Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 161729
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
129 PM EDT Mon Apr 16 2018

.SYNOPSIS...
The low pressure system that brought storms and a cold front to the
Mid Atlantic this morning, will slowly propagate northeast away from
the region on Tuesday. Another area of low pressure organizing over
the Midwest will propagate towards New England on Thursday. As it
does so, our region will first see a warm front, followed quickly by
a cold front. Canadian high pressure will move into the area for
the weekend.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
The steady moderate to heavy rainfall has moved out of the area
this morning, therefore the Flash Flood Watch was cancelled.
There will remain some residual flooding into this afternoon and
evening. Several Flood Warnings and Flood Advisories remain in
effect, so please see these statements for the latest updates.

A warm front remains in place across basically the I-95
corridor early this afternoon. Its parent low pressure system
has now moved to Chester and Lancaster counties in
Pennsylvanian. This low will continue to lift across eastern
Pennsylvania through the remainder of today, before lifting into
New York state through the late afternoon and into this evening.
As it does so, it will continue to lift the warm front across
the area, as well as pull the cold front across the area as
well.

As the low lifts north of the area and the fronts move across
the area, there will remain a chance for scattered showers and
thunderstorms through the afternoon as additional short
wave/vorticity impulses move across the area. However, most
places this afternoon will remain dry.

Winds will remain gusty 20 to 30 mph, with higher gusts reaching
30-40 mph at times into this afternoon. Directions will remain
northeast-easterly ahead of the warm front, then become more
south-southwesterly behind the warm front, before swinging to
west-southwest behind the cold front this afternoon.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM TUESDAY/...
By early this evening, low will be departing to the NE into NY
State into New England dragging a final surface trough through
the area. In addition, systems` upper low will still be centered
near western PA with the broad circulation continuing to spin
shortwaves through the area. The upshot of this is that mainly
cloudy skies with some continuing scattered showers are likely
to affect parts of the area at least into this evening and
likely through the overnight across the southern Poconos. In
fact as temperatures drop off into the low to mid 30s tonight
across the far north, any rain showers will change over to snow
showers with continuing cool, gusty, west winds. Temps will be a
bit warmer farther south with lows mainly in the upper 30s to
low 40s over SE PA through central, S NJ, and the Delmarva.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Made few changes to the long term forecast in order to focus on the
ongoing weather tonight.

Fair weather is expected from Tuesday night into Wednesday as high
pressure arrives across the area. It will be a bit warmer than
Monday/Tuesday, but still slightly below normal for mid-April. Highs
will generally be in the mid/upper 50s north/west and low/mid 60s
south/east. These values will be 2 o 4 degrees below normal.

Another low pressure system will approach the area later Wednesday
and last into Thursday evening. The system will be progressive, so
even though the low is depicted by the models as being rather
strong, it will not have large window of opportunity when our area
will be in the warm sector, and thus have more moisture for
precipitation. We therefore have mostly chc pops in the fcst for Wed
night/Thu and slgt chc pops into Thu night. Temperatures will remain
mostly at or a little below normal this period. The warmest day will
be Thursday (near normal) with mid/upper 50s for highs across the
north and low/mid 60s over Delmarva and srn NJ.

High pressure from Canada builds in for late this week and into the
weekend. Mostly fair weather is expected with a continuation of
below normal temperatures.

&&

.AVIATION /17Z MONDAY THROUGH FRIDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

Today...Conditions remain between MVFR and IFR early this
afternoon, and will remain so through much of the remainder of
the afternoon. However, by late this afternoon and into this
evening, we expect an improving trend to VFR. There will remain
a chance for scattered showers during the afternoon hours, with
an occasional thunderstorm possible. However, we will not
include thunderstorms at this time unless we see them on radar.

E/SE winds north of the warm front will shift to SW/W this
afternoon as the warm front and low pressure lift north of the
area. Winds speeds will be around 10 to 15 knots, with gusts to
around 20 to 30 knots for many locations. Potential for some
erratic winds/gusts around showers. Moderate confidence.

Tonight...mainly VFR. Moderate confidence.

Outlook...

