Flash Flood Warning 66, NWS Philadelphia/Mount Holly

Area Forecast Discussion
National Weather Service Mount Holly NJ
1054 AM EDT Sat Aug 11 2018

.SYNOPSIS...
A nearly stationary boundary will remain near or in the northern Mid-
Atlantic through early next week, with a series of surface lows
developing and moving along the front. A stronger low will push the
front out to sea on Tuesday. A backdoor cold front may approach the
northern Mid-Atlantic Wednesday or Thursday before a cold front
moves in from the west late this week into the following
weekend.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
The first round of showers and thunderstorms will continue to
exit far northeast Pennsylvania and northern New Jersey this
morning as the first of several short wave/vorticity impulses
moves to our northeast. A break in action will occur for most of
the area for the remainder of this morning and into the early
afternoon behind this disturbance. However, showers and
thunderstorms will develop once again through this afternoon as
additional short waves/vorticity impulses move across the area.

Cold front continues to slowly sag southward into the region
today, which will also help focus the showers and thunderstorms
this afternoon. CAPE values remain elevated and will generally
be on the order of 500-1000 J/kg with some higher amounts across
southern New Jersey, Delaware, and eastern shore of Maryland.
Also, PW values are expected to increase to around 2 inches by
this afternoon. There will still not be much in the way of 0-6
km shear, so the concern remains for several rounds of slow
moving showers and thunderstorms producing heavy rainfall.
Although any thunderstorms that build high enough could produce
some locally gusty winds.

We have decided to expand the Flash Flood Watch farther south
and west across much of the rest of Delaware, Maryland, and New
Jersey as they could see some heavier rains that could train
this afternoon and evening as well.

Much cooler today behind the cold front, as highs today will be
in the 70s in the southern Poconos and far northern NJ, and
otherwise mostly in the low to mid 80s. Across southern NJ and
Delmarva, which will still be in the warm sector, highs may
approach 90.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY NIGHT/...
Weak low pressure slowly moves through the region this evening.
Showers and thunderstorms will continue through the evening hours,
and the Flash Flood Watch is in effect until 1 am tonight.

Based on latest model QPF output, there appears to be a lull in the
precip from just after midnight tonight until daybreak Sunday, but
will carry chance PoPs to close out the period.

Another warm and muggy night on tap.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
Overall, little change to the previous forecast and thinking for the
long-term period.

The overall model suite is in decent agreement through Tuesday, but
the smaller-scale details regarding convective evolution Sunday
through Tuesday will likely lack much clarity until the near-term
(within 24 hours of the event(s)). The synoptic-scale pattern in
place, however, is quite favorable for several cycles of convection,
aided by warm/moist air transport downstream of a slow-moving upper
low in the eastern Ohio Valley and central Appalachians Sunday and
Monday. Hi-res models (with varying degrees of support from the
larger-scale models) appear to be favoring the central/southern CWA
for more numerous storms Sunday, with the quasi-stationary boundary
sagging southward with time. This makes sense given contributions
from antecedent convective outflows and the large-scale digging of
the upper low during this period. Additionally, upper-level
divergence from a downstream 250-mb jet streak in southern New
England would be positioned in southern NJ and Delmarva.
Nevertheless, would like to see more agreement among the hi-res
simulations regarding the convective evolution before making the
move to increase PoPs in the south and decrease (somewhat) in the
north. PWs will be near 2 inches on Sunday, so locally heavy rain
with any storms is certainly a threat.

The 00Z NAM provides a particularly troubling picture of the heavy
rain potential on Monday. The upper low pivots to a more north-south
orientation as a vort max ejects from the base of the larger-scale
trough. A 250-mb jet streak intensifies downstream along the spine
of the Appalachians, aiding in the development/intensification of a
surface low in vicinity of the lee of the Appalachians in the
central/southern Mid-Atlantic. Deep large-scale lift develops to the
north of the low in a region of strong theta-e advection and upslope
flow coincident to the nose of the strengthening jet streak. The NAM
produces widespread 2-3+ inch totals in central/eastern PA
(generally west of the Fall Line). The GFS/ECMWF/CMC are not as
aggressive (though the coarser resolution has at least some role in
this); however, the 00Z ECMWF does look reasonably similar in the
precipitation evolution during this period. With continued favorable
thermal/moist profiles for heavy rain, this is most certainly a
period to watch.

