NWS Philadelphia/Mount Holly wrote its last area forecast discussion before the first event at May 28, 8:55 PM EST, 5 minutes earlier.
Area forecast discussion, May 28, 8:55 PM EST, 5 minutes before
Area Forecast Discussion
National Weather Service Mount Holly NJ
955 PM EDT Fri May 28 2021
.SYNOPSIS...
Low pressure will develop across the area this evening and remain
through Saturday. A slow moving front and another low will cross
just east of Delaware and New Jersey Sunday and Sunday night.
Improving conditions are expected for Monday as high pressure begins
to build towards the region. The dry weather will continue into the
middle of next week until low pressure and a front approach from the
west.
&&
.NEAR TERM /THROUGH SATURDAY/...
A shortwave trough currently over the Upper Midwest will continue to
slowly approach the area this evening into Saturday.
This shortwave will begin to close off upstream of the area on
Saturday while also showing signs of cutting off as the Canadian
longwave to its north pulls away. At the surface, High Pressure is
currently positioned NW of the area with an area of low pressure
located over the western Appalachians along a nearly stalled
boundary. A secondary low is beginning to develop SE of the primary
low in Virginia (also along the stalled boundary) and this low is
expected to track generally NE this evening, being located off the
NJ coast by midnight. As the mid-lvl flow becomes largely meridional
(i.e. from the S-SE) as the low cuts off to our west, the boundary
will largely stall just offshore through the weekend. Several other
waves of low pressure will develop and track along this boundary,
passing in the general vicinity of our area and keeping
precipitation chances elevated through the period.
Our area is currently in and will largely (apart from perhaps far
southern Delmarva) remain in the cool sector for this system as it
progresses out to sea. Showers associated with the 850mb warm front
are currently moving over the area, however the main slug of rain
will hold off until late this afternoon into the early evening. Not
much has changed regarding the thinking for this event, a fairly
widespread 1-2 inches of rain looks likely through Saturday morning
as a fairly impressive 925mb deformation band develops along the
north side of the low track. The consensus axis of heaviest rainfall
still looks to roughly be in the vicinity of I-95, but there is
still a bit of spread on where exactly this sets up. A few hundred
J/kg of elevated instability will be present SE of I-95, so kept
mention of thunder in those areas. However even outside of this
zone, there could be locally embedded (but not electrified)
convective elements within the broader stratiform precipitation
band. Given that the warm sector will largely remain south of the
area (inhibiting the development of sfc-based convection), do not
think there is much of a severe threat, but can't totally rule it
out in far southern Delmarva.
There will likely be a lull in steady precip later tonight as the
first low pulls out to sea, however additional rounds of rainfall
through (at least) the day on Saturday look likely as another low
develops along the boundary stalled just off the coast. This low and
thus its deformation zone will be positioned further SE than the low
this evening, so consequently expect the precipitation max on
Saturday to shift further south and east... and the Poconos/NW NJ
could even be dry by Saturday afternoon. Otherwise Saturday will be
a rather dreary day with low clouds, rain, breezy NE winds and high
temperatures near records for daily low maximums. Forecast highs are
expected to largely be in the low to mid 50s, with some locations in
the far north not even getting out of the 40s. It will be quite the
change from last weekend when temperatures were in the 90s!
---
Today was Joe Miketta's last shift at WFO PHI. He has retired in
glory. I was told to write in the AFD this message from him:
"Forty years. Good enough."
He was and is the very best. Happy times, Joe.
&&
.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
The poor weather from the near term continues into the short term as
the upper low continues across the area and surface low pressure forms
offshore the Carolinas/VA and moves northward along NJ/DE
areas. This will keep a persistent E/NE flow across the area
with cool and humid conditions. Highs Sunday will struggle to
get to the low 60s for Delmarva and it will be mostly in the
mid/upper 50s for most areas. Thick clouds and frequent showers
are expected. The NE/E winds will keep conditions unpleasant.
&&
.LONG TERM /MONDAY THROUGH FRIDAY/...
Fair weather will be across the area during the beginning of the
long term period as the upper low pressure system moves away and
carries the surface low with it. High pressure from the Ohio Valley
arrives bringing reduced amounts of clouds and seasonable temps.
Highs Monday and Tuesday will be mostly in the 70s with some 60s for
the higher elevations of the Poconos and NE PA. Lows will generally
range from 45 to 55 degrees for the area.
For the middle of next week, the high will move offshore and a
return flow of heat and humidity will develop across the Middle
Atlantic. Wednesday will feature temps close to normal, but for
Thu/Fri, highs will be in the low/mid 80s, which are 4 to 6 degrees
above normal. We will go along with the NBM pops for now with mostly
chc pops for the area. There are some low-end likely pops as well
for Wed night/Thu and again Fri. The higher pops will favor the
inland areas of ern PA and northern-most NJ.
&&
.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.
Tonight... Conditions deteriorating to and largely remaining IFR
through the night as rain, heavy at times moves through the
terminals. Rain should decrease in intensity later tonight with VSBY
improvements, but low CIGs will persist. Localized and mainly brief
LIFR is possible, and there is also a low risk for a rumble of
thunder mainly south of PHL. Winds northeast at 10 to 15 kt with
gusts of 20 to 25 kt. Moderate confidence.
