2026 Mid-Atlantic Severe Storm General Discussion

[southmdwatcher]

Heck of a time for Sterling radar to go down or have a substantial delay.

[wxmeddler]

KLWX is out, they're troubleshooting. But there are the TDWR's around. The Tornado warning was dumb IMHO.

[Eskimo Joe]

8 minutes ago, southmdwatcher said:

Heck of a time for Sterling radar to go down or have a substantial delay.

Infrastructure Week!

[southmdwatcher]

I switched to the TDCA radar on GR2Analyst, but certain products aren't available with the terminal radars. Clearly there was quite a bit of rotation, but it has weakened.

[southmdwatcher]

Quite a bit of lightning with this storm.

[GATECH]

6 minutes ago, wxmeddler said:

KLWX is out, they're troubleshooting. But there are the TDWR's around. The Tornado warning was dumb IMHO.

Couldn’t pull up the TDWRs, rotation was broad out of KDOX.   That storm produced no wind at the surface, my max wind gust was 5mph for the same storm.

[SolidIcewx]

Seemed to peak around 9:15pm but broad like what was stated.

[frd]

12 hours ago, vortex95 said:

Maybe we can do ok overnight.  The WV MCS looks solid.  Nocturnal sometimes makes a sig difference, at least for big rains.

You were correct ! A Flash Flood Warning was issued here last night and early morning. Training cells for almost an hour. 1.42 of rain here.

3 inches for the month so far. 

Pattern looks active later in the week. 

 

WPC  https://www.wpc.ncep.noaa.gov/discussions/hpcdiscussions.php?disc=pmdepd

 

[vortex95]

5 hours ago, frd said:

You were correct ! A Flash Flood Warning was issued here last night and early morning. Training cells for almost an hour. 1.42 of rain here.

3 inches for the month so far. 

Pattern looks active later in the week. 

 

WPC  https://www.wpc.ncep.noaa.gov/discussions/hpcdiscussions.php?disc=pmdepd

 

One area actually got what the RRFS was forecasting.  6.41" Midlothian VA!  RRFS overdid the areal coverage.  HRRR was a bit high but still  2.00" max a Franconia VA not far S of DC metro. 

Looking at the wind reports, it appears the Appalachians barrier for bow echoes/derechoes was a big factor here.
https://www.spc.noaa.gov/climo/reports/260816_rpts.html
 

[AdamHLG]

Are we done for a while? 

[mappy]

little storm dropped out of PA. Brief heavy downpour, few rumbles of thunder 

[SnowenOutThere]

Severe storm just past Cvill is rotating anticyclonically

[Kmlwx]

NAM nest sends pretty robust UH tracks over the area tomorrow.

[WxUSAF]

3 minutes ago, Kmlwx said:

NAM nest sends pretty robust UH tracks over the area tomorrow.

Absolute chasm of a gap between the mesos with how they depict tomorrow. 

[yoda]

5 minutes ago, Kmlwx said:

NAM nest sends pretty robust UH tracks over the area tomorrow.

Morning discussion from LWX seems to suggest sneaky severe day.  While likely do be MRGL, they do mention much higher threat possible 

 

Latest guidance is a bit slower and further west/northwest with

the position of a cold front on Thursday. SLP progs hint at two
subtle warm front type features that will lift northeast during
the day on Thursday ahead of a pair of weak surface lows (one
near PA/NJ, and the other near central VA). Where this front
ends up just prior to peak heating will be crucial in
determining the severe weather threat locally on Thursday.

Forecast soundings show strong mid-level capping west of the
front Thursday afternoon, with no capping and notably stronger
CAPE approaching or exceeding 2000 J/kg east of it. The
consensus is for this front to be more or less over I-95
Thursday afternoon during peak heating, though there is some
variance anywhere from near the Blue Ridge to the Chesapeake
Bay. Mid-level lapse rates start the day unimpressive, around 5
C/km likely due to saturation aloft associated with a weak wave
of showers, but steepen slightly closer to 6 C/km by afternoon
due to some cooling aloft.

