2019 Mid-Atlantic Severe Wx - General Discussion

[yoda]

26 minutes ago, Kmlwx said:

Thursday continues to look interesting on CIPS and GFS. 

12z looked same as 00z I guess re CIPS?

[Kmlwx]

Thursday looks like our next good potential for something organized. 

[frd]

From Mount Holly for today,  and I noticed a 90 degree reading possible in Southern Delaware. 

Looks like severe potential lower but the odds of getting into some thunderstorm activity better than yesterday 

000
FXUS61 KPHI 201026
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
626 AM EDT Mon May 20 2019

.SYNOPSIS...
A cold front associated with low pressure moving through the
Great Lakes into Canada will cross our region this afternoon
and evening. High pressure is then expected for Tuesday into
Wednesday. A warm front arrives in our area late Thursday night
and Friday, followed by a cold front on Saturday which may stall
to our south on Sunday.

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A quiet start to the morning after a muggy and humid night.
Temperatures will once again be on the rise, with most places making
it into the mid to upper 80s. Portions of southern Delaware and the
Eastern Shore of Maryland may in fact reach 90. Slightly cooler
along the shore and in the higher terrain of the Poconos with
highs in the mid to upper 70s.

Another chance for showers and thunderstorms this afternoon as a
cold front moves southeastward across the mid-Atlantic. The
severe threat appears to be lower than yesterday, though non-
zero. The Storm Prediction Center has our area under a Marginal
Risk for severe thunderstorms. Instability looks to be lower
than yesterday with ML CAPE values forecast to top around 2000
J/kg. Shear will be a little lower as well, with 0-3 km shear
forecast to be less than 30 knots, thus a little less supportive
of stronger thunderstorm cells. With the timing of the front,
storms look to fire a little further southeast than yesterday,
likely initiating along the Delaware River Valley by 4 to 5 pm
and moving offshore by 9 to 10 pm. There could be some localized
flooding concerns in areas that see brief heavy rainfall, but
storm motion should prevent as much training as was seen
yesterday.

 

[frd]

Marginal risk today,  here but wow to the High Risk in Oklahoma and Texas. Going to be some incredible videos coming from that area. 

I am sure some of the best storm chasers in the country are there today, as it has been talked about for over a week, due to the high potential for large and long track d tornadoes.   

 

 

[mappy]

On 5/18/2019 at 6:22 PM, Kmlwx said:

Sunday doesn't look that impressive anymore locally. But we are close to a slight from SPC. We'll see. 

Meanwhile - looks like Ian and our guys are in for a nice chasecation!

they have done well so far. saw a couple tornadoes friday, some structure saturday then traveled yesterday. looks like they will be in the texas panhandled area today. doubtful they head towards OKC. 

[yoda]

12z NAM looks okay I guess for Thursday afternoon

[frd]

1 hour ago, mappy said:

they have done well so far. saw a couple tornadoes friday, some structure saturday then traveled yesterday. looks like they will be in the texas panhandled area today. doubtful they head towards OKC. 

I believe I read many schools have been cancelled in the high risk areas today out West due to the nature of the forecast, timing of the storms, and the probabilities of extensive severe weather and tornadoes. 

 

 

 

[mappy]

5 minutes ago, frd said:

I believe I read many schools have been cancelled in the high risk areas today out West due to the nature of the forecast, timing of the storms, and the probabilities of extensive severe weather and tornadoes. 

 

 

 

yes, public schools closed out there today. OU closed too. 

[Kmlwx]

35 minutes ago, yoda said:

12z NAM looks okay I guess for Thursday afternoon

SARS has been showing some sig hail matches for Thursday PM. Too far out to say anything at this point - but between CIPS and the models generally suggesting a severe weather threat - it bears watching. I'm hardly watching our area for today - all eyes are on the plains. 

[nj2va]

1 hour ago, frd said:

I believe I read many schools have been cancelled in the high risk areas today out West due to the nature of the forecast, timing of the storms, and the probabilities of extensive severe weather and tornadoes. 

 

 

 

That was a wise decision to close schools today...hope everyone out there stays safe.

[frd]

Pretty crazy sounding there 

 

[frd]

Mount Holly update at 330 PM 

NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
A very warm/hot and also humid afternoon in progress with some areas
closing in on 90 degrees, however the dew points have dropped a
little mainly along the I-95 corridor.

