Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
356 am EDT Thursday Oct 2 2014
high pressure over the Canadian Maritimes will influence our
weather through Friday. Then, a strong cold front, associated with
potent low pressure in Ontario, will move across the area Friday night
into Saturday morning. Behind the front, high pressure will build
to the south and east through Monday, then a series of impulses
look to affect the region through at least midweek.
Near term /until 6 PM this evening/...
overnight water vapor loop shows a well-defined spin in the
atmosphere that is associated with an upper-level low over southern
New England. The low is forecast to move offshore today.
Marine layer and stratocu has been established across the region
over the past 30 hours as a persistent northeasterly flow around the
low has drawn cool/moist air from the Atlantic moisture inland.
These clouds are expected to linger over the area once again today.
There should be an opportunity to see more appreciable breaks in the
clouds, particularly south and west of philly later this morning.
However, deeper mixing at these sunnier locations will result in
redevelopment of stratocu during the afternoon.
The bulk of the lift with the low will stay offshore and over New
England, but a brief period of light rain or drizzle certainly
possible early this morning near the coast. Any lingering precipitation
near the coast will shift offshore by middle morning as the upper low
pulls away from the area.
Forecast maximum temperatures are in the 70s today except for the upper 60s
along the New Jersey coast (where thicker cloud cover will limit daytime
heating) and in the higher elevations of northwest New Jersey and the Poconos.
Leaned toward the warmer met guidance for philly and points south
and west (where less cloud cover would allow for highs to reach the
Short term /6 PM this evening through 6 am Friday/...
the upper low pulls farther away from the coast tonight. Ridge
building will occur along the eastern Seaboard. Conditions will be
favorable for radiational fog to develop over the Lehigh Valley and
western suburbs of philly where the surface-925 mb ridge axis is
forecast to be positioned overhead. Downstream of this low-level
ridge axis, marine layer will remain established under light
easterly flow. Accordingly, coastal locations have the best chance
of seeing stratus return late tonight.
Forecast min temperatures range from the upper 40s in higher elevations of
northwest New Jersey/northeast PA to near 60s along the New Jersey and Delaware coast.
Long term /Friday through Wednesday/...
high pressure over eastern Canada will ridge down westward on Friday and this
feature coupled with low pressure over the open Atlantic will keep Ely
flow over the region. As this takes place, a strong area of low
pressure will be developing near the Great Lakes and moving into Ontario.
The models still differ a bit in the details of the evolution of the
low with its ultimate placement and strength, but agree on the overall
The potent cold front associated with this low will extend far S from this
low and will work its way from west to east from Friday night into Sat.
Friday during the day should be dry with precipitation still to the west. During the
evening hours precipitation will begin to move in from the west and by daybreak
Sat precipitation chances will exist everywhere, with the best chances from the
I-95 Corridor North and west.
There is very good dynamics with this front and negative tilted trough and
the Gulf of Mexico is open so the threat of heavy rain is there. However,
antecedent conds have been dry.
During the morning hours of Sat seems to be the best shot of rain for
most of US, with the cold front passage late morning Erly afternoon depending on
location, and precipitation coming to and end behind the frontal passage from SW to
NE. The second half of Sat should be better than the first.
Then Sat night through Monday looks dry as high pressure builds in from the
S and spreads northeastward.
Strong cold air advection moves in Sat night behind the front and it will be a
bit breezy. We will have our first true touch of fall with temperatures
not hitting 60 in many areas on sun and any wind making it feel
cooler. The wind should decrease during the day.
Beyond Mon, a series of disturbances will bring some additional
shots of precipitation through midweek with the models differing on the shortwave
details which are nearly impossible to resolve at this time scale.
Did not make any changes to the extendd beyond Monday night as the
European model (ecmwf) was delayed in its arrival, and could not analyze it in time
for the forecast issuance.
Temperatures will start out near normal and end near normal after a significant
drop with the cold front passage over the weekend.
Aviation /07z Thursday through Monday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
Marine stratocu persists over the region early this morning. Ceilings
have taken a bit longer to lower to MVFR south and west of Abe-ttn.
Still expect MVFR ceilings to develop at all terminals by 09z. Ceilings
around 2-3 kft should slowly improve to VFR between 14-17z although
MVFR may continue well into the afternoon at Acy where marine layer is
most established. North-NE winds around 5 knots at sunrise will increase to
around 10 knots this afternoon.
VFR expected this evening. There is a potential for fog and low clouds
to develop again between 06z-12z Friday. For the 06z tafs, kept
flight restrictions above IFR for now at kphl since the end of the
30-hour forecast covers this time window.
Friday...mostly VFR. High confidence.
Friday night...increasing rain chances from west to east and MVFR/IFR in
periods of rain, some of it heavy. East to southeast wind. MDT to high
Sat...MVFR/IFR early in rain, some of it heavy, then becoming VFR
with rain ending from SW to NE. Cold front passage and wind shift from east to west-northwest. MDT
Sun-Mon...VFR. Gusty northwest wind sun. High confidence.
here was a change to the headline for today and tonight,
converting the Small Craft Advisory into a Small Craft Advisory for
hazardous seas. Winds will be below 25 knots during this time but seas
will continue to build to 5-6 feet.
Friday...Small Craft Advisory conds will likely persist on our waters through the day
and Small Craft Advisory has been extendd to account for this as persistent southeasterly
flow continues. Seas will continue to run around 5 feet. Could be
Sat...strong cold front passage. Wind shift back towards the west-northwest later in the day
behind the frontal passage. A gusty wind is expected in advance of the
front, then there could be a brief lull before the y pick up again
behind the front in the cold air advection. Small Craft Advisory seems likely. Gusty winds also
possible in the heavier rain showers...mostly in the Morning.
Sun...gusty northwest wind will continue before subsiding during the morning.
Seas should also drop below Small Craft Advisory conds to around 3-4 feet.
Monday...no marine headlines anticipated.
persistent northeast winds have resulted in positive tidal
departures between 1-1.25 feet. Do not expect anomalies to increase
much today as the onshore winds subside a bit. This should result in
tides below minor flooding threshold for this morning's and
tonight's high tide cycles.
Marine...Small Craft Advisory for hazardous seas until 6 PM EDT
Friday for anz450>455.