Upper low swings eastward on Tuesday, but the attendant cold air
aloft will be favorable for diurnal convection across some/most of
the area. PoPs maintained/increased a little bit (especially
north/west of the urban corridor, where topographic effects may
provide additional lift).

Wednesday and Thursday look a little drier, though cannot rule out
precipitation entirely owing to the apparent approach of a backdoor
cold front during this period. The dry look of the CMC/ECMWF
necessitate keeping PoPs maxed at slight-chance during this period.
Additionally, think increasing temperatures is a must owing to the
potential for more diabatic heating with increased sunshine.

Another system appears to approach the area late in the week, but
timing differences among the models are quite large by this point.
Given the evolution of extratropical transition in the Pacific
during the coming week, think slow/amplified flow downstream in
North America is preferred. Would think the slower ECMWF is the more
likely outcome during this period as a result, which means precip
chances may be higher the following weekend as opposed to Friday.
Given the uncertainty, kept slight-chance to low-chance PoPs during
this period for now.

&&

.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Today...A few hours for late this morning into the early
afternoon of VFR conditions is now expected as the first round
of showers and thunderstorms has exited the area. However,
additional showers an thunderstorms will develop through the
remainder of the morning, but especially this afternoon. The
showers and thunderstorms will likely temporarily lead to MVFR
or even IFR conditions this afternoon into this evening.
Generally light and variable winds for much of today, although
any direction is expected to be southerly across southern New
Jersey and central/southern Delaware and Maryland. The rest of
the area will likely see mostly east or southeast wind
directions this afternoon

Tonight...Showers and thunderstorms taper off in the evening. There
is the potential for sub-VFR conditions, especially after midnight,
but it all depends on where the heavy rain falls. Low confidence in
sub-VFR conditions. LGT/VRB to nearly calm winds.

OUTLOOK...

Sunday through Tuesday: Predominantly VFR, though sub-VFR CIGs/VSBYs
possible with scattered showers/storms through the period. In
addition, may see more prolonged sub-VFR CIGs during the nighttime
hours. Winds generally east or northeast 5 to 10 kts through Monday
becoming more westerly/southwesterly Monday night and Tuesday.
Low confidence.

Tuesday night and Wednesday: Generally VFR with west or northwest
winds 5 to 15 kts. Low confidence.

&&

.MARINE...
Sub-SCA conditions on the waters today. Showers and
thunderstorms will impact the waters with reduced VSBYs, locally
gusty winds, and lightning strikes into this evening.

OUTLOOK...

Sunday through Wednesday: Sub-advisory winds/seas expected, though
will need to watch winds/seas on Monday and Tuesday given potential
for a surface low to develop near the coast. Showers/thunderstorms
are possible each day, with locally higher winds/waves to be
expected in their proximity.

Rip Currents...

There is a low risk for the development of dangerous rip
currents at New Jersey and Delaware beaches today.

&&

.TIDES/COASTAL FLOODING...
The combination of the new moon and astronomically higher tides
will result in widespread minor coastal flooding tonight. The
main threat will occur with the high tide cycles this evening
and tonight, which is the higher of the two tide cycles. A
Coastal Flood Advisory is now in effect for all coastal areas,
the NJ and DE oceanfront, the back bays, Raritan Bay, Delaware
Bay, and the tidal Delaware River due to the widespread minor
coastal flooding anticipated tonight.

Depending on where the heavy rain falls today, this may
exacerbate the coastal flooding concerns tonight.

