071 
fxus61 kphi 050146 
afdphi 


Area forecast discussion 
National Weather Service Mount Holly New Jersey 
946 PM EDT Friday Jul 4 2008 


Synopsis... 
a wet summertime pattern will remain across the area overnight and 
the weekend. High pressure over the Atlantic will continue to pump 
warm and humid air across our region. A stalled front and weak 
disturbances moving along it will keep showers and thunderstorms 
plentiful tonight and at least through Saturday night. 


&& 


Near term /through Saturday/... 
the heaviest rain, along with numerous thunderstorms, are 
currently located over the Delaware-Maryland-Virginia peninsula heading into 
southern New Jersey. This is where most of the heaviest rain and 
thunderstorm activity will be concentrated during the next several 
hours. While more stratiform rain is still expected from about 
Philadelphia north and west, have kept a mention thunderstorms for 
Philadelphia city during the overnight hours just in case a stray 
thunderstorm moves through, but have taken mention of 
thunderstorms out everywhere else in eastern PA and the northern 
half of New Jersey. Have also taken out the mention of heavy rain 
in these locations since the heaviest rain will occur with 
thunderstorms over the Delaware-Maryland-Virginia and in southern New Jersey. 
Did not make any adjustments to temperatures or winds at this time. 


&& 


Short term /Saturday night/... 
much of the same weather from the near term periods will blend on 
into the short term. A slowly deepening 500 mb low to our west will 
only encourage more moist air from the south and east to move 
across our area. Weak vorticity maximums and daytime heating will only 
encourage more showers and thunderstorms to up. Met/mav probability of precipitation 
generally categorical or likely in many areas...but closer to hi 
chance up north. Can't disagree with this presently, so decided to 
just go along with it. Temperatures will be coolish with mainly middle to 
upper 70s and some low 80s over the Delaware-Maryland-Virginia. 


&& 


Long term /Sunday through Friday/... 
the stationary frontal zone will eventually weaken (or drift 
north) by early next week. This will leave US in a Summer pattern 
with a Bermuda high well to our south and east pumping in plenty 
of warm humid air. Showers and thunderstorms will continue to 
affect the area, mainly during the afternoon and evening hours. 
Computer models are now hinting that a stronger cold front may be 
able to cross the region Wednesday night. If this does indeed 
occur, the shower and thunderstorm pattern could possibly end 
Thursday. With plenty of clouds and shower activity around, high 
temperatures Sunday will only reach the lower to middle 80s in the 
philly metropolitan area. By Monday the heat begins to return with highs 
pushing into the upper 80s. Tuesday and Wednesday, and possibly 
even Thursday, could see the 90 degree mark once again. 


&& 


Aviation /02z Saturday through Wednesday/... 
a short wave moving along the stationary front is triggering an area 
of rain with embedded thunderstorms moving out of south central PA, the 
eastern Panhandle of WV and northern Virginia this afternoon. Models are 
in agreement that this moves right along the front tonight, and so 
our tafs are for deteriorating conditions, ultimately IFR, beginning 
late this afternoon and continuing through daybreak. We back off to 
MVFR tomorrow morning, but with the front in the area we don't 
expect any kind of widespread breakout into VFR conditions. With a 
front nearby and an impulse moving along it, wind directions are 
expected to be variable in nature. We are not forecasting 
significant speeds. 


Outlook... 
because of the proximity of the front, and then because of a 
developing warm and humid flow as the Bermuda high begins to be the 
main influence, at least scattered showers and thunderstorms will be 
possible through the outlook period. 


&& 


Marine... 
the front is forecast to remain nearly stationary well into tomorrow, 
when it may begin to move north as a warm front. This indication 
has been fairly consistent over subsequent runs in the various 
models, and so we are going with it. One anomalous thing we do 
notice is that the NAM is forecasting a developing and mercurial 
two-Standard-deviations-off-the-normal gradient wind overnight. 
This is associated with a 1014 mb impulse moving along the front 
and pushing up against a 1022 mb high well off the coast. As 
surprising as it is, this results in BUFKIT winds out of the 
southwest reaching gusts to around 40 knots between 08z and 10z. We 
have not forecast this, but we'll watch the winds at Chesapeake 
light overnight as an early sign that we've under-forecast winds 
/they would pick up before 44009 winds would/. 


Otherwise, with the exception of variable winds for the first period 
or two over the Bay and northern coastal waters, we continue to 
forecast south to southwest winds of modest to moderate speeds, and 
we continue to cap any seas at 4 feet. This applies out to Wednesday. 


&& 


Phi watches/warnings/advisories... 
PA...none. 
New Jersey...none. 
Delaware...none. 
Maryland...none. 
Marine...none. 


&& 


$$ 
Synopsis... 
near term... 
short term... 
long term... 
aviation... 
marine...