An upper-level trough will continue to shift eastward through
tonight from the Great Lakes, adjacent Canada and New England. Low
pressure will track well to our north, however its cold front
crosses our region through early this evening. As the cold front
arrives, it may combine with a lee side trough. The convection
allowing models (CAMs) generally agree that convection continues to
develop, especially around the Philadelphia metro southwestward. In
addition, some other convection will continue to develop especially
near terrain influences and near the residual lee side trough. As of
19z, only some showers with no lightning being detected as
convective development is shallow thus far. Visible satellite
imagery does show some taller cumulus near and west of I-95. For now
went no higher than scattered convection (chance PoPs), as the
overall organization should be lacking.

The latest mesoscale analysis shows around 500-1000 J/KG of MLCAPE
and this should increase to around 1500 J/KG by late afternoon. The
0-3KM shear ranges from 30-40 knots with the strongest across the
far northern areas. Some strong storms are anticipated with a few
potentially going severe. There is some dry air aloft and combined
with steeper low-level lapse rates results in better DCAPE and
potentially strong surface winds. Locally strong to damaging wind
gusts are possible, however this threat looks to be with any robust
convective cores as precipitation loading will enhance the
downdraft. There is not a lot of forcing, thus convection will be
driven by the airmass and the incoming surface front. Once the cold
front shifts offshore early this evening, the convection will end
with clearing taking place. Cold air advection increases in the wake
of the cold front, and this should keep some wind going from the
northwest. This will also result in a cooler overnight, especially
as the dew points drop into the 40s for much of the region by
daybreak. Low temperatures are mainly a MOS/continuity blend.

 

 

 

[Kmlwx]

Slight risk for Thursday for northern parts of the area. Then we have a 15% extended outlook nearby for day 5 (not yet in our area). Looks like LWX is pretty bearish on the weekend. 

SARS continues to print out some hefty analogs for Thursday, though. Some big hail showing up. We'll see how it pans out.

[high risk]

3 hours ago, Kmlwx said:

Slight risk for Thursday for northern parts of the area. Then we have a 15% extended outlook nearby for day 5 (not yet in our area). Looks like LWX is pretty bearish on the weekend. 

SARS continues to print out some hefty analogs for Thursday, though. Some big hail showing up. We'll see how it pans out.

               I'm in for Thursday, especially after seeing the NAM nest forecast soundings and simulated reflectivity, although I like areas north of our region even better.

[Kmlwx]

1 minute ago, high risk said:

               I'm in for Thursday, especially after seeing the NAM nest forecast soundings and simulated reflectivity, although I like areas north of our region even better.

Yeah - it definitely seems like north is the better location for storms - and this is reflected in the slight risk area from SPC. 

[yoda]

2 minutes ago, high risk said:

               I'm in for Thursday, especially after seeing the NAM nest forecast soundings and simulated reflectivity, although I like areas north of our region even better.

12z NAM soundings look good as well IMO, esp between 21z THUR and 03z FRI

[Kmlwx]

SARS is also still kicking back a lot of large hail matches on some runs. 

[yoda]

5 minutes ago, high risk said:

               I'm in for Thursday, especially after seeing the NAM nest forecast soundings and simulated reflectivity, although I like areas north of our region even better.

I wonder if that action on sim reflectivity in SW PA/W MD would reach us in the few hours after the 12z NAM NEST run ends

[high risk]

1 minute ago, Kmlwx said:

SARS is also still kicking back a lot of large hail matches on some runs. 

 

           I'm not surprised.     The lapse rates look quite healthy for the east coast, and the shear profiles (as currently modeled) would support splitting supercells.

 

[Kmlwx]

7 minutes ago, high risk said:

 

           I'm not surprised.     The lapse rates look quite healthy for the east coast, and the shear profiles (as currently modeled) would support splitting supercells.

 

There's even been some SARS matches of 4.5in hail  - Hail is one of those harder things to come by around these parts. Every now and then a swath will get absolutely plastered. Time will tell for Thursday!

[Kmlwx]

CIPS at the 60hr mark on the 12z run has some robust events showing up in the analogs. 5/14/2010 - which appears to have been a big day for hail around the area. 6/24/1996 which had some local tornadoes among the other reports. 6/23/2015 - which had wind damage in the area. 

