Area Forecast Discussion
Issued by NWS Mt. Holly, NJ
FXUS61 KPHI 280233
Area Forecast Discussion
National Weather Service Mount Holly NJ
933 PM EST Mon Feb 27 2017
Low pressure will organize and develop over the Northern and Central
Plains tonight and lift a warm front through our region tomorrow.
The cold front associated with this low is expected to arrive in our
region Wednesday night. An upper level trough builds into the
Northeast for the end of the week. Weak low pressure passes through
the region on Friday, then high pressure returns for the
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
900 PM ESTF: Minor modifications to temperatures and dew points.
Added slight chance PoPs to southern NJ and Delmarva to account
for light rain showers.
At 3 pm, temperatures were in the lower to mid 50s across the
coastal plain and Delaware Valley. Cooler north and west. Skies
were partly sunny along the coast, but transitioned quickly to
cloud cover over the interior. The composite radar does show
some light returns across the Delmarva and PA, but one has to
head to western PA to experience any rain at ground level.
Southwest winds were mainly 10 to 15 mph with some gusts up to
With the lower layers quite dry, none of the near-term high
resolution models I`m looking at indicate the rain will make it into
our region this evening, although clouds will thicken and lower. But
after midnight, the WAA increases and looks to be strongest across
southern NJ and the Delmarva and up across the Poconos. As a
result, small POPS have been added to these areas. Any precipitation
will be light.
Overnight lows will drop into the 30s and 40s. South to southwest
winds will drop to 10 mph or less, with many locales dropping to
light and variable.
.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
The biggest change during this period is centered around POPS. So
we`ll start there. It appears the low to mid-level clouds that get
in here tonight will depart around daybreak tomorrow. Both Plan View
data on AWIPS and forecast soundings from BUFKIT indicate that we
should see some sun the first half of the day tomorrow, although it
may be filtered through some high clouds. POPS have been removed
from the first half of the day. I left the slight chance/chance POPS
in for the afternoon. Precip chances appear to ramp quickly late in
the day tomorrow into the evening hours.
High temperatures tomorrow afternoon will run 15 to 20 degrees above
normal. Southerly winds in the 10 to 15 mph range with some gusts up
to 20 mph will help drive up the temperatures.
.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
Primary focus remains on the Wednesday and Wednesday night period.
Wednesday...strong warm air advection will allow for temperatures
well above normal, and near record highs. This, despite forecast
persistent cloud cover, morning showers, and a robust inversion that
will likely not erode until very late in the afternoon.
Late Wednesday afternoon into Wednesday evening...Still looking at a
risk of severe storms within the warm sector ahead of the cold
front. From the previous forecast, the risk of severe has increased
slightly as model soundings are showing even more instability. Model
soundings continue to show significant shear values, In fact, the
directional shear has increased (yesterday it was looking like the
shear would be almost entirely speed shear). The biggest question
mark at this point will be how quickly or if the previously
mentioned inversion will erode. By the latest model soundings, it
looks like this should happen no later than 21Z, but could be as
early as 18Z. I think it is likely to happen as the models have had
a cold bias in the boundary layer with recent warm air advection
Timing: The severe threat will begin once the inversion erodes mid
to late afternoon. There is some uncertainty with when the front
will arrive, but the severe threat may diminish well ahead of the
front as by late evening (03Z) any instability looks to be elevated.
Hazards: Primary hazard concern continues to be strong winds.
Through out the day, there looks to be a 60 to 70 kt jet between 850
and 700 mb. At that level, it won`t take much to mix down the
stronger winds. There is increasing concern for hail given the model
soundings showing a deeper unstable layer. Also an increasing threat
of heavy rain leading to poor drainage flooding. Latest model
soundings show precipitable water values well above the 90th
percentile for this time of year. Additionally, we could have a
brief period of training storms ahead of the main line of storms,
especially if the cold front is slower to arrive. As for the
tornado threat, still think this threat is somewhat limited
given LCLs above 2000 ft AGL. Will continue to monitor this as
we get closer to the event.
Late Wednesday night into Friday...strong cold air advection with
breezy northwesterly winds. In a change from the previous forecast,
it looks like Thursday could be just as windy as Friday. At this
point, it looks like we will have at least 3 consecutive days of
below normal temperatures. As for precip chances, there could be
some lake effect snow showers that move into the Poconos, Northwest
NJ, and the Lehigh Valley Thursday or Thursday night. A fast moving
low is still expected to dig across the region on Friday, though it
looks to be relatively weak and the exact track is uncertain so it
is hard to say at this point where or how widespread precip will be
with this system.
Saturday and Sunday...High builds south, keeping us in the cold air
on Saturday. However, as it shifts east on Sunday, low level flow
will become southwesterly, allowing for another warming trend that
looks to continue into Monday.
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.
This afternoon and tonight...VFR with a light southerly wind
developing. Winds may go light and variable. The exceptions could be
KMIV and KACY where visibilities could drop into the MVFR range. A
few sprinkles or light showers could also develop in response to a
spike in WAA.
Tuesday...VFR with an increasing southerly wind. By afternoon, the
terminals could experience 10 to 15 kt with gusts up to 20 kt. Once
again, the exceptions could be KMIV and KACY where visibilities
could drop into the MVFR range in the morning. A few sprinkles or
light showers also remain possible. Shifting to late in the day,
scattered showers are expected to develop once again.
Wednesday and Wednesday night...Thunderstorms are expected,
primarily Wednesday afternoon or Wednesday night. With any storms or
showers, MVFR or even IFR conditions are expected. There will be an
abrupt shift to breezy northwesterly winds with the cold front which
should arrive Wednesday night.
Thursday and Friday...Mostly VFR conditions. There is a small chance
of lower conditions with rain and snow showers Thursday night into
Friday. Very breezy northwesterly winds are possible both days.
Saturday...Mostly VFR conditions expected.
This afternoon and tonight...No headlines. South winds diminishing
to 5 to 10 kt with seas 2 to 4 ft. Some light showers possible south
of Little Egg Inlet after midnight.
Tuesday...No headlines. South winds 5 to 10 kt during the first half
the day than increasing to 10 to 15 kt with gusts up to 20 kt in the
afternoon. Some light showers possible south of Little Egg Inlet
through about mid morning, and again later in the afternoon.
Wednesday...southwesterly winds at or above 25 kt likely, especially
on the coastal waters. Periods of showers and thunderstorms
possible, especially on Wednesday.
Wednesday night...Thunderstorms and showers possible. An abrupt
shift to northwesterly winds is expected with a cold front either
late Wednesday night or Thursday morning.
Thursday and Friday...Northwesterly winds gusting above 25 kt are
likely through out the period. There is an increasing risk for gale
force gusts both days.
Saturday...winds and seas subsiding below SCA criteria through the
Record high temperatures for Wednesday, March 1st.