2024 Severe Weather General Discussion

[AmericanWxFreak]

12z 3k NAM

 

@WxUSAF

[AmericanWxFreak]

HRRR runs have been consistently showing a much more broken line then the NAM is advertising. Here is the 13z HRRR 

 

[yoda]

Updated morning AFD from LWX 

NEAR TERM /THROUGH TONIGHT/...
A stout inversion just off the surface this morning has led to
widespread low stratus across Central to Northern VA as warm air
advects atop this layer. Increasing southerly winds through the
day will eventually mix out these clouds by around noon time.
Still on track for hot and very humid conditions this afternoon,
with peak heat indices of 100-105 west of the Blue Ridge, and
105-110 to the east. Heat Advisories continue for most of the
area, with Excessive Heat Warnings along the I-95 urban corridor
from Baltimore to Fredericksburg into Southern MD.

The continued evolution of the parameter space this evening
continues to favor the development of a line of showers and
thunderstorms ahead of a cold front sweeping through the area.
Aided by subtle mid-level height falls, lee troughing east of
the Blue Ridge, and abundant instability given the high
heat/humidity will favor an increasing risk for strong to severe
thunderstorms. SPC has upgraded to a Slight Risk (level 2 of 5)
across northern VA into northern MD (I-66 north to the MD/PA
border). Damaging wind gusts are going to be the primary threat.
A tornado or two is also possible, especially in north-central
MD where 25-30 kts of 0-1 and 0-3 km shear are present.

As for thunderstorm timing, expect convection to begin to bubble
over areas just east of Alleghenies (ahead of the dry slot) early to
mid-afternoon before advancing toward the I-81 corridor and Blue
Ridge around 20-22z/4-6pm. Beyond this point convection continues
east toward the metros between 22-2z/6-10pm. Convection gradually
wanes before midnight with any severe threat wrapping up after
sunset. Convection looks to be fairly progressive with most of
the guidance either forming a line or a combination of
multicellular clusters. Even with that said, any thunderstorms
that due form will be efficient rain producers given PWAT values
upwards of 2.2 inches.

[MN Transplant]

22 minutes ago, AmericanWxFreak said:

HRRR runs have been consistently showing a much more broken line then the NAM is advertising. Here is the 13z HRRR 

 

The HRRR is backing DPs down to the upper 60s to around 70 and lowering the available CAPE.  The NAM seems more realistic per usual, but it is also usually aggressive in these scenarios.  It'll probably end up somewhere in between.

[Kmlwx]

Activity breaking out near Winchester. A bit on the early side - but I'd say that could be a good sign. 

[dailylurker]

5 minutes ago, Kmlwx said:

Activity breaking out near Winchester. A bit on the early side - but I'd say that could be a good sign. 

I just commented in the observation thread how their seems to be some rising motion in the clouds already. 

[Kmlwx]

They don't seem to be maintaining at least thus far (the mountain showers)

[Kmlwx]

Of note - CSU MLP page has severe potential for Sun through Wed next week. Doesn't mean it'll verify - but maybe we get some change in luck for precipitation at least. 

[yoda]

Watch coming soon

 

[yoda]

Mesoscale Discussion 1569
   NWS Storm Prediction Center Norman OK
   1152 AM CDT Wed Jul 10 2024

   Areas affected...South-central Pennsylvania...central
   Maryland...northern/central Virginia

   Concerning...Severe potential...Watch likely 

   Valid 101652Z - 101845Z

   Probability of Watch Issuance...80 percent

   SUMMARY...Widely scattered to scattered storms will pose a threat of
   mainly damaging winds and a tornado or two. A severe thunderstorm
   watch is likely for parts of Virginia into south-central
   Pennsylvania.

   DISCUSSION...A very moist airmass is in place across the
   Mid-Atlantic. Dewpoints are in generally in the low/mid 70s F.
   Morning observed soundings from the region suggest even limited
   heating would lead to surface-based destabilization. Current surface
   observations already show temperatures in the upper 80s to low 90s F
   which should be sufficient. Visible satellite shows a few updrafts
   beginning to deepen within the Blue Ridge. Modest mid-level ascent
   will occur this afternoon, particularly for northern Virginia into
   south-central Pennsylvania. Coupled with the approach of a cold
   front from the west, widely scattered to scattered storms are
   expected. The greatest potential for supercells will be in
   south-central Pennsylvania into central Maryland/northern Virginia
   where effective shear will be 35-40 kts. Farther south, multicells
   will be the predominant mode. Damaging wind gusts will be the
   primary hazard this afternoon. A low-end tornado threat will also be
   present for northern Virginia into south-central Pennsylvania, where
   low-level shear will be slightly greater nearer to the surface low.
   This is also supported by KCCX/KLWX VAD data. A severe thunderstorm
   watch is likely for parts of the Mid-Atlantic, though uncertainty is
   greater with southern extent.

