Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 191344
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
944 AM EDT Thu Oct 19 2017

.SYNOPSIS...
A dry frontal boundary will move toward the area tonight into
early Friday. Otherwise, high pressure remains in control of the
weather for much of the rest of the week into the weekend. A
frontal boundary is forecast to affect the area early next week,
bringing a return of unsettled weather.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Mid morning surface analysis shows a broad area of high pressure
over the Southeast and mid-Atlantic states. This high was weakened
and shifted south of our area over the past 24 hours. Meanwhile, a
cold front was located over the Upper Midwest, stretching
southwestward into the Central Plains. The cold front will approach
from the west as it moves through the eastern Great Lakes/Ohio
Valley this afternoon.

GOES-16 water vapor satellite imagery (CHs 8-10) show a weak
shortwave trough aloft passing thru the region this morning. Other
than thin cirrus streaming across the area, this system will have no
other impacts on our sensible weather today.

The warm sector will clearly be established over the region today
with southwesterly flow continuing ahead of the cold front. High
temperatures were tweaked upward by a couple of degrees for the mid
morning ESTF update and reflects a warmer solution than any
guidance. Forecast highs are in the mid 70s across most of the
area, except cooler in the higher elevations of NE PA/NW NJ and
along the coast.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/...
Weak surface cold front passes through the region tonight. With
a lack of moisture and no upper level support, conditions will
be dry with its passage. Outside of some evening cirrus, skies
should clear out after midnight.

Surface high pressure reestablishes itself over the
Appalachians after midnight.

Some patchy ground fog is possible prior to the passage of the
cold front. Dew points will fall behind the passage of the
front.

Lows tonight will be in the upper 40s to around 50. Lows in the
Philly metro area will be in the low 50s.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Quiet weather is expected for the end of this week into the
weekend as high pressure will be in control of the weather
through the end of the week before moving offshore for Sunday
and Monday.

Ridging aloft builds across the area late this week into the
weekend, which will help keep temperatures several degrees above
normal. As the surface high and ridge aloft moves offshore
Sunday, return flow and southwest flow aloft develops. This will
help increase clouds, but no precipitation is expected through
Sunday.

As we go into Sunday, an area of low pressure is forecast to
develop near the Lower Mississippi Valley along a frontal
boundary located across the central part of the country. It is
then expected to strengthen as it moves northward along the
frontal boundary and toward the Great Lakes Monday night into
Tuesday. The front is expected to move toward our area Tuesday
into Tuesday night, although there is some timing differences
between the GFS and ECMWF. The GFS pushes the front through
quicker, moving the precip through Tuesday into Tuesday night.
The ECMWF slowly moves the front through slower, keeping precip
across the area Tuesday night through Wednesday night. For now,
we have the greatest chances for precipitation Tuesday and
Tuesday night.

&&

.AVIATION /13Z THURSDAY THROUGH MONDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

VFR through the TAF period. Patchy ground fog with brief MVFR
VSBY is possible from around 04-12Z Friday.

SW winds less than 10 KT, becoming less than 5 KT tonight.

OUTLOOK...

Friday-Monday...VFR conditions expected. Winds may gust around
15 knots Friday, Sunday, and Monday.

&&

.MARINE...
SW winds 5-10 KT, increasing to 10-15 KT with gusts to 20 KT
this afternoon on the Atlantic coastal waters. Winds shift to
the NW tonight after the passage of a cold front. Seas will
generally be around 3 ft on the coastal waters and 2 ft or less
in the Delaware Bay...predominately in a SE swell of 9 or 10
seconds.

OUTLOOK...

Friday-Monday...Conditions expected to remain below Small Craft
Advisory levels through the period.

&&

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

&&

$$
Synopsis...Robertson
Near Term...Klein
Short Term...MPS
Long Term...Robertson
Aviation...Klein/Robertson/MPS
Marine...Klein/Robertson/MPS



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