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000
FXUS61 KPHI 240717
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
317 AM EDT Mon Jun 24 2019

.SYNOPSIS...
High pressure loses its grip over the area today as it moves
offshore. Low pressure will move across the Great Lakes and
then into Canada today through Tuesday. Its associated fronts
will move across the Middle Atlantic region. High pressure will
build back in from the south for the mid to late week period.
Another low will move towards the region next weekend dragging a
cold front southward through the area.
&&

.NEAR TERM /THROUGH TODAY/...
High pressure off the Mid-Atlantic coast continues to drift out to
sea. Meanwhile, a warm front approaches from the west.

With clear skies, light winds, and slowly increasing low-level
moisture with dewpoints creeping up to around 60/low 60s, some
patchy fog will develop through the pre-dawn hours. That fog should
burn off quickly after sunrise, and the day starts out sunny.

High clouds out ahead of a warm front lifting through the Ohio
Valley and Appalachians will spread into the region during the day,
resulting in filtered sunshine by late afternoon.

Some weak mid-level shortwaves may spark off some afternoon showers
and thunderstorms across western zones, and those storms could make
it as far east as the I-95 corridor. However, with H5 riding
building in from the west, would not expect activity to become
widespread or well organized. Will keep PoPs capped at chance for
far western portions of the forecast area, and slight chance as far
east as Philadelphia.

Southwest flow will usher a more humid airmass into the region with
surface dewpoints climbing well into the 60s throughout the day.
Temperatures will be a bit warmer than Sunday, generally in the mid
to upper 80s.
&&


.SHORT TERM /TONIGHT THROUGH 6 PM TUESDAY/...
H5 ridge moves over New Jersey early in the evening, and then moves
offshore shortly after midnight. Low pressure passes north and west
of the region late tonight, and as it does, will drag a warm front
through the region after midnight tonight. With the support of 500
mb shortwaves, showers and thunderstorms will form to the west, and
pass through the region tonight.

Some showers and thunderstorms are possible in the evening, but the
bulk of the activity will hold off until after midnight and into
Tuesday morning.

Surface-based CAPE values will generally be less than 200 J/kg, but
MU CAPE values at 0-1 km will be as high as 1500 J/kg. So there is
some support for convection, but the main threat will be for heavy
rain. With surface dewpoints well in the 60s and low 70s, PWATs will
be over 2 inches, and given the flooding that occurred last week,
the ground remains saturated, and it will not take much rainfall for
flooding to occur. However, with winds aloft at 25-35 kt, storms
should be moving quickly enough to limit widespread flash flooding.
Still cannot rule out localized flooding in heavier showers and
thunderstorms.

Since the main threat will be in the pre-dawn hours, it will be
important to check the roads Tuesday morning before your morning
commute.

Low pressure departs Tuesday morning, and showers and thunderstorms
taper off late. Some wrap-around precip may keep some lingering
activity across northern and eastern zones into the afternoon, but
most of the region should dry out during the day.

Winds shift to the west behind the departing low, and it will take
some time for appreciably dryer air to filter into the region. Highs
on Tuesday top off well into the mid and upper 80s.
&&


.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...

Tuesday night through Friday... A summer pattern expected with
building H5 heights and sfc high pressure across the western
Atlantic. This will help to pump above average temperatures and
increasing humidity to many areas of the East. Guidance is
showing several days in a row of max temperatures right around
90 for much of the region. This would be the first `heat wave`
by definition, but a day in the upper 80s would stop the
stretch. Nonetheless, we haven`t had a week like this yet this
summer, so getting ready for the heat would be advised. A couple
scattered showers or a tstm possible Thu, but well keep the chc
low since no organized system will be present and the weather
will otherwise be precip free with skies generally mainly clear
to partly cloudy.

Next weekend...Many of the longer range models are showing an deep
upper low across Ontario/Quebec dropping southward into New
England by early next week. An associated sfc low and sharp cold
front are depicted sweeping N to S across our area Saturday
night and Sunday. This will likely put an end of the early
season heat and bring a refreshing dry/cool air mass of the
last day of June and into July. We`ll have more details as the
week progresses.
&&

.AVIATION /07Z MONDAY THROUGH FRIDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

Today...Patchy morning fog, otherwise VFR. Some late day SHRA/TSRA
possible at KRDG, but confidence not high enough to include in the
TAF at this time. SW winds less than 10 kt.

Tonight...Scattered SHRA/TSRA possible in the evening, but the bulk
of the activity will hold off until after 06Z Tuesday. Sub-VFR
conditions, possibly IFR or lower in the heaviest rainfall. VSBY
restrictions in patchy fog as well. Light south winds.

Tuesday...Lingering SHRA/TSRA taper off Tuesday morning, then
generally VFR for the rest of the day. West winds less than 10
kt.

Outlook...

Tue night thru Fri night...Mostly VFR. Patchy morning fog and
also some haze possible.

&&

.MARINE...
Sub-SCA conditions today through Tuesday. Showers and thunderstorms
with locally heavy rain will develop late tonight through Tuesday
morning. VSBY restriction in fog possible as well late tonight.

Outlook...

Tue night thru Friday...sub-SCA. Mostly fair thru the period.

Rip Currents...

There will be a low risk for the development of dangerous rip
currents today with seas running 2-3 feet and southerly winds around
10-15 kts this afternoon.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...None.

&&

$$
Synopsis...Fitzsimmons
Near Term...MPS
Short Term...MPS
Long Term...Fitzsimmons/O`Hara
Aviation...Fitzsimmons/MPS
Marine...Fitzsimmons/MPS