   ..Wendt/Guyer.. 07/10/2024

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...AKQ...CTP...LWX...RNK...

[Kmlwx]

Knowing our luck - the various popcorn stuff developing will lower instability and ruin any more consolidated threat later  

But I'll take the rain at this point if it moistens up the ground and also cools the house down. 

[Eskimo Joe]

3 minutes ago, Kmlwx said:

Knowing our luck - the various popcorn stuff developing will lower instability and ruin any more consolidated threat later  

But I'll take the rain at this point if it moistens up the ground and also cools the house down. 

/Maryland

[vastateofmind]

Aaaaaaand....there's the watch.

Those (very hot) breezes and gusts are definitely verifying IMBY today.

[yoda]

STW until 10pm

 

[yoda]

URGENT - IMMEDIATE BROADCAST REQUESTED
   Severe Thunderstorm Watch Number 518
   NWS Storm Prediction Center Norman OK
   140 PM EDT Wed Jul 10 2024

   The NWS Storm Prediction Center has issued a

   * Severe Thunderstorm Watch for portions of 
     District Of Columbia
     Maryland
     Southern Pennsylvania
     Virginia
     Far Eastern West Virginia
     Coastal Waters

   * Effective this Wednesday afternoon and evening from 140 PM
     until 1000 PM EDT.

   * Primary threats include...
     Scattered damaging wind gusts to 65 mph likely
     A tornado or two possible

   SUMMARY...Scattered storms will continue to develop and intensify
   across the region, with the most sustained storms potentially
   focused across southern Pennsylvania, interior Maryland, into
   northern/central Virginia. Damaging winds will be the most common
   severe concern.

   The severe thunderstorm watch area is approximately along and 60
   statute miles east and west of a line from 50 miles northeast of
   Hagerstown MD to 40 miles east southeast of Lynchburg VA. For a
   complete depiction of the watch see the associated watch outline
   update (WOUS64 KWNS WOU8).

[yoda]

20/5 tor probs... 70/10 wind probs on the watch

[aldie 22]

This one feels like a nothing until after dark kind of potential. Lots of obs of full sun high temps and dews but no activity then the sun goes down and we have a bunch of hit and miss areas

[BlizzardNole]

I'd love to have one of those night thunderstorms with lots of lightning. 

What a wild day in western NY with a large area under enhanced.  Already several tornado warnings

[Kmlwx]

Boundary pushing well inland from the bay

[Eskimo Joe]

6 minutes ago, Kmlwx said:

Boundary pushing well inland from the bay

Looks like it set up right along MD 97.

[Kmlwx]

My eyes are on the stuff just N of CHO

[aldie 22]

Best case scenario in my mind is the line forms and moves more south to north as it slides across and some training occurrs.

[Eskimo Joe]

Hope the radar improves soon because man the current stuff is not reassuring.

[Kmlwx]

Echo tops are very respectable on that cell N of Culpeper. I think radar actually looks somewhat decent. Nothing super intense but at least it seems stuff is forming in a roughly linear shape - not just isolated pop ups. 

[Eskimo Joe]

New HRRR does a 7 - 10 split in DC. . .

[87storms]

Knowing our luck - the various popcorn stuff developing will lower instability and ruin any more consolidated threat later  
But I'll take the rain at this point if it moistens up the ground and also cools the house down. 

I want my theory of “wind and clouds prior to storm chances to not be a good thing” to be wrong. We def do need the rain.

[Jrlg1181]

1 hour ago, Kmlwx said:

My eyes are on the stuff just N of CHO

On my work route near the CHO airport... about a half inch of rain... 2 different showers, no thunder

Very tropical feel to the rain, very very warm rain water .

[aldie 22]

I hear thunder at least....that's a new sound this year

[dailylurker]

36 minutes ago, Kmlwx said:

Echo tops are very respectable on that cell N of Culpeper. I think radar actually looks somewhat decent. Nothing super intense but at least it seems stuff is forming in a roughly linear shape - not just isolated pop ups. 

That line headed our way (DC area) is looking healthy. No outflow or signs of collapsing. Let's get it.

[batmanbrad]

yes that cell heading in the general direction of Warrenton is definitely on a strengthening trend and heading NE towards DC metro