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Area Forecast Discussion (AFD)

Issued by Philadelphia/Mt Holly (PHI)

FXUS61 KPHI 212353

Area Forecast Discussion
National Weather Service Mount Holly NJ
753 PM EDT Sat Sep 21 2019

High pressure will continue to move slowly off the Carolina coast 
tonight and Sunday. A weak surface low in the Midwest on Sunday 
night will lift northeastward into New England and far southeast 
Canada by Tuesday. An attendant cold front will move through the Mid-
Atlantic region Monday night. High pressure build into the Northeast 
for midweek, with another cold front moving through the area Thursday
night. Another broad surface high will follow to close the week.


Virtually a carbon copy of Friday night's weather tonight. High
pressure remains to our south offshore of the Carolinas and a 
weak surface trough remains across the area. Although some cloud
cover may develop overnight, vertical moisture remains limited,
so precipitation is not expected, regardless of any short 
wave/vorticity impulses. Some patchy fog may also develop 
tonight, especially for valleys and lower lying areas.


The ridge aloft breaks down on Sunday, while the high remains 
offshore of the Mid-Atlantic coast and the weak surface trough 
remains near the area. This will allow for the return flow to 
continue through Sunday. Very warm temperatures and increasing 
moisture are expected through Sunday. Later Sunday, there is a 
chance some showers may develop to our west. They are mostly 
expected to stay out of our area and remain near the surface trough 
as it drifts westward through the day, there will be a slight chance 
across the Poconos late in the afternoon.


Sunday night through Tuesday...

Warmth continues Monday as the upper-level ridge to our southwest 
feeds warm return flow into the mid-Atlantic and Northeast. 
Meanwhile to our west, another shortwave trough will make its way 
across the Great Lakes as a surface low and cold front track across 
the Keystone state. Showers and thunderstorms should hold off for 
most of the day as the main low-level convergent forcing remains 
along the front. A few showers and storms may begin to move into our 
western counties by late morning. However, the best chances should 
hold off until late afternoon into the evening. Severe weather is 
not expected at this point given the lack of instability, though a 
few stronger thunderstorms may still be possible. Highs look to top 
in the mid to upper 80s with the axis of warmest temperatures along 
the I-95 corridor from New York to DC. 

Dry weather returns Tuesday as the front pushes south of the CWA and 
winds turn northwesterly. Cooler temperatures will result in 
forecast highs about ten degrees cooler in the mid to upper 70s.

Tuesday night through Saturday...

Low pressure over northern New England continues to depart Tuesday 
night. Meanwhile, surface high pressure builds in from the west with 
the center of the high building into West Virginia. High pressure 
will then dominate much of the midweek period, with the high sliding 
off the Southeast U.S. coast during the day Wednesday, and then 
moving out to sea Wednesday night.

Low pressure tracking across Canada will drag a weak cold front 
towards the region Wednesday night, but it will not fully cross 
until late Thursday. The bulk of the upper shortwave energy looks to 
stay well north of the region, so will only carry slight chance PoPs 
for the southern Poconos, Lehigh Valley, and northern New Jersey.

High pressure returns thereafter, building nearly overhead on Friday 
before moving offshore on Saturday. Another frontal system may 
approach for Saturday night.

Highs during the middle to the end of the week will mostly be a few 
degrees above normal, generally topping off in the mid to upper 70s. 
The warmest day looks to be Thursday, when the area is in the warm 
sector ahead of the approaching cold front, when highs will be in 
the low to mid 80s.


The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, 
KMIV, KACY and surrounding areas.

Tonight...Mostly VFR conditions expected. Patchy fog may develop for 
a few locations, mainly RDG, MIV, and ACY. Southwest winds 5-10 
knots or less early this evening, then light and variable overnight.

Sunday...VFR conditions expected. Light and variable winds early, 
increasing out of the southwest 5-10 knots during the day, with 
gusts 15-20 knots possible.


Sunday night...Mainly VFR expected. Light southwest winds. 

Monday and Monday night...Mainly VFR expected. MVFR or lower 
possible in scattered afternoon showers. Southwest winds around 5 to 
10 knots with some gusts around 15 to 20 knots (more likely closer 
to KACY). Winds will turn to the west and then northwest late behind 
a cold frontal passage. 

Tuesday through Tuesday night...Mainly VFR expected. Northwest winds 
around 5 to 10 knots. 

Wednesday through Wednesday night...Mainly VFR expected. Northwest 
winds around 5 to 10 knots turning southwest late.  

Thursday...Mainly VFR expected. Southwest winds around 5 to 10 knots.


Tonight...Conditions expected to remain below advisory levels 

Sunday...Conditions expected to remain below advisory levels, 
although winds may gust around 20 knots at times in the afternoon.


Sunday night through Monday night...Sustained south to southwest 
winds around 15-20 knots will gust up to 25 knots at times, 
especially over the ocean waters. Winds will begin to die down late 
Monday night. Seas will build to around 5 feet by Monday afternoon 
and evening before subsiding slightly overnight.

Tuesday through Thursday...Conditions are expected to remain 
below Small Craft Advisory criteria.


There is a MODERATE risk for the development of dangerous rip 
currents at New Jersey and Delaware beaches through Sunday.




Near Term...Davis/Robertson
Short Term...Davis/Robertson
Long Term...Davis/MPS