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Area forecast discussion 
National Weather Service Mount Holly New Jersey
411 PM EDT Mon Oct 24 2016

high pressure near Hudson Bay Canada will build closer to our region
through mid week. A warm front on Thursday will be followed by a
cold front Thursday night as low pressure redevelops from near Lake
Erie Thursday to Long Island Friday morning. Weak high pressure
quickly follows Friday night before low pressure and its associated
frontal systems cross the mid Atlantic states Saturday. High
pressure will become dominant over our area by next Monday.


Near term /until 6 am Tuesday morning/...
a relatively quiet night expected tonight across the area. Partly to
mostly cloudy skies late this afternoon and early evening will
become mostly clear later this evening overnight. Clouds may begin
increasing across the northern areas as we approach daybreak
Tuesday. Also, with these advancing clouds, it is possible for some
sprinkles or flurries to occur across our far northern areas as some
enhanced moisture/lift moves into the area within the northwest
flow. Any precipitation amounts are expected to be light.

Winds will remain gusty for the late afternoon hours, diminishing
some around sunset and through the evening. With an area of low
pressure well to our north and high pressure well to our northwest,
we continue to keep a tight pressure gradient across the area. This
will keep a steady flow across the area through tonight with winds
generally 5-10 mph overnight, even once the gusts drop off.

Temperatures will cool significantly tonight compared to last night
with widespread 30s, and some 40s. However, with the expected wind
and possible increase in clouds late, we do are not expecting
widespread frost, so we do not anticipate a frost advisory for
tonight/Tuesday morning at this time.


Short term /6 am Tuesday morning through 6 PM Tuesday/...
there could continue to be some sprinkles/flurries at the start of
the day Tuesday due to the enhanced moisture/lift across the area
within the northwest flow. Any precipitation should dissipate
through the morning, however, clouds cover should expand and
increase in coverage across the area during the day.

Winds will again become gusty through the day with gusts reaching 25-
30 mph at times across the area. With the winds, it will feel much
cooler than the actual air temperature with is expected to be mostly
in the 50s, with 40s across the far northern areas.


Long term /Tuesday night through Monday/...
500mb: the cold trough over the northeast USA weakens to the
Maritimes Wednesday. A strong short wave over the Great Lakes
region moves off the mid Atlantic coast Friday, with a following
short wave in the Dakotas moving to mid Atlantic coast Sunday.

Temperatures: the first 23 days of October have averaged nearly 4
degrees above normal. The midweek cold will Dent this above normal
departure but after all 31 days of reality have occurred, the
month as a whole should still average 2 to 3 degrees warmer than
normal. Calendar day averages Wednesday and Thursday should be 4
to 8 degrees below normal. Temperatures Friday and Saturday will
probably average a bit above normal, then cool to near normal
Sunday and Monday.

Forecast basis: unless otherwise noted, a 50 50 blend of the 12z/24
GFS/NAM MOS guidance Tuesday night-Wednesday night, thereafter the
12z/24 GFS mexmos Thursday which was modified warmer i95 sewd for
a 6pm Max temp with probability of precipitation modified 14% higher in accordance with
multimodel consensus and 12z/24 gefs 12 hr pop for .10, then the
15z/24 wpc guidance Thursday night- Monday was followed almost
verbatim. The 12z European model (ecmwf) was toned down in its extremes (caa Friday
and waa for sunday) as it was not in good agreement with the
Meeker looking UK/GFS/ggem.

Tuesday night...frost freeze expected over much of the non urban
region of eastern PA and NJ, probably ending the growing season from
the Lehigh Valley eastward into much of central and northern New Jersey.
This is likely to be the coldest night of the season so far for many
locations. However, record lows are not expected. Mostly clear with
northwest winds decoupling after 10 PM and becoming nearly toward
dawn. Npw is posted. Confidence: above average.

