Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
946 PM EDT Thursday Mar 26 2015
a strong cold front sweeps through the region this evening. Low
pressure will form along this front east of the middle Atlantic coast
Friday afternoon and head northeast out to sea late 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/...
snow map posting for extreme northwest portion of the forecast area early Friday.
Uncertainty regarding how much precipitation is left when it turns cold
enough to snow. We may need an Special Weather Statement for snow over higher terrain
near and north of I-80 early friday?
The grids even have a chance of snow down to near phl around
daybreak but too warm to accumulate.
Thunder chances tonight are now very limited.
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 at that time,
which am expecting. Precipitation ending from northwest to southeast during the afternoon as
a wave of low pressure forms offshore east of the Virginia convective available potential energy.
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 /02z Friday through Tuesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy, and surrounding areas.
Through tonight...at 01z variable conditions ranging from IFR in
showers/St/fog to VFR high ceilings parts of the Delaware-Maryland-Virginia. The varied
conds will basically even out to MVFR or IFR in rain/St/fog with
rain becoming widespread overnight, especially behind the cold front passage this
Kmiv/kacy cold front passage between 02z-04z/27. After the briefly gusty northwest wind
25-30 knots with the cold front passage this evening...then the northwest wind settles
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 where periods of showery rains may linger
through the day. 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
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
Winds shifting to northwest with the cold frontal passage late this
evening. Winds will gust behind the frontal passage but should
diminish through the day.
Seas are running around 6 to 8 feet on the ocean this evening 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...drag 948
short term...drag/meola 948