Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
628 am EDT Wednesday Oct 7 2015
high pressure, stretched from south central Canada to the middle
Mississippi Valley today, will build into our region through Thursday
before moving offshore Thursday night. A cold front is then forecast
to move through our area late Friday into early Saturday. High pressure
builds into our region Sunday and Monday, then a cold front arrives
Near term /until 6 PM this evening/...
630 am estf: variable cloudiness...generally high cloudiness
southeast of I-95 while weak cold air advection cloudiness vicinity of I-95 nwwd.
Minor adjustments in variable sky cover and temperatures through about
15z with higher gusts on the coastal waters.
Today...considerable cloudiness along and northwest of I-95 for a
while this morning that thins- diminishes midday or afternoon to
average p/c most of the forecast area except possibly MO cloudy Northwest Hills/
mountains where clouds at or above 2500 feet may persist into this Wednesday
evening. Maximum temperatures similar to ydy. 00z-06z/7 NAM guidance looks a
touch too cool while it is noted the 00z-06z/7 GFS is still quite
mild via its 2m and 850 mb temperature forecasts of 71f and nearly 12c
respectively. Since the 00z/7 ec continues on the cooler side of
the operational ensemble spread...with about a 68f 2m 18z
temperatures at phl...have forecast mostly 70 to 77f today for Max's,
around 75 today in phl.
There seems to be a cool bias to the MOS guidance daytime Max's
recently. So our new forecast temperatures are still Above All 00z/7 NCEP MOS
guidance and about 4 to 7 degrees above the climatological norm.
Northwest wind gusts around 15 miles per hour by this afternoon.
Short term /6 PM this evening through 6 am Thursday/...
tonight...clear to partly cloudy. Generally light winds, with perhaps
some patchy fog toward daybreak Thursday, especially in the more
rural, sheltered areas north of I-78. Noting here that patchy fog may
be more extensive northwest of I-95 Thursday morning if the 00z-06z/7
GFS NAM and European model (ecmwf) modeled cloud cover does not materialize. GFS
NAM and European model (ecmwf) tsecs are quite moist near 5000 feet tomorrow morning.
For early Thursday mornings forecast... the GFS leading edge of
the 5000 feet deck would be near kmpo/krdg at 00z/8, while the NAM
is slightly more delayed with its leading edge only vicinity kmpo at
00z/8...and the 00/7 ec is similar to the NAM this evening.
Thereafter the clouds would overspread- cover all of New Jersey south of
I-78 at 12z Thursday with the trailing edge still back in east central
PA. We'll see how this works.
Min temperatures a bit above normal and still no frost risk yet...as the
first frost of the season will be later than normal in the northwest
portion of our area.
Median date first frost for kmpo and kfwn is October 7.
Spotty nice color now north of I-80.
Long term /Thursday through Tuesday/...
the synoptic setup is comprised of an initial zonal flow Thursday
which then amplifies Friday from the Great Lakes into the east
through Saturday. This is courtesy of short wave energy that
sharpens the trough some as it moves across southern Canada. There
is some guidance that carries a stronger short wave in the base of
this trough, which leads to a closed low forming to our south during
the weekend. The next trough slides across the northern tier of
states Monday and arrives into the northeast Tuesday. The main time
frame for rain across the County Warning Area is later Friday into early Saturday as
a cold front moves through. We used a model blend with continuity
for Thursday into Saturday, then blended the 00z wpc guidance with
continuity thereafter. Some adjustments were then made following
additional collaboration with our neighboring offices.
For Thursday...a zonal flow aloft will allow surface high pressure
to quickly shift offshore of New England by evening. This should
result in light winds that become southerly as some return flow
starts to become established. A short wave will start to sharpen an
upper-level trough across the Great Lakes during Thursday, with a
warm front organizing to our southwest through the night. This may
start to toss some more cloudiness our way, especially at night. The
presence of the departing surface high will be accompanied by a bit
For Friday and Saturday...an upper-level trough amplifies from
southeastern Canada to the Ohio Valley, which drives low pressure to
our north. A trailing cold front is forecast to arrive late in the
day and move through during Friday night. There could be some
initial warm air advection induced showers Friday morning to midday mainly across
our western zones, therefore some low probability of precipitation were retained. This will
also result in increasing cloudiness during Friday, however a
stronger southerly flow will help boost afternoon temperatures
especially from the Interstate 95 corridor on south and east /away
from the immediate coast/.