The extent of any clouds and showers cast some uncertainty on
the extent of heating and instability later in the day. The
background environment is favorable for strong to severe
updrafts and even supercells. An 80-90+ kt upper jet will pivot
over the area, with its right entrance ascent positioned over
the surface frontal zone in the afternoon. Mid-level heights
stay relatively steady, but PVA (strongest north) will be
prevalent ahead of the aforementioned mid/upper wave and jet.

Flow will increase through the column, with 25-40 kts in the
2-5 km AGL layer and effective deep layer bulk shear around 40
kts. SRH also increases to 100-200 m2/s2. Initial discrete cells
in this environment may quickly grow upscale into a line
capable of surges of strong to severe straight-line wind and a
few embedded spin ups. Some hail can`t be ruled out in the
strongest storms due to cooling temps aloft. Finally, although
Corfidi vectors are not too low (10-15 kts), on the mesoscale
some backbuilding or training potential may exist on the tail
(southwest) end of any developing line heading into the evening.

Again, the highest potential will be along and east of the front
which currently appears to be near I-95 during the afternoon
into the early evening hours.

Although somewhat conditional based on (1) the placement of the
front, and (2) the degree of instability, Thursday`s severe
weather and excessive rainfall risk bears monitoring. For now,
given the uncertainties listed above, the risk is more in the
Marginal (level 1 out of 5) bin for severe weather (i.e. any
damaging winds, large hail, tornadoes), but with a conditionally
much higher ceiling than most typical late summer days. The
excessive rainfall/flood risk may be even more conditional due
to uncertain mesoscale factors and lingering drought.

[Kmlwx]

The pattern continues as well with me being in the office tomorrow...always. 

[WxUSAF]

1 hour ago, WxUSAF said:

Absolute chasm of a gap between the mesos with how they depict tomorrow. 

NAM and Canadian mesos are bullish. Hrrr has a few storms. FV3 says maybe some breeze and clouds?

[Kmlwx]

25 minutes ago, WxUSAF said:

NAM and Canadian mesos are bullish. Hrrr has a few storms. FV3 says maybe some breeze and clouds?

Not saying this hasn't been the case in prior years - but this year seemingly has been significant in terms of distance between CAM solutions even up to the morning of events. 

[WxUSAF]

34 minutes ago, Kmlwx said:

Not saying this hasn't been the case in prior years - but this year seemingly has been significant in terms of distance between CAM solutions even up to the morning of events. 

Certainly has felt like that. This time there seems to be some synoptic differences driving the variance. Stormier solutions seem farther south with the low.

[WxUSAF]

Slight risk added for basically 95 and points east for tomorrow 

[frd]

Another Flood Watch, been the summer of flood watches and brown patch. 

I bet they expand the Flood Watch SW later today.  

 

 

 

 

 

Flood Watch
National Weather Service Mount Holly NJ
Issued by National Weather Service New York NY
208 PM EDT Wed Aug 19 2026

DEZ001-NJZ009-010-012>022-025>027-PAZ070-071-101>106-200900-
/O.NEW.KPHI.FA.A.0008.260820T1600Z-260821T0600Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
New Castle-Hunterdon-Somerset-Middlesex-Western Monmouth-Eastern
Monmouth-Mercer-Salem-Gloucester-Camden-Northwestern Burlington-
Ocean-Cumberland-Atlantic-Coastal Atlantic-Coastal Ocean-
Southeastern Burlington-Delaware-Philadelphia-Western Chester-
Eastern Chester-Western Montgomery-Eastern Montgomery-Upper Bucks-
Lower Bucks-
Including the cities of Camden, Flemington, Oxford, West Chester,
Pennsville, Trenton, Perkasie, Wilmington, Collegeville, Doylestown,
Lansdale, New Brunswick, Kennett Square, Media, Sandy Hook, Chalfont,
Atlantic City, Pottstown, Philadelphia, Norristown, Morrisville,
Wharton State Forest, Cherry Hill, Hammonton, Honey Brook,
Moorestown, Long Beach Island, Somerville, Mount Holly, Jackson,
Millville, Glassboro, and Freehold
208 PM EDT Wed Aug 19 2026

...FLOOD WATCH IN EFFECT FROM THURSDAY AFTERNOON THROUGH LATE
THURSDAY NIGHT...

