Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 261034
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
634 AM EDT TUE JUL 26 2016

.SYNOPSIS...
A cold front will stall near or just to the south of the area
today. This front will gradually lift north by the end of the week
with areas of low pressure developing along this boundary causing
periods of showers and thunderstorms, mainly toward the end of the
work week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
An impulse traveling in the mid level flow was passing overhead
early this morning and it was accompanied by a surface trough.
Both features should pass off the coast with decreasing dew point
temperatures in their wake.

We are expecting patchy fog and low clouds early this morning,
especially where heavy precipitation fell. Both should be quick to
dissipate this morning as the atmosphere begins to mix and dew
point readings lower.

The sky is forecast to be mostly sunny for today with only some
cirrus overhead along with scattered cumulus developing.

Maximum temperatures are expected to be in the middle 90s for
today, except in our far northern counties and along the immediate
coast. Afternoon dew point readings should be in the 60s in our
northern and central counties and in the lower 70s in the south.
Heat index values will likely fall just short of 100 in the urban
corridor from Trenton to Philadelphia to Wilmington. As a result,
we will not issue a Heat Advisory or Excessive Heat Warning. The
same is true for some of our Delmarva counties which may just
nudge their excessive heat criterion of a 105 heat index. All
other areas in our region should also remain below their criteria.

The atmosphere will likely remain capped over much of our
forecast area for this afternoon so we are not anticipating any
showers and thunderstorms with one exception. There should be
marginal instability across Talbot County and Caroline County in
Maryland and Sussex County in Delaware along with a slightly
weaker cap there. We will mention a slight chance of precipitation
for those counties.

The wind should favor the west and northwest around 10 mph for
today.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/...
Weak high pressure is forecast to nose into our region from the
west for tonight. As a result, we are expecting a mainly clear
sky. The only exception will be our far southern counties where
there may be some lingering scattered shower and thunderstorm
activity.

Temperatures are expected to fall into the 60s in our northern
counties and into the 70s elsewhere with a light and variable
wind.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
The stalled frontal boundary across the delmarva will be the main
focus of attention over the next few days. Available medium range
guidance all keep the high pw air just south of the boundary with
values in excess of 2". Heat indices Wednesday look to top out in
the lower to middle 90s climbing to the middle to upper 90s from
the Philadelphia metro area southward to the delmarva Thursday.
Precipitation chances remain confined to southern portions of the
forecast area Wednesday with increasing chances Thursday into
Friday for the remainder of the area.

Temperatures Wednesday on track to be a couple of degrees cooler
than today, but with building heights Thursday temps rebound into
the mid 90s in the metropolitan areas with upper 80s/lower 90s
near the water.

Forecast for the Thursday through Saturday period remains
complicated. Medium range deterministic guidance is highly
divergent as to the evolution of the shortwave trough spinning up
a surface wave on the retreating warm front. The ECMWF remains on
the slower end of the solution while the GFS is faster and
generates a lot more QPF. The Canadian is in between. At this
point, forecast will lean heavily on ensemble means are probably
the most sensible approach until more agreement develops across
the medium range guidance. In the sensible weather this would
suggest keeping pops fairly constrained during the day Thursday
with the best chances for storms late Thursday night through
Friday.

Precipitation chances will continue through the weekend before
dryer air moves into the mid-Atlantic early next week.
Temperatures this weekend and early next week expected to be
closer to climatological normals.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Areas of low clouds and fog are expected through about 1200Z.
Otherwise VFR conditions are anticipated through the TAF periods
under a mainly clear sky. We are not forecasting any precipitation
at or around our TAF sites.

A light and variable wind early this morning should settle into
the west and northwest around 10 knots for today. The wind is
forecast to become light and variable for tonight.

Outlook...
Wednesday through Saturday...Mainly VFR conditions expected.
Scattered showers and thunderstorms Thursday and Friday, with
MVFR/IFR conditions possible with any shower and thunderstorm
activity.

&&

.MARINE...
The wind direction should favor the northwest and west this
morning before backing toward the southwest and south for this
afternoon and evening. The wind may turn around toward the north
late tonight. Speeds should remain 15 knots or less. Wave heights
on our ocean waters are expected to favor the 2 to 3 foot range.
Waves on Delaware Bay should be 2 feet or less.

Outlook...
Wednesday through Saturday...Sub-advisory conditions are expected
to continue on the area waters through most of the work week.
Expect higher winds and waves in and near scattered showers and
thunderstorms that will be more likely at the end of the week.

Rip Currents...
There is a low risk for the development of dangerous rip currents
for today. We are anticipating an offshore wind this morning
around 10 mph becoming south to southwest for this afternoon.
There will likely be a southerly 2 foot swell with a period of
about 5 or 6 seconds.

The probably risk for the development of dangerous rip currents
on Wednesday is also low. Conditions will be similar to those of
today except the wind should be mainly onshore during both the
morning and afternoon hours.

&&

.CLIMATE...
The last time the temperature reached or exceeded 98F at PHL was
three years ago on July 18, 2013. The last 100-degree day at PHL
occurred four years ago on July 18, 2012.

Record high temperatures for Today through Thursday are below.

Site     26th       27th       28th
----     ----       ----       ----

PHL...   101-1892   101-1940   100-1941

ABE...    98-1940    98-1955    97-1949

ACY...    96-2011    99-2005    98-1999

ILG...    99-1894   100-1894   101-1894

TTN...    99-1892   100-1894   101-1894

GED...    97-2012    98-2005    99-1949

RDG...    99-1940    98-1955    99-1941

MPO...    89-1949    91-1955    93-1949

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...None.

&&

$$

Synopsis...Manning
Near Term...Iovino
Short Term...Iovino
Long Term...Manning
Aviation...Iovino/Manning
Marine...Iovino/Manning
Climate...Staff


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