2024 Severe Weather General Discussion

[Terpeast]

7 minutes ago, high risk said:

         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.

That puts round 1 in the 5-7pm time frame, which gives us lots of room for heating to maximize convection after initiation. Hopefully we all benefit. 

[yoda]

11:15am LWX AFD update 

NEAR TERM /THROUGH TONIGHT/...
Overall not much change to the current forecast. Still monitoring
the influx of moisture pushing north this afternoon and winds aloft
to determine the extent of our severe weather threat later today.
The current 12z KIAD this morning shows plenty of dry air in
the mid to upper levels and even at the surface. PWATS this
morning are around 1.43 inches with low level RH values ta 45
percent and mid level RH values around 55 percent. 12z KRNK
sounding to the south is a bit drier with PWATS around 1.14
inches.

As a result, expect an excessively hot and humid afternoon ahead of
a strong shortwave disturbance/cold front that is set to cross
tonight into early Thursday morning. Convective activity looks to be
a bit more organized although some uncertainty remains with the
better forcing forecast north of the area up across PA/NJ.

Severe THREATS:This convective activity 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 afternoon (between
3-7pm). 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)
continues to increase per the latest 12z guidance although some
uncertainty remains to how widespread this threat will be
resolved with two rounds of convection set to take place.
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. This threat has lowered somewhat in the
last few model runs, but something that we are still
monitoring at this time. 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. Some urban
locations especially from DC points south and east may push up and
over 100 degrees. Of course this will be determined by how much
low level moisture influx there is over the region and how early
convective initiation takes place. Models have dewpoints
quickly getting back into the low 70s this afternoon with
precipitable water values on the order of 1.8-2.2 inches. The
confidence for Heat Advisories still remains low although a few
areas may touch criteria for a brief period of time. Overall
heat index values this afternoon will run between 98 to 104
degrees during the peak of the afternoon. Will continue to
monitor the need for any such heat-related products.

SEVERE TIMING:Expect convective initiation to kick off along
the lee side trough later this afternoon before propagating east
of the metros tonight (between 3-7pm). 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 limited 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 tonight and Thursday morning as the cold
front slowly pushes through. The severe threat at this point may
be on it`s way down due in part to the initial round of
thunderstorm activity during the afternoon and evening hours.
We`ll have to continue to monitor this timeframe though as some
of the latest guidance has trended toward isolated activity
mainly east of the Blue Ridge this afternoon with the next round
blowing up west of the Alleghenies this evening and propagating
east overnight. Lows tonight will fall into the mid to upper
60s with low to mid 70s along and east of I-95.

[Eskimo Joe]

Looks like some initiation is starting in SW West Virginia per visible satellite.

 

[Kmlwx]

Kind of a paltry 1630z outlook

[Eskimo Joe]

Latest SPC meso-analysis shows respectable mini EML from DC north into southern PA, and also a boundary of DCAPE from I-70 south. This looks like a day where some big cell goes across Parr's Ridge and everyone else waits for the main show after sunset.

[Eskimo Joe]

Looks like a severe thunderstorm watch going out to our NW in PA and Ohio?

[WxUSAF]

1pm temps and dews:

DCA: 94/68

BWI: 96/65

IAD: 95/62

[Eskimo Joe]

3 minutes ago, WxUSAF said:

1pm temps and dews:

DCA: 94/68

BWI: 96/65

IAD: 95/62

HRRR overmixing bias strikes again. It's also too low on the CAPE as well. Looks like a outlier.

[WxUSAF]

9 minutes ago, Eskimo Joe said:

HRRR overmixing bias strikes again. It's also too low on the CAPE as well. Looks like an outlier.

16z run was a bit more robust looking than the previous few hours so perhaps it’s catching up to conditions.

[Eskimo Joe]

The aggressive CAMs appear to have some sort of Round 1 initiation along I-81 around 3:30 pm. That's my benchmark to see how things are breaking today. If we get to say 4:30 and there's nada, then we can probably expect a benign evening. 

