Severe Thunderstorm Warning 309, NWS Philadelphia/Mount Holly

934 
WWUS51 KPHI 172307
SVSPHI

Severe Weather Statement
National Weather Service Mount Holly NJ
Issued by National Weather Service Baltimore MD/Washington DC
707 PM EDT Mon Aug 17 2026

DEC003-PAC029-045-172330-
/O.CON.KPHI.SV.W.0309.000000T0000Z-260817T2330Z/
New Castle DE-Chester PA-Delaware PA-
707 PM EDT Mon Aug 17 2026

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 730 PM EDT
FOR NORTHWESTERN NEW CASTLE...CENTRAL CHESTER AND SOUTHWESTERN
DELAWARE COUNTIES...

At 706 PM EDT, a severe thunderstorm was located over Marshallton, or
near West Chester, moving southeast at 25 mph.

HAZARD...60 mph wind gusts.

SOURCE...Radar indicated.

IMPACT...Damage to roofs, siding, trees, and power lines is 
         possible.

Locations impacted include...
West Chester, Coatesville, Westtown, Downingtown, Kennett Square,
Parkesburg, West Grove, Cheyney, Landenberg, Elam, Lionville,
Marshallton, Concordville, Lionville-Marchwood, North Star, West
Goshen, South Coatesville, Avondale, Modena, and Exton.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Frequent cloud to ground lightning is occurring with this storm. Move
indoors immediately. Lightning is one of nature's leading killers.
Remember, if you can hear thunder, you are close enough to be struck
by lightning.

Torrential rainfall is occurring with this storm, and may lead to
flash flooding. Do not drive your vehicle through flooded roadways.

&&

LAT...LON 3999 7594 4012 7568 4001 7558 3985 7546
      3983 7547 3984 7553 3984 7560 3983 7565
      3980 7571 3976 7575 3972 7578 3977 7581
TIME...MOT...LOC 2306Z 324DEG 21KT 3994 7573 

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...<.75 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$
EST

288 
WWUS51 KPHI 172317
SVSPHI

Severe Weather Statement
National Weather Service Mount Holly NJ
Issued by National Weather Service Baltimore MD/Washington DC
717 PM EDT Mon Aug 17 2026

DEC003-PAC029-045-172326-
/O.CAN.KPHI.SV.W.0309.000000T0000Z-260817T2330Z/
New Castle DE-Chester PA-Delaware PA-
717 PM EDT Mon Aug 17 2026

...THE SEVERE THUNDERSTORM WARNING FOR NORTHWESTERN NEW CASTLE...
CENTRAL CHESTER AND SOUTHWESTERN DELAWARE COUNTIES IS CANCELLED...

The storm which prompted the warning has weakened below severe
limits, and no longer poses an immediate threat to life or property.
Therefore, the warning has been cancelled.  However gusty winds and
heavy rain are still possible with this thunderstorm.

To report severe weather, contact your nearest law enforcement
agency. They will relay your report to the National Weather Service
Mount Holly NJ.

LAT...LON 3999 7594 4012 7568 4001 7558 3985 7546
      3983 7547 3984 7553 3984 7560 3983 7565
      3980 7571 3976 7575 3972 7578 3977 7581
TIME...MOT...LOC 2313Z 327DEG 25KT 3988 7568 

$$

EST

Area Forecast Discussion
National Weather Service Mount Holly NJ
Issued by National Weather Service New York NY
225 PM EDT Mon Aug 17 2026

.WHAT HAS CHANGED...
No significant changes.

&&

.KEY MESSAGES...
1. A cold front passes through the region this evening.

2. Another cold front is expected to cross through the region
Wednesday night into Thursday resulting in additional shower
and thunderstorm chances. Likely remaining unsettled late
Friday into the first half of the weekend.

