Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 212358
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
758 PM EDT Thu Sep 21 2017

.SYNOPSIS...
Tropical storm Jose is expected to weaken as it meanders off the New
England coast through this weekend. Meanwhile, high pressure over
southeastern Canada will expand southward into the mid Atlantic
states. During the early to middle part of next week, Hurricane
Maria is forecast to move northward over the offshore Atlantic
Ocean waters between Bermuda and the Middle Atlantic states. A
cold front is expected to move through our area in the Wednesday
and Thursday time frame as Maria probably passes by, well to
our east.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
630 PM ESTF: minor adjustments to a few temps tonight, especially
warmer by a couple of degrees early this evening...but
effectively no change to your forecast.

Tropical Storm Jose is expected to continue its gradual weakening
through tonight while still remaining nearly stationary about
150 miles southeast of Nantucket, MA or about 330 miles due east
of LBI, NJ.

It still has impressive winds in the observed data from southern
New England to our Texas Tower buoy 70 mi e of NJ.

Drier air over the west portion of southern new England and the
Hudson Valley may not arrive in our area until sometime tomorrow
or tomorrow (Friday) evening.

In the meantime...high clouds will prevail tonight with some
spotty sc at 6000 ft here and there.

The setup for radiational fog in the river valleys of NE PA and
NW NJ may  not be nearly as favorable as in recent days (and as
climo) because of variably thick high cloud cover from Jose.

Low temperatures should range from the mid 50s along the I-80
corridor to the mid 60s along the I-95 urban corridor and near
the coast.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
The NHC forecasts Tropical Storm Jose to undergo post-tropical
transition Friday. The center of Jose will either continue to
stall near its current position or start to drift ever so slowly
westward but still remain comfortably offshore by several
hundred miles.

Winds gusts to 20-25 MPH are possible in NJ on Friday as the
western fringe of Jose`s wind field edges westward slightly.

Also, there is multimodel guidance indicating not only some
denser cirrus cloudiness from Jose but also a deck of 6000
broken is likely to develop in NJ.

A westward drift would allow for denser cloud cover from Jose to
spread back toward the northern mid-Atlantic coast on Friday and
perhaps as far inland as the Delaware Valley late in the day.
Temperatures will have a dependency on how far west the cloud cover
progresses. For now, clouds shouldn`t have a huge impact on
temperatures across inland locations from I-95 west. Forecast
highs range from the upper 70s in the higher elevations of NE
PA/NW NJ and near the coast to mid 80s near Phila and points
S/W.

Friday is still expected to remain dry with outer rain bands from
Jose staying offshore. However, could see scenario, albeit an
unlikely one, where one of these bands reaches the coast during the
morning.

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
The forecast challenges during this time frame will be high temps
Saturday through Monday and the eventual track of Hurricane Maria.

A complex mid-level pattern will evolve over the eastern US and
southwest Atlantic, with a southern stream rex block, eventually
breaking down with the approach of height falls associated with a
northern stream trough late in the period. Meanwhile, Hurricane
Maria is forecast to move northward through a weakness in the
subtropical ridge, under the increasing influence of a mid-level
trough along the eastern fringe of the rex block, e.g., remnants
of Jose, by the middle of next week.

In terms of high temperatures, the first full week of fall will
average above normal across our area. In fact, high temps in the
Saturday through Monday period will be around 10 degrees above
normal! The airmass will be generally dry with a light surface flow
in place. It will be cooler near the coast with a sea-breeze on
Saturday, and a more pronounced synoptic onshore flow Sunday into
Monday. There is some uncertainty in high temps, given the spread
exhibited in the ensembles, although a similar air mass lends to
more of a persistence forecast.

With the synoptic flow becoming onshore during the second half of
the weekend and persisting into the midweek, low-level moisture will
gradually increase, with perhaps some contribution from the remnants
of Jose as well. We are noting some of the GEFS ensemble members
bringing measurable precipitation into the coastal plain on Tuesday,
well in advance of the anticipated cold frontal passage Wednesday
into Thursday. Therefore, we have maintained slight chance PoPs in
the coastal plain beginning Monday night, expanding to chance PoPs
over the entire region on Wednesday.

The forecast also becomes uncertain in the Tuesday through Thursday
period and will be highly dependent on the eventual track of Maria,
including the extent of its interaction with the approaching cold
front. We continue to stay closer to a consensus of the guidance,
which takes the cold front offshore Wednesday night, thereby
introducing a drying trend by Thursday.

