2019 Mid-Atlantic Severe Wx - General Discussion

[MN Transplant]

In Alexandria right now.  It is roaring.

[jacindc]

6 minutes ago, MN Transplant said:

In Alexandria right now.  It is roaring.

Ditto on Capitol Hill. Sun is almost out, but it is just POURING. 

 

[high risk]

Dynamics, ftw!

[Mrs.J]

33 minutes ago, Poodleusier said:

I got a mix of pea to marble sized hail just a little east of you.  Made quite a racket with the wind blowing it into windows on west side of house.  Got 0.56" in 10 minutes with that storm.

Yea the wind blowing it into the windows is how I knew it was hail. Was raining so hard had to open the back slider to confirm it and size. And yep got close to the same amount of rain. With that line and the stuff behind it got .66” total. Station up to 1.71” for the day. 

[smokeybandit]

Got about 5 minutes of rain from that line.

[87storms]

Just some rain. No T&L here. Need summertime level conditions to return.

[Sparky]

0.98" on the day.  About .60 of that in the overnight and another .40 in the afternoon thunderstorm.  Right now my temp has fallen to the upper 50s, when I was out on the deck a minute ago I could see my breath, lol.  I think it is very close to fogging up here unless the winds hurry up and kick in.

[yoda]

00z GFS sim radar looks intriguing at 72 hours on 00z MON (8pm SUN) and then again at hours 93 and 96 as you go from 21z MON into 00z TUES and as you go on Wednesday into Thursday

[CAPE]

Mount Holly's take this morning on the active upcoming period and severe potential for Sunday and esp Monday for most of our region.

The aforementioned cold front will be approaching the lower Great Lakes east-northeast to northern/central New England on Sunday, with several weak perturbations moving west-to-east near the boundary. Convection should readily develop along/downstream of the front by afternoon, mainly to our north/west but probably also in our CWA as well. The 00z GFS is depicting a stronger vort max approaching the northern Mid-Atlantic during the evening, with a round of strong/widespread convection in our area by this time. The 00z ECMWF is fairly similar, which provided enough confidence to raise PoPs to high-chance and even likely in northern portions of the CWA Sunday afternoon/night. Precipitation will wane late Sunday night as nocturnal stabilization takes over and the strongest large-scale lift moves to our east. The CAPE/shear parameter space would be sufficient for severe storms Sunday afternoon/evening, and I am rather concerned the GFS is underdoing instability in the pre-frontal warm sector given increasingly warm/moist conditions. Moreover, BUFKIT soundings/hodographs suggest a substantial amount of low-level shear/helicity may exist. Will need to watch Sunday afternoon/night closely for the severe-weather threat in the coming days. After perhaps a brief reprieve late Sunday night into Monday morning, chances of strong convection return Monday afternoon. Both the 00z GFS and ECMWF depict another strong perturbation moving through the northern Mid-Atlantic during the afternoon/evening. Once again, the CAPE/shear parameter space is favorable for severe storms, though shear may be somewhat weaker than the previous day. However, the pre-frontal warm sector may be more unstable (using model sounding comparisons Sunday versus Monday). Complications from antecedent convection will exist (increasing the uncertainty in the forecast by this point), not to mention the model volatility already in place with the perturbations responsible for the larger-scale lift associated with the convection. Nevertheless, I am becoming quite concerned with the severe threat both of these days, and hydro issues will be an increasing concern as well given the multiple rounds of storms that may affect the area.

[Kmlwx]

CIPS was down from around late afternoon yesterday until this morning. Looks like the 0z run did not come out properly. We'll have to wait for the 12z run for any new information from that side of things. The severe weather CIPS page (which only runs at 0z) won't refresh until tomorrow morning it seems. 

[yoda]

12z GFS soundings for KIAD and KDCA and KBWI at 00z MON (8pm Sunday) are pretty impressive considering its 60 hours out

[yoda]

18z NAM soundings look tasty from 21z SUN to 09z MON

[Eskimo Joe]

Really surprised we aren't in a D2 or D3 slight.

[Kmlwx]

3 hours ago, Eskimo Joe said:

Really surprised we aren't in a D2 or D3 slight.

Are you bullish on this threat window? 

[yoda]

Waiting on the new 00z NAM... but 18z NAM soundings were pretty nice for 21z and 00z tomorrow 

[George BM]

Just now, yoda said:

Waiting on the new 00z NAM... but 18z NAM soundings were pretty nice for 21z and 00z tomorrow 

Psssst... We abscond the 18z hrdps.

