Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
537 am EDT sun Oct 4 2015
high pressure over Quebec will extend southward over our area
through Monday, keeping a stationary frontal boundary well to
our south. Meanwhile, the forecast track of Hurricane Joaquin
takes it close to Bermuda, and well away from our area. A low
pressure system will develop off the Carolinas on Tuesday and
move northeast offshore, followed by a weak cold front moving
through our region on Wednesday. High pressure will move pass by
to our north on Thursday with a stronger cold frontal passage
possible on Friday or Saturday.
Near term /until 6 PM this evening/...
the GFS initialization at 500mb looks stronger than the NAM and
includes a stronger, broader blocking ridge over the northeast. The
thermal's were split between the NAM at 850mb and GFS at 925mb.
The running theme continues with the deep/dt being a slower evolution
of the overall pattern.
We will keep the Wind Advisory going until 10 am this morning.
Winds are very slowly decreasing, but we are still getting some
gusts in the upper 40s (mph). Used latest nam's 925mb winds as
a timing basis. Its trend is still slowly downward. While it will
remain windy, we should stay just below criteria today. Confidence
increases as the day progresses.
Otherwise, mention of some drizzle or light rain follows the
mesoscale hrrr and hi res arw the closest as they are matching the
ongoing drizzle observation the best. Its mention is mainly from the i95
corridor southeast. Given the movement of slightly drier air into
the region this afternoon, we have made the middle to late afternoon
dry before starting to bring back chances late as another slug of
deeper low level moisture is predicted to move our way. Any
clearing or partial clearing looks to be confined to the Poconos.
We were conservative with maximum temperatures close to a model blend. The
pressure gradient for the Day Peaks this morning with a slight
relaxation for the afternoon. Slightly drier air, better mixing
though keeps gusts relatively the same.
Short term /6 PM this evening through 6 am Monday/...
moistening onshore flow continues tonight and we bring back chances
for light rain or drizzle again to the southeastern part of our County Warning Area.
In interior areas, we should finally start seeing a relaxation in
the winds, although gustiness as high as 30 to 40 miles per hour will likely
persist along the immediate coast. The fetch for most of our County Warning Area is
still from the ocean. So other than the Poconos, not confident about
much clearing in our County Warning Area. We went with the more conservative,
cloudier guidance and our min temperatures are toward the higher range of
the stat guidance for this reason.
Long term /Monday through Saturday/...
a period of transition in the long term portion of the forecast
as Rex block over eastern North America breaks over the weekend.
As this occurs, the middle-level flow over our area will gradually
transition from easterly this weekend to westerly on Tuesday. A
cut-off low over the southeastern US /the bottom half of the
aforementioned block/ will gradually fill and move northeastward
off the middle Atlantic early next week.
The main story will be the continued onshore flow in the Monday-
Tuesday time frame, although the gustiness should largely abate
by Tuesday. A weak, dry cold frontal passage is anticipated on
Wednesday, followed by a more substantial cold front late Friday
into Saturday. Temperatures will be at or below average on Monday, and
at or above average thereafter.
Monday...the flow will be relatively weak aloft as the region
will be located within a col between systems, and under the
influence of the confluent quadrant of an upper-level jet,
moving offshore just to our east. This results in subsidence
which will gradually dry out the column, especially northwest
of I-95, where the maritime influence decreases. Thus, expect
a dry day with increasing sunshine away from the coast, where
northeast winds may gust 25 to 30 miles per hour at times.
Tuesday through Thursday...westerly flow aloft is anticipated in
this period. Although embedded shortwaves are evident, the area
will largely be within the confluent region of an upper-level
jet over southern Canada. Therefore, moisture should be limited
enough to preclude precip, even with the weak cold front on
Friday and Saturday...
a more substantial short wave and accompanying cold front/area
of low pressure will increase chances for precipitation. Although the
models are fairly consistent timing this feature late Friday
into early Saturday, given the transition to a more zonal flow,
this could certainly change.
Aviation /10z Sunday through Thursday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy, and surrounding areas.
06z tafs continue windy MVFR conditions through most of the
Rest of overnight...ceilings mainly between 1000-2000ft, some IFR ceilings
possible closer to the coast. While some non visibility restricting
drizzle is possible at all terminals, we just carried it at kacy
and kmiv withe some up to MVFR restrictions. Northeast winds will
average 12 to 18 knots with higher gusts except for far northwest
airports and terminals.
