Areal Flood Advisory 354, NWS Philadelphia/Mount Holly

Area Forecast Discussion
National Weather Service Mount Holly NJ
933 AM EST Fri Dec 21 2018

.SYNOPSIS...
Low pressure stretched along the Appalachians this morning will move
northward through tonight. An associated cold front will cross our
area by daybreak Saturday. High pressure will build into the region
Saturday into Sunday, then two weak clipper systems may track near
our region Sunday night and Tuesday night. High pressure then builds
in especially for Wednesday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Radar trends and high-res models suggest heavy rainfall will be
confined to the New Jersey coastal areas for the rest of the
morning. Rain will taper to scattered showers from west to east
during the course of the day, and some instability later this
afternoon may support isolated thunder. A rather warm start to the
day with many areas experiencing temperatures into the 60s.

From the 351 AM discussion...
A full-latitude trough from the Midwest to the Gulf of Mexico will
gradually shift eastward today. An intense wind field is associated
with this feature, with a 120-knot 500 mb jet rounding the base of
the trough and starting to lift up the eastern side. The combination
of the robust wind field and strong low-level warm air advection and
short wave energy is resulting in large scale ascent and therefore
periods of rain this morning. An analysis early this morning shows
an axis of precipitable water nearing 2 inches advecting across much
of our region. This will result in times of heavy rain, especially
within any convective elements. There is some weak instability
working northward across Delmarva, and therefore some embedded
thunder is possible this morning especially near and east of I-95.
As the main low-level jet and associated strong warm air advection
lifts north of our area, the rain is expected to lessen and become
more showery by midday especially as a dry slot arrives this
afternoon. The heavy rain can lead to some flooding with some
impacts for the morning commute. Given the strength of the wind
field, the rain/showers are moving quite rapidly therefore this may
lessen the heavy rain threat and reduce any persistent training.
Some training though of heavier cells will result in locally heavier
rain with an enhanced flood threat, and this may be closer to the
coast through about midday.

As we go through the afternoon, some additional showers are expected
however this may shift westward some as the midlevel feature
approaches and the dry slot moves through. Some cooling aloft may
also result in some low-topped convection to our west or southwest
that could arrive into parts of our region later this afternoon into
the early evening. It is not all that clear how much instability
could develop and whether or not it will be enough to result in some
lightning.

The strong wind field coupled with a much warmer boundary layer
across much of the area is resulting in gusty winds. The strongest
winds have been mostly from the Philadelphia metro on south and
eastward, with some gusts to around 50 mph noted earlier. While all
areas within the wind advisory area may not technically reach
criteria, given the robust wind field and mixing we will maintain
the advisory through mid-morning.

As for the temperatures, a rather mild day is expected. A model
blend including the LAMP guidance was used for the hourly
temperatures, and high temperatures are mainly a MOS blend.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
The upper-level trough will move across the East tonight and start
to lift out as a 120-knot 500 mb jet lifts up its east side. This
will take deepening surface low pressure into eastern Canada, with
its trailing cold front crossing our area late tonight and early
Saturday morning. Associated with the trough axis and a ribbon of
lift, showers should be more active across the western areas in the
evening then taper off through the night. Cold enough air may not
arrive into the Poconos until after the showers end.

As for Saturday, low pressure moves farther away however a tight
pressure gradient will be present. Some cooling occurs and this will
allow more efficient mixing especially as the boundary layer warms
some. The forecast soundings show about 30 knots of wind present to
mix down, therefore have peak wind gusts very near this. Given the
cyclonic flow and residual moisture, there may be a fair amount of
clouds around until some drier air arrives toward evening. High
temperatures are a multi-model/continuity blend.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Winds will diminish quickly Saturday evening and into the overnight
hours. Flow aloft turns zonal through the beginning of the week,
however a couple shortwave troughs are forecast to pass quickly
across our region amid this flow regime, one being Sunday night and
the other being Tuesday night. These are expected to bring couple of
clipper systems across the region. At this time, guidance varies on
the intensity and placement of these features and therefore how much
precipitation, if any, they produce. That being said, even the
higher end of the guidance is not very robust with accumulations.
Therefore, kept PoPs considerably low for both systems given lack of
confidence at this point. Thermal profiles will support mostly snow
toward the north and mostly rain toward the south with a rain/snow
mix somewhere along I-95. Sensible weather will remain seasonable
and fair between these systems.

