Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 202304
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
704 PM EDT Tue Jun 20 2017

.SYNOPSIS...
High pressure will gradually build east towards the region through
Thursday. That high will shift off shore by the end of the week.
A pair of cold fronts are expected this weekend or early next
week.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Regarding tornado surveys: Public Information Statements were
issued for two confirmed EF-0 tornadoes yesterday (one in Berks
County, PA and the other in Sussex County, DE).

Minor adjustments were made to sky cover, temperature and winds
for the 630 PM ESTF update. Had to knock down temperatures a
few degrees in far southern NJ and mid Delmarva where high
clouds briefly tempered heating late this afternoon. These
clouds are quickly thinning out early this evening but should
increase one again overnight as a shortwave disturbance
approaches from the west.

Previous Discussion...
Westerly winds gusting to around 20 mph late Tuesday afternoon
will gradually shift to the southwest during the evening hours
and subside to under 10 mph before midnight. Clouds which
developed over interior sections on Tuesday will quickly
dissipate toward evening, with mainly clear skies expected for
most of the overnight hours. Closer to the coast...clouds
associated with a stalled front may persist through the
overnight hours. The GFS is suggesting a chance of rain showers
with these clouds...but have decided to follow ECMWF guidance
and keep the mention of showers out of the forecast. Minimum
temperatures tonight expected in the mid 50s in the far north to
the upper 60s in the far south.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
A weak boundary settling across the CWA during the late morning and
early afternoon hours will bring some additional cloudiness and
slight chance of showers and scattered thunderstorms, but widespread
showers are not expected. Southwesterly winds are expected to pick
up from late morning through the afternoon hours with gusts around
or over 20 mph possible at times.  High temps in the mid 70s are
expected in the far north, and in the mid 80s in the south.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
Wednesday night and Thursday...Surface high slowly builds east
towards our region before shifting off shore. As a result,
expect mostly dry conditions unless the high weakens or moves
off shore faster than currently anticipated.

Friday...southwesterly flow over our region, thanks in large part to
the Bermuda high once again develops. The biggest impact will be
increasing dew point temperatures. Though temperatures won`t be
appreciably higher than what we will see through mid week, expect
heat index values to be increasing.

Saturday through Monday...A pair of cold fronts are expected through
this period. There is considerable model disagreement as to both the
timing of the fronts and if the first or second cold front will be
the stronger front. Looking at the larger picture, it looks like the
pattern will tend to be less progressive through this period (3 or 4
Rossby waves depending on the model and time period you look at).
Therefore, the forecast favors a solution closer to the ECMWF with
the initial front arriving Saturday, but likely only resulting in a
modest temperature gradient. The second, and likely stronger, cold
front should arrive Monday night. Have kept precip chances through
much of this period, given the uncertainty of the timing of the
fronts. However, I do not expect the weekend to be a complete
washout as the highest chances for showers and thunderstorms will
likely be with and just ahead of the first cold front.

Tuesday...Assuming the cold front arrives Monday night, temperatures
by Tuesday should be 5 to 10 degrees below normal, with highs
ranging from the upper 60s to mid 70s.

&&

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

Expect VFR conditions at all TAF locations tonight with
southwesterly winds below 10 KT. Generally VFR conditions are
expected again on Wednesday, but an isolated shower or even a
thunderstorm cannot be completely ruled out. Wind gusts around 20 KT
are expected from late morning through the afternoon hours.

Outlook...

Thursday...mostly VFR conditions are expected.

Friday through Sunday...Increasing chances for showers and
thunderstorms through this period. MVFR or lower conditions are
possible with any showers or thunderstorms. Otherwise, expect mostly
VFR conditions.

&&

.MARINE...
The SCA for seas now only covers the coastal waters from Sandy Hook
NJ south to Little Egg Inlet, and only until midnight. After seas
drop below 5 feet in this area this evening, sub-SCA conditions are
expected for the remainder of the overnight hours, and on Wednesday,
although there could be so gusts in the 20 KT range during the
afternoon.

Outlook...

Thursday...winds and seas are expected to remain below SCA criteria.

Friday...winds and seas will begin to build and may be at or just
below SCA criteria by late in the day.

Saturday and Sunday...SCA conditions are possible, especially for
seas on the ocean waters.

RIP CURRENTS...

A moderate risk for the development of dangerous rip currents will
persist through Wednesday and possibly into Thursday along the coast
of Delaware and New Jersey due to a long period southeasterly swell.

&&

.TIDES/COASTAL FLOODING...
Very high astronomical tides are expected in association with
the new moon on Friday. That, combined with a brief period of on
shore flow on Thursday could result in minor coastal flooding
with the Thursday afternoon and evening high tide primarily for
the Atlantic coastal areas and the shores of the Delaware Bay.
Minor coastal flooding may continue with the Friday afternoon
and evening high tide.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory until midnight EDT tonight for ANZ450-451.

&&

$$
Synopsis...Johnson
Near Term...Klein/Miketta
Short Term...Miketta
Long Term...Johnson
Aviation...Johnson/Miketta
Marine...Johnson/Miketta
Tides/Coastal Flooding...



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