Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
109 am EDT Tuesday Mar 31 2015
a fast moving low pressure system should sweep through the area
later today. A high pressure system will build into the region
for Wednesday and move offshore on Thursday. The next cold front
should move through the region late Friday. A secondary cold front
should move through the area late Saturday followed by a high
pressure system for the start of next week.
Near term /until 6 am this morning/...
for this estf update we extended precipitation chances deeper into the
overnight close to the Interstate 80 corridor. Some slight
temperature adjustments were made based on current observation.
The shortwave crossing the region has touched off an area of precipitation
over northern areas. It has been predominantly rain, though some snow
was reported in the Poconos. Expect this precipitation to continue for
the next few hours. This precipitation is supported by the hrrr. Have
introduced some low probability of precipitation across the northern tier accordingly. Have also
increased cloud cover in this area. Once this precipitation moves thru,
expect a dry night and a quiet night elsewhere.
Short term /6 am this morning through 6 PM Wednesday/...
a fast moving clipper system will be good for about 6 hours of
precipitation across the area Tuesday. The good news is that most
areas will have rain. Only the higher elevations of the southern Poconos
will have snow Tuesday with a small accumulation...1 to 2 inches
possible. The precipitation will arrive across the west during the
late morning and will overspread the del valley/Delaware-Maryland-Virginia and New Jersey by
afternoon. Overall quantitative precipitation forecast of about 0.25 expected. High temperatures Tuesday
will range from the low/middle 40s north to the middle 50s south. Highs
will remain closer to the middle 30s over the higher elevations north.
Long term /Wednesday night through Monday/...
long term begins with a split flow pattern and the departing
clipper system, but by the end of the week we see the upper level
pattern transition to more of a zonal flow pattern.
Tuesday night...clipper system exits. Models are in relatively
good agreement of how quickly it will exit (with precipitation cutting
off for all but coastal areas by 06z), even though there remain
some minor differences with the track of the low.
Wednesday and Thursday...surface high builds over our region
Wednesday, but quickly shifts off shore. As it does so, low level
flow will become more southerly and southwesterly resulting in
significant warm air advection. Highs on Thursday should be about
10 to 15 degrees higher than Wednesday, and above normal!
Thursday night into Saturday...models came into considerably
better agreement over the last 24 hours, with the GFS generally
trending more towards the European model (ecmwf) solution. Models are in relatively good
consensus that we will stay in the warm sector Thursday night into
early Friday until the initial cold front slowly slides through
Friday afternoon into Friday night. Through this time though, a
weak upper level short wave trough, and being under the right rear
quadrant of an upper level jet will allow for some chances of rain
even before the front enters the region. Chance for rain continue
with the passage of the front and as the next upper level jet
approaches the region.
Sunday into Monday...still considerable uncertainty how quickly
the next cold front will move into the region, and when it does
if there will be any precipitation. For now, continued to keep the
frontal passage dry as there will be limited opportunity for
moisture advection between the two frontal passages.
Aviation /06z Tuesday through Saturday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy, and surrounding areas.
The 06z tafs will bring all of our sites to low MVFR or IFR
conditions this afternoon with a high degree of uncertainty
about the wind directions this afternoon and early evening.
Rest of the overnight VFR with some middle to high level clouds.
Light west winds.
This morning a middle level ceiling arriving, some rain possible late
at kabe and krdg. South to South West winds averaging 5 to 10
This afternoon at kabe and krdg ceilings and visibilities lowering to IFR.
Rain may mix with or change to snow late. Especially kabe. Tarmac accums
not expected. Local kphl airports rain arrives and ceilings and visibilities
lowering to the border between MVFR and IFR conditions. Kmiv and
kacy similar evolution, but later in the afternoon.
Winds will be tricky as it depends upon the track of the low.
We are expecting it to pass to the south of all the terminals
across Delaware-Maryland-Virginia. There will be a slow backing of the winds from
south to northeast as the afternoon progresses. Speeds should be
around 10 knots.
This evening, conditions bottoming east ot IFR early and then
improving conditions the rest of the evening. Precipitation should end by
04z all terminals. Winds will continue to back toward the north
and then northwest with average speeds around 10 knots, but some
gustiness to around 20 knots from the kphl airports
Overnight improving conditions continuing with a VFR ceiling becoming
clear and northwest winds averaging around 10 to 15 knots.
Wednesday through Thursday...generally VFR conditions. Breezy
southwesterly winds later on Thursday.
Thursday night through Friday night...MVFR conditions expected
with rain showers. Slight chance of thunderstorms Thursday night
into Friday morning as the front moves through.
Saturday...conditions improving as precipitation moves out.
based on the latest observations, all flags will be dropped with
the latest forecast update. Overall, a west wind is anticipated and could
gust as high as 20 kt, but even that has been generous
Sub-Small Craft Advisory late after that and into Tuesday morning. The next clipper
Tuesday could once again produce Small Craft Advisory winds Tuesday afternoon into the
Tuesday night...winds and seas should remain just below Small Craft Advisory
Wednesday...sub Small Craft Advisory conditions expected.
Thursday through Friday...southerly and southwesterly winds will
likely increase above 25 knots for at least part of this period. Seas
on the ocean will likely increase to Small Craft Advisory criteria as well. Agree
with previous shift that wave watch guidance is a bit too high for
wave heights with this pattern, so undercut guidance slightly.
Saturday...considerable uncertainty, but waves above 5 feet are