* WHAT...Flash flooding caused by excessive rainfall is possible.

* WHERE...Portions of northern Delaware, including the following
  area, New Castle, New Jersey, including the following areas,
  Atlantic, Camden, Coastal Atlantic, Coastal Ocean, Cumberland,
  Eastern Monmouth, Gloucester, Hunterdon, Mercer, Middlesex,
  Northwestern Burlington, Ocean, Salem, Somerset, Southeastern
  Burlington and Western Monmouth, and southeast Pennsylvania,
  including the following areas, Delaware, Eastern Chester, Eastern
  Montgomery, Lower Bucks, Philadelphia, Upper Bucks, Western Chester
  and Western Montgomery.

* WHEN...From Thursday afternoon through late Thursday night.

* IMPACTS...Excessive runoff may result in flooding of rivers,
  creeks, streams, and other low-lying and flood-prone locations.
  Creeks and streams may rise out of their banks. Flooding may occur
  in poor drainage and urban areas.

* ADDITIONAL DETAILS...
  - Multiple rounds of showers and thunderstorms are expected across
    the area beginning Thursday afternoon through Thursday evening.
    Rainfall rates of 1 to 3 inches per hour are possible. Rainfall
    amounts of 1 to 2 inches are possible with localized amounts of 3
    to 5 inches which could cause flash flooding.
  - http://www.weather.gov/safety/flood

PRECAUTIONARY/PREPAREDNESS ACTIONS...

You should monitor later forecasts and be prepared to take action
should Flash Flood Warnings be issued.

&&

$$

DeSilva

 

 

 

[vortex95]

Deep layer shear is good tomorrow, and there an solid 250 mb jet involved, unlike last time, so better dynamically.  HRRR really makes the CAPE stand out over the entire bay.  PWATs come up nicely during the day, so do sfc dew points.

[Eskimo Joe]

2 hours ago, vortex95 said:

Deep layer shear is good tomorrow, and there an solid 250 mb jet involved, unlike last time, so better dynamically.  HRRR really makes the CAPE stand out over the entire bay.  PWATs come up nicely during the day, so do sfc dew points.

Do you think this is an I-95 and east event, or are the western suburbs in play?

[MillvilleWx]

8 hours ago, frd said:

Another Flood Watch, been the summer of flood watches and brown patch. 

I bet they expand the Flood Watch SW later today.  

 

 

 

 

 

Flood Watch
National Weather Service Mount Holly NJ
Issued by National Weather Service New York NY
208 PM EDT Wed Aug 19 2026

DEZ001-NJZ009-010-012>022-025>027-PAZ070-071-101>106-200900-
/O.NEW.KPHI.FA.A.0008.260820T1600Z-260821T0600Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
New Castle-Hunterdon-Somerset-Middlesex-Western Monmouth-Eastern
Monmouth-Mercer-Salem-Gloucester-Camden-Northwestern Burlington-
Ocean-Cumberland-Atlantic-Coastal Atlantic-Coastal Ocean-
Southeastern Burlington-Delaware-Philadelphia-Western Chester-
Eastern Chester-Western Montgomery-Eastern Montgomery-Upper Bucks-
Lower Bucks-
Including the cities of Camden, Flemington, Oxford, West Chester,
Pennsville, Trenton, Perkasie, Wilmington, Collegeville, Doylestown,
Lansdale, New Brunswick, Kennett Square, Media, Sandy Hook, Chalfont,
Atlantic City, Pottstown, Philadelphia, Norristown, Morrisville,
Wharton State Forest, Cherry Hill, Hammonton, Honey Brook,
Moorestown, Long Beach Island, Somerville, Mount Holly, Jackson,
Millville, Glassboro, and Freehold
208 PM EDT Wed Aug 19 2026

...FLOOD WATCH IN EFFECT FROM THURSDAY AFTERNOON THROUGH LATE
THURSDAY NIGHT...

* WHAT...Flash flooding caused by excessive rainfall is possible.

