2024 Severe Weather General Discussion

[Eskimo Joe]

Quote

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
301 PM EDT Tue Jun 25 2024.SYNOPSIS...
Dry conditions look to continue through tonight as high pressure slowly pushes offshore. Excessive heat and humidity return Wednesday ahead of a strong cold front approaching from the Ohio River Valley. The cold front will cross the region late Wednesday afternoon into early Thursday morning bringing the next risk for strong to severe 
thunderstorms. High pressure briefly returns from the north and west late Thursday into Friday. Unsettled conditions are possible this weekend which comes with increasing heat and humidity.

 

SEVERE THREAT: All eyes shift to Wednesday as the excessive heat and humidity return ahead of a strong shortwave disturbance/cold front that are set to cross the region 
Wednesday afternoon into late Wednesday night. Convective activity looks to be a bit more organized compared to what we saw this past weekend and earlier this week. This is due largely in part to a lee trough ahead of the main boundary leading to increased height falls and a quickly moistening thermodynamic profile which should initiate convection mid to late Wednesday afternoon. The Storm Prediction Center continues to highlight the majority of the forecast area north of Interstate 64 in a Slight Risk (Level 2 out of 5) Wednesday afternoon and evening. 

The primary threats with these thunderstorms will be damaging winds and large hail. The threat for damaging winds (70 mph or more) continue to increase per the latest 12z guidance although some uncertainty remains to how widespread this threat will be resolved. Additionally, there is a secondary threat of an isolated tornado mainly along the PA/MD line and back into portions of western MD given the back flow. CAM guidance hints at this threat as well as additional high supercell composite values down across the central VA Piedmont and central/southern MD. Isolated instances of urban and poor drainage flooding are also possible given increased PWAT values above 1.5 inches. With the antecedent dry conditions expect a bit more runoff as water will have a bit of a harder time percolating through. 

Ahead of the front, south to southwesterly flow will help boost afternoon temperatures into the mid to upper 90s. Of course this will be determined by how much convective debris funnels into the area overnight Tuesday into early Wednesday morning. One uncertainty is the influx of low level moisture into the area. Models have dewpoints quickly getting back into the mid to upper 60s Wednesday afternoon with precipitable water values on the order of 1.8-2.2 inches. With that said, the confidence for heat advisories across the area is a bit lower. Current forecast projections amongst the guidance suggest heat indices on the order of 98 to 104 degrees Wednesday afternoon. Will continue to monitor the need for any such heat-related products.

As for timing, expect convective initiation to kick off along the lee side trough mid to late Wednesday afternoon before propagating east of the metros Wednesday night. Storms will feed off of CAPE values between 1500-2500 j/kg. This is especially true east of the Alleghenies where the bulk of the instability looks to remain untapped from early morning showers and 
convective debris. 0-6 km shear values will be on the order of 30-40 kts with lapse rate 6-7 degrees C/km favoring well organized storms. This is backed up in several hi-res CAMS and 
model soundings. Convection is slow to wane as we get into Wednesday night and Thursday morning as the cold front slowly pushes through. The severe threat at this point will be on it's way down due in part to the initial round of thunderstorm activity during the afternoon and evening hours. Lows Wednesday night will fall into the mid to upper 60s with low to mid 70s along and east of I-95. 

 

[Eskimo Joe]

Latest HRRR, while at range, is an absolute snooze fest for severe across the board. We get multiple rounds of strong showers after some early crapvection ruins the afternoon potential. The upside is that we all get at least a half inch of much needed rain.

[high risk]

3 minutes ago, Eskimo Joe said:

Latest HRRR, while at range, is an absolute snooze fest for severe across the board. We get multiple rounds of strong showers after some early crapvection ruins the afternoon potential. The upside is that we all get at least a half inch of much needed rain.