High pressure builds in Wednesday under a ridge amplifying across
the eastern US. This will clear things out for our area and bring in
some colder and drier air. Another shortwave approaches the area
Thursday bringing an increasing chance for showers throughout the
day and the potential for widespread rainfall again by Thursday
night into Friday. Temperatures will remain largely around normal
through the entire extended period.

&&

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

Today...MVFR/IFR ceilings with visibilities varying from VFR to IFR
at times this morning with periods of rain at varying intensity. The
rain becomes more showery through the day and should tend to
decrease in coverage. Some thunder possible this morning and then
again later this afternoon, however the coverage looks to be limited
and therefore not included in the TAFs. Southeast to south winds 10-
15 knots with gusts up to 30 knots (highest especially closer to the
coast), then diminishing by later this morning and through the
afternoon.

Tonight...MVFR/IFR ceilings may improve to VFR for a time with
showers ending. South to southwest winds around 10 knots, becoming
west and increasing some toward daybreak Saturday. Low confidence
regarding the ceiling heights.

Saturday...Mainly VFR and drying out. West-northwest winds winds 15-
20 knots with gusts to around 30 knots.

OUTLOOK... Saturday night...VFR. West-northwest winds diminishing to
10 knots or less.

Sunday and Monday...Mainly VFR. However, some rain and/or snow
showers possible Sunday night into Monday.

Tuesday...VFR expected. However, some light rain and/or snow showers
will be possible Tuesday night.

&&

.MARINE...
A Small Craft Advisory is now in effect for Delaware Bay and the
adjacent Atlantic Coastal waters. The advisory goes through tonight
for now, as there is some potential for some gales during Saturday.

From the 351 AM discussion... Despite a robust wind field, strong
low-level warm air advection is reducing the depth of mixing. Some
coastal wind gusts have been to gale force while farther offshore
the mixing thus far has been less. We will keep the Gale Warning
going for now, expiring from south to north starting at 7 AM.
Locally stronger winds are possible with heavier showers or a
thunderstorm. A Small Craft Advisory will then be needed following
the gales, however there may be a period of low- end gale force
gusts Saturday afternoon.

OUTLOOK... Saturday night...SCA conditions expected through the
evening hours with winds and seas subsiding to below SCA conditions
through the overnight hours.

Sunday and Sunday night...Sub-SCA conditions are expected.

Monday and Monday night...SCA conditions possible later in the
afternoon and evening hours.

Tuesday and Tuesday night...Sub-SCA conditions expected with winds
diminishing through the day.

&&

.HYDROLOGY...
On average, the heaviest precipitation is expected to fall through
early this afternoon. Regardless of model, they all show tropical
connectivity, a convective contribution, and well above normal PW's
for this time of year.

Total rainfall amounts of 1.5-3.0 inches are expected. Locally
higher amounts are possible, especially if any thunderstorms and
training occur. These amounts can be broken down further...1.50 to
2.50 inches south of the PA Turnpike and I-195 in NJ and 2.0 to 3.0
inches to the north.

Rainfall across specific basins...

Passaic - 2.50 to 3.00" Raritan - 2.00 to 3.00" Delaware north of
Trenton - 2.00 to 3.00" Delaware south of Trenton - 1.75 to 2.75"
Schuylkill and the rest of SE PA - 1.75 to 2.00"

Even without thunderstorms, a long duration rainfall event is
expected to lead to significant rises on many local creeks and
streams and even the larger rivers. The latest forecasts from MARFC
indicate that around 15 forecast points/gauges will reach at least
caution stage and a few (namely, Pine Brook, Macopin Dam, Boonton
below the dam, Pemberton, and Blackwells Mills) will reach flood
stage.

The Flood Watch continues. Nuisance poor drainage/low lying flooding
first followed by stream/river flooding, assuming the expected
rainfall comes to fruition. And if river flooding does occur, it
could likely last into the next week.

