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FXUS61 KPHI 252233

Area Forecast Discussion
National Weather Service Mount Holly NJ
633 PM EDT Tue Sep 25 2018

A warm front will lift north of the area this evening. A cold 
front will move across the East Coast later on Wednesday, and 
stall south of the area as high pressure builds out of the 
Midwest and into New England Thursday. A weak area of low 
pressure is forecast to move along the front to our south on 
Friday, then another cold front is forecast to move across the 
East Coast Saturday. High pressure builds across the Northeast 
Saturday night into Sunday, then offshore on Monday.


Moderate to heavy rain showers, along with some isolated 
thunderstorms, developed on a warm front along the I-95 
corridor. Heavy rain has resulted in flooding and flash flooding
across parts of the area. 

This swath is showers is moving to the north and east, and will
affect mainly northeast New Jersey through sunset, possibly an 
hour or so after sunset as well. 

Behind this area of showers, another light area of showers may 
pass through from the south and west. More showers over central
PA may affect the region after midnight tonight, but those
should be light as well.

The biggest threat for areas along the frontal boundary will be
flooding rains. PWATs are high (around 2 inches) and training 
of storms as they propagate to the northeast is possible. With 
low FFG values, especially along the urbanized I-95 corridor, 
flash flooding will also remain a threat through this evening. 

The warm front should start to move northward, albeit slowly, 
through tonight. It may even start to wash out overnight with a 
southerly flow developing across the area.


The warm front should be north of the forecast area on 
Wednesday and the start of the day looks to be a bit on the 
dreary side as low clouds remain across the region. As we head 
towards late morning, the clouds should start to lift and some 
clearing may occur. 

A cold front will move towards our area from the west Wednesday
afternoon, crossing through our region on Wednesday evening. 
Temperatures are expected to rise into the 70s and 80s across 
the forecast area, which will help to increase the surface 
instability. Showers and thunderstorms are expected to develop 
ahead of the front in the warm sector by Wednesday afternoon and
then continue through Wednesday evening/night as the front 
makes its way towards the coast. SPC continues to have much of 
our forecast area in a Slight Risk for severe storms. While the 
shear doesn't look great, it should be enough to allow for 
strong enough updrafts within convection. Storm motion continues
to look like it will be on the faster side so heavy rainfall 
should move through quickly and not persist at any one location 
for too long of a time. 

However, much of the severe potential remains conditional on 
the timing of the front. A slightly later arrival and/or slower 
moving front and we may not see quite as much action across the 
area. A slower front may also mean that rainfall rates persist 
over locations longer, increasing the flash flood threat. 

Storms will start to end from west to east as the front moves 
through with a northwest flow developing behind the front.


The cold front that moves across the area late in the day 
Wednesday will continue to push offshore through Wednesday 
night. There will likely still be some showers across portions 
of southern New Jersey, Delaware, and Maryland into the evening 
as the front moves offshore. There may even be some lingering 
showers across far southern Delaware and Maryland overnight as 
there could be some enhanced moisture and lift just north of the
front as it sags south of the area.

Thursday should be dry for most places, except again southern 
New Jersey, Delaware, and Maryland where moisture may begin to 
move into the area late in the day ahead of the frontal boundary
to our south that may begin lifting back toward the area as a 
warm front. Showers may continue to spread northward overnight 
Thursday into Friday as the warm front lifts across the area, 
and an area of low pressure develops along the boundary to our 
south and moves out to sea during the day Friday.

Another weak, and dry frontal boundary is forecast to move 
across the area on Saturday, with high pressure building into 
the area overnight Saturday. This should bring dry weather back 
to the forecast, and a brief return of cooler weather.

Sunday through Tuesday night...Once the cold front passes to 
our south, we will enjoy a couple days of dry weather before the
front begins to lift north as a warm front, preceding another 
area of low pressure moving out of the Great Plains toward the 
Great Lakes. Highs should remain near normal in the low 70s to 
the south and low 60s to the north over the southern Poconos. As
the front lifts north Monday night, highs should rise a few 
degrees more on Tuesday into the mid 70s for most areas. At this
time, any rain looks to hold off until late Tuesday night into 
early Wednesday morning. Confidence in the progression of the 
warm front is still relatively low as models have not reached a 
consensus on the placement/development of the low to our west.


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

Tonight...IFR/LIFR in SHRA/TSRA, otherwise, VFR this evening,
then becoming MVFR/IFR tonight. SHRA/TSRA will continue across 
the area through this evening. Any thunder chances should 
diminish by around 00Z at the terminals. 

Winds are generally south to southeast around 10 knots with 
some higher gusts this afternoon. Winds will lighten this 
evening to around 5 knots or so and remain out of the south 

Wednesday...MVFR/IFR conditions to start the day but 
improvement to VFR is expected around midday. Periods of 
MVFR/IFR possible in showers and thunderstorms ahead of an 
approaching cold front. West to southwest winds around 10 knots.


Wednesday night...Showers and thunderstorms possible in the 
evening may lower conditions, then becoming VFR overnight. Winds
shift to northwest then north behind the front and may gust 
15-20 knots.

Thursday...Generally VFR expected. North winds early become 
east then southeast during the day.

Thursday night-Friday...VFR early Thursday evening, becoming 
MVFR overnight into Friday with a chance of showers. Southeast 
winds Thursday night become more easterly Friday.

Friday night...MVFR conditions early become VFR during the 
evening and overnight. Winds become northwest.

Saturday-Sunday...VFR conditions expected.


The Small Craft Advisory continues on the ocean through 
Wednesday night. 

Strong southeasterly flow continues across the coastal waters 
this afternoon. Winds have already started to decrease on the 
ocean and we have lost most of the higher gusts. However, some 
gusts around 25 knots may occur through this evening. 

Seas remain well above 5 feet through Wednesday. 

Showers and thunderstorms over the waters are possible through 
Wednesday. Winds and seas will be higher in the vicinity of any 
thunderstorms that develop.


Wednesday night...Small Craft Advisory remains in effect 
through Wednesday night as seas remain elevated.

Thursday...Small Craft Advisory may need to be extended as seas
may remain elevated into the day and winds may gust around 25 
knots early in the day.

Thursday night-Sunday...Conditions likely to remain below Small
Craft Advisory criteria, although winds may gust around 20 
knots at times.


Seas remain around 7-8 feet with a period around 8 seconds and 
winds blowing out of the east-southeast around 15 to 20 knots 
over the waters. This combination is expected to lead to a 
higher risk for rip currents along the ocean front. Therefore we
have issued a High Rip Current Risk through this evening.


Water levels on the back bays of Ocean county continue to
recede. Will cancel the Coastal Flood Advisory.

On the Chesapeake Bay, a Coastal Flood Advisory remains in 
effect for the eastern shore of Maryland.


NJ...High Rip Current Risk until 9 PM EDT this evening for NJZ014-
DE...High Rip Current Risk until 9 PM EDT this evening for DEZ004.
MD...Coastal Flood Advisory until midnight EDT tonight for MDZ008-
MARINE...Small Craft Advisory until 6 AM EDT Thursday for ANZ450>455.


Near Term...Meola/MPS

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