Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 252345

Area Forecast Discussion
National Weather Service Mount Holly NJ
745 PM EDT Tue Oct 25 2016

High pressure will move across eastern Canada through Thursday while
nosing down across our area Wednesday into Wednesday night. An area
of low pressure will move north of our area Thursday into Thursday
night, lifting a warm front across the area early Thursday morning,
then a cold front later in the day Thursday. High pressure briefly
affects the area late Friday night then builds south of the area
over the weekend. Another low pressure system is forecast to slide
eastward just north of the area around Sunday. High pressure is then
expected for Monday.


Skies clearing out across the region with diminishing winds. Many
of the automated surface observation sites are showing either calm
winds or winds less than 5 KT, so the area has already begin to
decouple. Temps should begin to drop off fairly rapidly, and with
surface dewpoints in the 20s, expecting frost and freeze
conditions across the CWA.

Philly metro and surrounding PA suburbs, Cape May County, and
much of Delmarva, have a frost advisory for less risk of damaging
near 32F for an hour or two near the approximate 725 am sunrise.

The NJ shore and DE beaches, where winds may stay up through much
of the night due to heat sink water temperatures in the upper 50s,
looking to keep the wind actively drawing cooler land airmass
toward the water should prevent frost or a freeze.

The growing season has already ended in the Poconos and far
northwest NJ.

Forecast basis: 50 50 blended 12z/25 GFS/NAM MOS then lowered 1
degree in parts of northwest NJ and and eastern PA.

These low temps should average 5 to 7 degrees below normal, which
means far from a record and its seasonally about the time the
growing season ends in a larger section of PA and NJ.

Forecasters during the day Wednesday will post a note in this
AFD, also via a PNS, about what counties met the requirement of 50
coverage of below freezing temps to end the season.


Variably thin bands of cirrus will allow plenty of sunshine,
however much less wind will also limit mixing potential. Max temps
a few degrees cooler than they were this Tuesday afternoon and
again about 5 to 7 degrees below normal. Quite a nice fall day.

This part of the forecast was based on a 50 50 blend of the
12z/25 GFS/NAM Mos, modified slightly warmer by the 2m temps of
the 12z EC. For PHL thats 51F, so that should mean a high of 55 in


On Wednesday night, high pressure continues to push through
eastern Canada, with our area being on the very far southern edge.
Meanwhile, an area of low pressure will be moving through the Ohio
River Valley and into the eastern Great Lakes. A warm front will
be to our south, and cold air will be trapped north of this
frontal boundary and on the southern edge of the high to our
north. For much of the overnight hours Wedensday, we do not expect
any precipitation. But as we move into Thursday morning, light
precipitation could begin moving into our area with the
overrunning moisture, and a short wave moving across our area
north of the warm front. With temperatures below freezing across
our northern areas, we could have a period of sleet and freezing
rain. Soundings do not look very conducive to much snow, but there
could still be some snow mixing in at times. This could be our
first wintry precipitation event of the season and lead to some
slippery conditions come Thursday morning.

As the low continues to push eastward, the warm front should lift
northward across the area, or at least partly through the area, and
rainfall will overspread the rest of the area. The areas that
have frozen/freezing precipitation should change over to all rain.
The rain will likely continue through the day and into the
evening, before the cold front sweeps through and the rain
eventually clears out overnight Thursday. There is some
instability during the evening across the coastal areas, so it
would not be surprising if some isolated rumbles of
thunder/lighting occurs. As the front sweeps through during the
evening however, regardless of thunder, we will likely have a
period of gusty winds of 20-30 mph. Interestingly, the warmest
temperatures Thursday may occur during the evening and just before
midnight, before the cold air filters in behind the front.

Friday is expected to be dry as the low pulls away front the area
and high pressure approaches from the west. We expect gusty winds
during the day Friday with gusts of 25-30 mph possible. With the
cool northwest wind, it would not be surprising to see some lake
effect showers to move in across the area from the northwest, so we
have a slight chance of showers across the northern areas. The high
briefly affects the area Friday night, which should keep dry weather
in the forecast.

