Area Forecast Discussion
Issued by NWS Mt. Holly, NJ-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KPHI 221030
Area Forecast Discussion
National Weather Service Mount Holly NJ
630 AM EDT Wed Mar 22 2017
Strong northwest flow will develop today in between the
departing low to our northeast and approaching high from the
northwest. The high will build across the east coast Wednesday
night into Thursday, then shift offshore Thursday night. A warm
front will lift to our northwest Friday, while a backdoor cold
front pushes through the area Saturday. This front is forecast
to stall near the southern portions of the area or just to our
south into early next week. A couple of low pressure systems may
form along the boundary and move eastward as well.
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --Cold front continues to work its way south through the region,
and is through almost all of PA and northern NJ. Cold front
should be off the Atlantic coast between 8am-10am. NW winds
beginning to increase over the Poconos to 15-20 MPH with gusts
up to 30 MPH. Some flurries and brief snow showers have
developed in the wake of the cold front, aided by some upper
level support from a strong shortwave. Accumulating snow is not
Will adjust hourly grids to account for latest surface obs.
Otherwise, low pressure over eastern Quebec moves towards the
Canadian Maritimes and intensifies today as high pressure over
the Northern Plains digs towards the Great Lakes. This will
result in a tight NW pressure gradient across the Northeast and
into the Mid-Atlantic. Winds at the top of the mixed layer will
range from 35-40 KT, and with strong CAA, most of those winds
will mix down to the surface. NW winds should range from 20-30
MPH with 30-40 MPH gusts. Wind gusts should stay under Wind
Meanwhile, a deep upper trough will dig into the Northeast
U.S., and H8 temps will drop to -12C to -15C throughout the day
today. Highs will be 15-20 degrees below normal, topping off in
the low 20s in the Poconos, and in the low 30s for much of
northern NJ. For SE PA and central and southern NJ, highs will
be in the mid to upper 30s, and in SE MD and DE, highs will be
in the low 40s.
Minimum wind chills today will be in the single digits in the
Poconos and in the teens for much of PA and NJ.
-- End Changed Discussion --
.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/...
Low pressure over the Canadian Maritimes moves offshore as
surface high pressure over the Great Lakes builds towards the
Ohio Valley. The pressure gradient over the area will relax, and
winds diminish to 5-10 MPH this evening.
Lows tonight will remain some 15-20 degrees below normal,
dropping into the single digits in the higher elevations of the
Poconos and northern NJ, and otherwise in the teens to around
.LONG TERM /THURSDAY THROUGH TUESDAY/...
The extended forecast starts off quiet for Thursday, but
becomes unsettled for the majority of the rest of the forecast.
On Thursday, high pressure builds across the area, then pushes
offshore Thursday night. Dry conditions will prevail across the
area through Thursday night.
On Friday, a warm front will lift to our northwest during the
morning hours. At the same time, a short wave/vorticity impulse
will slide across the area. This is expected to help create an
area of precipitation that is forecast to move across the area
during the morning into the early afternoon hours Friday.
Depending on how early this precipitation begins, there could
be a period of a wintry mix of freezing rain/sleet/snow across
portions of eastern Pennsylvania and northern New Jersey. The
rest of the area should remain all rain with warmer
Friday night is expected to start out dry as the precipitation
associated with the warm front moves away from the area.
However, a backdoor frontal boundary is forecast to be
approaching the area from the north overnight. It will likely
not reach the area until the daytime Saturday, but there could
be a slight chance for some showers across the northern areas
overnight as a short wave approaches.
Saturday begins an extended period of possible unsettled
weather across the area. A backdoor cold front will sink through
the area during the day Saturday, then likely stall just to our
south. It may waver north across our area at times late in the
weekend into early next week as a couple of waves of low
pressure form and move along the boundary. Along with the waves
of low pressure on the front, there will also be several short
wave/vorticity impulses moving across the area through the
period as well. This will lead to a chance of precipitation
each day from Saturday through Tuesday of next week. Sunday
night into Monday morning is forecast to be the potential for
the heaviest rainfall of the period as the front is forecast to
lift into the area as one wave of low pressure move across the
area. Another possibility is if temperatures are cold enough
across far northeast Pennsylvania and far northwest New Jersey,
a wintry mix may occur.
.AVIATION /10Z WEDNESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.
VFR through the TAF period with unlimited CIGs/VSBYs as high
pressure builds east.
NW winds will increase to 15-25 KT with 30-35 KT gusts from
late morning through this afternoon.
NW winds diminish to 5-10 KT after 00Z Thursday.
Thursday-Thursday night...VFR with winds diminishing through
Friday...A period of MVFR or slightly lower conditions possible
with a period of light rain; mostly during the morning into
early afternoon. If precipitation begins early enough, a wintry
mix is possible, especially for northern areas. Southwest winds
may gust 20- 25 knots.
Friday night...Conditions improving to VFR.
Saturday-Sunday...MVFR or IFR conditions with periods of rain
Cold front moves across the waters this morning. A tight NW
pressure gradient develops across the waters. Gale force winds
will develop this morning and will continue into this evening.
For NJ ocean waters, Gale Warning runs until 03Z Thursday, and
for the DE ocean waters and DE Bay, the Gale Warning will run
until 00Z Thursday.
Thursday-Thursday night...Conditions expected to be below Small
Craft Advisory levels.
Friday-Friday night...Small Craft Advisory conditions likely to
return to the waters.
Saturday-Saturday night...Conditions expected to fall below
Sunday...A return to Small Craft Advisory levels expected.
Dry and windy conditions in place today, with NW winds ranging
from 20-30 MPH with 30-40 MPH gusts. Min RH Values will range
from 25-35 percent. After coordinating with fire weather
partners on Tuesday, soil moisture is still rather high in many
areas, so do not plan on issuing any statements regarding fire
MARINE...Gale Warning until 11 PM EDT this evening for ANZ450>453.
Gale Warning until 8 PM EDT this evening for ANZ430-431-454-