* WHERE...Portions of northern Delaware, including the following
  area, New Castle, New Jersey, including the following areas,
  Atlantic, Camden, Coastal Atlantic, Coastal Ocean, Cumberland,
  Eastern Monmouth, Gloucester, Hunterdon, Mercer, Middlesex,
  Northwestern Burlington, Ocean, Salem, Somerset, Southeastern
  Burlington and Western Monmouth, and southeast Pennsylvania,
  including the following areas, Delaware, Eastern Chester, Eastern
  Montgomery, Lower Bucks, Philadelphia, Upper Bucks, Western Chester
  and Western Montgomery.

* WHEN...From Thursday afternoon through late Thursday night.

* IMPACTS...Excessive runoff may result in flooding of rivers,
  creeks, streams, and other low-lying and flood-prone locations.
  Creeks and streams may rise out of their banks. Flooding may occur
  in poor drainage and urban areas.

* ADDITIONAL DETAILS...
  - Multiple rounds of showers and thunderstorms are expected across
    the area beginning Thursday afternoon through Thursday evening.
    Rainfall rates of 1 to 3 inches per hour are possible. Rainfall
    amounts of 1 to 2 inches are possible with localized amounts of 3
    to 5 inches which could cause flash flooding.
  - http://www.weather.gov/safety/flood

PRECAUTIONARY/PREPAREDNESS ACTIONS...

You should monitor later forecasts and be prepared to take action
should Flash Flood Warnings be issued.

&&

$$

DeSilva

 

 

 

The sad reality is, it's been a lot of bad luck for some and a lot of fortunate luck for others. This isn't a case where everyone has been skunked. Your area has been getting shafted while my parents down in Rehoboth has gotten hit multiple times, flush this summer. It's been a tough pill to swallow for many. Baltimore proper, especially east Baltimore has gotten trucked several times while the west side gets shafted. It's why I hate convective season around here. Need a synoptic scale gully washer to get everyone involved with good rain and some boomers. 

[high risk]

8 hours ago, vortex95 said:

Deep layer shear is good tomorrow, and there an solid 250 mb jet involved, unlike last time, so better dynamically.  HRRR really makes the CAPE stand out over the entire bay.  PWATs come up nicely during the day, so do sfc dew points.

      Yeah, this is a pretty solid setup:  good dynamics, good deep layer shear, and moderate instability.   CAMs suggest that most areas north of DC are close to a lock to get storms, while there is a bit more uncertainty for areas south of DC.

[yoda]

7 hours ago, Eskimo Joe said:

Do you think this is an I-95 and east event, or are the western suburbs in play?

06z Day 1 OTLK moved SLGT back west a bit to just west of BR... MRGL back west of i81 corridor 

[yoda]

30 wind and 5 tor for Delmarva 

[yoda]

Hazardous Weather Outlook
National Weather Service Baltimore MD/Washington DC
650 AM EDT Thu Aug 20 2026

ANZ530>543-DCZ001-MDZ008-011-013-014-016>018-504-506-508-
VAZ053>057-527-211100-
Chesapeake Bay north of Pooles Island MD-
Chesapeake Bay from Pooles Island to Sandy Point MD-
Chesapeake Bay from Sandy Point to North Beach MD-
Chesapeake Bay from North Beach to Drum Point MD-
Chesapeake Bay from Drum Point MD to Smith Point VA-
Tidal Potomac from Key Bridge to Indian Head MD-
Tidal Potomac from Indian Head to Cobb Island MD-
Tidal Potomac from Cobb Island MD to Smith Point VA-
Patapsco River including Baltimore Harbor-
Chester River to Queenstown MD-Eastern Bay-
Choptank River to Cambridge MD and the Little Choptank River-
Patuxent River to Broomes Island MD-
Tangier Sound and the inland waters surrounding Bloodsworth
Island-District of Columbia-Cecil-Southern Baltimore-
Prince Georges-Anne Arundel-Charles-St. Marys-Calvert-
Central and Southeast Montgomery-Central and Southeast Howard-
Southeast Harford-Fairfax-Arlington/Falls Church/Alexandria-
Stafford-Spotsylvania-King George-
Central and Southeast Prince William/Manassas/Manassas Park-
650 AM EDT Thu Aug 20 2026

This Hazardous Weather Outlook is for the Maryland portion of the
Chesapeake Bay, Tidal Potomac River, and I-95 corridor through
central Maryland, northern Virginia, and District of Columbia.

