmlwx said:

To be honest - the parameters (and I know these don't necessarily guarantee anything) for today and tomorrow look about as good as any event we've seen this year so far. If we can get decently unstable tomorrow I could see it being a 10% tor day - especially given that text from SPC in the day 2. Very doubtful they'd introduce that until D1 though. 

I think a lot of areas will see storms this PM - the question is how severe they will be.

       Hard to argue with this.      I'm still more bullish for today than most, but I understand the question marks.    For tomorrow, the potential is real.    My only concerns are the weaker lapse rates (although they are now progged a bit better than earlier guidance) and potential weak sfc wind speeds (although the NAM nest seems to be weaker than some other models)

       I'd still prefer today's lapse rates with tomorrow's wind profiles, but good luck getting those two to align in this region.....

52 minutes ago, Kmlwx said:

12z HRRR argues for a period of sunshine around DC for a little while at least. 

     Even without full heating, the lapse rates today in the forecast soundings look good, so I don't think we need to get much above 84 or so to have an active late day.

I completely get that SPC doesn't want to issue a huge SLGT on a day like today from TN to the northern NY border, but I would still argue for a SLGT in our area.   The CAMs still really like DC metro later today, and that's reflected in HREF probabilities.    Both the ops (left) and para (right) indicate high probabilities of updraft helicity exceeding 25.   (That's a low end threshold, but it still reflects that there is strong agreement in intense cells with at least weak rotation.   And the probabilities of higher UH thresholds are not terrible either....)

36 minutes ago, yoda said:

MRGL remains for Day 2 on 1730 SPC OTLK... but talks of an upgrade

 

 

              Yeah, I really thought they should have pulled the trigger, but it's not a big deal if they wait.     SPC mentions questions about coverage/intensity; I thought that the most of the entire suite of 12z CAMs looked good with those aspects, but they clearly want to see if the trends in the guidance hold.

18 minutes ago, Kmlwx said:

I doubt we ever see a TOR based high risk in this area. Although...isn't it more about the number of reports than the intensity of individual events? Say we had a vigorous system (perhaps tropical in nature or hybrid) and it was clear that while there wouldn't be EF-5 stuff...we'd get a large amount of EF-0 to EF-2 and it was high confidence - would that be enough to trigger a high hypothetically? I doubt SPC would ever do that for a tropical system, though. 

    It would be a once-in-a-lifetime event, but if it can happen in upstate NY and in central NC.....      May 31, 1985 showed that outbreaks with high-end events CAN happen in the east.

   I envision a deepening 980 sfc low over NW PA during an afternoon, with intense wind fields at all levels and all CAMs showing discrete convection and strong, long-track UH signals over the Mid-Atlantic.   Of course, in an intense synoptic setup, we usually screw it up with either early morning crapvection.....

   A HIGH here would never happen for a TC remnant event.

9 minutes ago, yoda said:

I don't think we will ever see a high risk here -- even the derecho in late June that was rampaging through the Ohio Valley the night of the infamous 00z LWX sounding (102/70 I think it was with nearly 6000 SBCAPE) only garnered a moderate risk on the 2000 SPC OTLK and the 0100 OTLK

        This would be an awesome discussion over a few beers at an AMS conference.     For the 2012 event, CAM guidance was really limited.    The NAM nest had little handle on this event, and the HRRR had some good runs but was still experimental.     There were real questions about whether the derecho would survive crossing the mountains, and even at 1z, SPC still wasn't totally sure how far east it would maintain strength.      I still envision getting to a point in such an event where there is agreement that an intense derecho will blast through the Ohio Valley and make it to the coast, and SPC will launch the HIGH.      It won't happen right away, but we'll get there.