Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 231357
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
957 AM EDT Fri Jun 23 2017

.SYNOPSIS...
Low pressure will track well north of our area Friday and Saturday.
An associated cold front will cross our region during Saturday as
some tropical moisture moves ahead of and along it. High pressure
will then build well to our southwest Sunday into Monday. A weak
cold front will move through our area later Monday. High pressure
will then build across the Mid Atlantic Tuesday and Wednesday,
before shifting offshore Thursday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Round one of three is moving through the region now. So far, no
embedded thunderstorms have developed, and surface temperatures
are running a bit lower than previously expected. It appears
that we remain capped with this first round. The associated
shortwave trough with this round should clear the area by mid
day.

Upstream, there are some pockets of clearing apparent on
satellite. It still remains to be seen when and how long we
will clear out this afternoon. Thus, it also remains uncertain
how much instability we will have by this afternoon when the
next shortwave trough approaches our region. However, north and
west of the fall line, if we get some clearing, we will have
modest CAPE values and 0-6km shear values near or above 40 kt
(considerably higher than what models were depicting with
yesterday`s runs). Thus, could see some storms organize with a
severe wind, and possibly hail threat. At this point it
looks like a stronger cap will be in place over our Coastal
Plains, so not expecting any convection to initiate there, but
if storms become organized over the higher terrain, they could
move into the Coastal Plains late in the day.

With SW flow tapping into a subtropical airmass, highs today should
top off in the upper 70s to low 80s north and west of I-76, and in
the mid to upper 80s across most of southern and eastern NJ,
southeast PA, and the Delmarva. With dewpoints in the low 70s, the
heat index will be in the low to mid 90s.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/...
Any showers and thunderstorms early will taper off in the evening.
Warm and humid conditions remain in place as the subtropical airmass
remains over the region. Overnight lows will be in the low to mid
70s, and dewpoints will be in the upper 60s to low 70s.

The remnant low of Cindy moves towards the Appalachians this
evening, and then towards the Delmarva prior to daybreak Saturday.
Showers and scattered thunderstorms will move into far western zones
after midnight, and then the heaviest precip will hold off until the
pre-dawn hours. Given the abundant moisture across the region, rain
may be heavy at times, and cannot rule out localized flooding.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
A ridge of high pressure will be across the Middle Atlantic region
Sunday. A fair weather day is expected with temperatures right
around seasonal norms. The airmass will be much drier than both
Friday and Saturday, so it will be a good day for outdoor
activities.

A surface cold front and a slow moving upper trough will affect the
weather from Monday afternoon into Tuesday. The system will not have
a great deal of moisture to work with, but the colder temperatures
aloft will help develop showers and a few tstms during the period.
Pops are only in the slight chc or low chc range attm. Temperatures
thru the period will mostly be around 5 degrees below normal for
late June. Highs will be in the mid/upper 70s across the north and
close to 80 near metro Philadelphia and over Delmarva.

The rest of the long term looks dry with slowly moderating
temperatures and rising humidity levels. Highs will remain below
normal Wednesday and then rise to near normal for Thu/Fri. Most of
the models are showing high pressure across the area, slowly moving
offshore by Friday. A few showers Fri afternoon far N/W are
possible according to the 00Z EC.

&&

.AVIATION /14Z FRIDAY THROUGH TUESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

The fist round of showers, with brief MVFR conditions possible,
will move over the TAF sites through 16Z. After that, expect a
return to VFR conditions for several hours. Another round of
SHRA/TSRA possible in the late afternoon and early evening, and
some storms could be strong to possibly severe. Heavy rain is
possible, and MVFR/IFR conditions possible.

Conditions dry out in the evening, and then heavy rain, scattered
thunderstorms, and IFR and lower conditions possible in the pre-dawn
hours Saturday morning.

SW flow 5-10 KT today through tonight. Gusts to 20 KT possible this
afternoon.

OUTLOOK...
Saturday/Saturday night...Lower CIGS/VSBYS with showers and
tstms mostly in the morning. Conditions improving late.
Sunday/Monday morning...VFR expected.
Monday afternoon thru Tue...Mostly VFR. Sct showers/tstms.

&&

.MARINE...
Mostly Sub-SCA conditions through this morning. SCA conditions
develop this afternoon on the ocean with 25-30 KT gusts and 4-6
ft seas. Will also hoist a SCA for DE Bay, as 25 KT gusts
likely, but that would be for this afternoon and early evening.

One round of showers and scattered thunderstorms will impact the
waters this morning through midday, and then another round of
showers and potentially strong thunderstorms possible late this
afternoon and early this evening. With both rounds, gusty winds
will be possible in the vicinity of any showers and
thunderstorms.

SCA conditions on the ocean through tonight.

The remnant low of Cindy will approach late tonight, and showers and
scattered thunderstorms with heavy rain will move into the waters
after midnight tonight and into the pre-dawn hours on Saturday.

OUTLOOK...
Saturday/Saturday night...SCA conditions. Showers/tstms
Saturday and Saturday evening.
Sunday/Sunday night...sub-SCA conditions. Fair.
Monday/Tue...Sub-SCA with sct showers late. Few tstms Tue.

RIP CURRENTS...
There is a moderate risk for the development of dangerous rip
currents at NJ ocean beaches and a low risk for the development
of dangerous rip currents at DE ocean today. However, even with
a low risk...the bigger diurnal difference in the tide cycle as
we approach the date of this months new moon could mean some
rapidly changing conditions.

&&

.TIDES/COASTAL FLOODING...
High astronomical tide levels are expected in association with the
new moon today. Based on the latest guidance, not expecting
widespread minor coastal flooding with the high tide cycle this
afternoon and evening. Will hold off on issuing a Coastal Flood
Advisory, as tide levels should fall just short of minor flooding
thresholds.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory until 6 PM EDT Saturday for ANZ450>455.
     Small Craft Advisory until 9 PM EDT this evening for ANZ430-
     431.

&&

$$
Synopsis...O`Hara
Near Term...Johnson/MPS
Short Term...MPS
Long Term...O`Hara
Aviation...Johnson/MPS/O`Hara
Marine...Johnson/MPS/O`Hara
Tides/Coastal Flooding...



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