NWS Philadelphia/Mount Holly wrote its last area forecast discussion before the first event at Apr 3, 6:43 PM EST, 1 hour 56 minutes earlier.
Area forecast discussion, Apr 3, 6:43 PM EST, 1 hour 56 minutes before
Area Forecast Discussion
National Weather Service Mount Holly NJ
743 PM EDT Wed Apr 3 2024
.SYNOPSIS...
A strong area of low pressure will continue across the northern
Middle Atlantic region tonight and then it will pass by Cape Cod
Thursday. After that, it will remain nearly stationary through
Friday. For Sunday into Monday, high pressure in place across
southern Canada noses down into the Mid Atlantic region. A warm
front may move into the area early next week.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
The system is presently crossing the area with gusty showers and
tstms and areas of heavy rains. Several severe thunderstorm
warnings and even a tornado warning were issued earlier. A
tornado watch that was in effect earlier was cancelled at 7 PM.
We have also canceled the High wind warning and the wind
advisory from earlier too. We will still have some gusty winds
perhaps up to 35 mph for a few more hours, but winds will trend
down overnight. Pops/wx grids and temps were adjusted too to
keep up with the trends.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
As we go into Thursday, low pressure will be moving into the
northeast states, while a second will be moving out of the Great
Lakes region. The second low will eventually be absorbed by the low
across the northeastern states later in the day Thursday into
Thursday night. Meanwhile, the mid-level low will drift across the
area through the day as well, which will bring cold air aloft into
the region. With the westerly flow across the area, along with the
weakening surface low and the cold mid-level low, low-mid level
lapse rates will increase significantly across the area. This will
combine with enhanced moisture to lead to not only rain showers
across the area, but there will be graupel/hail showers across much
of the area as well. There will also be a chance for some
thunder/lightning to occur with some of these showers during the day
as well. Any showers that develop during the day will begin to
diminish through the evening and overnight.
For Friday through Friday night, the low pressure will remain near
the northeast states, with a steady northwest flow across the area.
By Saturday and Saturday night, the low will begin shifting offshore
and out to sea. As the mid-level low pinwheels to our northeast as
well, multiple short wave/vorticity impulses will move across the
area, which will combine with some enhanced moisture across the area
and lead a chance of showers Friday into Saturday. Low-mid level
lapse rates will become steep again Friday afternoon, and with cold
temperatures aloft, there could once again be another round of
possible graupel/hail showers. We will keep this out of the
forecast for now, but we may need to update the forecast and put
this in if Thursday pans out. For Saturday, it looks like the
graupel/sleet chances are less likely due to weaker lapse rates.
There will also be a chance of snow showers across the higher
elevations of northeast Pennsylvania and northwest New Jersey
through the period, especially at night as temperatures cool. We
expect mostly an inch or less across much of the area.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
By Sunday, the low pressure that has been lingering across the
northeast states will be moving out to sea, while high pressure in
place across southern Canada noses down into the Mid Atlantic
region. The high may continue into Monday before splitting, with the
southern portion moving to our south as a warm front moves into the
area Tuesday into Wednesday. Dry weather is expected for Sunday
into Monday. However, as this warm front lifts into the region
and multiple short wave/vorticity impulses move into the area,
there will be increasing chances for precipitation Tuesday into
Wednesday.
&&
.AVIATION /00Z THURSDAY THROUGH MONDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.
Tonight...IFR/LIFR early then improvement from W to E overnight.
VFR possible by dawn for the wrn sites and MVFR for the ern
sites. Winds shifting to NW then W with gusts up to 20 kts
possible. Medium confid.
Thursday...Scattered showers, some with graupel (or small hail)
will be possible mainly midday/afternoon on Thursday, with MVFR
ceilings possible. Westerly winds 10-20 kt.
Outlook...
Thursday night...Sub-VFR conditions may develop overnight across the
area. Showers during the evening will diminish overnight. West to
northwest winds 5-10 knots. Moderate confidence.
Friday-Saturday...Generally VFR. Scattered showers possible each
day. West to northwest winds 10-15 knots with gusts 20-30 knots
during the day. Moderate confidence.
Sunday-Sunday night...VFR conditions expected. North to northwest
winds 10-15 knots with gusts 15-20 knots during the day, diminishing
to 5-10 knots or less overnight. Moderate confidence.
Monday...VFR conditions expected. West to northwest winds 5-10
knots, becoming southwest overnight. Moderate confidence.
&&
.MARINE...