There remains the potential for minor coastal flooding with the
evening high tide cycles at least Sunday night, and possibly
Monday night as well.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Flash Flood Watch through late tonight for PAZ054-055-060>062-
     070-071-101>106.
     Coastal Flood Advisory from 1 AM to 5 AM EDT Sunday for PAZ070-
     071-106.
NJ...Flash Flood Watch through late tonight for NJZ001-007>010-
     012>022-025>027.
     Coastal Flood Advisory from 7 PM this evening to 1 AM EDT
     Sunday for NJZ012>014-020>027.
     Coastal Flood Advisory from 10 PM this evening to 2 AM EDT
     Sunday for NJZ016.
     Coastal Flood Advisory from 1 AM to 5 AM EDT Sunday for NJZ015-
     017>019.
DE...Flash Flood Watch through late tonight for DEZ001-002.
     Coastal Flood Advisory from 7 PM this evening to 1 AM EDT
     Sunday for DEZ002>004.
     Coastal Flood Advisory from 10 PM this evening to 2 AM EDT
     Sunday for DEZ001.
MD...Flash Flood Watch through late tonight for MDZ008-012-015.
MARINE...None.

&&

Synopsis...CMS
Near Term...Robertson/MPS
Short Term...MPS
Long Term...CMS
Aviation...CMS/Robertson/MPS
Marine...CMS/MPS
Tides/Coastal Flooding...

Hazardous Weather Outlook
National Weather Service Mount Holly NJ
433 AM EDT Sat Aug 11 2018

NJZ001-007>010-PAZ054-055-060>062-101>105-120845-
Sussex-Warren-Morris-Hunterdon-Somerset-Carbon-Monroe-Berks-Lehigh-
Northampton-Western Chester-Eastern Chester-Western Montgomery-
Eastern Montgomery-Upper Bucks-
433 AM EDT Sat Aug 11 2018

...FLASH FLOOD WATCH IN EFFECT THROUGH LATE TONIGHT...

This Hazardous Weather Outlook is for northern New Jersey,
northwest New Jersey, east central Pennsylvania, northeast
Pennsylvania and southeast Pennsylvania.

.DAY ONE...Today and Tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Flash Flood Watch.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

Heavy rain with any showers and thunderstorms could lead to
localized flooding Sunday and Monday.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

NJZ015-017>019-PAZ070-071-106-120845-
Mercer-Gloucester-Camden-Northwestern Burlington-Delaware-
Philadelphia-Lower Bucks-
433 AM EDT Sat Aug 11 2018

...FLASH FLOOD WATCH IN EFFECT THROUGH LATE TONIGHT...
...COASTAL FLOOD ADVISORY IN EFFECT FROM 1 AM TO 5 AM EDT SUNDAY...

This Hazardous Weather Outlook is for central New Jersey, southern
New Jersey and southeast Pennsylvania.

.DAY ONE...Today and Tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Flash Flood Watch.
   Coastal Flood Advisory.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

Minor tidal flooding is possible around the time of the evening high
tide on Sunday.

Heavy rain with any showers and thunderstorms could lead to
localized flooding Sunday and Monday.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

DEZ001-NJZ016-120845-
New Castle-Salem-
433 AM EDT Sat Aug 11 2018

...FLASH FLOOD WATCH IN EFFECT THROUGH LATE TONIGHT...
...COASTAL FLOOD ADVISORY IN EFFECT FROM 10 PM THIS EVENING TO 2 AM
EDT SUNDAY...

This Hazardous Weather Outlook is for northern Delaware and
southern New Jersey.

.DAY ONE...Today and Tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Flash Flood Watch.
   Coastal Flood Advisory.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

Minor tidal flooding is possible around the time of the evening high
tide on Sunday.

Heavy rain with any showers and thunderstorms could lead to
localized flooding Sunday and Monday.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

NJZ012>014-120845-
Middlesex-Western Monmouth-Eastern Monmouth-
433 AM EDT Sat Aug 11 2018

...FLASH FLOOD WATCH IN EFFECT THROUGH LATE TONIGHT...
...COASTAL FLOOD ADVISORY IN EFFECT FROM 7 PM THIS EVENING TO 1 AM
EDT SUNDAY...

This Hazardous Weather Outlook is for central New Jersey and
northern New Jersey.

.DAY ONE...Today and Tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Flash Flood Watch.
   Coastal Flood Advisory.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

Minor tidal flooding is possible around the time of the evening high
tide on Sunday.

