Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
355 am EDT sun may 3 2015
a large area of high pressure over the eastern United States today
will gradually move offshore on Monday. A cold front is forecast to
weaken as it drops southward across the area Tuesday through early
Wednesday. High pressure returns late in the week. The high will
eventually shift off the East Coast next weekend.
Near term /until 6 PM this evening/...
high pressure will be over the southeastern Continental U.S. Today. Southwesterly flow will
increase and temperatures will warm in response. Highs are expected to
be in the middle to upper 70s, with some locations making a run at 80
degrees. No precipitation is anticipated. There will be some scattered clouds
on an otherwise beautiful day.
Short term /6 PM this evening through 6 am Monday/...
the area of high pressure will move eastward and off the CST and a generally
clear sky is in store with light wind.
Long term /Monday through Saturday/...
the center of surface high pressure will move off the middle-Atlantic
coast on Monday. Southwesterly return flow around the high will draw
even warmer and more humid air up the eastern Seaboard. Monday will
contend with April 18th for the warmest day so far this year with
highs 80-85 degrees (except cooler along the coast and in the
poconos). Conditions across the forecast area will be dry through
Monday night owing to strong subsidence present beneath the 800 mb
A cold front will move slowly southward through the area Tuesday
afternoon and night. Clouds overspreading northeast PA and northwest
New Jersey will result in slightly cooler highs in the 70s on Tuesday.
Farther south in the warm sector, highs Tuesday have the potential
to be close to monday's from about philly southward if the front
and its associated cloud cover hangs back to the north. Moisture
will pool along the front as noted by precipitable waters increasing to near
1.5 inches and surface dewpoints to near 60f by the afternoon.
BUFKIT soundings from the 00z GFS and 21z sref show modest
instability (ml cape around 500 j/kg) while the 00z NAM depicts a
considerably more unstable environment (ml cape at or above 1000 j/kg).
Went more conservative with forecast coverage of thunderstorms
due to the presence of weak shear and limited forcing in addition
to the questionable instability. A general weakening trend is
expected with the convection after sunset, although showers may
linger into the overnight as slightly better lift associated with
an upper shortwave trough arrives late.
The front may either continue to sag southward slowly or even stall
over the Delaware-Maryland-Virginia Wednesday morning. Lift associated with the front
itself should weaken as the boundary is expected to become
increasingly diffuse. Consequentially, coverage of showers expected
to be relatively low on Wednesday. Thunderstorm chances confined to
the lower Delmarva, where these locations have the best chance of
residing in the warm sector to the south of the boundary. The cold air advection
behind the front is not significant, so the trend of above normal
temperatures should continue into Wednesday. However, we will have to watch
for the possibility of onshore flow to develop. This may prevent
temperatures from reaching 70f in the coastal plain, especially the
easterly wind becomes enhanced by a seabreeze.
Expansive high pressure over the eastern Seaboard will provide a
mainly dry pattern Thursday through Saturday. The humidity is
forecast to increase a bit Friday and Saturday as southerly return
flow develops with the surface high moving offshore. Cannot rule out
the possibility of a a shower developing during the afternoon hours
Friday and Saturday but the subsidence inversion underneath the
ridge should minimize the convective potential. Above normal
temperatures will persist with highs in the 70s to near 80f each day.
Aviation /08z Sunday through Thursday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
VFR conds will prevail through the taf period with high pressure to the southeast
today moving offshore tonight. The flow will become southwesterly by afternoon but
will be less than 10 kts. Only scattered clouds are anticipated. With
light flow, still expecting another sea breeze at kacy and kmiv.
At these locations, wind could reach 10 knots or so.
Monday and Monday night...VFR. Southwesterly may gust to 20 knots late in the
Tuesday and Tuesday night...predominately VFR. Scattered rain showers and isolated thunderstorms and rain
during the afternoon and night could yield local MVFR/IFR conditions.
Wednesday...rain showers may linger into Wednesday but most of the terminals
should dry out. Some model solutions are indicating easterly winds
to develop. Will have to watch for low clouds and MVFR ceilings to
accompany marine layer.
Wednesday night and Thursday...VFR.
the Small Craft Advisory that just won't quit continues to hold strong on the southern
ocean waters. As high pressure builds in, the though has been that the
seas should subside. However, they have been loath to do so.
Therefore, the latest Small Craft Advisory has been extended until 15z. The low off
the coast is likely keeping things stirred up enough. Hopefully
the warmer air over the waters today will finally allow the flags
to be lowered. Once this Small Craft Advisory comes down, no additional flags are
expected during the remainder of the near and short term periods.
Monday through Thursday...winds and seas should remain below Small Craft Advisory
criteria. The strongest winds are expected Monday and Tuesday as
high pressure moves offshore and a S-SW flow around 15-20 knots ensues.
relative humidity values near 30 percent, along with occasional wind
gusts to near 20 miles per hour may enhance the fire weather risk late in
the day on Monday.
Marine...Small Craft Advisory until 11 am EDT this morning for