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