Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 190557

Area Forecast Discussion
National Weather Service Mount Holly NJ
157 AM EDT Sat Aug 19 2017

As low pressure tracks well to our north, a cold front moves
through late tonight into early Saturday. High pressure then
builds in late Saturday and remains in place into Monday before
shifting offshore. The next cold front is scheduled to arrive
during Wednesday, then Canadian high pressure builds in for
Thursday and Friday.


The last of the rain has moved offshore and we should remain
precipitation free through the the rest of the night.

Warm and muggy conditions continue across the region. Fog and
low clouds are developing as the low level moisture remains high
across our area. The cold front is making progress eastward but
has yet to reach our the region. Once the front moves through
the region this morning, we should start to see the mugginess

The wind will be generally less than 10 MPH overnight at
varying directions which may begin to favor the northwest and
west with the arrival of the cold front. Low temperatures are
expected to be mostly in the upper 60s and lower 70s.


front should be offshore early Saturday morning, and once west
to northwest winds increase a bit, the drier airmass spreads
east, and any lingering fog will burn off. Skies clear out in
the afternoon. Dewpoints drop about 10-15 degrees, generally
into the mid 60s, but temps will be fairly warm, topping off in
the upper 80s to near 90 across the urban corridor of I-95 from
Trenton to Wilmington, and in the Delmarva. Upper trough
approaches from the west, and this may bring isolated late day
showers and thunderstorms to far western portions of the
forecast area.


Summary...Lowering of the dew points through Sunday although
remaining warm to hot, then moistures increases again with some
convection especially Wednesday with the next cold front. A
noticeably cooler and drier airmass arrives for Thursday and
Friday in the wake of the cold front.

Synoptic Overview...An upper-level trough is forecast to exit
the Northeast Saturday night and Sunday, then the flow aloft
turns more zonal through early next week. Another trough is
forecast to amplify across eastern Canada and the Great Lakes to
the Northeast Tuesday into Thursday, which then remains in the
Northeast on Friday. We used a blend of continuity/guidance for
Saturday night through Sunday night, then blended in the 12z WPC

For Saturday night and Sunday...The axis of an upper-level
trough is forecast to slide across the region Saturday night,
then quickly move across and exit New England Sunday. A short
wave embedded within this trough is forecast to move through
Saturday night, although it may shear out to the east-northeast.
While some drying is expected to move in, enough lingering
moisture and instability combined with lift may allow for some
convection to arrive from the west before weakening. We
therefore carried some slight chance PoPs in Saturday evening
across parts of the western zones. The flow aloft then turns
more zonal on Sunday with surface high pressure building in.
This should be accompanied by more pronounced drying, and with
plenty of heating during the day Sunday the dew points are
anticipated to lower to more comfortable levels. A northwesterly
breeze on Sunday may be light enough to allow for a sea breeze
to develop in the afternoon.

For Monday and Tuesday...The zonal flow aloft continues at
least into Tuesday. This drives high pressure eventually
offshore as it weakens some later Monday. The next upper-level
trough amplifies eastward from the Midwest and Upper Great Lakes
Tuesday. This will start to back the flow more southwesterly,
and there may be a lee- side trough present on Tuesday. As the
moisture begins to increase once again combined with the
possibility for some convergence and enough instability, some
convective development is possible Tuesday afternoon. We will
carry slight chance PoPs as a result for Tuesday. Any isolated
convection especially inland should tend to diminish during the
night. It will turn more humid during this timeframe.

For Wednesday through Friday...The prospects for convection
will depend on the timing of an incoming cold front Wednesday.
This will be due to an upper-level trough arriving from the
west, however a pre-frontal trough may serve as the primary
focus for showers and thunderstorms. We will continue with
chance PoPs with the idea for at least scattered convection
possible Wednesday. As of now, the cold front should be offshore
to start Thursday and Canadian high pressure builds
southeastward, which arrives over our area on Friday. A
noticeably cooler and drier airmass overspreads our region for
Thursday and Friday.


The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Overnight...A mix of VFR and MVFR. Low level moisture remains
in place and some local low clouds and/or fog has started to
develop. The extent of the low clouds/fog is of lower

Saturday...Any fog dissipates early, otherwise VFR. Northwest
winds increase to 5-10 knots, then shift to the west or
southwest in the afternoon. Isolated late day shower or
thunderstorm possible near KRDG/KABE.

Saturday night and Sunday...VFR overall. Southwest winds 5
knots or less becoming northwest Saturday night, then northwest
winds near 10 knots Sunday.

Monday and Tuesday...Mainly VFR. Southerly winds around 10

Wednesday...Sub-VFR at times with some showers and
thunderstorms possible as a cold front arrives. Southwest winds
5-10 knots, becoming west.


Tranquil conditions will remain in place through Saturday.

Fog may develop late tonight and into Saturday morning, which
could reduce VSBYs down to 1 NM.

Saturday night through Wednesday...The conditions are
anticipated to be below Small Craft Advisory criteria.

The rip current risk for Saturday is currently outlooked as




Near Term...Iovino/Meola
Short Term...MPS
Long Term...Gorse
Marine...Gorse/Meola/MPS is the U.S. government's official web portal to all federal, state and local government web resources and services.