We fielded questions yesterday regarding our mainstem rivers.
Assuming the expected rainfall comes to fruition, portions of the
Passaic are the most likely to exceed flood stage followed by
portions of the Raritan. As of this afternoon, the heaviest rain is
forecast across the Passaic basin. As a result, moderate to major
flooding is possible. The last time portions of the Passaic River
experienced major flooding was during 2011 with Irene and Lee. The
flooding threat isn't as high for the Schuylkill or Delaware rivers.
At the moment, we are not seeing water levels reaching flood stage
on either river, but we can't rule out some locations getting as
high as action/caution stage.

A bit more regarding the Delaware...although water levels are not
expected to rise to flood stage at this time (signifying widespread
minor flooding), some nuisance flooding would be possible if some
gauges reach caution stage. When the Delaware runs high, it could
hinder/slow down flow on the Lehigh causing water levels to run a
bit higher. This could cause spotty minor flooding near and around
Easton. Further south, River Road in Pohatcong Township on the NJ
side is a low spot that can see some water as could PA 32 in Yardley
Borough.

The main message here is to keep an eye on future forecasts. Our
crests our dependent on rainfall. So if there is a shift in the
heavy rain, flooding will be worse in different locations that we
are currently highlighting (e.g. - the more significant flood
concerns in NJ attm could shift west if the axis of heavier rain
shifts west).

&&

.TIDES/COASTAL FLOODING...
The latest model forecasts continue to show minor to moderate
flooding for most locations on the Atlantic coast, Delaware Bay, and
tidal Delaware River around the time of high tide today. We remain
concerned that models are generally underforecasting tidal levels
during the high tide, as a result of a typical low bias models
exhibit in these regimes and the lack of accounting for expected
rainfall.
The ESTOFS continues to trend higher than the ETSS, and the forecast
remains slightly higher than the ESTOFS because of the above-
mentioned concerns.

The most likely locations to reach moderate flooding are coastal
portions of Middlesex and Monmouth Counties, where a coastal Flood
Warning remains in effect this mornings high tide. Other locations
may require warnings should confidence increase in moderate
flooding; locations of greatest concern are Cape May and Delaware
Bay, given the favorable southeasterly surface flow. For now,
though, a Coastal Flood Advisory remains in effect for the
central/southern New Jersey coast, the Delaware Atlantic coast,
Delaware Bay, and the tidal Delaware River for the Friday daytime
high tide.

For the eastern shores of Chesapeake Bay, minor flooding is still a
possibility, but most models remain under advisory levels during the
high tide Friday.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Flood Watch through late tonight for PAZ054-055-060>062-070-
     071-101>106.
     Coastal Flood Advisory until 2 PM EST this afternoon for
     PAZ070-071-106.
NJ...Flood Watch through late tonight for NJZ001-007>010-012>027.
     Coastal Flood Advisory until 10 AM EST this morning for
     NJZ020>027.
     Coastal Flood Advisory until 11 AM EST this morning for NJZ016.
     Coastal Flood Advisory until 2 PM EST this afternoon for
     NJZ015-017>019.
     Coastal Flood Warning until 11 AM EST this morning for
     NJZ012>014.
DE...Flood Watch through late tonight for DEZ001>004.
     Coastal Flood Advisory until 10 AM EST this morning for
     DEZ002>004.
     Coastal Flood Advisory until 11 AM EST this morning for DEZ001.
MD...Flood Watch through late tonight for MDZ008-012-015-019-020.
MARINE...Small Craft Advisory until 6 AM EST Saturday for ANZ430-431-
     450>455.

&&

Synopsis...Franklin
Near Term...Franklin
Short Term...Gorse
Long Term...Staarmann
Aviation...Gorse/MPS/Staarmann
Marine...Franklin/Gorse/MPS
Hydrology...
Tides/Coastal Flooding...

Hazardous Weather Outlook
National Weather Service Mount Holly NJ
1101 AM EST Fri Dec 21 2018

NJZ001-007>010-PAZ054-055-060>062-101>105-221615-
Sussex-Warren-Morris-Hunterdon-Somerset-Carbon-Monroe-Berks-Lehigh-
Northampton-Western Chester-Eastern Chester-Western Montgomery-
Eastern Montgomery-Upper Bucks-
1101 AM EST Fri Dec 21 2018

...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...This afternoon and tonight.

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

   Flood Watch.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

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.