The Marine Dense Fog advisory, the Storm Warning and the Gale
were all taken down as of 8 PM. A Small craft advisory was
raised where the Gale and Storm flags were taken down. The SCA
will continue into Thursday with gusts to 30 kts overnight and
just seas thru Thursday. The seas of 8 to 11 ft will gradually
come down later tonight into Thursday, but will remain above 5
ft much of Thu on the ocean.
Outlook...
Thursday night-Saturday night...Small Craft Advisory conditions
possible for much of the coastal waters during the late week into
early to middle part of the weekend period.
Sunday-Monday...Conditions expected to remain below advisory levels
into early next week.
&&
.HYDROLOGY...
A Flood Watch is in effect for northern Delaware, all of our
Pennsylvania zones, and for our urban/I-95 corridor New Jersey
zones from through 6 PM Thursday.
While the heaviest rain is departing the region over the next
few hours, an additional round of light rain is possible later
this evening, followed by another round of showers tomorrow.
Therefore, no changes to the flood watch at this time. Many
areal flood warnings are in effect with smaller river and stream
flooding occurring, and we have a slew of river forecast points
also forecast to go into MINOR flood, like along the
Schuylkill, Rancocas, Raritan and Passaic Rivers. The Passaic at
Pine Brook and the Millstone at Blackwells Mills may reach
MODERATE flood stage Thursday.
If you live in an area that is conducive to flooding, this is
the time to prepare.
We attach words like MINOR and MODERATE to river flooding. What
do these words mean?
MINOR FLOODING: Minimal to no property damage, but some public
threat can be expected (e.g. inundation of roads).
MODERATE FLOODING: Some inundation of and roads near
streams/rivers are expected. Evacuations of people and/or the
transfer of property to higher elevations can be anticipated.
MAJOR FLOODING: Extensive inundation of structures and roads.
Evacuations of people are on a larger scale. The transfer of
property to higher elevations is needed.
To stay on top of the flooding potential, visit these websites.
If you want to see the flooding threat in terms of
probabilities, check out this Hydrologic Ensemble Forecast link:
weather.gov/erh/mmefs
Our AHPS website has been updated and upgraded to our new
National Water Prediction Service (NWPS) website:
water.noaa.gov
If you live in the Passaic or Raritan basins, keep in mind that
inundation mapping is available:
water.weather.gov/AHPS/inundation.php
To view river observations and our forecasts in table form,
check out our dashboard: weather.gov/phi/hydrodashboard
&&
.TIDES/COASTAL FLOODING...
The evening high tide has passed on the Atlantic ocean front.
For the overnight high tide, it looks as if there will be one
more round of tidal flooding. Therefore, the Coastal Flood
Warning for Middlesex, Monmouth, Ocean, and southeastern
Burlington counties remains in effect, and a coastal flood
advisory for the next high tide has been issued for Cape May
and Atlantic Counties. No major changes with the coastal flood
advisory on the tidal Delaware River. Some road closures, beach
erosion, and breaching of sand dunes can be expected in these
areas.
We are between the full/new moon cycles and therefore the
astronomical contribution is lower and the peak surge occurring
near low tide on the Atlantic coast should limit the potential
for major flooding. Elsewhere, another round of widespread minor
coastal flooding is forecast with the late tonight and early
Thursday morning high tide.
No widespread minor flooding is anticipated for the Maryland
Eastern Shore at this time.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Flood Watch through Thursday afternoon for PAZ054-055-060>062-
070-071-101>106.
Coastal Flood Advisory until 2 PM EDT Thursday for PAZ070-071-
106.
NJ...Flood Watch through Thursday afternoon for NJZ001-007>010-012-
013-015>019.
Coastal Flood Warning until 10 AM EDT Thursday for NJZ012>014-
020-026-027.
Coastal Flood Advisory until 2 PM EDT Thursday for NJZ017>019.
Coastal Flood Advisory from 3 AM to 7 AM EDT Thursday for
NJZ022>025.
DE...Flood Watch through Thursday afternoon for DEZ001.
MD...None.
MARINE...Small Craft Advisory until 1 PM EDT Thursday for ANZ431.
Small Craft Advisory until 7 PM EDT Thursday for ANZ450>455.
&&
SYNOPSIS...Gorse/RCM
NEAR TERM...Dodd
SHORT TERM...RCM/Robertson
LONG TERM...RCM/Robertson
AVIATION...Dodd/Robertson
MARINE...Dodd/Robertson
HYDROLOGY...
TIDES/COASTAL FLOODING...