Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
633 am EDT sun Oct 4 2015
high pressure over Quebec will extend south over our area through
Monday, keeping a stationary front well offshore. Meanwhile, the
forecast track of Hurricane Joaquin takes it close to Bermuda,
and well away from our region. Low pressure will develop off the
Carolinas on Tuesday, moving northeast and offshore, followed by a
weak cold front moving through our area on Wednesday. High pressure
will 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 /12z Sunday through Thursday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy, and surrounding areas.
Preliminary thoughts for 12z tafs, not much change from 06z
This morning...a higher MVFR ceiling is predicted to occur generally
between 2k and 3k. Exception will be at kmiv and kacy. Some
drizzle on 88d being detected and we carried it with a MVFR
restriction for a couple of hours at kacy and kmiv. Not expected
to impact other terminals. Drizzle also likely at lower Delaware-Maryland-Virginia
airports early. Northeast winds should average 15 to 20 knots
with gusts around 30 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 bringing the VFR ceiling close to kphl by the end
of the afternoon. Maintaining a higher MVFR ceiling for the rest
of the terminals and airports farther to the southeast. 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.
Sunday overnight...we are lowering ceilings into the MVFR category
again. Aside from kacy, no gusts were carried. North to northeast
winds should average around 10 knots.
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.
no change in the coastal flood headlines. On the tidal Delaware
as the previous shift noted, the etss and dbofs guidance has
been running half a foot to foot too high. Thus applying the
same correction factor, this would result in minor tidal flooding
with tonight's high tide cycle and possibly none at all with this
We are finding a similar scenario in Chesapeake Bay where cbofs
guidance verified half a foot too high with the concluded high tide
cycle. Here the etss guidance was showing smaller errors and would
take Cambridge to minor, but not our threshold for issuing advisories
with this evening's high tide cycle.
On the ocean front, we will keep the coastal flood warnings up
through the higher afternoon high tide cycle especially for the back
bays which have had a tough time draining. The subsequent overnight
high tide cycle is astronomically approximately half a foot lower.
This may require an advisory for minor tidal flooding, but dont want
a step down double headline for now.
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.