Correct.   The HRRR is the earliest with convection, and the shear won't increase until later in the day, so its early afternoon storms are not exciting.   That said, I'd take its solution in a heartbeat, as it has multiple rounds of storms and good rainfall.    The 18Z NAM Nest has severe storms, as it waits until later when the shear has improved a lot, but some people (me!!!) miss out, and there is no round 2 later in the evening or overnight.    That run legitimately pissed me off.

[Eskimo Joe]

3 minutes ago, high risk said:

Correct.   The HRRR is the earliest with convection, and the shear won't increase until later in the day, so its early afternoon storms are not exciting.   That said, I'd take its solution in a heartbeat, as it has multiple rounds of storms and good rainfall.    The 18Z NAM Nest has severe storms, as it waits until later when the shear has improved a lot, but some people (me!!!) miss out, and there is no round 2 later in the evening or overnight.    That run legitimately pissed me off.

Yea this is looking like more and more of a bust in the severe department. Too many things getting mis-timed.

[high risk]

13 minutes ago, Eskimo Joe said:

Yea this is looking like more and more of a bust in the severe department. Too many things getting mis-timed.

Maybe.    The HRRR is on its own with such an early round 1.    Its doing weird things with the mixing again, but I'm not sure if that is driving the early show, or if it's just different handling of the forcing.   If things hold off until later when the shear increases, I think there is some higher end wind potential.   Heck, if just we boost the dew points in the HRRR but keep its timing, the still sizable downdraft CAPE might overcome the weak shear and give some pockets of higher winds.

[Roger Ramjet]

We need rain, period!! I like severe weather, but whatever solution produces the most rain is the model I will hugging!!

[MN Transplant]

4 hours ago, Eskimo Joe said:

Yea this is looking like more and more of a bust in the severe department. Too many things getting mis-timed.

The 00z HRRR is about 100/52 for DCA tomorrow afternoon.  That is not happening.

[high risk]

36 minutes ago, MN Transplant said:

The 00z HRRR is about 100/52 for DCA tomorrow afternoon.  That is not happening.

      Yep.   You have to toss the HRRR solutions, because it has no instability to work with when it tries to initiate convection.

[KAOS]

3 hours ago, Roger Ramjet said:

We need rain, period!! I like severe weather, but whatever solution produces the most rain is the model I will hugging!!

This

[WxUSAF]

Hope the euro busts bad 

[yoda]

Day 1 OTLK from SPC still mentions potential upgrade 

.Ohio Valley into northern Mid Atlantic...
   Ahead of digging mid-level troughing, one or more convectively
   generated perturbations may contribute to increasing thunderstorm
   development across the mid into upper Ohio Valley by this afternoon,
   beneath modest west-southwesterly mid-level flow (on the order of
   30+ kt).  Although lower-level wind fields may be initially more
   modest, various model output suggests that convection could become
   fairly widespread and contribute to strengthening conglomerate
   surface cold pools accompanied by potentially damaging wind gusts.
   Potential instability across and east of the Allegheny Mountains
   remains a little more unclear, but it is possible that vigorous
   convection may be maintained along the leading edge of the outflows
   as they spread eastward into northern Mid Atlantic coastal areas by
   early this evening.  While the magnitude of the convective surface
   gusts may be mostly marginally severe in nature, one or more swaths
   of potentially damaging gusts are possible, and severe wind
   probabilities may still need to be increased once sub-synoptic
   developments become more unclear.

[yoda]

And LWX HWO mentions isolated tornadoes possible in each 3 parts for the region 

.DAY ONE...Today and Tonight

Hot and humid conditions are expected this afternoon, with highs
in the mid to upper 90s and peak heat indices between 100 to 105
degrees.

Isolated to scattered severe thunderstorms capable of producing
damaging wind gusts, large hail, and isolated tornadoes are
possible this afternoon into the evening. There is the potential
for considerable wind damage, but confidence is low at this time.

[CAPE]

39 minutes ago, WxUSAF said:

Hope the euro busts bad 

That's ugly.

FV3 Hi-res would work.

[yoda]

3 minutes ago, CAPE said:

That's ugly.

FV3 Hi-res would work.