&&

.DISCUSSION...
KEY MESSAGE 1...A cold front will pass through the region this
evening. Most surface dew points will reside in the the lower half
of the 70s with elevated PWAT values. MLCAPE values will increase to
1000 to 1500, perhaps as high as 2000 J/kg. There remains through
the early evening the potential for some brief locally heavy rain.
Although shear will be limited and organized convection remains not
likely.

Behind the cold front temperatures and dew points will only fall
slightly later tonight. There may be areas of patchy fog in rural
locations, especially where any early evening showers take place
that would moisten the ground even further. High temperatures on
Tuesday will be just about identical to Monday, but dew points will
drop some with mainly lower and middle 60s further north, and upper
60s to around 70 well south. While warm, it should feel more
comfortable compared to Monday.

KEY MESSAGE 2...A cold front is expected to cross through the
region Wednesday night into Thursday resulting in more shower
and thunderstorm chances.

In the wake of tonight's cold front, weak high pressure will
briefly build into the region for Tuesday and much of Wednesday.
An upper-low will traverse portions of Ontario and Quebec
during this time, passing north of the region Wednesday night.
To the south of the upper-low, broad troughing will be in place
across much of the northeast, with a few embedded shortwaves
pivoting around the base of the trough. At the surface, a cold
front will begin to approach the area late Wednesday, and cross
through the region late Wednesday night into early Thursday.

Timing discrepancies remain with the frontal passage among the
model guidance. Some guidance indicates the front passing through
the region primarily during the overnight hours Wednesday night and
clearing the region Thursday morning, while there is some
guidance suggesting slower timing. At this point, timing
uncertainties limit confidence in whether or not there will be any
notable severe weather or flash flooding concerns, but this will
continue to be monitored in subsequent forecast cycles. If slower
solutions come to fruition then the chances of impacts from heavy
rain would increase. For now, PoPs peak in the high end chance - low
end likely range for the majority of the area Thursday.

Longer range NWP and AI guidance suggests that the pattern remains
unsettled later Friday and into the weekend as the front could get
hung up just south or even over the area with multiple areas of
weak low pressure riding along and mid-level troughing remaining in
place. PoPs currently are mainly in the chance to likely range each
day due to the present uncertainties in timing and placement of
these features and any progression in the long wave pattern. At this
time PoPs for this period are relatively higher further south and
east.

In terms of temps, Tuesday and Wednesday look to be fairly warm
with modestly increasing humidity. Highs look to be mainly in the
upper 80s to around 90. Temps currently look a bit cooler in
the wake of the front, with highs in the low to mid 80s and lows
in the upper 50s to mid 60s late this week and into the
weekend. Part of the reason for this will be due to more in terms
of cloud cover.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Today... A round of SHRA, perhaps a TSRA, may pass across the
terminals in the late afternoon/early evening with brief sub-VFR
conds. Will include PROB30 groups to handle this potential. NW
winds 5 to 10 kt. Moderate confidence.

Tonight...Lingering SHRA possible through 06Z or so. Generally
VFR outside of any SHRA. N-NW winds 5 to 10 kt. Moderate
confidence.

Outlook...

Tuesday through Wednesday...VFR. No sig wx expected.

Wednesday night through Friday...Periods of scattered showers
and perhaps storms are likely, with the greatest chance
currently appearing to be late Wednesday night into Thursday.
Sub-VFR conditions are possible with any showers or storms.

&&

.MARINE...
A few showers and thunderstorms possible early evening.

Seas subside to 2 to 4 feet as well. Thus, sub-SCA conditions
expected tonight.

Outlook...

Tuesday through Friday...No marine headlines currently
anticipated with winds under 25 kts and seas under 5 feet.
Scattered showers and perhaps storms could lead to periods of
visibility restrictions Wed night through a portion of Thu.
Another round of restricted visibilities are increasingly
likely late Friday into Saturday.

Rip Currents...

West winds at 10 to 15 mph this afternoon. Breaking waves will
average 1 to 2 feet. There will be an increasing southerly swell
with a 5 to 7 second period. This results in a LOW risk for the
development of dangerous and life threatening rip currents for
the Jersey Shore and Delaware Beaches.