[yoda]

Well then, the 03z MON sounding at KIAD is certainly fun to look at from the 00z NAM

[yoda]

 

[yoda]

00z NAM NEST lights up DC metro between 22z and 01z 

[high risk]

10 hours ago, Eskimo Joe said:

Really surprised we aren't in a D2 or D3 slight.

          Seems pretty likely that we'll wake up Sunday morning to a slight risk.     Good instability + good deep layer shear + likely initiation  puts us in the game for sure.      

           Waking up Sunday to a SLGT for Monday seems quite plausible too. 

[yoda]

00z GFS sim radar likes Monday night, Tuesday night, and Thursday night

[AmericanWxFreak]

[yoda]

Interesting Day 1 and 2 updates from SPC... day 1 - today - is 2/15/5 with talk of cellular activity producing hail and supercell possible

Tomorrow (Monday) talks about a potential bow complex coming through in the afternoon

[jewell2188]

A cold front will approach the area from the north today. The
front will stall out nearby on Monday and remain nearly
stationary across the area through the middle of next week. It
may finally shift southeast of the region by Saturday.

&&

.NEAR TERM /THROUGH TONIGHT/...
A very warm and humid air mass will be in place today coupled
with a lee-side trof and weak 500 mb wave will aid in t-storm
development this afternoon. Mid-level flow will be relatively
strong with 40kt at 500mb contributing to 30-40kt of 0-6km bulk
shear. A few severe t- storms are expected late this afternoon
through late this evening. Northern and central Maryland appears
to be at greatest risk of severe thunderstorms with t-storm
coverage decreasing markedly south of I-66. Damaging wind gusts
appear to be the biggest threat given the moderately strong flow
aloft and fast storm motions (~ 30kt). The severe wx threat
should wane after 10PM or so, but risk of t- storms will likely
persist well into the overnight hours.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
Monday still appears as it will be the most active day this
week with a slow moving front nearby and ripples of upper level
energy aiding in t-storm formation. Shear and storm motions will
be weaker suggesting an increased flash flood threat especially
given mid- level flow becoming parallel to sfc front which will
also favor training. CAPE values, on the other hand, are
expected to be much higher than on Sunday, which also support a
severe wx and flash flood threat. A flash flood watch may be
issued for some areas at this time tomorrow once confidence in
location of t-storms increases. Simulated satellite imagery from
various global models indicate convection will be more
widespread and intense than today.

 

[CAPE]

Some excerpts from this morning's AFD from Mount Holly on the potential for late today into the evening-

A third perturbation arrives late today, and this is the one that should produce stronger convection. There are two main forecast questions associated with this perturbation. Where will it track, and how will the downstream environment destabilize? Regarding the first question, the 00z NAM tracks it along the Mason-Dixon Line. The 00z GFS tracks it across northern Virginia eastward to Delmarva. The 00z ECMWF is much farther north (generally through PA/NJ). These differences are critical because convection will likely develop in close proximity to this vort max. Hi-res models are similarly variable, with HRRR runs developing strong convection anywhere from eastern PA/central NJ to central/southern MD eastward through Delmarva.

Where the environment remains relatively unperturbed by the predecessor precipitation/clouds, BUFKIT soundings show MLCAPE approaching 1000- 1500 J/kg this afternoon in an adequately sheared (30-35 kts deep- layer bulk wind difference) environment. Low-level helicity will also improve through the day, with hodographs exhibiting modest curvature (0-3 km SRH approaching 150 J/kg by evening). Where convection develops, mixed convective modes may occur initially with all types of severe possible, though convection-allowing guidance is tending to develop a mesoscale convective system rather quickly. Timing of the stronger storms looks to be after 3 pm and may peak during the evening hours based on the latest HRRR/NAM Nest simulations.

[Eskimo Joe]

16 hours ago, Kmlwx said:

Are you bullish on this threat window? 

Ask me each day, it's highly conditional on debris clouds.

[Eskimo Joe]

For the record, I prefer tomorrow for more widespread flooding and severe activity.

[Kmlwx]

Wow look at NAM nest for tomorrow PM

[Eskimo Joe]

Could be an ENH kind of day tomorrow if we arent socked in with debris clouds.

[jewell2188]

10 minutes ago, Kmlwx said:

Wow look at NAM nest for tomorrow PM

Nudge that south a bit and I’ll take it.