Saturday, the high pushes well south, while a warm front north of
the area shifts eastward. The front will likely stay north of the
area Saturday into Saturday night and keep any precipitation north
of the area. However, we keep a slight chance of precipitation as it
is possible the some moisture may affect our northern areas if the
front is a little farther south.

On Sunday, an area of low pressure is forecast to move eastward
along the warm front located to our north, eventually pulling a cold
front across the area. The precipitation associated with this front
may dry out as it approaches, but there is a chance for some
scattered rainfall to affect the area.

High pressure once again is expected to move into the area later on
Monday and Monday night, bringing dry weather to the area.


The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

Tonight...VFR. SKC. NW winds diminishing to less than 10 KT, but
some gusts to 20 KT possible at KPHL through around 04Z. Nearly
calm winds possible late tonight into Wednesday morning.

Wednesday...VFR bands of variably thin cirrus aoa 20000 ft.
Northwest wind becoming north late in the day.

Wednesday night...VFR for most of the night. Precipitation and lower
conditions may begin moving into western areas toward daybreak. Some
sleet or freezing rain may be possible for areas located north of
the TAF sites around daybreak.

Thursday...Conditions lowering to MVFR or IFR with rain spreading
across the area. Some sleet or freezing rain may be possible for
areas located north of the TAF sites Thursday morning.

Thursday night...MVFR or IFR conditions with rain during the
evening, then improving conditions overnight. Gusty northwest
winds 20-30 knots possible during the evening with a cold frontal

Friday...Generally VFR, some MVFR CIGS possible for northern
areas. Gusty northwest winds 20-30 knots during the day.

Friday night-Saturday night...Generally VFR.

Sunday...Generally VFR, some MVFR CIGS possible for northern
areas. Gusty northwest winds 20-25 knots.


Will go ahead and cancel the SCA in effect for DE Bay, as winds
continue to diminish. For the northern Atlantic waters, based on
latest model guidance, seems as of winds may gust to 25 KT into
Wednesday morning, so will extend the SCA until 10Z for
ANZ450-451. On all other ocean waters, SCA should be able to come
down by 2 AM. marine headlines anticipated.

Wednesday night...Sub-Small Craft Advisory conditions expected.

Thursday...Sub-Small Craft Advisory conditions early, with
increasing winds late in the day with a warm front lifting through
the area. Small Craft Advisory conditions likely by late afternoon

Thursday night...Small Craft Advisory conditions likely, with a
brief period of Gale force gusts possible during the evening near
the timing of a cold frontal passage.

Friday-Friday night...Small Craft Advisory conditions likely to
continue through the day and into the evening Friday. Conditions
should drop below Advisory levels overnight.

Saturday-Saturday night...Winds and seas may approach Small Craft
Advisory levels during the day into the evening Saturday.


Our forecast indicates October should average 2 to 3.5 degrees above
normal for PHL and ABE. Forecasts are trending warmer beyond Thursday.
This should result in average temperatures ranking between 15 and
20th warmest Octobers on record. This is only noteworthy in that
the excessive monthly warmth of July, August, September eased in
October. Will reevaluate Sunday.


PA...Freeze Warning from midnight tonight to 9 AM EDT Wednesday for
     Frost Advisory from midnight tonight to 9 AM EDT Wednesday for
NJ...Freeze Warning from midnight tonight to 9 AM EDT Wednesday for
     Frost Advisory from midnight tonight to 9 AM EDT Wednesday for
DE...Freeze Warning from midnight tonight to 9 AM EDT Wednesday for
     Frost Advisory from midnight tonight to 9 AM EDT Wednesday for
MD...Freeze Warning from midnight tonight to 9 AM EDT Wednesday for
     Frost Advisory from midnight tonight to 9 AM EDT Wednesday for
MARINE...Small Craft Advisory until 2 AM EDT Wednesday for ANZ452>455.
     Small Craft Advisory until 6 AM EDT Wednesday for ANZ450-451.


Near Term...Drag/MPS
Short Term...Drag
Long Term...Robertson
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