This morning...a higher MVFR ceiling is predicted with no visibility
restrictions. Northeast winds should mix a bit more and will
average 15 to 20 knots with gusts 30 to 35 knots closer to the
coast and between 20 and 30 knots inland airports/terminals.
This afternoon...far northwest terminals ceilings becoming VFR.
Elsewhere we are maintaining a higher MVFR ceiling. Wind direction and
speed similar to the morning.
Sunday evening...ceilings remaining MVFR at kmiv and kacy with some
gusty northeast winds continuing as high as 20 to 30 kts.
Elsewhere we will forecast a VFR cig, but highest confidence far
northwest. We keep northeast winds at about 10 to 15 knots, but
drop the gusts. Highest confidence of this forecast occurring is
for northern airports.
Monday...any remaining MVFR ceilings gradually improving to VFR
during the day. Northeast winds continue with the highest gusts
at kacy and kmiv of 25 to 30 knots.
Monday night and Tuesday...VFR. Northeast winds at Acy and miv
could gust 20 to 25 knots.
Wednesday and Thursday...VFR conditions expected at this time,
with MVFR possible in patchy fog Wednesday night and Thursday.
the gale warnings have been extended deeper into the night along
the ocean and lower Delaware Bay based on the latest guidance
trend of decreasing the winds slightly slower. We kept the same
expiration time for the upper Delaware Bay as they should see
Sunday night through Tuesday...
the Gale Warning has been extended for the southern waters
excluding Delaware Bay through 12z Monday. Thereafter, winds should
decrease from gale to Small Craft Advisory criteria through this
Wednesday through Thursday...winds are expected to remain below
Small Craft Advisory criteria, but seas will remain at or above five feet
at least through Wednesday. Therefore, a Small Craft Advisory for
hazardous seas will likely be needed during this time frame.
820 PM update to cancel the coastal Flood Warning for the Delaware
River and the upper Delaware Bay (new Castle County, Delaware and Salem
County, nj) and replace it with a coastal Flood Advisory through
Sunday evening. Both the etss and dbofs tidal prediction came in
between one-half and one foot too high with this past high tide
cycle this afternoon/ evening. This guidance has also verified too
high with previous high tide cycles over the past couple of days.
The etss and ofs guidance may have partially taken into account
the bias and have trended lower for the early morning and late
afternoon/evening high tide on Sunday but likely are still too
high. The ofs prediction keeps Reedy Point and Philadelphia below
moderate stage for both high tides tomorrow while the etss
prediction is right at moderate. The in-house regression guidance,
which has verified the best thus far, barely gets Reedy Point to
minor tidal flood stage on Sunday.
The coastal flooding issues will continue across the region through
the remainder of the weekend as the deep northeasterly winds
The worst of the flooding (widespread moderate) will continue over
Cape May County New Jersey and eastern de, particularly in the back bays as
the onshore flow has not allowed the water that made it in there
during previous high tide cycles to drain. We'll continue to
highlight the threat of locally major tidal flooding in some of
these vulnerable back bays.
Along the Jersey Shore from Atlantic County northward, coastal
flooding are forecast to be near the upper end of minor. However,
will keep the coastal Flood Warning up as once again the back bays
will be at risk to moderate coastal flooding.
The coastal Flood Advisory was cancelled for the Eastern Shore of
the Maryland Chesapeake Bay. Water levels did not increase as previously
forecast. The newest tidal guidance, which took into account the
previous bias, no longer forecast advisory level flooding through the
The threat for moderate coastal flooding looks to end by Monday,
though minor flooding may occur.
PA...coastal Flood Advisory until midnight EDT tonight for paz070-
New Jersey...coastal Flood Warning until 6 PM EDT this evening for
Wind Advisory until 10 am EDT this morning for njz024>026.
Coastal Flood Advisory until midnight EDT tonight for
Delaware...coastal Flood Warning until 6 PM EDT this evening for
Wind Advisory until 10 am EDT this morning for dez004.
Coastal Flood Advisory until midnight EDT tonight for dez001.
Marine...Gale Warning until 10 am EDT Monday for anz452>455.
Gale Warning until 6 am EDT Monday for anz431-450-451.
Gale Warning until 2 am EDT Monday for anz430.