Heavy rain with any showers and thunderstorms could lead to
localized flooding Sunday and Monday.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

DEZ002>004-NJZ020>027-120845-
Kent-Inland Sussex-Delaware Beaches-Ocean-Cumberland-Atlantic-
Cape May-Atlantic Coastal Cape May-Coastal Atlantic-Coastal Ocean-
Southeastern Burlington-
433 AM EDT Sat Aug 11 2018

...COASTAL FLOOD ADVISORY IN EFFECT FROM 7 PM THIS EVENING TO 1 AM
EDT SUNDAY...

This Hazardous Weather Outlook is for central Delaware, southern
Delaware and southern New Jersey.

.DAY ONE...Today and Tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Coastal Flood Advisory.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

Minor tidal flooding is possible around the time of the evening high
tide on Sunday.

Heavy rain with any showers and thunderstorms could lead to
localized flooding Sunday and Monday.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

MDZ008-012-015-019-020-120845-
Cecil-Kent MD-Queen Annes-Talbot-Caroline-
433 AM EDT Sat Aug 11 2018

This Hazardous Weather Outlook is for northeast Maryland.

.DAY ONE...Today and Tonight.

The probability of widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

Heavy rain with any showers and thunderstorms could lead to
localized flooding Sunday and Monday.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

ANZ430-431-450>455-120845-
Delaware Bay waters north of East Point NJ to Slaughter Beach DE-
Delaware Bay waters south of East Point NJ to Slaughter Beach DE-
Coastal waters from Sandy Hook to Manasquan Inlet NJ out 20 nm-
Coastal waters from Manasquan Inlet to Little Egg Inlet NJ out 20 nm-
Coastal waters from Little Egg Inlet to Great Egg Inlet NJ out 20 nm-
Coastal waters from Great Egg Inlet to Cape May NJ out 20 nm-
Coastal waters from Cape May NJ to Cape Henlopen DE out 20 nm-
Coastal waters from Cape Henlopen to Fenwick Island DE out 20 nm-
433 AM EDT Sat Aug 11 2018

This Hazardous Weather Outlook is for Atlantic coastal waters and
Delaware Bay Waters.

.DAY ONE...Today and Tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

CMS

Special Weather Statement
National Weather Service Mount Holly NJ
242 PM EDT SAT AUG 11 2018

NJZ009-015-PAZ061-062-105-106-111915-
Hunterdon-Mercer-Lower Bucks-Upper Bucks-Lehigh-Northampton-
242 PM EDT SAT AUG 11 2018

...A LINE OF STRONG THUNDERSTORMS WILL AFFECT SOUTHERN HUNTERDON...
NORTHWESTERN MERCER...SOUTHEASTERN LEHIGH...NORTHWESTERN BUCKS AND
SOUTH CENTRAL NORTHAMPTON COUNTIES...

At 241 PM EDT, radar indicated strong thunderstorms were located
along a line extending from near Zionsville to Lumberville. Movement
was northeast at 20 mph.

Winds up to 45 mph and pea size hail are possible with these storms.

Locations impacted include...
Bethlehem, Quakertown, Perkasie, Byram, Bedminster, Hellertown,
Flemington, Tinicum, New Hope, Dublin, Ferndale, Frenchtown, Milford,
Riegelsville, Stockton, Pleasant Valley, Revere, Zionsville,
Lumberville and Ottsville.

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

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

These storms 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 4032 7482 4031 7505 4039 7535 4048 7554
      4064 7529 4062 7520 4059 7519 4061 7516
      4057 7497 4049 7480
TIME...MOT...LOC 1841Z 238DEG 21KT 4049 7543 4039 7506

JRK

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
244 PM EDT SAT AUG 11 2018

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

0234 PM     FLOOD            PENCOYD                 40.01N  75.21W
08/11/2018                   MONTGOMERY         PA   DEPT OF HIGHWAYS

            FLOODING ON I-76 WESTBOUND AT EXIT 339.

&&

EVENT NUMBER PHI1801239

STAARMANN

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
250 PM EDT SAT AUG 11 2018

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

1111 AM     FLOOD            1 ESE BRIDLE RUN        40.32N  75.30W
08/11/2018                   BUCKS              PA   DEPT OF HIGHWAYS

            FLOODING IMPACTING BOTH DIRECTIONS OF PA 113 AT
            BETHLEHEM PIKE.

