Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
337 am EDT Friday may 29 2015
high pressure will reestablish itself off the East Coast today
into Saturday. A cold front is forecast to move across the area
Saturday night into Sunday, then stall across our southern areas
or just south of the area Monday into Tuesday. High pressure will
build to our north early next week, before trying to nose its way
into our area Wednesday into Thursday.
Near term /until 6 PM this evening/...
as of 3 am the cold front was through almost all of our region with
the exception of portions of the Delaware-Maryland-Virginia peninsula. With the drier
air in the wake of this front, should have a comfortable day on tap
with lower dew points than yesterday and highs only slightly above
Models continue to show some qpf, first with lingering convection
along and south of the front this morning (which seems reasonable
given how persistent showers have been in northeastern Maryland
overnight), and then with an area of showers and storms in the far
western sections of our County Warning Area this afternoon. There is limited
synoptic scale lift, so any convection is unlikely until the
boundary layer inversion dissipates, which in the wake of the cold
front, may not happen until very late this afternoon. All that being
said, made few changes to the probability of precipitation from the previous forecast. Did
include mention of thunder, as it does appear there is enough
instability (if the inversion dissipates) for thunderstorms.
Short term /6 PM this evening through 6 am Saturday/...
the next cold front continues progress east over the Great Lakes
region, but still looks to stay far enough west of our region to
have limited impact tonight. With the persistent southeasterly low
level flow, could see fog along the coastal waters. However, this
will be dependent on how much moist air advection will occur in the
later half of the day, as dew points will likely start the day in
Long term /Saturday through Thursday/...
the surface high and ridge aloft will get pushed eastward
Saturday ahead of an approaching cold front, with southwest flow
both at the surface and aloft developing. This will allow for a
couple of short wave/vorticity impulses to move across the area
late Saturday while daytime instability develops as well. An
increase in shower/thunderstorm activity is possible, especially
for the western portions of the area.
The cold front is forecast to move into the area Saturday night
and slowly move across the area into Sunday. The GFS and European model (ecmwf)
have pretty good agreement with the timing of the precipitation.
Both agree that Sunday looks to be the period with highest
probability for precipitation as the front moves across and south
of the area. Precipitable water values increase to near 2 inches, so there could
be a period of heavy rainfall with any showers that develop during
the time period. There remains instability forecast ahead of the
front, so we will keep thunderstorms in the forecast, but once the
front passes, thunderstorm potential decreases.
High pressure returns to our northeast early next week as the
frontal boundary pushes south and likely stalls just south of our
area. With the high to our northeast, this will keep easterly flow
across the area. Southwest-westerly flow aloft will remain across
the area as well. Several short wave/vorticity impulses will
likely move across the area early next week, which could help
create precipitation across the area. It is looking like we could
have a period with good soaking rains, just hopefully it does not
come too quickly. With the easterly flow across the area, the
atmosphere should be stable, so we keep thunderstorms out of the
forecast Monday and Tuesday due to lack of instability.
The high pressure across the northeast should build south across
the area Wednesday into Thursday, starting another dry period.
Aviation /07z Friday through Tuesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
Mostly VFR conditions for the taf period. The cold front is now
south of all the taf sites, and drier air is continues to advect
over the region.
There is also a small possibility of fog and low stratus developing
after 03z tonight across much of the region as depicted in time
height displays of both the GFS and NAM. However, models appear to
be underestimating the amount of dry air advection currently, so
despite easterly/southeasterly winds for much of the period,
conditions below VFR seem unlikely for kphl, kabe, krdg, kttn, and
kpne. At kilg, kmiv, and kacy where the marine layer is more likely
to advect in, low stratus (around 2000 to 3000 feet agl) is possible.
Winds will slowly shift from northeasterly now, to easterly by 15z,
to southeasterly after 18z. However, wind speeds are expected to
stay around or below 10kt.
Saturday...lower conditions possible early, then becoming VFR
during the day. Scattered showers and thunderstorms possible which
may locally reduce cigs/vsbys. Gusty south-southwest winds around
Saturday night-Tuesday...an extended period of MVFR/IFR
conditions possible. A chance of rain each day. Best potential for
thunderstorms is Sunday as a cold front moves through the area.
Wind become northeast behind the front and continue through
Tuesday. Winds could gust to 20 knots at times Sunday night
Winds and seas should remain below small craft criteria today and
tonight. There may be some gusty winds in the vicinity of
thunderstorms through about middle day.
Saturday-Tuesday...seas may return to 5 feet or greater late on
Saturday ahead ahead of an approaching cold front. Seas may remain
elevated into Tuesday, and winds may increase to 25 knots Monday
new weblink, works best on firefox. Displays the forecast graphic et cetera.
Low risk continues through Friday.
Substantial upwelling occurred yesterday with the southerly flow,
especially nnj waters where 44065 water temperature dropped almost 9
degrees in 24 hours down into the upper 40s earlier this morning.
Chilly to swim most of central and nnj beaches despite well above
normal land temperatures.
may 2015...a top 5 warmest on record for large portions of our area.
Conservative values listed below from our 5 am sft and cooling the
near midnight Sunday night may 31 low temperature due to northerly flow cold air advection Sunday
Allentown will probably average very close to 65.9 or 6 degrees
above normal. Por back to 1922. At least 5th warmest on record.
Philadelphia will probably average close to 69.7 degrees or 5.8
degrees above normal. Second warmest on record.
Number 3 would be 69.2 in 2004.
Atlantic City may 2015 65.9 or 4.8 above normal and probable #3
por back to 1874
Wilmington Delaware solid por back to 1916 locked into #4 warmest
No available monthly historical data for kmpo kged kttn and krdg.