NWS Philadelphia/Mount Holly wrote its last area forecast discussion before the first event at Sep 3, 1:07 PM EST, 53 minutes earlier.
Area forecast discussion, Sep 3, 1:07 PM EST, 53 minutes before
Area Forecast Discussion
National Weather Service Mount Holly NJ
207 PM EDT Sun Sep 3 2023
.SYNOPSIS...
High pressure is forecast to continue influencing our weather
into the mid to late week period. A cold front is expected to
arrive from the northwest on Friday night and Saturday.
&&
.NEAR TERM /THROUGH MONDAY/...
No significant changes with the mid day update. A ridge axis
will slowly migrate eastward into the early week, with our
region remaining on the eastern edge through Labor Day. High
pressure centered to the southwest will remain in control
through Monday as well. Today will begin a prolonged period of
above normal temperatures. In fact, NAEFS Percentile charts show
850 mb temperatures for the next several days in the 99th
percentile or greater.
Aside from a diurnally driven cumulus field through this
afternoon, do not expect much else in the way of cloud cover
into this evening. 850 mb temperatures will increase into the
18-20 C range, with the result being surface temperatures in the
upper 80s/low 90s, something we have not seen in several days.
We continue to expect a deep mixed layer, which will have dew
points mixing out into the low to mid 60s. Heat index values
will be very close to air temperatures with the lower humidity,
and apparent temperatures should stay well below Heat Advisory
criteria for today.
Tonight will be another quiet evening. Skies will be mostly
clear with temperatures falling into the upper 60s/low 70s.
Depending on the location, this is around 5-10 degrees above
normal for early September. Some passing clouds are expected
late Sunday into Monday as a weak shortwave rides overtop of the
ridge, but not expecting much overall from this.
For Labor Day, temperatures will increase even further as 850
mb temperatures get above 20C in some spots. With deep mixing
expected again, surface temperatures will get into the low to
mid 90s. Dew points look to be a bit higher for Monday, though
currently have heat index values below Heat Advisory levels.
Some records look to be in jeopardy though. See the climate
section below for more info.
&&
.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
Upper level ridge axis will very slowly build eastward Monday
night through Tuesday night, shifting from eastern Ohio to
central PA during this time. Weak passing shortwave will be
departing the area to the south Monday evening, and can't
completely rule out a shower with it, but have kept POPs below
slight chance as coverage looks very low if anything happens.
Winds shift northwesterly behind the shortwave but lows will, if
anything, be even milder than tonight, with upper 60s to lower
70s expected in most of the area. Dew points will creep up a bit
more as well, so patchy fog is possible late at night.
Tuesday, with the ridge axis building closer, temps likely end
up similar to Monday, in fact inland areas could get a touch
hotter. The the shift from a westerly to a northerly wind may
allow more of a sea breeze to make its way inland, so coastal
areas look a little cooler. The higher dew points suggest heat
indices a little warmer overall than Monday, but still just shy
of heat advisory levels. A few models hint that there could be
enough sea- breeze convergence to fire off a shower or t-storm
across interior southern NJ or the Delmarva, but for now held
POPs at sub-slight chance.
Very little difference between Monday night and Tuesday night
other than the lack of a passing shortwave. Dry with
unseasonably warm temps again.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Main issue in the long term is how long the ridge lasts before
it breaks down and gives us relief from the heat. GFS remains
faster than other models, breaking the ridge down starting
Thursday, but ECMWF and GGEM hold it mostly until Friday, so
have warmed up temps several degrees Thursday. This brings
potential for additional records, so have added Thursday to the
climate section below. Overall, though just more unseasonably
hot and dry weather Wednesday and Thursday with the ridge
passing by. Best consensus right now suggests Wednesday as the
hottest day, so that's what we have in our present forecast,
though we're only talking about a degree or so difference. Dew
points will remain in the upper 60s, so looks like we'll stay
just shy of advisory levels.
