Area Forecast Discussion
Issued by NWS Mt. Holly, NJ
FXUS61 KPHI 211342
Area Forecast Discussion
National Weather Service Mount Holly NJ
942 AM EDT TUE JUN 21 2016
A frontal boundary extended along the Interstate 95 corridor in
our region this morning and it should remain in that area into
this afternoon. The front is forecast to pass off the coast
tonight. Weak high pressure will cross the region on Wednesday. A
low pressure system will cross the southern Great Lakes Wednesday
night, passing over northern New Jersey on Thursday and moving to
our east Thursday night. High pressure will return for Friday and
persist through the weekend. A cold front will approach from the
west on Monday.
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
We were experiencing a break in the action at mid morning with no
precipitation in our region. A band of high clouds extended across
Chester County in Pennsylvania southeastward to southern New
Jersey and central Delaware. The remainder of our forecast area
was under a mostly sunny sky.
It appeared as though the frontal boundary had settled along the
Interstate 95 corridor in our region at 930 am. Dew point readings
had already fallen into the 50s in our northern counties while
they remained in the upper 60s ahead of the boundary.
We are not expecting any precipitation in our region for the
balance of the morning hours, except perhaps a passing shower or
two on the upper Delmarva. However, showers and thunderstorms are
anticipated to develop in the vicinity of the front during the
CAPE values are forecast to increase to 1500 to 2000 J/kg over
our central and southern counties with daytime heating. We
continue to expect strong thunderstorms to develop and the
potential exists for damaging wind gusts and hail along with
frequent cloud to ground lightning. Some of the thunderstorms may
produce rainfall of an inch or two in a short period of time
leading to localized flooding in areas of poor drainage. Our
recent dry conditions should prevent any widespread flooding from
The showers and thunderstorms are forecast to move southeastward
after they develop. Meanwhile, dry air is expected to continue
filtering into our northern counties during the afternoon and
that area should remain rain-free.
Maximum temperatures are expected to be mostly in the 80s in the
northern part of our forecast area and near 90 degrees in the
.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/...
A broad brush tonight. dewpoints rise a bit and there may be a
secondary band of convection that develops in E PA and NJ during
the early night, separate from the probably going out to sea SVR
over the Delmarva. Eventually the dry air aloft dominates near and
It will cool down significantly near and north of I-78 tonight
where pwat dries to .8". Sfc temps probably down into the 50s (FWN
and MPO 53). It will be more difficult to cool below normal from
PHL south and east where residual warmth and rh will be difficult
to erode behind the cold front.
Note the 50s in southern NYS and N central PA at 10z this
Patchy dense fog possible late at night, especially nw NJ and e
Wind becoming northwest everywhere.
This part of the forecast was a 50 50 blend of the 00z/21 gfs/nam
mos with adjustments as needed.
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Wednesday...Weak high pressure will slide across the Mid-
Atlantic, keeping us dry for the day.
Thursday...Low pressure will cross the lower Great Lakes region
pushing east through the day. The low will cross our area Thursday
afternoon/evening and then move off to the northeast late
Thursday could be quite an active day across the region. The
center of the low looks to move across Pennsylvania and into
northern NJ, and with considerable moisture available we could see
some decent rainfall across our area. Meanwhile, the southern
portions of the forecast areas will remain firmly placed in the
warm sector, allowing for destabilization to occur through the
day. The possibility for strong to possibly severe thunderstorms
will continue across the area, especially the Delmarva and extreme
With the recent spate of dry weather across our region, we could
certainly use some good rainfall. However, PWATs are running high,
1.50-2.00 inches and this could very well lead to heavy rain
falling across the forecast area. We will need to monitor the
threat for any flood/flash flood concerns. At this time, expect
poor drainage and low lying areas may experience localized
Friday through Sunday...Surface high pressure will build across
the region, drying us out through the weekend. With an east
southeast flow at the surface, especially along the coast, we will
be slightly cooler through the weekend than we have been the past
few days. Highs will reach into the 80s on Friday and Saturday but
the airmass will modify through the weekend and by Sunday, we will
see temperatures creeping back into the upper 80s to lower 90s.
Monday...Low pressure will cross eastern Canada early in the
week. The attendant cold front will approach our area from the
west on Monday. The models show that the front will move through
our area sometime later Monday or Tuesday but some timing and
strength issues remain.
.AVIATION /14Z TUESDAY THROUGH SATURDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.
Today...VFR sct-bkn aoa 5000 ft. Showers/tstms vicinity the TAF
sites from KPNE/KPHL/KILG southeastward to KACY and KMIV sometime
between 18z and 24z/21. Pls see TAFS for our best effort on timing
and keep checking through the day. Thinking strongest storms with
brief IFR conditions in heavy rain, possible hail and potential
westerly wind gusts 40-50kt vicinity KMIV and KACY. This latter
expectation is subject to change. Otherwise, gradient west wind to
15-18kt KRDG/KABE and possibly KTTN by midday. Vicinity KPHL the
gradient wind is predominantly southwest with a possible period of
gusts to 20 kt early this afternoon. Meanwhile vicinity KACY and
KMIV gradient southwest wind gusts to around 23 kt are expected
This evening...Mainly VFR cigs. A chance of showers and
thunderstorms from around KPHL southeastward which could briefly
lower conditions to MVFR or IFR.
Late Tonight...VFR becoming Clear with a northwest wind. patchy
mvfr fog possible at the non urban taf sites.
Wednesday through Wednesday evening...mainly VFR.
Late Wednesday night through Thursday evening...Conditions
varying between VFR and MVFR with a chance of showers. Also, there
is a chance of thunderstorms that may reduce conditions into the
Late Thursday night and early Friday morning...Mainly VFR with
patchy fog possibly reducing the ceiling and visibility into the
MVFR or IFR range.
Late Friday morning through Saturday...Mainly VFR.
SCA issued for the DE and far southern NJ waters where the NAM
continues highlighting 25 kt gradient sw wind gusts this
afternoon. Also expect probable sct 35-50 kt westerly wind gusts
associated with thunderstorms this afternoon/ evening.
Winds and seas probably below sca criteria late tonight behind
the cold front.
RIP CURRENTS...There is a moderate risk for the formation of
dangerous rip currents today along the southern and central New
Jersey shore. For the Delaware Beaches, the south southwesterly
flow is more off shore, so have chosen to go with a low risk for
now. Across the Monmouth County shore, a cold front is expected to
arrive relatively early in the day, bringing a shift to
northwesterly flow, limiting the risk there.
Wednesday through Thursday...No marine headlines are anticipated.
Thursday night and Friday...Wave heights on our ocean waters may
build near 5 feet in a southeast to northeast flow.
Friday night and Saturday...No marine headlines are anticipated.
MARINE...Small Craft Advisory from 1 PM this afternoon to 7 PM EDT this
evening for ANZ430-431-453>455.