Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
536 PM EDT Thursday Mar 26 2015
a strong cold front sweeps through the region tonight into Friday
morning. A weak low pressure system may form along this front as it
resides offshore on Saturday. Strong Canadian high pressure is
expected to move through the region on Sunday into Monday before
another cold front passage later on Monday. Another shot of high
pressure for Tuesday and Wednesday is expected ahead of the next
complex low pressure system on Thursday.
Near term /until 6 am Friday morning/...
we will probably update snow amts in NE PA and northwest New Jersey by 630 PM for
a period of snow between 4 am and 8 am.
Busy now with thunderstorms vicinity Harrisburg heading for reading PA.
Showers will continue to move through the region this afternoon with
isolated thunder remaining possible. Temperatures have warmed behind
the warm front and should rise a couple of more degrees over the
next few hours in the continuing warm advection before the cold
front arrives tonight.
The cold front will cross the region this evening bringing in
another round of rain. Instability looks limited along the frontal
boundary but there is enough that some thunderstorms may develop
as the front is crossing the region.
Things turn colder behind the cold front as we see strong cold air
advection taking place. Temperatures will drop quickly behind the
front, about 10 to 20 degrees colder. Temperatures will fall into
the 30s and 40s overnight, with some upper 20s across the southern
Poconos. With the colder temperatures, there may be a changeover to
or a mix of rain and snow as the front moves offshore and the
precipitation starts to diminish. Rainfall amounts will generally be
around a half of an inch or less with little to no snow accumulation,
though we'll monitor the forecast for the Poconos.
Short term /6 am Friday morning through 6 PM Friday/...
the cold front makes its way off the coast Friday with some lingering
rain hanging around - probably mixed with ice pellets or wet snow
at daybreak vicinity I-95 nwwd if precipitation is on going, which we think it
will be. Precipitation ending from northwest to southeast during the afternoon as a wave of
low pressure forms offshore.
Temperatures will be much cooler on Friday in many areas compared to
todays maximum temperatures. Highs will be in the 40s to near 50 across the
region on Friday with plenty of cloud cover around. Northwest winds
may be gusty early but should relax as the front moves offshore.
Long term /Friday night through Thursday/...
5-wave model guidance shows broad troughing in the east with broad
ridging across the western states through most of the longterm
period. The pattern aloft has a fast flow look without much blocking
which adds to a bit of the uncertainty/timing of embedded
shortwaves within the middle-level flow. Towards the end of the
period a nearly zonal flow looks to take shape.
Friday night - Saturday...deep anomalous middle-level trough will be
overhead as stronger northern stream energy tries to phase with
weaker, slower moving, southern stream energy. Even with minimal
phasing surface cyclogenesis looks to occur to the south of our
region late on Friday. This weak inflection will move along the
aforementioned cold front sitting offshore on Saturday and could
throw some light precipitation back across the region during the
day. Thinking that a majority of the lift and moisture with this
system will remain to our northeast, over New England, and farther
offshore. The passage of the middle-level low could also spark a few
instability showers during the afternoon. Thermally we will be
dropping below freezing throughout the column by Saturday afternoon
so most of the precipitation should fall as snow. Trying to combat
any daytime heating, even with a multitude of clouds and northerly
winds, will be tough with boundary layer temperatures expected to be
in the middle to upper-30s...the one caveat would be stronger dynamic
cooling with the placement of an inverted trough/mesoscale banding
feature...though it is ill-defined across our area at this time.
Sunday...ridging to our south re-establishes it self across the
region for the second half of the weekend. This will provide mostly
conditions across the region as temperatures remain well below
Monday...ridging slides off the southeast coast and a return flow
with low-level warm air advection kicks in. Temperatures may be able
to warm to above normal, as we continue the tumultuous early season
temperature swings. There does not appear to be a great deal in
moisture surge with this next system, as it approaches from the
west. With the lack of moisture we keep the slight chance probability of precipitation in
the forecast, though the better lift will accompany the advancing
cold front later Monday afternoon so probability of precipitation may be increased in time.
Tuesday - Thursday...the flow aloft, as mentioned above, remains
quick and active. Numerous embedded waves of energy slide through
the region during this timeframe, each carrying the chance for
showery activity. The better chances for showers will be Wednesday
into Thursday as another system pushes in from the west. Another low-
level moisture surge is expected with this system as temperatures
look to remain at or slightly above average for the first couple
days of April...this could easily change with time.
Aviation /22z Thursday through Tuesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy, and surrounding areas.
Through tonight...currently MVFR-VFR ceilings predominant phl/kilg
while IFR conds vicinity showers kmiv and kacy and IFR conds prevail
elsewhere. The varied sub VFR conds will continue through the night,
basically degrading back to IFR with showers becoming widespread
overnight, especially the cold front passage this evening.
The cold front passage will probably be accompanied by a brief northwest wind gust of
25-30 kts and a heavy shower as per the hrrr. We now have upgraded
for thunder at krdg.
The cold front passage is being advanced faster and expect through krdg/kabe
near 23z, kphl/kpne/kttn/kilg near 02z, and kmiv/kacy between
03z-04z/27. Gusty southerly winds this afternoon will become
briefly gusty northwest to 25-30 knots with the cold front passage this evening...then
settle back a bit during the night. Icing should develop in precipitation
toward dawn near and northwest of the I-95 corridor including kphl,
especially near 5000 feet as a sub freezing layer is modeled to
drives southeastward while precipitation is on-going.
Friday...IFR or MVFR conds at daybreak in precipitation will improve to
VFR ceilings across the terminals from northwest to southeast during
the morning except not reaching kmiv and kacy until sometime
during the afternoon. Winds will be out of the northwest with
speeds around 10 knots, a few gusts to 20 knots.
Friday night - Saturday...MVFR or lower possible in rain/snow
showers. Northerly winds.
Sunday - Monday...VFR. Northerly winds veer towards the southwest
and begin to gust Monday afternoon.
Tuesday...VFR. Winds veer towards the west-northwest...gusts
mww updated for gale force gusts. Mws issued for gale force gusts
through about 8pm today. Have had a number of reports of gale
force gusts along our coasts this afternoon.
Otherwise a Small Craft Advisory remains in effect across the area
waters, ending on the Delaware Bay at 12z Friday and on the ocean
front at 22z Friday.
Southerly winds across the waters this afternoon will start to veer
to the west as a cold front approaches the waters. The cold front
will reach the area waters in the 05-09z time frame and then move
offshore, leaving US with northwest winds. Winds will gust behind
the frontal passage but should diminish through the day.
Waves are running around 4 to 6 feet on the ocean this afternoon and
will remain elevated through Friday. Waves on the Bay are generally
around 2 to 4 feet.
Friday night - Saturday...seas will subside late Friday evening but
could increase a tad Saturday with a northerly surface flow
developing. Could see Small Craft Advisory seas Saturday afternoon.
Sunday - Tuesday...possible Small Craft Advisory conditions Sunday through Tuesday.
Winds veer towards the west and then southwest by Monday as high
pressure slides offshore. A cold front slides through on Monday
evening and winds may stay above Small Craft Advisory through Tuesday night.
Marine...Small Craft Advisory until 6 PM EDT Friday for anz450>455.
Small Craft Advisory until 8 am EDT Friday for anz430-431.
near term...meola/drag 537
short term...meola/drag 537