I'd take the 06z NAM NEST and the 06z NAM 

[Eskimo Joe]

46 minutes ago, WxUSAF said:

Hope the euro busts bad 

Complete whiff?

[aldie 22]

48 minutes ago, WxUSAF said:

Hope the euro busts bad 

Ji has turned into DT on FB he only uses the euro now as his go to...he's already speaking about a leesburg split 

[yoda]

5 minutes ago, Eskimo Joe said:

Complete whiff?

Basically 

 

[WxUSAF]

11 minutes ago, CAPE said:

That's ugly.

FV3 Hi-res would work.

 

6 minutes ago, Eskimo Joe said:

Complete whiff?

Lately it seems euro just loves the next storm/rain event, but hates the one that’s on the doorstep. It’s been bullish for Saturday for a few cycles now. But it was bullish on today before…

[yoda]

06z NAM 

 

[aldie 22]

3K NAM skips my area with two rounds first to the north second develops just east...that sounds fun

[Eskimo Joe]

12 minutes ago, yoda said:

Basically 

 

LOL 

[dailylurker]

14 minutes ago, WxUSAF said:

 

Lately it seems euro just loves the next storm/rain event, but hates the one that’s on the doorstep. It’s been bullish for Saturday for a few cycles now. But it was bullish on today before…

I'm sticking to winter weenie rule. We don't pay attention to the euro this close in range to a storm unless it shows what we want. 

[SnowenOutThere]

1 hour ago, yoda said:

probabilities may still need to be increased once sub-synoptic developments become more unclear.

Think someone accidentally put an unwanted un there

[yoda]

I think everyone would take the 12z HRRR

Wouldn't mind the 12z NAM either

[EastCoast NPZ]

2 hours ago, yoda said:

Basically 

 

Fits the summer.  I have no doubt this happens.

[yoda]

Okay then... @WxUSAFwill take the 12z NAM Nest supercell lol... comes barging through at 20z/21z

[Eskimo Joe]

The latest SPC meson analysis definitely shows a weak EML, with mid level lapse rates trying to touch 7°c/km, plenty of DCAPE, and Total Totals are already pushing 50 near DC. But there's just no real shear to move things along. The morning balloon out of IAD has a convective temp of 94°, and mid level lapse rates of 7.2c/km. All in all, probably enough for several rounds of thunderstorms regionwide today, perhaps a few decent updrafts. it wouldn't shock me if SPC introduced a 30% wind in the area, but I would argue that would be from DC and points north where there's slightly better upper level support.

I'd gladly take the rain though. Our mesonet stations show the 2" and 5" soil moisture values are crispy.

EDIT: RNK and PIT soundings show a bit of an EML too.

[WxUSAF]

42 minutes ago, yoda said:

Okay then... @WxUSAFwill take the 12z NAM Nest supercell lol... comes barging through at 20z/21z

That would make for an entertaining commute home 

[JenkinsJinkies]

So how much will the forecasted rain totals be walked back?

[high risk]

1 hour ago, Eskimo Joe said:

The latest SPC meson analysis definitely shows a weak EML, with mid level lapse rates trying to touch 7°c/km, plenty of DCAPE, and Total Totals are already pushing 50 near DC. But there's just no real shear to move things along. The morning balloon out of IAD has a convective temp of 94°, and mid level lapse rates of 7.2c/km. All in all, probably enough for several rounds of thunderstorms regionwide today, perhaps a few decent updrafts. it wouldn't shock me if SPC introduced a 30% wind in the area, but I would argue that would be from DC and points north where there's slightly better upper level support.

I'd gladly take the rain though. Our mesonet stations show the 2" and 5" soil moisture values are crispy.

EDIT: RNK and PIT soundings show a bit of an EML too.

         There is actually some very solid agreement now in the 12Z guidance.   There is a round 1 in the 21-23Z time frame which has a cluster or broken line of cells, focused mostly north of DC, which would have some significant wind potential.   

         There is then a more widespread round 2 later in the evening that would bring welcome rain to most of the area.