Some guidance is showing a stronger short wave at the base of the
trough, which sharpens the trough even more and closes it off to our
south. This initially slows the cold front from clearing our
southern zones later Friday night and Saturday morning, therefore
some rain or showers may linger for a time Saturday morning. There
looks to be enough alignment between forcing and instability to
allow for some isolated thunderstorms Friday afternoon and evening
as the front arrives. Overall, the rainfall amounts are not
anticipated to be all that heavy. We do indicate some improvement
from north to south during Saturday, however there is less certainty
with the details as this will depend on the trough amplification to
our south. Given enough clearing and light winds Saturday night,
temperatures may near the frosty middle 30s across the far north toward
For Sunday and Monday...the upper-level trough starts to weaken
Sunday as ridging builds up the Ohio Valley. This will force surface
high pressure into our area, with any lingering closed low probably
staying to our south and east. This should progress out to sea
Monday as the next upper-level trough begins to amplify some across
the Great Lakes region. It will be noticeably cooler during this
time frame along with drier air working in. As of now, we maintained
a dry forecast based on surface high pressure working in for a time.
For Tuesday...the model guidance overall shows a decent upper-level
trough swinging across the Great Lakes and into the northeast. This
pushes a cold front into the area late, however at this time the main
surface low is forecast to track well to our north. In addition, the
deep moisture looks to reside offshore and therefore little left for
the frontal boundary to work with. As a result, probability of precipitation were left at
slight chance or lower at this time.
Aviation /10z Wednesday through Sunday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy, and surrounding areas.
Today...VFR. Scattered-broken clouds at or above 3500 ft, most predominant ceilings
vicinity krdg/kabe. Northwest wind gusts near 15 knots this afternoon.
Tonight...VFR. Scattered-broken clouds at or above 4000 feet vicinity krdg spreading
east during the night. How extensive the ceilings is unknown at this time.
Light northwest to north wind confidence on forecast ceilings is below
Thursday...possible local MVFR early due to fog, otherwise VFR.
Light southerly winds.
Friday...VFR with increasing clouds, then conditions tending to
become MVFR later in the day and at night as showers and isolated
thunderstorms move through. South to southwest winds increasing to
around 10 knots, then becoming west and northwest late in the day
and at night.
Saturday...patchy fog possible early, otherwise mostly VFR. It
appears that any showers are to the south and east of the area.
Northerly winds mainly 10 knots or less.
Sunday...VFR and winds should favor a northwest to west direction at
less than 10 knots.
Delaware bay: no marine headlines through at least tonight.
Atlantic coastal waters: hazardous 5 to 6 foot 12 second period
swells over the Atlantic waters from departing Joaquin are slowly
subsiding and we may be able to discontinue the Small Craft Advisory for the nnj
waters midday today but continue elsewhere through 4 PM.
Winds north-northwest at 5 to 15 knots with a few gusts near 20 knots today.
Thursday...high pressure shifts offshore allowing for a southerly
flow to occur, however conditions are expected to be below advisory
Friday and Saturday...a cold front moves through Friday night and
early Saturday morning. A southerly flow ahead of the front will
increase Friday, then shift to northwest and north in its wake at
night into Saturday. The winds should gust 25 to 30 knots for a time
mainly in the Post-frontal environment later Friday night and
Saturday morning. This will also allow the seas to build to near 5
feet on the Atlantic coastal waters for a time.
Sunday...the conditions overall are anticipated to below Small Craft
Advisory criteria as high pressure begins to build in from the
the first 6 days of October were at or below normal each day but
that 2 to 5 degree below normal 6 day average will be eliminated
by Saturday morning as notable above normal temperatures occur
today through Friday.
Marine...Small Craft Advisory for hazardous seas until 2 PM EDT this
afternoon for anz450>455.
near term...drag 629
short term...drag 629