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

Synopsis...
low pressure over southeast Virginia 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 early 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.

&&

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 dewpoint- 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 skycover. Confidence: average or
below average.

Friday...probably drying out after thursdays anticipated short
wave passage. Confidence: average or below average.

&&

Aviation /10z Saturday through Wednesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.

VFR conds early this morning will worsen somewhat after daybreak 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 (saturday 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 604a
aviation...amc/drag
marine...amc/drag
tides/coastal flooding...
rip currents...

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