Area Forecast Discussion
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FXUS61 KPHI 211945
Area Forecast Discussion
National Weather Service Mount Holly NJ
245 PM EST Tue Feb 21 2017
High pressure, centered along the New England coast this
afternoon, will continue to drift southeastward through
Thursday before a cold front approaches from the west Friday.
The cold front will arrive Saturday afternoon with high pressure
then building over the area through Monday.
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
An active upper air pattern, which features a trough well north of
the Great Lakes through tonight that weakens some. This has surface
low pressure with it and a cold front that extends southward. A
closed low is gradually moving across the Gulf Coast states and
northern Gulf of Mexico. Meanwhile, a narrow but high amplitude
ridge axis is centered along the East Coast this afternoon and this
will weaken some as it shifts eastward through tonight.
Our sensible weather is driven by surface high pressure that will
continue to shift eastward away from our coast. This will maintain a
southerly flow regime along with some warm air advection aloft. A
cold front well to our west is forecast to weaken as it moves east
and nearly dissipates toward morning. This weakening is due to the
main energy sliding well to our north through tonight, and the
thermal gradient washing out. There still remains an area of short
wave energy preceding it late tonight, and the associated weak lift
may be enough to produce a few showers mainly across the northern
areas. Farther south, some sprinkles cannot be ruled out near
There remains plenty of cloud cover to our southwest this afternoon,
although some thinning is noted. While clouds should dominate
overall tonight, the thicker cloud cover looks to hold off until
after Midnight. This along with some warming aloft and increase in
the surface dew points should keep temperatures from dropping as
much tonight. The far southern areas may see temperatures creep up
some toward daybreak as the low-level flow veers more from the
southwest. Low temperatures were mostly a MOS/continuity blend.
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
The upper-level flow will be more zonal Wednesday in response to
energy amplifying across the West, and a strong closed low near the
northeastern Gulf of Mexico. This flow regime will drive weak low
pressure up across the Midwest and upper Great Lakes region, pulling
a developing warm front to our northwest by the end of the day. This
setup will feature warm air advection, which will be aided by the
low-level flow becoming more southwesterly. The more notable warm
air advection is forecast to be from the Ohio Valley on westward.
Backing up a bit, a weakening short wave traversing the area in the
morning may produce a few showers (mainly north) and sprinkles.
Given the warming aloft and not a lot of mixing, cloud cover may
hold in through about Midday before some clearing occurs. The amount
of cloud cover will have an impact on the afternoon temperatures,
however boundary layer warmth may start to win out again and
therefore went with some of the warmer guidance (close to
continuity). Despite it turning warmer once again, it looks like
highs should fall short of records.
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
The period from Wednesday night through Friday is expected to
feature unseasonably mild weather as high pressure over the
western North Atlantic maintains a southerly surface flow in our
region. It appears as though Thursday will be the warmest of
the three days with maximum temperatures running about 25
degrees above normal. The record high temperatures for
Wednesday, Thursday and Friday are listed below in the climate
section of this product.
A partly cloudy sky (mainly cirrus) is expected for Wednesday
night into Thursday morning. An increase in low level moisture
may result in patchy fog at that time.
Another mid level impulse is forecast to approach from the west
late on Thursday and it should pass over our region late on
Thursday night. The feature is expected to bring an increase in
cloud cover along with a chance of rain showers. The chance of
rain showers may linger into Friday, especially in parts of
eastern Pennsylvania and central and northern New Jersey.
A strong cold front is expected to extend from the Great Lakes
to the Texas Gulf Coast late on Friday. The boundary will
continue to progress eastward and it should pass through our
region on Saturday afternoon. We will continue to mention an
increasing potential for rain showers on Friday night into
Saturday along with a chance of thunderstorms on Saturday
High pressure and dry weather are anticipated to follow the
cold front for Sunday and Monday. Temperatures should be
considerably colder than those ahead of the front. However,
readings are forecast to remain slightly above normal at that
.AVIATION /20Z TUESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.
Rest of this afternoon...VFR with any ceiling above 15000 feet.
Southeast to south winds mostly 10 knots or less, becoming
Tonight...VFR overall. Ceilings should lower to 8000-10000 feet,
however there is a chance for MVFR ceilings developing toward
daybreak from near ABE on northward. Some showers are possible after
08z mainly near and north of a line from ABE to TTN. Southerly winds
5 knots or less, or locally light and variable.
Wednesday...Local MVFR ceilings possible to start mainly from ABE
northward, otherwise VFR ceilings. A few showers or sprinkles may be
around mainly in the morning. Southwest winds 5-10 knots.
Wednesday night and Thursday morning...Mainly VFR with patchy
fog possibly lowering conditions to MVFR or IFR for a time.
Thursday night and Friday...Mainly VFR. However, there is a
chance of showers which may result in a period of MVFR or IFR
Friday night and Saturday...An increasing potential for showers
along with MVFR and IFR conditions. Also, there is a chance of
thunderstorms on Saturday afternoon.
The conditions are expected to remain below Small Craft Advisory
criteria through Wednesday. High pressure will continue to shift
offshore through tonight into Wednesday. This will allow the surface
flow to turn from southeast to south and southwest tonight and
Wednesday. Some slight enhancement may occur into this evening up
Delaware Bay within the southeast flow.
Wednesday night through Friday night...No marine headlines are
Saturday...Southerly wind gusts around 25 knots are possible.
Wave heights on the coastal waters off Delaware and New Jersey
may build to 5 or 6 feet.
High temperature records for Wednesday through Friday. Most of
these records will probably remain intact.
Wednesday 2/22 Thursday 2/23 Friday 2/24
ACY 68-1991 72-1985 75-1985
PHL 68-1997/1974 75-1874 74-1985
ILG 69-1997/1974 72-1985 78-1985
ABE 68-1974 71-1985 76-1985
TTN 66-1997 74-1874 74-1985
GED 72-1997 no data no data
RDG 70-1974 72/1932/1922 77-1985
MPO 56-1997 60-1977 60-1984