Severe Thunderstorm Warning 325, NWS Philadelphia/Mount Holly

Area Forecast Discussion
National Weather Service Mount Holly NJ
713 AM EDT Thu Aug 27 2026

.WHAT HAS CHANGED...
Flood Watch expanded to include the Lehigh Valley and Berks
County.

Updated the aviation section for the 06Z TAFs.

&&

.KEY MESSAGES...
1. A warm front on Thursday will bring the next chance for
widespread rain.

2. A cold front is expected to follow close behind on Friday.

&&

.DISCUSSION...
KEY MESSAGE 1...A warm front tomorrow will bring the next
chance for widespread rain.

Early morning convection has not been initialized well by the
CAMs with many of the 06Z guidance missing it entirely.
Ironically, the previous 00Z and 18Z guidance hi res runs
displayed the morning convection a bit earlier. Right now, the
greatest threat from these storms looks to be localized flash
flooding, but a severe thunderstorm cannot be fully ruled out.

High pressure moves offshore with southerly return flow behind
a warm front will bring dew points into the low 70s. Showers and
thunderstorms will start moving into western areas before
daybreak and continue through the day. CAMS producing some
organization to convective activity largely focused on the I-95
urban corridor.

As for the hazards, there is a SLIGHT (2 out of 4) risk for
excessive rainfall. Precipitable water values increase to
perhaps as high as 150% of normal for this time of year.
The hires guidance suggests that heaviest precipitation will be
generally along the I-95 corridor and points northwest. Hires
guidance has also pointed to areas along the I-78 corridor
potentially seeing heavy rainfall amounts as well. Generally
around 1-2 inches of rain with localized QPF values in excess of
3 inches. Widespread flash flooding still seems unlikely, but
the localized threat remains elevated. The Flood Watch was
expanded to include the Lehigh Valley and Berks county and
remains in effect for northern NJ and the I-95 corridor.

For severe hazards, latest CAMS and HREF guidance show SBCAPE
values remaining around 1500-2500 J/kg with ensemble maximums
in excess 3000 J/kg. Deep layer shear forecasts remain around
30kt with a strongly veering profile aloft. Boundary layer flow
is not particularly strong but surface winds are more backed
than previous forecasts so an isolated tornado is possible
primarily along and west of I-95. That said, damaging wind gusts
and hail will remain the greatest threat. Dominant mode should
be multicell convection but a supercell can't be ruled out
especially where cloud bearing shear is maximized. SPC has
expanded the area of a slight risk (2 out of 5) to now include
much of the area.

KEY MESSAGE 2...A cold front will cross the area Friday.

The timing of this cold front will be critical in the risk for
thunderstorm hazards. There are differences between models in
both the timing, and if this will be a single cold front, or an
initial cold front with a reinforcing shot of cold air advection
coming in behind it. Saturday and Sunday appear to be dry across
most of the area with the exception of southern areas Saturday
where low probabilities of showers and storms will exist.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Thursday...Mainly VFR. Light south winds in the morning become
more out of the south-southwest at around 10 knots during the
afternoon with gusts to 20 knots for KMIV/KACY. For the Lehigh
Valley and I-95 terminals, showers and potentially an embedded
thunderstorm are possible in the morning which was handled with
VCSH with a PROB30 for -TSRA. As the potential for showers and
thunderstorms increases from midday into the evening, VCTS and
PROB30 groups for TSRA for most terminals to account for this
activity.

Thursday night...VFR as showers and storms exit, but patchy fog
possible mainly across the I-95 corridor and RDG/ABE. Winds
light and variable. Low confidence.

Outlook...

Friday...Periods of MVFR or lower are possible in showers and
storms.

Saturday through Monday...Prevailing VFR conditions.

&&

.MARINE...
No marine hazards expected. Southerly winds with gusts near 20
kt possible.

Outlook...

Thursday night and through Sunday...No marine hazards expected.