.DAY ONE...Today and Tonight

Numerous thunderstorms are expected between about 3 PM and 9 PM.
These storms may contain damaging wind gusts and potentially a
couple of tornadoes, especially near northeast Maryland. There is
also a threat of urban flash flooding, with the highest risk near
and northeast of Baltimore.

[yoda]

Morning discussion from LWX 

DISCUSSION...
KEY MESSAGE 1...Severe weather is possible, mainly east of the
Blue Ridge this afternoon into early evening.

A slow-moving cold front arcs down the Saint Lawrence River
Valley to the lower Great Lakes back into the central Great
Plains. To the south, a largely stationary front was attempting
to lift slowly northward as a warm front, and stretched from the
Carolinas back to Oklahoma. Showers and thunderstorms were
persistently trekking west to east along the northern front,
with a weak surface low and MCV/shortwave crossing Illinois.
This shortwave will be the impetus for convective development
across the Mid-Atlantic later today as the local area sits in
between the two aforementioned fronts.

Most instability this morning is rather weak and elevated in
nature, but is expected to increase rapidly in the I-95 corridor
from south to north as higher moisture air advects into the
area, as well as near the Appalachians ahead of an approaching
shortwave, both by late this morning. For now, weak lift and CAPE is
keeping things limited to a few WAA showers near the metros.

Additional development, perhaps even deeper convective cores,
is possible by as early as late morning given the anticipated
rapid increase in CAPE and lift.

Flow aloft is seasonably strong by late August standards, with a
100+ knot 300 hPa jet streak expected to pivot over the Saint
Lawrence River Valley into northern New England by evening. The
tail of this upper jet may actually strengthen and persist near
the Mason-Dixon Line early this evening, which could briefly
enhance large scale ascent locally via RRQ dynamics.

In the mid levels, the previously mentioned shortwave has
trended notably deeper and a bit slower over the last 12-24
hours. This brings the axis of the shortwave, its enhanced flow,
and PVA across the Appalachians around midday, then across
areas near and east of the Blue Ridge/Catoctin Mountains east to
I-95 and the Chesapeake Bay during peak heating. In addition to
bringing large scale ascent, this pushes effective deep layer
bulk shear into the 35- to 50-knot range later today (highest
north/northeast). Shear of this magnitude is favorable for
sustained, organized updrafts, including line segments and
supercells (discrete or line-embedded).

Thermodynamically, the atmosphere will be very moist, especially
further east. Strong low-level theta-e advection is expected to
persist through early evening ahead of the approaching shortwave
and cold front. Widespread clouds will limit heating somewhat,
especially west of the Blue Ridge where the storm threat is
notably less, but with the strong low-level moisture advection
and slow-but-steady cooling aloft, the net result should be
about 1000-2000 J/kg MLCAPE in the moist plume east of the Blue
Ridge heading into this afternoon, possibly as early as late
morning. The moist low-level advection beneath cooling aloft
may also result in re-generative CAPE and multiple rounds of
thunderstorms in any one location. This would be most likely
from near the DC metro north and east where large scale ascent
is strongest, with the added component of enhanced low-level
convergence along bay or river breezes (and eventually composite
outflow boundaries).