&&

EVENT NUMBER PHI1801240

STAARMANN

Special Weather Statement
National Weather Service Mount Holly NJ
258 PM EDT SAT AUG 11 2018

NJZ016-021-111945-
Salem-Cumberland-
258 PM EDT SAT AUG 11 2018

...A STRONG THUNDERSTORM WILL AFFECT NORTHEASTERN CUMBERLAND AND EAST
CENTRAL SALEM COUNTIES...

At 258 PM EDT, a strong thunderstorm was located over Fairton, or
over Bridgeton, moving northeast at 15 mph.

Winds up to 45 mph are possible with this storm.

This storm will be near...
  Millville around 315 PM EDT.
  Seabrook Farms around 325 PM EDT.
  Rosenhayn around 335 PM EDT.
  Olivet and South Vineland around 340 PM EDT.
  Vineland around 345 PM EDT.

Other locations impacted by this storm include Centerton.

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

Frequent cloud to ground lightning is also 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 3936 7517 3934 7519 3937 7523 3936 7524
      3938 7526 3940 7529 3960 7513 3942 7490
TIME...MOT...LOC 1858Z 222DEG 12KT 3940 7523

JRK

Special Weather Statement
National Weather Service Mount Holly NJ
313 PM EDT SAT AUG 11 2018

NJZ007-009-PAZ061-062-105-112000-
Hunterdon-Warren-Upper Bucks-Lehigh-Northampton-
313 PM EDT SAT AUG 11 2018

...A LINE OF STRONG THUNDERSTORMS WILL AFFECT CENTRAL HUNTERDON...
SOUTHWESTERN WARREN...SOUTHEASTERN LEHIGH...NORTHWESTERN BUCKS AND
SOUTHEASTERN NORTHAMPTON COUNTIES...

At 312 PM EDT, radar indicated strong thunderstorms were located
along a line extending from near Zionsville to near Revere. Movement
was northeast at 15 mph.

Winds up to 45 mph and pea size hail are possible with these storms.

Locations impacted include...
Allentown, Easton, Bethlehem, Emmaus, Quakertown, Wilson, Bedminster,
Hellertown, Flemington, Tinicum, High Bridge, Clinton, Alpha, Glen
Gardner, Ferndale, Hampton, Frenchtown, Lebanon, West Easton and
Milford.

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

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

These storms 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 4064 7473 4046 7492 4040 7528 4035 7537
      4047 7557 4055 7552 4065 7532 4070 7513
      4070 7485
TIME...MOT...LOC 1912Z 211DEG 11KT 4047 7546 4053 7512

JRK

Special Weather Statement
National Weather Service Mount Holly NJ
324 PM EDT SAT AUG 11 2018

NJZ017-021>025-112015-
Coastal Atlantic-Cumberland-Atlantic-Atlantic Coastal Cape May-Cape
May-Gloucester-
324 PM EDT SAT AUG 11 2018

...A LINE OF STRONG THUNDERSTORMS WILL AFFECT ATLANTIC...EASTERN
CUMBERLAND...SOUTHERN GLOUCESTER AND NORTHERN CAPE MAY COUNTIES...

At 324 PM EDT, radar indicated strong thunderstorms were located
along a line extending from Dividing Creek to near Marmora. Movement
was northeast at 20 mph.

Winds up to 45 mph and pea size hail are possible with these storms.

Locations impacted include...
Vineland, Atlantic City, Millville, Ocean City, Cumberland,
Pleasantville, Somers Point, Ventnor City, Brigantine, Northfield,
Absecon, Margate City, Buena, Egg Harbor City, Laurel Lake, Weymouth,
Woodbine, Sea Isle City, Estell Manor and Newfield.

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

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

These storms 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 3939 7437 3930 7454 3930 7462 3933 7468
      3927 7459 3929 7455 3918 7467 3917 7468
      3918 7468 3921 7516 3925 7520 3956 7502
      3950 7440 3944 7439 3941 7440 3944 7435
      3948 7438 3949 7431
TIME...MOT...LOC 1924Z 215DEG 16KT 3927 7509 3923 7465

JRK