Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 222045 CCA
AFDPHI

Area Forecast Discussion...CORRECTED
National Weather Service Mount Holly NJ
445 PM EDT Sun Oct 22 2017

.SYNOPSIS...
High pressure located over eastern Canada and the western North
Atlantic this afternoon will continue to drift farther out to
sea during tonight and Monday. A cold front is forecast to
approach from the west on Tuesday and it should pass through our
region on Tuesday night. Low pressure is expected to develop
along the front and it should pass over or near New England and
southeastern Canada on Wednesday and Thursday. High pressure is
anticipated to follow for Friday and Saturday. Another cold
front may approach from the west on Sunday.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
High pressure located over New England will continue to move
northeast resulting in southeasterly flow to continue on the
backside of the departing high. This will allow the moisture
transport from the Atlantic to continue into the region. Low
clouds and fog formation will be the main highlights overnight
given the increased moisture and light winds. Unlike the last
few nights, radiational cooling is not expected to be as
aggressive so stuck close to MET/MAV guidance with lows in the
50`s.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
A strong cold front will continue to advance eastward in wake
of the departing high toward our region. This will allows a
strong southerly to southeasterly moisture flow to continue. Fog
and low clouds will persist throughout a good portion of the
day, likely even slower to burn off than today. However,
sunshine will likely break through at times in the afternoon
tomorrow. Several models are also hinting at a couple of passing
light showers across northern NJ and Eastern PA, so have
continued with slight and low chances of showers. The majority
of the steadier showers will hold off till the evening. The low
clouds and fog may keep temperatures down a bit from what the
MOS guidance has, particularly for northern NJ and PA. Still,
highs should reach the mid 70`s in Delmarva and 60`s to low 70`s
in the Lehigh Valley, Poconos and northern NJ.

&&

.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
A deepening mid level long wave trough will be in the process
of settling over the eastern half of the country on Monday night
and Tuesday. A negative tilt short wave is forecast to lift
northeastward on the front side of the trough and its axis
should pass over our region early on Tuesday.

A slow moving cold front is expected to extend from the eastern
Great Lakes to the eastern Gulf of Mexico on Monday evening.
The boundary will move eastward and it should arrive in our
region late on Tuesday.

The slow forward progress of the front will allow it ample time
to tap into Gulf moisture and eventually into some Atlantic
moisture as it approaches and moves into our region. As a
result, we are anticipating moderate to heavy rainfall at times.
We have increased our rainfall projections mainly into the 1 to
2 inch range with locally higher amounts possible. Due to the
recent dry spell, we are not expecting any flooding issues other
than some poor drainage flooding. Leaf-clogged drains will
enhance the possibility of ponding of water on roadways.

We remain under a marginal risk for severe weather on Tuesday.
The negative tilt short wave and the approaching cold front
suggest the potential for a QLCS set-up. If a narrow convective
line develops, it should work its way from west to east across our
region from late Monday night into early Tuesday afternoon.

Moderate to heavy rain is anticipated to linger near the coast
into Tuesday evening until the front begins to make its way out
to sea.

The cold front and its associated cloud cover and precipitation
will continue to move slowly eastward on Wednesday as a wave of
low pressure develops along the boundary and moves up into New
England and vicinity. The axis of the mid level long wave trough
is forecast to pass overhead on Thursday and it should finally
kick the surface system well to our east.

Surface high pressure is expected to begin building into our
region from the southwest and south on Thursday before it slides
out over the ocean on Friday and Saturday. We should experience
some clear for late in the week and the early part of the
weekend.

The model guidance differs in handling the timing of our next
cold front. It appears as though it will arrive around Sunday,
so we will indicate a chance of showers at that time.

Daytime temperatures should be near 10 degrees above normal on
Tuesday. Readings are forecast to drop back near normal on
Wednesday. Slightly below normal temperatures are anticipated
for Thursday with readings rebounding to normal or slight above
normal for Friday and the weekend.

&&

.AVIATION /19Z SUNDAY THROUGH FRIDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

VFR through this evening. Low clouds and stratus are likely to
form and at least form a broken ceiling overnight around the IFR
level at all TAF sites. Visibilities will likely fall as well
with fog formation toward sunrise, with restrictions of IFR or
locally LIFR right likely around sunrise. It will likely take
till mid and late morning to see lifting ceilings and
visibilities. The 18z TAFS featured general trends for the
overnight hours and the day Monday. Given higher than normal
uncertainty, the timing and exact degree of restrictions will
likely need to be fined-tuned with the upcoming 00z/06z TAFS.

OUTLOOK...
Monday night through Tuesday night...Conditions lowering to
MVFR and IFR in showers. Isolated thunderstorms and moderate to
heavy rain are possible, along with a south wind gusting around
25 or 30 knots.

Wednesday...A chance of morning showers with conditions
improving to VFR.

Wednesday night through Friday...Mainly VFR.

&&

.MARINE...
Wave heights look to be in a fairly stable state of around two
feet through tomorrow morning then build in the afternoon but
stay under four feet. Winds will also be under 10 knots into
Monday then increase to around 10 knots during the afternoon.
Some patchy fog and/or low clouds are possible overnight and on
Monday which may limit visibilities in a few locations.

OUTLOOK...
Monday night and Tuesday...A Small Craft Advisory is in effect
for southerly wind gusts near 30 knots. Localized gale force
gusts are possible on Tuesday. Waves on our ocean waters should
build to 7 to 10 feet.

Tuesday evening...A Small Craft Advisory may need for southerly
wind gusts near 30 knots. Waves on our ocean waters are
forecast to be 7 to 10 feet.

Late Tuesday night through Thursday night...A Small Craft
Advisory may be needed on our ocean waters for wave heights of 5
to 6 feet, even as the wind becomes west to northwest around 10
to 20 knots.

Friday...No marine headlines are anticipated.

&&

.EQUIPMENT...
44091 buoy drifted away from its mooring and has since been
recovered. Its return to service date is still unknown, though
we`ll try to have an answer Monday afternoon.

Weather observations at KVAY may be incomplete for the
remainder of the day.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory from midnight Monday night to 6 PM EDT
     Tuesday for ANZ430-431-450>455.

&&

$$

Synopsis...Iovino
Near Term...Gaines
Short Term...Gaines
Long Term...Iovino
Aviation...Gaines/Iovino
Marine...Gaines/Iovino
Equipment...Staff



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