Area Forecast Discussion
Issued by NWS Mt. Holly, NJ-- Highlight Changed Discussion --
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FXUS61 KPHI 010414
Area Forecast Discussion
National Weather Service Mount Holly NJ
1214 AM EDT FRI JUL 1 2016
Weak high pressure will continue to move offshore overnight. A cold
front, attached to low pressure over Canada, will cross the area
later Friday and Friday night. High pressure will build in for the
weekend and persist into the holiday. A warm front may begin to
push into the region next Monday night and into Tuesday.
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
-- Changed Discussion --1230 am update: Adjusted temperatures down slightly based on
current obs especially across the northern half of the region.
Moisture advection has been slower to develop further north.
Otherwise no major changes.
Tonight...showers and a few isolated thunderstorms should begin
to move into the southeast portion of our region after midnight.
88D reflectivity images continue to show shower activity over the
coast waters just to our south and east at 930 PM. Weak
instability burst. Pwat increases to 1.6" by 12z Fri PHL south (up
from the near 1 inch of today). Fog or stratus may develop toward
dawn Friday. Light south wind.
FCST Basis: 50 50 blend of 12z/30 gfs/nam MOS but POPS raised
se of the NJT and DE tonight for an instability burst shower or
garden variety thunderstorm in the 03z-09z time frame.
Confidence: average. doubts about how much fog tonight and whether
it can rain tonight.
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.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SATURDAY/...
Friday...mixed clouds and sun, warm and more humid. Chance of
showers/isolated thunderstorms during the morning. The primary
thunderstorm event should develop eastward near and south of the
Mason-Dixon line late in the afternoon with what I think is decent
potential for scattered severe thunderstorms arriving Delmarva
sometime after 5PM. That is where modeled MLCape is 1400+J,
multi-model TT50, KI pooled 34+ and 0-6Km Bulk shear is 35-45 kt.
South to southwest wind. Potential exists for svr further n
through our CWA as per SWODY2.
12z/30 UK/GGEM and EC override on the almost non existent afternoon
NAM QPF, even though the NAM instability pooling looks correct.
Mid 80s continues to look good for max temps much of the area
Friday. its possible we`ll see some 88`s Philadelphia southwestward
since 850MB warms to 15C by 12z. Guidance max temps may be biased
low by modeled morning qpf.
FCST Basis: 50 50 blend of 12z/30 gfs/nam MOS but POPS raised to
likely Delmarva because of EC/GGEM?UK qpf and modeled instability
Confidence: above average.
.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
The last of the showers and thunderstorms associated with the
eastward moving cold front will be across the region Friday
evening. The arrival of the cooler and drier air will cause pops to
decrease from west to east overnight.
The upcoming holiday weekend looks great with high pressure
building in sat and remaining in control of the weather thru
monday. We will begin to show some increase in pops Monday, with
some slgt chcs or small chc pops across the Delmarva and se PA by
mon afternoon. It shouldn`t be enough to hinder any outdoor
activities for that day. The air will be pleasantly dry on sat,
then some increase in humidity by the 4th. Temperatures will be
near normal with highs in the low/mid 80s in most areas.
The operational models are indicating a disturbance approaching
from the south/southwest Monday night and lasting into Tue. It
appears that a warm front and humid air will crease a round of
showers/tstms for (mostly) the srn parts of the fcst areas. we
will carry chc pops in the fcst attm. Details will be sorted out
as the time frame draws nearer. Temperatures again near normal, or
maybe a degree or two above. It will likely be rather humid as
well. We will continue with a dry and seasonably mild fcst for
Wed-Thu next week.
.AVIATION /04Z FRIDAY THROUGH TUESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.
Tonight...VFR under mostly clear skies to start but MVFR or IFR
conditions in st/fog/haze possible after 06z/01. Isolated showers
or thunderstorms possible 03z-09z se of the NJT and DE. Light
southerly wind. Confidence: Average since there is uncertainty
regarding extent of any showers and st/fog development late
Friday...becoming VFR sct-bkn aoa 4000 ft after any early morning
IFR/MVFR lifts by 15z. Brief MVFR or IFR conditions possible in
showers and thunderstorms, especially late day. Thinking that
scattered severe thunderstorms will be developing eastward across
the Delmarva into southern NJ sometime after 21z/01. a prob30
group was added to all taf sites after 18z to account for the
chance of convective activity. SPC keeps almost the entire CWA under
marginal risk on Friday. South to southwest wind. Confidence:
above average due to multi-model consensus overriding the dry
12z/30 NAM afternoon qpf.
Friday night...VFR sct-bkn aoa 4000 ft with sct showers and
thunderstorms ending by 06z/02 with possible MVFR fog where it
rains late Friday afternoon/evening.
Saturday...Mainly VFR conditions expected. West to northwest wind
around 10 knots or less.
Sunday...Mainly VFR conditions expected. North to northwest winds
becoming west to southwest.
Monday...Mainly VFR conditions expected. Showers and thunderstorms
Monday night and Tue...Sct Showers and thunderstorms especially
Winds and seas should remain below SCA criteria tonight through
Friday. A few gusts to 22 kt are possible on the coastal waters
late this afternoon as the sea breeze ramps up, but should stay
below 25 kt.
Water temperatures on Thursday were around 4 to 5 degrees above
normal for late June...mid 60s to lower 70s throughout the DE and
NJ beaches with exceptions.
From this time forward through September 30 we will be issuing a
day 2 SRF 1 line outlook for the media by 330 PM in the marine
section of this AFD as per next pgh below. This will better
support media early evening broadcasts while permitting our SRF to
run our day 1 forecast through sunset. We have an overwhelming
number of rip current related fatalities occurring near the
evening dinner hour, after beach patrols depart and its still
quite warm. For safety awareness purposes our Day2 will continue
issuing after sunset when presumably more beachgoers are out of
Rip Current Outlook for Friday...The risk for the formation of
dangerous rip currents tomorrow is low.
(Friday may yet border on moderate risk during the afternoon
depending on the strength of any onshore flow during the
afternoon, especially NJ.)
Friday night through Tuesday...Sub-SCA conditions most of the
time. Sct TSTMS with higher winds and seas Fri evening and again
RIP CURRENTS...Projecting a solid LOW for Saturday with a 3 ft
7sec se swell but an offshore wind. Sunday-Monday-Tuesday projecting
a LOW ENHANCED or possibly LOW end of a MODERATE risk where the
new moon tends to accentuate tidal fluctuations and thereby increases
current strength. The Sunday-Tuesday confidence projection is
average. In other words, caution is advised when using a projection
this far in advance, since a 1 foot difference in wave height
expectation and/or a significant change in onshore wind can easily
change the potential for dangerous rip current formation.
The Atlantic Basin continues quiet for awhile so that bodes well
for continuing the low risk, or possibly moderate risk for the
formation of dangerous rip currents.
Most fatalities from rip currents occur at unguarded beaches. The
vast majority of fatalities are on low-moderate risk days which
means there is a lack of awareness of the dangers of swimming at
unguarded areas, or near jetties and piers.