Stay tuned to the latest advisories and forecasts from the
National Hurricane for more information on Jose and Maria.

&&

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

Tonight...VFR cirrus, with a few sc near 6000 ft. Light or calm
wind.

Friday...VFR cirrus with a deck of sct-bkn clouds near 6000 ft
developing west southwestward across first the NJ coast Friday
then reaching the DE coast toward Friday evening. North wind
with scattered afternoon gusts 15-20 kt.

VFR thru the valid TAF period.


Outlook...

Predominantly VFR conditions are anticipated Friday night through
Monday across the terminals regionwide. There is the potential for
MVFR at ACY and MIV in -SHRA Monday night into Tuesday. Winds north
10 knots or less Friday night into Saturday night, then becoming
east-northeast on Sunday and continuing through Tuesday, generally
around 10 knots with gusts 15 to 20 knots at times.

&&

.MARINE...
SCA seas reissued sooner as swell finally back into the the
coastal waters late this afternoon. Still a little slow to get
into 44065 but the ene 10 second swell is easily evident at
44091 east of NJ.

Northerly winds are forecast to increase to 15- 20 kt during
early Friday morning. We may need to go back to a Small Craft
Advisory for winds and seas for the NJ coastal waters with the
potential for wind gusts near 25 kt between during the mid
morning hours Friday. Seas should also respond to the strengthening
wind on top of the E-NE swells from Tropical Storm Jose by
building to around 7 ft toward the early morning. Winds will
gradually relax during the afternoon but seas will likely still
be in the 5-6 ft range.

Outlook...

The Small Craft Advisory for hazardous seas was extended through
Saturday after collaboration with surrounding offices. However, we
anticipate this may eventually need to be extended further, with
guidance indicating waves remaining at or above 5 feet through at
least Tuesday.

Winds are expected to remain below 25 knots through Monday, but the
forecast becomes uncertain beyond as Maria moves northward off
the east coast per latest NHC forecast. The GEFS probabilistic
guidance suggests at least a 50 pct chance of wind gusts around
25 knots in the Tuesday - Wednesday time frame. This may well be
due to Maria`s wind field expanding at this point. Stay tuned.

Rip Currents...

We will extend the HIGH risk through Friday per the observation
of late this afternoon from LBI and the recently increased
swells having arrived along our NJ and De coasts.


Outlook:

Saturday...At least a moderate risk for the formation of
dangerous rip currents and a good chance of high risk as Maria`s
se swell of 15 seconds builds to 2 or possibly 3 feet and those
swells are on a collision course with the leftover 9 or 10
second ne swell from Jose. Its probably going to be rough water
and bit chaotic in the surf zone.

Sunday through Thursday are outlooked high risk days with the
greatest risk Tuesday or Wednesday of next week, due to leftover
Jose swells combined with building arriving southeast swells of
15 seconds to between 8 and 10 feet Tuesday and Wednesday.
Breaking surf along the beach surf zone play area will probably
reach 6 feet, if not a little higher. That should be almost
double the size of the breakers that occurred this Thursday
afternoon.

So despite the very warm weather and still rather warm ocean
water temps (low-mid 70s), I wouldnt be going out there unless
you`re a certified lifeguard. The waters are going to get rougher
again, even with the distant passage of Maria next week.


&&

.TIDES/COASTAL FLOODING...
Expect any tidal flooding with the two upcoming high tide cycles
(tonight and Friday morning) to be spotty with levels at NOS gauges
expected to reach minor threshold but just short of advisory.

&&

.CLIMATE...
Records may post here in a day or two for either Sunday or
Monday as its possible max temps may exceed 90 degrees.

Example: Allentown`s record for both Sunday and Monday is 90 -
set in 1970 on both days.


&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...High Rip Current Risk until 9 PM EDT this evening for NJZ014-
     024>026.
DE...High Rip Current Risk until 9 PM EDT this evening for DEZ004.
MD...None.
MARINE...Small Craft Advisory for hazardous seas until 8 PM EDT
     Saturday for ANZ450>455.

&&

$$
Synopsis...Franck
Near Term...Drag/Klein 758
Short Term...Klein/Drag 758
Long Term...Franck
Aviation...Drag/Franck/Klein 758
Marine...Drag/Franck/Klein 758
Tides/Coastal Flooding...758
Climate...758



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