NJZ015-017>019-PAZ070-071-106-221615-
Mercer-Gloucester-Camden-Northwestern Burlington-Delaware-
Philadelphia-Lower Bucks-
1101 AM EST Fri Dec 21 2018

...COASTAL FLOOD ADVISORY IN EFFECT UNTIL 2 PM EST THIS AFTERNOON...
...FLOOD WATCH IN EFFECT THROUGH LATE TONIGHT...

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

.DAY ONE...This afternoon and tonight.

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

   Flood Watch.
   Coastal Flood Advisory.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

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.

DEZ001-NJZ016-221615-
New Castle-Salem-
1101 AM EST Fri Dec 21 2018

...COASTAL FLOOD ADVISORY IN EFFECT UNTIL NOON EST TODAY...
...FLOOD WATCH IN EFFECT THROUGH LATE TONIGHT...

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

.DAY ONE...This afternoon and tonight.

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

   Flood Watch.
   Coastal Flood Advisory.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

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.

DEZ002>004-NJZ012>014-020>027-221615-
Kent-Inland Sussex-Delaware Beaches-Middlesex-Western Monmouth-
Eastern Monmouth-Ocean-Cumberland-Atlantic-Cape May-
Atlantic Coastal Cape May-Coastal Atlantic-Coastal Ocean-
Southeastern Burlington-
1101 AM EST Fri Dec 21 2018

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

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

.DAY ONE...This afternoon and tonight.

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

   Flood Watch.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

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.

MDZ008-012-015-019-020-221615-
Cecil-Kent MD-Queen Annes-Talbot-Caroline-
1101 AM EST Fri Dec 21 2018

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

This Hazardous Weather Outlook is for northeast Maryland.

.DAY ONE...This afternoon and tonight.

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

   Flood Watch.

Some minor coastal flooding is possible today.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

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.

ANZ450>453-221615-
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-
1101 AM EST Fri Dec 21 2018

This Hazardous Weather Outlook is for Atlantic coastal waters.

.DAY ONE...This afternoon and tonight.

There is a low probability of widespread hazardous weather.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

Gale force wind gusts are possible on Saturday.

.SPOTTER INFORMATION STATEMENT...

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

ANZ430-431-454-455-221615-
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 Cape May NJ to Cape Henlopen DE out 20 nm-
Coastal waters from Cape Henlopen to Fenwick Island DE out 20 nm-
1101 AM EST Fri Dec 21 2018

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

.DAY ONE...This afternoon and tonight.

There is a low probability of widespread hazardous weather.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

Gale force wind gusts are possible on Saturday.

.SPOTTER INFORMATION STATEMENT...

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

CMS

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1121 AM EST FRI DEC 21 2018

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

1115 AM     FLOOD            2 ESE ROXBOROUGH        39.99N 75.19W
12/21/2018                   PHILADELPHIA       PA   PUBLIC

            KELLY DRIVE EASTBOUND CLOSED BETWEEN
            STRAWBERRY MANSION DRIVE AND FOUNTAIN GREEN
            DRIVE DUE TO FLOODING. REPORT VIA SOCIAL
            MEDIA.

&&

CMS

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1126 AM EST FRI DEC 21 2018

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

1115 AM     FLOOD            1 ESE BRANCHBURG TWP    40.56N 74.69W
12/21/2018                   SOMERSET           NJ   OTHER FEDERAL

            THE NORTH BRANCH RARITAN RIVER GAUGE IN
            SOUTH BRANCH REACHED FLOOD STAGE.

&&

CMS

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1143 AM EST FRI DEC 21 2018

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

1045 AM     HEAVY RAIN       2 NNW NEFFS             40.72N 75.63W
12/21/2018  M1.65 INCH       LEHIGH             PA   TRAINED SPOTTER

&&

CMS

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1146 AM EST FRI DEC 21 2018

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

1124 AM     FLOOD            1 SSW ANCIENT OAKS      40.54N 75.59W
12/21/2018                   LEHIGH             PA   TRAINED SPOTTER

            SPRING CREEK ROAD CLOSED FROM FLOODING OF
            THE LITTLE LEHIGH CREEK. STORM TOTAL 2.35
            INCHES.

&&

CMS