Finally, PWs will approach or exceed 2 inches in the moist axis
near and east of I-95 this afternoon into early evening. Deep
warm cloud layers in the high PW airmass will yield heavy to
extreme instantaneous and sub-hourly rainfall rates in the
stronger precip cores. Individual cell motion is expected to be
progressive (30-40 mph) given enhanced flow through the column
and the potential for modest cold pool development with any
persistent cells, clusters or line segments. However, the wavy
slow-moving front approaching from the north may lie close to
parallel to the mean steering flow at times, especially when
modulated by outflow from potential multiple rounds of storms.
This, coupled with the bay breeze which often takes on a similar
orientation, plus the urban footprint that has seen heavy rain
recently raises a (primarily urban/poor drainage) flash flood
risk over the I-95 corridor in northeast Maryland, including the
Baltimore area. The threat is a bit more conditional further
south and west into areas like Annapolis and the DC/Capital
Beltway region; these areas also feature urban sprawl and
inherently lower FFG, but the training potential is more
conditional based on favorable outflow or cell interactions
given slightly further displacement from the synoptic front(s)
and bay breeze.

Multiple hazards are possible today, and are outlined below.

Damaging Wind...
Straight-line/downburst winds are likely the highest threat
today, at least from an areal coverage standpoint. Tall, skinny
CAPE profiles with modest pockets of mid-level dry air yield
DCAPE of 600-800 J/kg, which would be marginally favorable for
strong to severe downdrafts. Background mid-level flow may
approach 40 knots around 700 hPa. With the high PW air and
modest DCAPE, water-loaded downdrafts via precip drag would be
possible especially with any bowing line segments or collapsing
mesocyclones/mesovorticies. The lack of steeper lapse rates
(hence modest DCAPE) should keep most wind gusts within the
strongest storms in the 55-70 mph range, with more widespread
40-55 mph potential. Given heavy precip and late summer, leafed-
up trees, would anticipate scattered to numerous instances of
tree and branch falls and subsequent power outage potential. The
risk is highest near and east of I-95 where storms are most
likely to become linear and be a bit more intense, since they`re
further east in the moist axis with a little more time to heat.
To the west, especially west of the Blue Ridge, less moisture
and heating should keep the coverage of more intense storms low.

Tornadoes...
A conditional risk for a brief spin-up is evident for most areas
east of the Blue Ridge given the magnitude of low/mid-level flow
and high PWs/lower LCLs. Relatively greater tornado potential
may exist closer to the front near the I-70 corridor east of
Frederick where surface winds will be backed and low-level SRH
will be higher, especially in close proximity to the bay breeze
along the western shore of the Chesapeake Bay into northeast MD.
Potential would be further maximized by (1) discrete supercells
occurring earlier when the synoptic low-level winds remain
backed and SRH is higher on a broad scale, and (2) with any
favorable QLCS surge/mesovortex interactions with residual
outflow or the bay breeze. Although unlikely due to a lack of
stronger 0-1 km shear/SRH and steeper lapse rates, robust 3CAPE
near the bay could result in a conditional risk for a strong
tornado if all of the above factors were to coalesce.

Flash Flooding...
We have been in a wetter pattern recently, but the majority of
the region is still in or just coming out of drought. Poor
drainage and urban areas are susceptible to heavy rain,
especially the intense sub-hourly rates possible today,
regardless. Additionally, areas near and just northeast of
Baltimore have seen multiple episodes of heavy rain over the
last few weeks. Individual storms should move pretty swiftly,
but the slowing southwest end of any lines or clusters would
orient parallel to the nearby surface front, bay breeze, and
mean steering flow. This brings a risk of flash flooding to
northeast MD in particular, with a more conditional risk further
south and west into the greater DC metro.

Hail...
Although lapse rates aloft will be modest at best given the
moist profiles, supercellular shear and modest mid-level cooling
will be favorable for at least some marginal/spotty severe hail
potential. Should mid-level shear/cooling be more potent or
cells be more discrete, the hail risk could increase, but this
seems unlikely given the otherwise tropical-esque airmass.

The threat for severe weather and flooding appears highest
between 2 PM this afternoon and 8 PM this evening, progressing west
to east in one or two rounds. However, it may start a couple hours
earlier further west (or on the bay breeze), and could linger
through late evening over southern Maryland.

By later this evening, the departure of large scale lift and the
loss of daytime heating should end the severe/flood threat.

[RickinBaltimore]

36 minutes ago, yoda said:

There is also a threat of urban flash flooding, with the highest risk near
and northeast of Baltimore.

Ok, so North Point by Kane will be flooded. Duly noted.