Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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710
FXUS61 KPHI 231328
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
928 AM EDT Wed May 23 2018

.SYNOPSIS...
Weak low pressure will track north of the region into this
morning dragging a cold front south across the area. High
pressure builds in tonight and Thursday before shifting offshore
Friday. A cold front is forecast to move southward across our
area later Saturday night through Sunday, then stall in our
vicinity early next week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Showers that affected northern zones early this morning have
pretty much ended. There may be a stray shower or two over the
next hour or so as weak low pressure over eastern PA/western NJ
departs.

That low will continue to drag a weak cold front through the
rest of the region late this morning. Not much in the way of
"cold" air behind it, but there is a marked drop in surface
dewpoints behind the front. A downsloping westerly flow should
result in highs in the 70s in the mountains and right along the
coasts, and otherwise generally in the low 80s.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/...
High pressure will remain west of the area tonight. We will be
in a much drier and somewhat cooler air mass. Under mostly clear
skies, temperatures should drop into the low/mid 50s across the
northern areas and upper 50s/low 60s across the urban areas and
Delmarva. Winds will be light from the NW.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Thursday through Friday night...

High pressure will maintain fair and dry weather across the area
through this period with lots of sunshine. As this high moves over
the area Thursday, it will bring sunny skies with light winds and
low humidity. Highs will generally be in the upper 70s to low 80s
except several degrees cooler over the southern Poconos as well as
along the coast where a sea breeze will likely kick in by afternoon.

Thursday night into Friday, the high will move offshore setting up a
return flow from the SW bringing in warmer temperatures and
increasing dew points as well...though still not too humid.
Highs by Friday afternoon will generally reach the low to mid
80s except again, cooler near the coast and across the southern
Poconos. Lows Thursday night will generally be in the 50s to low
60s but as dew points continue to creep up Friday night it will
keep temperatures up as well with lows in the 60s.

Saturday through Tuesday...

SW flow ahead of the next wave continues to bring in warmer and
more humid air Saturday with some scattered to isolated showers
and thunderstorms possible in the afternoon, mainly north and
west of the I-95 corridor. Highs should reach the mid to upper
80s away from the coast with 90 degrees not out of the question.
Dew points in the mid to upper 60s will also make it feel quite
muggy. Right along the coast as well as the southern Poconos it
will still be cooler...generally in the upper 70s to low 80s.

Saturday night and beyond, the forecast gets more complex. The
GFS and the GEM both drag a backdoor cold front southward across
the area Sunday as high pressure moves into eastern Canada
while the ECMWF keeps this front to the north. Based on the
models recent handling of these types of patterns, tend to favor
the colder solution that brings the front south. At the same
time, tropical moisture associated with a large low over the
Gulf of Mexico will be pulled north into the area around high
pressure in the western Atlantic. This looks to set up a more
unsettled pattern Sunday into Memorial Day with increasing
chances for widespread showers and thunderstorms, some of which
could be heavy. Temperatures should be cooler with highs Sunday
mainly in the 70s to low 80s and highs Monday possibly only in
the 60s north and the 70s south. Again though, there is
increasing uncertainty in the forecast through this time
period...especially regarding the placement of the front which
will have an impact on both temperatures and precipitation. By
next Tuesday, the front may start to lift back to the north as
the next wave approaches from Ontario and Quebec but tropical
moisture looks to remain in the vicinity so we keep chances for
showers and storms in the forecast.

&&

.AVIATION /14Z WEDNESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Today...Conditions improve to VFR between 14-15Z. Winds will be
mostly 320-340 at 10-15 knots into the afternoon.

Tonight...Mostly VFR expected with clear skies. Winds will be
light NW or calm. The air mass should be too dry to support
much in way of fog tonight, perhaps some patchy ground fog in
rural areas. It will probably mot be included in the 12Z TAFs
with overall low confid in its occurrence.

OUTLOOK...

Thursday and Friday...VFR. Northerly winds around 10 knots early
Thursday backing to light SW by late Thursday with SW winds
increasing to near 10 knots Friday.

Saturday and Sunday...Mainly VFR Saturday and Saturday night. Sub-
VFR conditions may occur at times with developing showers and
thunderstorms by Sunday afternoon.

&&

.MARINE...
Sub-SCA conditions are expected and fair weather today and
tonight with high pressure building in behind the passage of a
weak cold front. Seas on the ocean will be mostly 2 to 3 ft.

OUTLOOK...

Thursday...The conditions are anticipated to be below Small
Craft Advisory criteria.

Friday and Saturday...Southwesterly flow increases allowing the seas
to build some. It is possible that wind gusts approach Small Craft
Advisory criteria at times Friday night and Saturday

Sunday...The conditions should be below Small Craft Advisory
criteria as a front settles southward.

&&

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

&&

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



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