[WxUSAF]

7 hours ago, WxUSAF said:

Hope the euro busts bad 

12z is generally in line with other guidance 

[Eskimo Joe]

Looks like upstate PA is the place to be. Euro is pretty dry in these parts for the evening.

[vastateofmind]

6 minutes ago, Eskimo Joe said:

Looks like upstate PA is the place to be. Euro is pretty dry in these parts for the evening.

Radar is intense up there...looks like Erie is about to get the snot beat out of it.

[Eskimo Joe]

lol...are BWI and DCA going to hit 100° today?

[midatlanticweather]

Looks like some crapvection heading this way. It does look like a storm fired in the middle of it.

[MN Transplant]

49 minutes ago, WxUSAF said:

1pm temps and dews:

DCA: 94/68

BWI: 96/65

IAD: 95/62

DP creeping back up at IAD.  63 on the new hourly, but 64 on the fast obs.

[MN Transplant]

1 minute ago, Eskimo Joe said:

lol...are BWI and DCA going to hit 100° today?

I hit 100 (rounded) which is higher than Saturday.

[vastateofmind]

44 minutes ago, MN Transplant said:

I hit 100 (rounded) which is higher than Saturday.

Yeah, I posted a reading of 103 in main obs thread a short while ago, which shocked me...because Sat felt so much more oppressive outside than it does this afternoon. There's a few cells down there in the Madison/Culpeper region that could either graze us from the south, or potentially expand to hit us, too. We'll probably see within the next 45-60 minutes.

[midatlanticweather]

So far.. The split is looking possible 

 

[dailylurker]

Looks like whiff. Shocker lol

[87storms]

Looks like whiff. Shocker lol

I like our setups better when it’s hot and humid with cumulus clouds instead of this alto/stratus stuff. Maybe we can get a prolonged break in the clouds closer to sunset.

[GramaxRefugee]

The batch that we do have is tracking toward the classic Potomac RIver - to - LaPlata  tornado alley.

The dew point up-and-down (and more down) measurements in the area weaken my confidence in anything holding together.

[TSG]

23 minutes ago, dailylurker said:

Looks like whiff. Shocker lol

 

21 minutes ago, 87storms said:

I like our setups better when it’s hot and humid with cumulus clouds instead of this alto/stratus stuff. Maybe we can get a prolonged break in the clouds closer to sunset.

 

6 minutes ago, GramaxRefugee said:

The batch that we do have is tracking toward the classic Potomac RIver - to - LaPlata  tornado alley.

The dew point up-and-down (and more down) measurements in the area weaken my confidence in anything holding together.

the main show isn't until later y'all, like 11pm-1am

[North Balti Zen]

Isn’t the rain really an after 10:00 pm thing?

[Eskimo Joe]

Looks like our shot at storms is starting to take shape over Central West Virginia.

[Eskimo Joe]

Pity meso for DC and points northeast

https://www.spc.noaa.gov/products/md/md1429.html

 

[North Balti Zen]

EJ - we need rain. RAIN. I don't care if it comes with wind, need rain. 

[Eskimo Joe]

10 minutes ago, North Balti Zen said:

EJ - we need rain. RAIN. I don't care if it comes with wind, need rain. 

Same. I'm legit worried we get a dry frontal passage. It looks like the CAMs absolutely blew chunks on this entire setup.

[TSG]

20z HRRR says we're in for a fun evening

[vastateofmind]

1 hour ago, midatlanticweather said:

So far.. The split is looking possible 

1 hour ago, dailylurker said:

Looks like whiff. Shocker lol

55 minutes ago, Eskimo Joe said:

Looks like our shot at storms is starting to take shape over Central West Virginia.

Interestingly enough...this first batch IS getting ready to split around my BY. Meh, there's some stuff going on out there in WV of interest...