Rip Currents...

On Thursday, winds remain southerly at 10 to 15 mph with gusts
to 20 to 25 mph. There is an east-southeasterly swell with a
period of 8-9 seconds and breaking waves around 2-3 feet. As a
result, there is a MODERATE risk for the development of
dangerous and life threatening rip currents at the Jersey Shore
and a LOW risk at Delaware Beaches.

For Friday, winds in the morning are more westerly at 5 to 10
mph before becoming more southwesterly in the afternoon at 5 to
10 mph. An east-southeasterly swell remains with a period of
6-7 seconds with breaking waves around 2-3 feet. As a result,
there is a MODERATE risk for the development of dangerous and
life threatening rip currents at the Jersey Shore and a LOW risk
at Delaware Beaches.

For specific beach forecasts, visit weather.gov/beach/phi

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Flood Watch from noon EDT today through late tonight for
     PAZ060>062-070-071-101>106.
NJ...Flood Watch from noon EDT today through late tonight for
     NJZ001-007>010-012-013-015-017>019.
DE...Flood Watch from noon EDT today through late tonight for
     DEZ001.
MD...None.
MARINE...None.

&&

DISCUSSION...WFO PHI
AVIATION...WFO PHI
MARINE...WFO PHI

Hazardous Weather Outlook
National Weather Service Mount Holly NJ
507 AM EDT Thu Aug 27 2026

MDZ012-015-019-020-280915-
Kent MD-Queen Annes-Talbot-Caroline-
507 AM EDT Thu Aug 27 2026

This Hazardous Weather Outlook is for northeast Maryland.

.DAY ONE...Today and tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

Preliminary Local Storm Report
National Weather Service Mount Holly NJ
1055 AM EDT Thu Aug 27 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0940 AM     Flood            Byram                   40.93N 74.72W
08/27/2026                   Sussex             NJ   Dept of Highways

            Flooding on US 206 in both directions North
            of CR 607/Lackawanna Dr in Byram Twp. All
            lanes closed northbound; closed southbound.

&&

MPS

Preliminary Local Storm Report
National Weather Service Mount Holly NJ
1241 PM EDT Thu Aug 27 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1209 PM     Flood            Claymont                39.80N 75.46W
08/27/2026                   New Castle         DE   Emergency Mngr

            Philadelphia Pike closed in Claymont DE in
            area of Claymont Fire Station due to roadway
            flooding.

&&

MPS

Preliminary Local Storm Report
National Weather Service Mount Holly NJ
101 PM EDT Thu Aug 27 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1238 PM     Flash Flood      Logan Twp.              39.80N 75.35W
08/27/2026                   Gloucester         NJ   Dept of Highways

            Flooding on US 130 Northbound At US 322
            (Logan Twp), 1 right lane of 3 lanes, right
            shoulder closed.

&&

MPS

Preliminary Local Storm Report
National Weather Service Mount Holly NJ
108 PM EDT Thu Aug 27 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0100 PM     Tstm Wnd Dmg     South Harrison Twp      39.70N 75.27W
08/27/2026                   Gloucester         NJ   Fire Dept/Rescue

            Tree and wires down. Time estimated.

&&

MJG

Preliminary Local Storm Report
National Weather Service Mount Holly NJ
114 PM EDT Thu Aug 27 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0109 PM     Flash Flood      Heathcote               40.39N 74.57W
08/27/2026                   Middlesex          NJ   Dept of Highways

            Flooding on US 1 Southbound At Raymond Rd
            (South Brunswick Twp), ramp lane closed.

&&

MPS

Preliminary Local Storm Report
National Weather Service Mount Holly NJ
120 PM EDT Thu Aug 27 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0110 PM     Tstm Wnd Dmg     Glassboro               39.71N 75.11W
08/27/2026                   Gloucester         NJ   Fire Dept/Rescue

            Tree down blocking roadway. Time estimated
            from radar.

&&

MJG