Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 282256
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
656 PM EDT THU JUL 28 2016

.SYNOPSIS...
Scattered showers and thunderstorms with locally heavy rainfall will
persist at times through the weekend. Drier and less humid weather
is expected for much of the next work week as high pressure builds
over the region.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
630PM ESTF:

Active through Noon Friday. FF potential continues fairly high and
the watch continues. Greatest concern is se PA, S NJ, ne MD,
central and northern DE, where it rained heard this afternoon, and
or where 3 hrly ffg is under 3".

svr wx threat is mainly delmarva and s tip of NJ through midnight
and then it may expand northward toward 4 am to near ILG-ACY axis
as low pres in northern VA cuts enewd through s NJ. tor parameter
remarkably large toward 09z on the sref in snj. so SVA 418 was
trimmed south.

LSR`s and PNS will be updated during the night.

we can use all damage reports, as well as unusual flooding reports
and any rainfall over 2 inches.

PWAT increase to 2.3" by 09z philly area. If it thunders at that
time, short term rainfall could easily be excessive for urban
areas.

normally heaviest rainfall occurs near the path of the sfc low,
near the most unstable air south of the south-ne wind sfc
convergence zone. Am expecting modeled qpf to be too far north.


so, another round of heavy rain looks to move in late tonight as
a wave of low pressure tracks northeastward along the stalled
front. Heavy rainfall with this second round may be more
widespread. Also, backed flow in the low levels ahead of the low
may provide a source of low- level helicity. Given very low LCL
heights, a weak tornado or two may occur toward early morning near
the front as long as instability remains near surface based.

630 PM ZFP wording on the Delmarva is somewhat confuded due to
svr wording terminating at midnight and gusty wind wording after
midnight but it doesnt read the second part of heavy rain and
gusty wind as Late.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
Precipitable water values of 2.2 to 2.4 inches will overspread
our forecast area from the south for tonight. Conditions are
expected to remain unstable, especially across our southern
counties. Also, surface low pressure approaching from the west
will result in the development of a favorable low level wind
profile for organized convection tonight. The surface wind should
begin to favor the east to south quadrant late tonight, especially
on the coastal plain, while winds around 800 HPa will be from the
southwest.

The very high precipitable water values should result in heavy
rainfall in any organized convection. As a result, the Flash Flood
Watch remains in effect for southeastern Pennsylvania, central and
southern New Jersey, Delaware and northeastern Maryland.

The cloud cover and high humidity will keep temperatures from
falling below the 70s for tonight except in the Poconos and far
northern New Jersey.

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
Highlights...

* Scattered showers/t-storms w/locally heavy rainfall this weekend
* Drier/less humid weather for much of the next work week

Details...

Friday night...

Dry weather expected Friday night with subsidence behind departing
shortwave. May see some patchy fog develop overnight with wet ground
and lingering low level moisture.

Saturday and Sunday...

A couple of additional shortwaves will move across our region this
weekend along with a frontal boundary in the vicinity.  Timing is
uncertain this far out, but more scattered showers and thunderstorms
are expected at times this weekend. Pwats will still be between 1.5
and 2 inches, so the threat will exist for locally heavy rainfall.
Clouds and the threat of precipitation should hold high temps mainly
in the 80s both days.

Monday through Thursday...

High pressure will build over the region, bringing us drier and less
humid weather.  There  still will at least be a low risk for a few
showers early in the work week, but either way dry weather should
dominate through Thursday. High temps will mainly be in the 80s.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Tonight...vfr showers with probably periods of ifr conds and gusty
winds to 25 kt in sct tstms, especially after 04z/29. otherwise
sustained winds under 10 kt will tend to become northeast toward
morning. Confidence is low for the timing of convection at any
particular TAF site, but high that storms will be in the region
through early Friday morning.

Friday...showers and thunderstorms end from west southwest to
east northeast. mvfr or ifr conds 12z-15z in showers/sct tstms
then improving to vfr cigs in the afternoon with a northeast
backing to north wind gust 20 kt.

Outlook...

Sat through Sun...Shra/tsra will lower cigs/vsbys at times
Otherwise VFR expected. Moderate Confidence.

Mon...Mainly VFR. Moderate Confidence.

&&

.MARINE...
A severe thunderstorm watch is in effect for most of the waters. There
is a potential for storms through this evening to produce locally
strong winds. An isolated waterspout is also possible through
early Friday morning.

S to SE winds 10-15 kt will become light tonight. Seas will
generally be around 1 ft. S-SW in the morning will increase to
10-20 kt and become NW in the afternoon and then N late in the day
across our northern coastal waters as a cold front passes thru.
Expect seas to respond by building to 2 ft in the morning and
possibly 3 to 4 ft during the afternoon in our coastal waters.

Outlook...Friday night through Tuesday...

There is a low risk for marginal small craft seas Friday night but
for now kept them just below 5 feet. Otherwise, winds/seas should
generally remain below small craft advisory thresholds through the
period.  Biggest concern for mariners will be the risk for
thunderstorms this weekend.  Drier weather should arrive early next
week.

RIP CURRENTS... There is a low risk for the development of dangerous
rip currents for today due to the relatively light wind and tranquil
seas. The probably risk for the development of dangerous rip
currents on Friday should primarily be low but it may approach
moderate along the NJ coast late in the day as alongshore N-NE
winds increase and surf builds to about 3 ft.

&&

.CLIMATE...
PHL heading for top 10 warmest July on record. tentatively, July
avg temp for PHL will be about 80.9, 8th warmest July in the
period of record since 1874. We have room to give on the low
side, so its unlikely to run a rank much different than #8.

ACY... already as of 5 pm this afternoon...is 10th wettest on
record with its monthly record of 13.098 set in 1959, the por
back to 1874.

daily record rainfall

      today    friday the 29th
acy 2.05 2012  2.21 - 1884

phl 8.02 2013  3.53 - 1980

ilg 2.34 1914  1.85 - 1913

abe 3.00 1916  1.64 - 1979

ttn 2.35 2012  2.84 - 1961

ged 1.98 1994  1.07 - 1969

rdg 3.57 1969  2.51 - 1961

mpo 2.15 1969  4.59 - 1969

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Flash Flood Watch through Friday morning for PAZ054-055-
     060>062-070-071-101>106.
NJ...Flash Flood Watch through Friday morning for NJZ001-007>010-
     012>027.
DE...Flash Flood Watch through Friday morning for DEZ001>004.
MD...Flash Flood Watch through Friday morning for MDZ008-012-015-
     019-020.
MARINE...None.

&&

$$
Synopsis...99
Near Term...Klein 656
Short Term...Klein 656
Long Term...99
Aviation...Klein/99 656
Marine...Klein/99 656
Climate...656


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