Scientific Forecaster Discussion
fxus61 kphi 221305
Area forecast discussion
National Weather Service Mount Holly New Jersey
805 am EST Wed Nov 22 2017
a cold front will move across the area early this morning while
an area of low pressure moves northeastward offshore the mid
Atlantic coast. High pressure will build toward the area
tonight, and control the weather Thursday and Friday. A cold
front is forecast to move across the area on Saturday while an
area of low pressure moves northeastward offshore the mid
Atlantic coast. High pressure builds across the area Monday,
then offshore Tuesday.
Near term /until 6 PM this evening/...
745a estf: a few notes... withdrew thunder from a large part of
the fcst area where it was before, confining to primarily the
coastal waters. 100 pop where you see it raining coastal New Jersey Delaware
for another hour or 2.
Rest of fcst unchanged. 930a update may be able to end much of
the rain except coastal sections NJ/de.
Note: rtpphi..we've set some data to missing as its erroneous
including Millville trace rain.
A few sites in Delmarva and southeast New Jersey will exceed
0.75 inches, with some localized 1.25"+ totals already recorded.
Pns will probably Post with some amts 1+ around 11 am.
Most hi-res guidance ended up doing reasonably well with the
event, though generally biased westward with the qpe maximum.
Some light showers may occur in the southern Poconos and
vicinity this morning in association with the upstream vort Max
moving through the northeast today. Temperatures are generally
too warm for snow, but some of the colder spots in Carbon/Monroe/
Sussex (nj) counties may see a few flakes before all is said
and done. Impacts will be negligible given the very light/very
brief duration of the precip.
Latest hi-res guidance keeps showers lingering along the coast
through late morning, so clouds may stick around longer in these
locations. Otherwise, drying/some clearing should be expected
farther to the west, with northwest winds becoming gusty this
afternoon as a cold front moves through the area. Temperatures
will remain fairly steady/mild this morning as cold-air
advection lags the front but should trend downward (slowly) this
afternoon. Made no changes to temperature forecast with this
Still a little uncertain about cloud cover later this morning
and this afternoon. The model forecasts look overly optimistic,
but given the fairly strong agreement, I am hesitant to deviate
in the negative direction. Still, a longer lasting
scattered/broken stratocumulus deck would not surprise ME,
especially if winds/mixing are stronger than forecast (with the
residual moisture from this morning's rain contributing to
generation/maintenance of the clouds underneath midlevel
Safe travels today.
Short term /6 PM this evening through 6 am Thursday/...
upstream of the potent vort Max moving through the region
today, a surface high will build into the Appalachians
overnight. With clear skies and a decreasing surface pressure
gradient, temperatures will be much colder tonight. Forecast
lows are several degrees below seasonal averages, ranging from
around 20 in the southern Poconos to around 30 in the urban
corridor and at the coast. Northwest winds will be decreasing
during the period, possibly becoming light and variable late.
The main uncertainty with the forecast is how quickly the winds
will die down, with the potential for some temperature error if
winds diminish faster than progged (i.E., It would be colder).
For now, I used a model blend, as I do not have much of a feel
for how quickly the winds decouple tonight. With the trend for
the past day being subtly slower with the incoming high (and
departing vort max), it may take a bit longer for the winds to
diminish than the models suggest.
Long term /Thursday through Tuesday/...
fairly quiet weather is expected for most of the extended
period through next Tuesday, with a chance of isolated showers
High pressure is forecast to build across the area Thursday
into Friday and bring dry weather to the region. Temperatures
are forecast to be near or slightly below normal Thursday,
before warming back to near or slightly above normal Friday.
The high builds offshore Friday night in advance of an
approaching cold front coming through the area Saturday. Also,
an area of low pressure is forecast to be moving northeastward
offshore of the mid- Atlantic coast on Saturday. This low is
currently expected to remain far enough offshore to not bring
major effects to the area Saturday. However, as the front moves
through Saturday there is a chance of isolated/scattered showers
across the area. For Saturday night into Sunday, the low moves
farther to our northeast with high pressure to our west. This
will keep a strong northwest flow across the area Saturday night
and Sunday. It is possible that some isolated lake effect
showers could make their way across our area Saturday night into
Sunday in the northwest flow. Temperatures remain above normal
Saturday before the front moves through the area, but falls back
to near normal or slightly below for Sunday.
By Sunday night, high pressure begins to approach from the west
and the flow turns more northerly, cutting off the lake effect
showers potential across our area. The high pressure fully
builds across the area Monday, then pushes offshore by Tuesday.
This will bring dry weather back to the area early next week.
Temperatures are expected to be near normal or slightly below
for Monday, then warm back to above normal Tuesday as return
Aviation /13z Wednesday through Sunday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
This morning...VFR ceilings this morning except brief MVFR/IFR
conds in showers vcnty kmiv/kacy/kttn til about 14z. Light
This afternoon..VFR sct clouds aoa 4000 ft. Northwest wind
increases with gusts to 25 kt.
Tonight...VFR with northwest winds diminishing. Confidence
Thursday-Friday night...VFR expected. Westerly winds Thursday-
early Friday. Becoming southwest later Friday into Friday night.
Saturday-Sunday...generally VFR. Isolated showers possible
which may occasionally lower conditions. Southwest winds early
Saturday, becoming northwest and gusting 20-25 knots Saturday
night into Sunday. Moderate confidence on showers and sub-VFR
conditions, high confidence on winds.
745a: dropped thunder from de Bay.
No changes to the small craft advisories this morning as
northwest winds will pick up late this morning and easily
exceed criteria this afternoon and evening. Seas will likely
hover around 5 feet through tonight, as well. Showers, possibly
with a couple lightning strikes, are possible til about 10 am in
the coastal waters.
Thursday-Saturday...sub Small Craft Advisory conditions
expected, although seas may be around 4 feet Thursday before
Saturday night-Sunday...Small Craft Advisory conditions likely
behind cold frontal passage.
the kdox radar remains out of service. Replacement parts are
expected to arrive today.
Marine...Small Craft Advisory until 6 am EST Thursday for anz450>455.
Small Craft Advisory from noon today to midnight EST tonight
near term...cms/drag 805