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Area forecast discussion 
National Weather Service Mount Holly New Jersey
825 am EDT Sat Jul 4 2015

Synopsis...
low pressure off the Delaware-Maryland-Virginia coast will move out to sea south of
Cape Cod by this evening. Weak high pressure follows late tonight
and Sunday, then shifts offshore Monday. A warm front moves slowly
northeast through the Middle Atlantic States Tuesday with a cold
front to follow late Wednesday or Thursday.

&&

Near term /until 6 PM this evening/...
the upper level trough is progressing slowly eastward across the
Great Lakes and Ohio Valley. Extensive middle clouds and areas of showers have
spread across the forecast area ahead of the trough and north of the
quasi- stationary frontal boundary extending west to east across Virginia. Showers
will continue to develop/spread across the area this
morning...however the best chance for the morning hours looks to be north/west of
phl based on the regional radar loop. Later in the day as low pressure
moves east of Delaware-Maryland-Virginia...probability of precipitation may be more likely S/east but
confidence is not high at this time. Cloud and showers today will
limit maximum temperatures to the upper 60s north/west and middle 70s S/E. Chance for
precipitation should decrease from west to east from middle afternoon Onward as
forcing for upward vertical velocity moves away from the area. However cloudiness will
linger as drier air will be somewhat slow to filter in behind the
low.

&&

Short term /6 PM this evening through 6 am Sunday/...
for tonight...the upper trough axis will continue moving eastward and
offshore by Sunday morning with drier air filtering in behind it.
Weak high pressure will build in at the surface. Any lingering showers
near the coast should move out before dark allowing for fireworks
to proceed. Evening clouds should clear from the northwest over night
with the drier air coming in. Wind will be rather light allowing
for min temperatures generally in the 50s except 60s in Delaware-Maryland-Virginia.

&&

Long term /Sunday through Friday/...
500mb: a trough centered near the Tennessee Valley Sunday will
weaken northeastward across the Middle Atlantic States Tuesday. A
weak west southwest flow prevails thereafter with weak embedded
disturbances.

Temperatures: calendar day temperatures near or slightly below
normal on Sunday warm to almost 5 degrees above normal Tuesday and
Wednesday and possibly remain above normal Thursday and Friday.

Forecast basis: unless otherwise noted, this 330 am Saturday July
4th forecast was generally a 50 50 blend of the 00z/4 GFS/NAM MOS
guidance Sunday-Monday, 00z/4 mex MOS Monday night and Tuesday,
then the 0521z/4 wpc gridded elements of maximum/min temp, 12 hour
pop, 6 hour dew point- sky-wind from Tuesday night through next
Friday with the exception of maximum temperatures Tuesday and Wednesday when
the 00z/4 GFS mex blended with the even warmer 00z/4 European model (ecmwf) 2m
temperatures prevailed.

The dailies...

Sunday...after any early morning patchy fog dissipates...sct-bkn
at or above 5000 feet. West wind gust 15 miles per hour. Confidence: above average.

Monday....increasing clouds. St/fog possible late Monday night?
South wind gust 15 miles per hour Monday afternoon. Confidence: above
average.

Tuesday...areas of showers and embedded thunderstorms with precipitable water of 1.75
to to 2 inches, MLCAPE 1200j, and weak steering which could mean
several intense thunderstorms with excessive short duration rainfall (poor
drainage flooding for starters). Southerly wind gust 20 miles per hour. Near
90f philly area. Confidence: above average.

Wednesday...likely a hot day. Thunderstorms late in the day ahead of the
approaching and eventually slowing cold front. 1000j MLCAPE. Could
be strong thunderstorms east PA. Heat index right now modeled 99 phl and near
100 Delaware-Maryland-Virginia. Will be reevaluated next several days. No heat index
action at this time in the morning severe weather potential statement. Confidence: above average.

Thursday...uncertainty on timing but thunderstorms are in the forecast with
another short wave passage. Also uncertainty on temps, dependent
on timing convective related sky cover. Confidence: average or
below average.

Friday...probably drying out after thursday's anticipated short
wave passage. Confidence: average or below average.

&&

Aviation /13z Saturday through Wednesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.

VFR conds this morning will worsen somewhat as areas of showers
develop/spread across the region. Showers are ahead of a shortwave
trough moving east from the Ohio Valley. There will be periods of MVFR
ceilings/visibilities with some of the heavier showers. Conds should improve
from middle/late afternoon on into the evening. Current light southeast winds
will increase some and back to the NE as low pressure develops later
this morning S of Delaware-Maryland-Virginia and then moves offshore.

Outlook...
Sunday...VFR scattered-broken at or above 5000 feet. West wind maximum gust 15 knots during
the afternoon. Patchy MVFR fog possible to start the day and again
late Sunday night. High confidence.

Monday...VFR scattered-broken at or above 5000 feet during the day with a chance of
IFR St/fog late Monday night ahead of a warm front. Southerly wind
maximum gust 15 knots during Monday afternoon. High confidence.

Tuesday...VFR scattered-broken at or above 5000 feet with scattered thunderstorms and asstd brief
IFR conds in heavy rain, especially east PA during the aftn-evening.
High confidence.

Wednesday...VFR scattered-broken with a pretty good chance of afternoon or nighttime
thunderstorms. IFR conds possible in thunderstorms. Confidence: average or above
average.

&&

Marine...
southeast winds early this morning will back to the east and NE later this
morning and afternoon as low pressure develops east of Delaware-Maryland-Virginia. Wind speed
and waves will increase some today but are expected to remain
below Small Craft Advisory levels. Winds should decrease and become northerly tonight as
the low pressure moves away and weak high pressure builds in.

Outlook...
Sunday night through Wednesday...no marine flags are anticipated as
of this writing. Confidence: average

&&

Tides/coastal flooding...
tonight (this evening). While some tidal locations may approach
minor tidal flooding levels, current data indicates they will
remain below advisory threshold.

&&

Rip currents...
there is a moderate risk of rip currents on Saturday along the
New Jersey shore given the continued onshore flow and moderate
period swells. The risk is low for Delaware.

&&

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

&&

$$

Synopsis...drag
near term...amc
short term...amc
long term...drag
aviation...amc/drag
marine...amc/drag
tides/coastal flooding...staff
rip currents...staff

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