Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 240040
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
840 PM EDT Tue May 23 2017

.SYNOPSIS...
A couple of areas of low pressure will pass to our south this
evening then east of our area overnight into Wednesday as they
combine and move along a frontal boundary. As an area of low
pressure moves into the Ohio Valley Wednesday night into Thursday,
an occluded front and warm front will lift toward our region. A
triple point low will develop and take over as the dominant low as
it moves across our area Thursday night. This low will move away
from the area Friday, with a weak frontal boundary or surface trough
crossing the area during the day. Weak high pressure may briefly
move across the area Friday night into early Saturday. Another
frontal system is expected to affect the area Saturday night into
Sunday, followed by another on Monday and Tuesday.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Updated were needed with the shield of rain moving in quicker
than earlier expected. Steady rains have already arrived across
srn Delaware and into the eastern shore of MD. Pops have been
increased in all areas except the Lehigh Valley and srn
Poconos/Nrn NJ. Categorical pops are now in the fcst for much
of srn NJ and Delmarva for the overnight. Qpf amts have been
increased as well. Temperatures and dew points grids and winds
have been decent so far, so no big changes there.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
Wednesday...scattered leftover showers possible in the morning
but it should dry out and be a decent afternoon everywhere.
Northeast wind becomes southeast in the afternoon.

This forecast was based on a 50 50 blend of the 12z/23 GFS/NAM.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
An unsettled weather pattern continues for much of the extended
forecast with several periods of rain possible.

On Wednesday night, an area of low pressure will be lifting
through the Ohio Valley and toward the southern Great Lakes region.
Meanwhile, an occluded front and warm front will be lifting toward
our area. A triple point low is forecast to develop to our
southwest overnight, which will likely slow down the northward
progression of the frontal boundaries. This will lead to an area
of rainfall overrunning the frontal boundary and lifting across
out area overnight Wednesday into Thursday morning. As the
short wave/vorticity impulse that helps create this area of
rainfall lifts north of the area, this area of rainfall will
move north as well early in the day. Then the question for the
afternoon becomes how far north the warm front progresses as
the triple point low approaches from the west. Another period of
rainfall is expected during the afternoon and evening, but
depending on how far north the front lifts, there could be a
chance of thunderstorms to develop later in the day for a
portion of the area. The best chance for this to happen would be
for portions of Delaware and the eastern shore of Maryland, as
well as far southern New Jersey. The rest of the area would
likely be stable enough to prevent thunderstorms, and just
receive rain.

By Thursday night, the triple point low will begin moving across the
area, pulling the occluded frontal system across the area as well.
This will lead to continuing scattered showers during the night
Thursday. On Friday, the low will continue to move to our northeast
and offshore of New England. A weak frontal boundary or surface
trough New England is forecast to move across the area during the
day. This could lead to another chance of scattered showers during
the afternoon.

Friday night through most of Saturday is expected to be dry as weak
high pressure quickly moves across the area. However, a warm front
will begin approaching the area from the south late in the day and
into the overnight hours as an area of low pressure lifts into the
Great Lakes region. As the low continues to lift through the Great
Lakes region Sunday, the warm front may lift across the area before
a triple point low forms and moves across the area as well. The
exact timing of these features is still a little uncertain, but
Saturday night through Sunday looks like there should be several
periods of showers, and possible thunderstorms if enough instability
builds on Sunday.

The low pressure system that moves across the Great Lakes over the
weekend is forecast to remain nearly stationary across south-central
Canada Monday into Tuesday. This may send a couple of frontal
boundaries across the area Monday and Tuesday, leading to additional
showers or thunderstorms early next week.

&&

.AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

Tonight...VFR lowering CIGS with potential MVFR Conds in
showers KACY/KMIV late at night while any period of showers
elsewhere should not lower conditions to MVFR. Northeast wind,
may gust 20 kt ACY.

Wednesday...VFR cigs inn the morning and then sct-bkn aoa 4000
ft in the aftn. MVFR/IFR conditions possible early in the day,
mainly at KMIV/KACY. northeast wind become southeast in the
afternoon. max gusts 15 kt.

Outlook...

Wednesday night-Thursday...Conditions lowering to IFR overnight and
continuing into Thursday as periods of rain affect the area late
Wednesday night into Thursday. Improvement to VFR possible for
southern areas later in the day.

Thursday night...MVFR to IFR conditions possible with low clouds and
fog/drizzle possible.

Friday-Friday night...Improving to VFR during the day and into the
night, scattered showers possible during the daytime. Gusty
northwest winds 20-25 knots.

Saturday...Generally VFR. Showers moving into the area later in the
day, which will lead to lowering ceilings.

Saturday night-Sunday...MVFR to IFR conditions possible with periods
of low clouds and rain. Thunderstorms possible Sunday. An
improvement to VFR possible Sunday outside of
showers/thunderstorms.

&&

.MARINE...
SCA continues DE Atlc waters late tonight and now extended
through the day tomorrow.

SCA added for the NJ waters, primarily there for hazardous 5 ft
seas. There is a chance the guidance might be a foot too high
but felt I had to issue since our fcst is for 4 to 6 ft.

Rip Risk for Wednesday...LOW but on the cusp of moderate. The
reason we dont issue the tomorrow forecast sooner... most of our
rip current fatalities occur between 6PM and 8PM. Therefore, we
want todays forecast available to any potential victims so they
have more information for decision making.

The safest way to swim the surf zone, is in sight of life
guards!!!


Outlook...

Wednesday night-Friday...Small Craft Advisory conditions
possible. Varies between wind and waves criteria each period.

Friday night-Sunday...Conditions expected to remain below advisory
levels.

&&

.TIDES/COASTAL FLOODING...
CFW for minor coastal flooding issued for the Wednesday evening
high tide cycle. A CF Watch may be needed for the Thursday evening
high tide cycle for Monmouth/Ocean and Middlesex counties but
that wont be issued, if at all, until sometime Wednesday.

This afternoons issuance is also appended to a blast email for
EM`s including an image with a followup Wednesday around or
shortly after 3 Pm.

Some of the highest astronomical tides of the year are occuring
late this week. The new moon cycle on Thursday, combined with a
possible prolonged easterly flow, we will probably see some of
our coastal sites exceed minor tidal flooding levels during the
Wednesday and Thursday evening tide cycles. There is also a
small chance that we could reach moderate levels in a few spots.

&&

.CLIMATE...
ACY is #6 wettest May on record with its 6.07. The record there for
May is 8.80 set in 1948....POR back to 1874.

Monthly avg temps should end up within .7 degrees of where they
are now, possibly edging on the warmer side of the current departures
as seen in our climate data ending the 22nd.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...Coastal Flood Advisory from 6 PM Wednesday to midnight EDT
     Wednesday night for NJZ012>014-020>027.
DE...Coastal Flood Advisory from 6 PM Wednesday to midnight EDT
     Wednesday night for DEZ002>004.
MD...None.
MARINE...Small Craft Advisory from 8 AM to 4 PM EDT Wednesday for
     ANZ450>453.
     Small Craft Advisory from midnight tonight to 4 PM EDT
     Wednesday for ANZ454-455.

&&

$$
Synopsis...Robertson
Near Term...PO
Short Term...Drag
Long Term...Robertson
Aviation...Drag/Robertson/PO
Marine...Drag/Robertson/PO
Tides/Coastal Flooding...
Climate...



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