Tuesday and Wednesday...Mostly VFR conditions are expected. A few
showers are possible, primarily for KABE and KRDG, which could lead
to brief reductions in the flight category. Moderate confidence.

Wednesday night and Thursday...Starting VFR, we may see conditions
lower as a warm front lifts through the area and precipitation moves
in. However, confidence is low at this time.

Thursday night and Friday...Mostly VFR expected behind a cold front
that will bring a shift to northwesterly winds and drier conditions.
High confidence.

&&

.MARINE...
We have extended the Gale Warning for the Delaware Bay and the
southern waters adjacent to Delaware, and also keep the Gale
Warning in place across the waters adjacent to New Jersey. While
many locations are not reaching gale force right now, as the low
pressure lifts to the north of the area and the cold front
slides through this afternoon, winds will likely increase again
to gale force for a period this afternoon.

The heaviest and steady rainfall is lifting through the northern
half of the New Jersey coastal waters, and behind this rainfall,
we expect scattered showers and possibly an occasional
thunderstorm through the remainder of the afternoon.

Tonight...A relative respite as winds should actually drop
below SCA levels this evening before starting to ramp back up
again overnight...likely to near or just below SCA levels by
early Tuesday.


Outlook...

Tuesday and Tuesday night...lingering elevated seas are possible on
the ocean waters through this time. Otherwise, winds should stay
below SCA criteria.

Wednesday and Thursday...Winds and seas are expected to be below SCA
criteria.

Thursday night and Friday...Winds and seas should increase once
again and may approach SCA criteria.

&&

.HYDROLOGY...
Flash Flood Watch will continue for now as heavy rain moves
through the area. Several Flood Advisories and Flood/Flash
Flood Warnings are being issued as well. Please see the latest
warnings and advisories for the latest information.

&&

.TIDES/COASTAL FLOODING...
130 PM Update: Coastal Flood Warnings have been allowed to
expire for coastal NJ and DE. Most tidal gauges captured minor
tidal flooding. However, the severity of flooding was
exacerbated by freshwater runoff from the heavy rain that
occurred with the morning high tide.

The Coastal Flood Warning for the upper Delaware Bay (New
Castle, DE and Salem, NJ counties) continues through 2 PM. Reedy
Point peaked at only one-tenth inch below moderate threshold
with the midday high tide.

The Coastal Flood Advisory for the tidal portion of the Delaware
River (including Philadelphia and Trenton) was originally only
valid through 3 PM but was extended through 5 PM since high tide
occurs at Philadelphia just before 3 PM and just after 4 PM at
Trenton.

A Coastal Flood Advisory was issued for the eastern and
northeastern shore of the Maryland Chesapeake Bay for this
afternoon and evening. Positive tidal anomalies about both
Tolchester and Cambridge tidal gauges have been increasing
steadily over the past few hours and has not been particularly
well forecast by models. Expect these surge values to remain
steady or even start to decrease heading toward the next high
tide (just after 5 PM at Cambridge and just after 8 PM at
Tolchester Beach) in conjunction with a wind shift from Sly to
Wly.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Coastal Flood Advisory until 5 PM EDT this afternoon for
     PAZ070-071-106.
NJ...Coastal Flood Warning until 2 PM EDT this afternoon for NJZ016.
     Coastal Flood Advisory until 5 PM EDT this afternoon for
     NJZ015-017>019.
DE...Coastal Flood Warning until 2 PM EDT this afternoon for DEZ001.
MD...Coastal Flood Advisory until 11 PM EDT this evening for MDZ008-
     012.
     Coastal Flood Advisory until 9 PM EDT this evening for MDZ015-
     019-020.
MARINE...Gale Warning until 5 PM EDT this afternoon for ANZ430-431-
     450>455.

&&

$$
Synopsis...Johnson
Near Term...Fitzsimmons/Robertson
Short Term...Fitzsimmons
Long Term...Johnson
Aviation...Fitzsimmons/Johnson/Robertson
Marine...Fitzsimmons/Johnson/Robertson
Hydrology...
Tides/Coastal Flooding...Klein



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