[yoda]

LWX afternoon AFD on Thursday afternoon threat:

For Thursday afternoon, a southwest flow behind the warm front
will bring a return to hotter and more humid conditions. Max
temps will top off well into the 80s for most areas, and some
areas may even approach 90 degrees. The increased heat and
humidity will lead to an unstable atmosphere, and with our area
between an upper-level high to the south and upper-level low to
the north, there should be moderate amounts of deep layer shear.
At the same time, a cold front will be approaching from the
north but latest guidance keeps this boundary well to our north
during peak heating before it drops down later Thursday night.
Therefore, the timing of the boundary and peak heating are
offset a bit. Having that been said, it will be a differential
advection pattern (northwest flow aloft and southwest flow at
the low-levels), which supports the development of convective
systems (MCS). Will carry the chance for showers and
thunderstorms Thursday afternoon and evening, and with the
instability and shear in place, some of those storms could be
severe. However, confidence still remains low due to uncertainty
in timing of a convective system and also with the cold front
arrival being after peak heating.

The boundary will settle overhead late Thursday night, and a
shower is possible, but most areas will likely be dry due to the
loss of heating.

[Kmlwx]

18z NAM nest has lost the earlier cells for Thursday and instead brings a squall line through parts of the area around 0z. Favors north parts of the area too. 

[Kmlwx]

I'll be honest - I'm not sure since SARS became publicly visible I've seen so many consistent model runs (even if it's the NAM out in time a bit) - return so many results. I'm used to it showing a bunch of "loose matches" but not many actual results in the boxes. There are a few soundings on the NAM in our area that have so many results they go out of the box for Thursday. 

Like @high risk has said - I think the main threat is north of the area. This might be a case where north of the Potomac stands the best changes. Will be interesting to watch model trends as we get closer and closer. 

Risk is there it seems for some big hailers (which except for isolated cases isn't super common around our area). I've seen a few soundings with interesting looking hodos too. 

[high risk]

2 minutes ago, Kmlwx said:

I'll be honest - I'm not sure since SARS became publicly visible I've seen so many consistent model runs (even if it's the NAM out in time a bit) - return so many results. I'm used to it showing a bunch of "loose matches" but not many actual results in the boxes. There are a few soundings on the NAM in our area that have so many results they go out of the box for Thursday. 

Like @high risk has said - I think the main threat is north of the area. This might be a case where north of the Potomac stands the best changes. Will be interesting to watch model trends as we get closer and closer. 

Risk is there it seems for some big hailers (which except for isolated cases isn't super common around our area). I've seen a few soundings with interesting looking hodos too. 

           I like the faster timing of the 18z NAM nest.    What I really like is the combination of shear and lapse rates - combinations like these are rare here, and I suspect they're driving the hits with the analogs.

 

[Kmlwx]

Just now, high risk said:

           I like the faster timing of the 18z NAM nest.    What I really like is the combination of shear and lapse rates - combinations like these are rare here, and I suspect they're driving the hits with the analogs.

 

Posting the SREF at range below - not for the specific map type - but because it outlines the best risk area really well (and as such the area outlined in SLGT right now for D3). 

[Kmlwx]

@high risk I suspect if @Eskimo Joe pops in here he might be more enthusiastic than he normally would be. He's generally pretty down on lapse rates in our parts unless we get an EML or something to advect in. Obviously he might find a reason to deb...but he'll be an interesting "weather vane" - let's crack out the WW007 severe weather scale! 

[Kmlwx]

Posted for those who don't want to go digging for it - 

[Eskimo Joe]

4 hours ago, Kmlwx said:

@high risk I suspect if @Eskimo Joe pops in here he might be more enthusiastic than he normally would be. He's generally pretty down on lapse rates in our parts unless we get an EML or something to advect in. Obviously he might find a reason to deb...but he'll be an interesting "weather vane" - let's crack out the WW007 severe weather scale! 

Looks pretty meh to me, but weather in general is less and less interesting to me with each passing season.  We haven't had a good storm since the derecho.

[Eskimo Joe]

On 5/19/2019 at 2:49 PM, yoda said:

2 inch hail marker on radarscope and maybe some slight rotation?

Saw a report and pics from Clear Spring, MD of 1.75" hail from that cell.  This area can get big hailers when there's a good aid to the updraft.  Interestingly enough, that was the same cell which got it's act together and dropped an EF-1 tornado in Lancaster County, PA (injuring 3 people).