Have some slight chance pops moving in from the west for
Thursday, mainly due to the GFS faster solution, but much higher
POPs Friday when the bulk of guidance has the front moving in.
Given some slower solutions and potential of an upper-low to
hang around, continue with chance pops Saturday, though right
now best chance of any thunder or severe weather looks to be
Friday. Temps will finally be back closer to normal Saturday, at
least that's what it currently appears, but the risk of showers
suggests that next weekend won't be as nice as this current
one.
&&
.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas...
Through Tonight...VFR conditions expected. some diurnally driven
clouds between 4 and 5K Ft AGL possible through 00Z, then late
tonight, may see mid level clouds between 10 and 15k FT AGL.
Winds should predominately be out of the west (slight variations
between WSW and WNW). However, a sea breeze is possible through
03Z near the coast, including KACY and possibly KMIV which could
bring a temporary shift to S winds. Wind speeds should stay less
than 10 kt. High confidence.
Monday...VFR. West/Northwest winds around 5-10 kt. Another sea
breeze may develop in the afternoon with S winds, though unclear
if it will reach as far inland as KACY and KMIV. High
confidence.
Outlook...
Tuesday...Mostly VFR. May be patchy late night/early morning
mist/light fog. Winds northerly around 5 kts. High confidence.
Wednesday...Mostly VFR. May be patchy late night/early morning
mist/light fog. Winds northwesterly 5-10 kts. High confidence.
Thursday...Mostly VFR. May be patchy late night/early morning
mist/light fog, then an isolated shower or t-storm possible
late or at night. Winds southwesterly 5-10 kts. Moderate
confidence.
&&
.MARINE...
No marine headlines are expected through Labor Day. Winds will
be out of the south/southwest around 10-15 kt through today.
Winds go more west/northwest around 5-10 kt tonight and tomorrow
morning, before going back to a more south/southwest direction
on Monday, still around 5-10 kt. Seas will be 3 to 4 feet
through Monday.
Outlook...
Monday night through Thursday...No marine headlines are
anticipated.
Rip currents...
For today, a south to southwest wind is expected which is more
shore parallel rather than onshore. However, with breaking waves
still 3 to 4 feet, a long period swell persisting, and multiple
swell groups present, we continued the HIGH risk for the
development of dangerous rip currents.
As we go through Labor Day, the only significant difference
from today is that waves look slightly lower, though latest
guidance is in the area of a few tenths of a foot difference.
Therefore, went with a HIGH risk for the development of
dangerous rip currents for both the Delaware and New Jersey
beaches.
&&
.CLIMATE...
Near record breaking heat is forecast for Monday thru
Thursday. Records for our climate sites are listed below:
Record High Temperatures
Mon Sept 4 Tue Sept 5 Wed Sept 6 Thu Sept 7
Site Record/Year Record/Year Record/Year Record/Year
Allentown (ABE) 94/1937 94/2018 96/1983 91/2016
AC Airport (ACY) 96/2018 93/1985 98/1983 94/1983
AC Marina (55N) 92/1985 94/1880 92/1985 92/1983
Georgetown (GED) 97/2008 93/2018 93/2018 94/1983
Mount Pocono (MPO) 88/1973 85/2018 88/2018 85/2015
Philadelphia (PHL) 93/2018 95/2018 95/2018 102/1881
Reading (RDG) 94/2008 93/2018 95/1943 97/1983
Trenton (TTN) 95/1929 95/1985 99/1983 94/1983
Wilmington (ILG) 95/2018 93/2018 98/1983 95/1983
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...High Risk for Rip Currents through Monday evening for NJZ014-
024>026.
DE...High Risk for Rip Currents through Monday evening for DEZ004.
MD...None.
MARINE...None.
&&
SYNOPSIS...Hoeflich/RCM
NEAR TERM...Hoeflich/Johnson
SHORT TERM...RCM
LONG TERM...RCM
AVIATION...Johnson/RCM
MARINE...Hoeflich/RCM
CLIMATE...