Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 250738
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
338 AM EDT WED MAY 25 2016

.SYNOPSIS...
High pressure will build off the Carolina coast today and persist
through Saturday. A cool front is forecast to settle across the
Northeast Thursday before moving back to the north. Another cool
front settles southward late Friday and Saturday, and as high
pressure shifts around offshore this front should get pushed
southward into our area later Sunday and Monday before lifting back
north. The next cold front may slowly approach from the northwest
later Tuesday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A ridge of high pressure will extend across the region today. After
some patchy early morning fog, a bright and sunny day is expected.
Temperatures will be well above normal with summer-like warmth
expected. High temperatures will be in the mid to upper 80s in
most areas. The immediate shore and higher elevations of the
southern poconos will be several degrees cooler. Humidity levels
will not be too oppressive. Winds will be mostly westerly or
southwesterly at 5 to 10 mph.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/...
The fair weather will continue tonight. Skies will be mostly clear
with some high clouds expected late. Low temperatures will range
from the upper 50s across the north and over rural areas...to the
mid 60s over the Delmarva and urban areas.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Summary...A stretch of very warm/hot conditions. An increase in the
humidity starts mainly later Thursday. A frontal boundary nearby
Thursday into Sunday combined with instability should trigger some
showers and thunderstorms mainly each afternoon and evening across
the interior, then the front pushes south some later Sunday through
Monday. There is less confidence with the temperature forecast
later Sunday and Monday given the flow turning more onshore.

The synoptic setup is comprised of a ridge in the east that
amplifies with time though the holiday weekend. There will be
several pieces of energy deflected around this ridge with a sharp
trough possibly occurring in the vicinity of the Canadian Maritimes
starting over the holiday weekend. This setup results in a frontal
zone becoming draped from about the Great Lakes to New England. This
front looks to meander north and south through Saturday before
another front arrives. The upper air pattern may then support this
front settling into our area more Sunday and Monday in conjunction
with low pressure well to our south. Some energy along this front
combined with plenty of heating to the south of it should result in
mainly some diurnally driven convection Friday through the holiday
weekend. Overall, a washout is not anticipated although there is
still questions regarding the details for later Sunday and Monday.
We used a model blend approach for Thursday through Friday night,
then blended in the 00z WPC Guidance with continuity thereafter.
Some adjustments were then made based on additional collaboration
with our neighboring offices.

For Thursday...The 925 mb temperatures are forecast to be between
+20C and +25C. This combined with west to southwest flow will drive
the temperatures well into the 80s for much of the area. The
exception will be the coastal areas where the surface flow may back
more southerly and allow some cooler ocean influence. We bumped up
the temperatures some especially away from the coast. Low pressure
tracking into the Great Lakes should provide enough of a downstream
push to move a front back north. A few showers and thunderstorms may
develop Thursday afternoon across mainly our western zones due to
terrain circulations and local convergence, however much of the
convection should reside to our west. In addition, the dew points
will be on the rise especially at night allowing for a more humid
feel to the air. The model guidance shows a rapid uptick in the
700 mb theta-e and PW values especially at night.

For Friday and Saturday...The ridge axis builds nearly over our
area. This will result in very warm/hot conditions along with a more
noticeable increase in the surface dew points. Some mainly diurnally
driven convection cannot be ruled out each afternoon and early
evening. The PW values are forecast to increase to near 1.50 inches
Friday and with the mid level flow more westerly this could result
in a bit more cloudiness. If this occurs, then perhaps the
temperatures are a little cooler especially Saturday. It appears
given the rather warm airmass in place, some places especially in
the urban areas of the I-95 corridor top out at 90 degrees Friday
afternoon. An area of low pressure is forecast to be slowly
approaching the Carolinas as the ridge aloft remains. Depending on
the organization of this feature some additional moisture may
eventually work northward toward our area.

For Sunday through Tuesday...As the ridge axis shifts a bit farther
north, high pressure at the surface near the Canadian Maritimes
drifts southward. This will turn our winds from the east Sunday and
Monday as a surface cool front gets pushed southward some. The
forecast challenge is how strong this push will be as it will
greatly impact the temperature forecast. As of now, we are still
expecting some cooling given an onshore flow and more clouds. There
should remain a corridor of instability especially in the interior
for some possible scattered convection Sunday mostly in the
afternoon, then possibly more showery Monday with the onshore flow.
The low to our south should be slow moving however some of its
moisture may enhance the convective potential across our area into
Tuesday.

&&

.AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

A great flying weather period expected today and tonight. Skies
will remain mostly clear across the region with gentle w/nw winds
this morning and then sw winds this afternoon. A bit of patchy fog
over the rural areas today..but none was included in the 06z tafs.
Tonight...skc with light sw winds at the terminals.

Outlook...
Thursday and Friday...VFR overall. A few afternoon and evening
showers and thunderstorms especially Friday mostly north and west of
KPHL may result in brief times of MVFR/IFR conditions. Southwest
winds mainly up to 10 knots, however less at night. A sea breeze may
turn the winds to the southeast at KACY each afternoon, and a bay
breeze possibly affecting KILG.

Saturday and Sunday...VFR ceilings at times. Some mainly afternoon
and evening showers and thunderstorms are possible each day, however
these look scattered.

&&

.MARINE...
Sub-sca conditions expected today and tonight with a ridge of high
pressure expected across the waters. Winds will be mostly nw/w this
morning and then back to sw this afternoon. Wind speeds will be
mostly 5 to 10 knots today and 10 to 15 knots tonight. Seas on the
ocean 2- 3 ft and 1- 2 ft across Delaware Bay.

Outlook...
Thursday through Sunday...A ridge over the area combined with high
pressure at the surface to our south and east will allow for mainly
a prolonged southerly flow across our area through Saturday night.
Winds should then shift more onshore during Sunday. The conditions
are expected to be below Small Craft Advisory criteria. Sea breeze
circulations each day may allow for a period of increased winds
nearshore during the afternoon and early evening.

&&

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

&&

$$
Synopsis...Gorse
Near Term...O`Hara
Short Term...O`Hara
Long Term...Gorse
Aviation...Gorse/O`Hara
Marine...Gorse/O`Hara



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