Saturday... Generally IFR with periods of rain (mainly light)
through much of the day, especially near and east/southeast of PHL.
Conditions could improve to low-end MVFR in the afternoon, mainly
near RDG and ABE. Northeast winds 10 to 15 kt with gusts 20 to 25
kt, and up to 30 kt at ACY. Moderate confidence.
Outlook...
Saturday night thru Sunday night...Mostly IFR with low CIGS and
frequent showers. Gusty NE to E winds much of the time.
Monday thru Wednesday...Mostly VFR. Patchy morning fog possible.
&&
.MARINE...
A rather chaotic period is expected over the waters as numerous
waves of low pressure pass just offshore. For the evening/overnight
period NErly wind gusts increase to 40kts and seas increase to 7-9ft
over the northern NJ waters. Further south winds will be lighter
(and more variable direction) and seas lower, but SCA conditions are
still expected as seas increase to 5-7ft. On Delaware Bay there may
be a lull in the winds overnight, but expect winds to pick up again
Saturday morning so kept the SCA going through the period to keep
headlines simple. NE winds increase again on Saturday, potentially
hitting Gale criteria on all ocean waters, so extended the gale
spatially to include all ocean waters and extended it temporally
through Sunday morning.
OUTLOOK...
Sat night thru Sunday night...Gales diminish overnight Sat night
with SCA conditions after that extending thru Sun night. Rains
and gusty winds with choppy seas.
Monday thru Tuesday...Mostly sub-SCA. Fair weather expected.
Rip Currents...
We have issued a HIGH risk of rip currents Saturday and Sunday
at the New Jersey and Delaware beaches, with very strong onshore
winds, high waves, and long-period swell all anticipated.
Conditions will be quite dangerous in the surf zone this
weekend, so best to stay out of the water.
&&
.TIDES/COASTAL FLOODING...
945 pm update: Advisory-level flooding has begun on the Atlantic
coast this evening. So far, expectations are for widespread
minor flooding to occur with this first round, so the advisory
was left untouched with the late evening update. However, we
have issued a coastal flood watch for the southern New Jersey
and Delaware Atlantic coasts (as well as the Delaware side of
the coast of Delaware Bay) for tomorrow night's high tide.
Confidence has increased sufficiently that moderate flooding
will occur in several locations in these areas. Farther north
along the New Jersey coast, confidence is a little lower, but
moderate flooding certainly cannot be ruled out. As an advisory
is already in effect here through Saturday night, did not change
the product for these locations at this time. Will continue to
evaluate the latest guidance, with further adjustments to the
coastal flood products possible. Valid portions of the previous
discussion below...
The Coastal Flood Advisory remains in effect for the Atlantic coast
and the tidal portions of the Delaware Bay and the Delaware River.
For the tidal portions of Middlesex, Monmouth, Ocean, and Burlington
Counties in NJ the Advisory is now in effect through the high tide
cycle late Saturday/ early Sunday. The other zone configurations
remain with the Advisory in effect for the high tide this evening/
tonight.
The elevated tides are thanks to a persistent east wind that is
forecast to back from the east/ northeast Saturday morning. Northeast
flow and elevated winds will then persist into Sunday. Confidence
is high there will be widespread minor flooding on the coast with
some sites potentially even reaching moderate flooding levels.
However do not have the confidence to upgrade to a warning, but
this will need to be watched carefully. Overall, have upped the
high tide forecast for the Saturday morning and late Saturday/
early Sunday morning high tide cycles. The Saturday night high
tide is still forecast to have the highest potential for
moderate (warning-level) flooding.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Coastal Flood Advisory from 2 AM to 7 AM EDT Saturday for
PAZ070-071-106.
NJ...High Rip Current Risk from 9 AM EDT Saturday through Sunday
evening for NJZ014-024>026.
Coastal Flood Advisory until 5 AM EDT Sunday for NJZ012>014-
020-026-027.
Coastal Flood Watch from Saturday evening through late
Saturday night for NJZ022>025.
Coastal Flood Advisory until 3 AM EDT Saturday for NJZ021>025.
Coastal Flood Advisory from 2 AM to 7 AM EDT Saturday for
NJZ017>019.
Coastal Flood Advisory until 4 AM EDT Saturday for NJZ016.
DE...High Rip Current Risk from 9 AM EDT Saturday through Sunday
evening for DEZ004.
Coastal Flood Watch from Saturday evening through late
Saturday night for DEZ002>004.
Coastal Flood Advisory until 3 AM EDT Saturday for DEZ002>004.
Coastal Flood Advisory until 4 AM EDT Saturday for DEZ001.
MD...None.
MARINE...Small Craft Advisory until 6 AM EDT Saturday for ANZ452>455.
Gale Warning from 6 AM Saturday to 6 AM EDT Sunday for
ANZ452>455.
Gale Warning until 6 AM EDT Sunday for ANZ450-451.
Small Craft Advisory until 6 AM EDT Sunday for ANZ430-431.
&&
Synopsis...O'Hara
Near Term...CMS/Carr/Miketta
Short Term...O'Hara
Long Term...O'Hara
Aviation...Carr/Fitzsimmons/O'Brien/O'Hara
Marine...CMS/Carr/O'Hara
Tides/Coastal Flooding...CMS/Haines