For Tuesday, north-northeast winds 5 to 10 mph in the morning
will gradually turn to be more southerly at 5 to 10 mph in the
afternoon. Breaking waves will average 1 to 2 feet. There will
continue to be a southeasterly swell with a 6 to 8 second
period. The result of these conditions is a LOW risk for the
development of dangerous and life threatening rip currents for
the Jersey Shore and Delaware Beaches.

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

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...None.

&&

DISCUSSION...
AVIATION...
MARINE...

Hazardous Weather Outlook
National Weather Service Mount Holly NJ
316 AM EDT Mon Aug 17 2026

MDZ012-015-019-020-181000-
Kent MD-Queen Annes-Talbot-Caroline-
316 AM EDT Mon Aug 17 2026

This Hazardous Weather Outlook is for northeast Maryland.

.DAY ONE...Today and tonight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

MPS

Special Weather Statement
National Weather Service Mount Holly NJ
Issued by National Weather Service Baltimore MD/Washington DC
555 PM EDT Mon Aug 17 2026

MDZ012-015-172245-
Queen Anne's-Kent-
555 PM EDT Mon Aug 17 2026

...A STRONG THUNDERSTORM WILL AFFECT NORTHEASTERN QUEEN ANNE'S AND
KENT COUNTIES...

At 554 PM EDT, a strong thunderstorm was located over Betterton, or
10 miles southeast of Aberdeen Proving Ground, moving east at 25 mph.

Winds in excess of 40 mph and pea size hail are possible with this
storm.

Locations impacted include...
Chestertown, Millington, Sudlersville, Betterton, Newtown, Sassafras,
Morgnec, Massey, Crumpton, Kennedyville, Galena, and Kingstown.

Torrential rainfall is also occurring with this storm, and may cause
localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

LAT...LON 3929 7618 3929 7617 3932 7619 3934 7616
      3933 7614 3933 7613 3935 7614 3937 7611
      3937 7599 3936 7598 3937 7595 3936 7589
      3938 7582 3938 7578 3937 7576 3914 7575
      3925 7623 3926 7621
TIME...MOT...LOC 2154Z 289DEG 21KT 3934 7604

EST

Preliminary Local Storm Report
National Weather Service Mount Holly NJ
616 PM EDT Mon Aug 17 2026

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

0549 PM     Tstm Wnd Gst     Reading Regional Airpor 40.38N 75.97W
08/17/2026  M53 MPH          Berks              PA   ASOS

&&

Preliminary Local Storm Report
National Weather Service Mount Holly NJ
620 PM EDT Mon Aug 17 2026

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

0520 PM     Tstm Wnd Dmg     Jefferson Twp           40.44N 76.16W
08/17/2026                   Berks              PA   Fire Dept/Rescue

            Tree down on wires. Time estimated from
            radar.

&&

Preliminary Local Storm Report
National Weather Service Mount Holly NJ
621 PM EDT Mon Aug 17 2026

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

0529 PM     Tstm Wnd Dmg     Shoemakersville         40.50N 75.97W
08/17/2026                   Berks              PA   Fire Dept/Rescue

            Tree down on wires. Time estimated from
            radar.

&&

Preliminary Local Storm Report
National Weather Service Mount Holly NJ
624 PM EDT Mon Aug 17 2026

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

0533 PM     Tstm Wnd Dmg     Mohrsville              40.47N 75.98W
08/17/2026                   Berks              PA   Fire Dept/Rescue

            Multiple trees down, including one blocking
            a roadway. Time estimated from radar.

&&

Preliminary Local Storm Report
National Weather Service Mount Holly NJ
631 PM EDT Mon Aug 17 2026

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

0551 PM     Tstm Wnd Dmg     Wyomissing              40.33N 75.97W
08/17/2026                   Berks              PA   Fire Dept/Rescue

            Tree down. Time estimated from radar.

&&