Wednesday...highs on Wednesday should be about 1 or 2 degrees
lower than Tuesday, or 5 to 10 degrees below normal. Northwest
winds becoming north with mostly sunny skies (bands of thin
cirrus). Confidence: average

Wednesday night through Thursday...most of the 12z deterministic
models (excluding the NAM on its much slower run) have come into
closer agreement with the more progressive timing of the GFS. The
good news with this solution is that cloud cover should increase
rather early on Wednesday night, limiting radiational cooling (and
also consequently making frost unlikely except in a few of the
traditional strong radiators prior to midnight). The bad news is
that even so, precip arriving ahead of the surface warm front due
to warm air advection aloft and a mid level short wave trough,
should be a wintry mix across the southern Poconos and northwest New Jersey.
Sref probs for 1 inch of snow are 20-30 percent. We couldn't use
the 12z/24 NAM prob of frozen pcpn, since it was so slow with its
pcpn onset. Therefore, presuming arrival of the pcpn between 4 am
and 10 am Thursday, there would be some snow, sleet and freezing
rain with a pretty good chance of slippery travel in the higher
terrain of Sussex and Monroe counties. We did not Post snow and
ice maps this evening since we are still in Chancy occurrence but
note that would see half an inch of snow in the kmpo-High Point
NJ area early Thursday if pcpn onset is still arriving near dawn.
Additionally, there could be a few hundredths of an inch of
ice...but again we're talking 60 hours out with lack of model
agreement. Social media has a Post on this and the severe weather potential statement continues
to highlight. It "may" be a brief advisory situation with rising
temperatures ending the hazard risk by noon. Wpc and multiple
ensemble guidance offer widespread one half of rain to our area,
especially PA and New Jersey where there is a chance of isolated 1 inch of
beneficial rainfall. There is a small chc of a late Thursday near
and south of phl and have gridded slight chance there. Southerly
winds may become gusty 25 kt late in the day. Confidence: average.

Thursday night...since the arrival of the precip has accelerated
in the past two days of modeling, is will probably lead to the rain
quickly ending Thursday evening. Patchy fog may follow for a time
overnight but its not been gridded-forecast. Confidence: average.

Friday...a short wave ridge slides over the region through the day,
leading to partly sunny skies and seasonable temps but breezy
with northwest winds gusting to 25 mph. The ec is colder than the
GFS/ggem with its 2m temps so confidence on temps Friday is below

Saturday...low pressure and a frontal system are forecast cross
the area with scattered showers expected, and possibly a gusty
low top thunderstorm as swi's are near zero, ki 30-34, and tt
near 50. 850 winds are modeled near 40kt, 700 winds 40-50 kt.

Sunday and Monday...considerable model variability. The thinking
right now is northwest winds and dry but confidence is a little
less than average on the outcome. Relied totally on the 15z wpc
forecast elements.


Aviation /20z Monday through Saturday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.

The following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.

VFR conditions will continue through the taf period. The scattered
to broken stratocumulus clouds around 4,000-6,000 feet this
afternoon will dissipate this evening and overnight with the loss of
daytime heating; although there could still a few lingering clouds
around overnight.

The main concern is the gusty winds today and again Tuesday.
Northwest winds will continue to gust around 25-30 knots this
afternoon. The gusts will diminish some around sunset to around 15-
20 knots, with the gusts expected to drop off overnight. The gusts
will return Tuesday with gusts 20-25 knots again, with some locally
higher gusts 25-30 knots possible.


Tuesday night and Wednesday...VFR. Northwest winds Tuesday
night and Wednesday become north Wednesday afternoon.

Wednesday night and Thursday...ceilings will lower to MVFR (with
localized ifr) by day break Thursday. Visibility restrictions possible
with periods of rain Thursday into Thursday evening. Sleet may briefly
be mixed with the rain at kabe. East to southeast winds Wednesday
night becoming southerly late in the day and may gust 25 kts at
kphl, kilg kacy and kmiv. Small chance of a tstm south of phl late
in the day or evening.

Thursday night...lingering MVFR or IFR conds in ending rain/drizzle
with stratus/fog possibly lingering through the night. Southwest wind
turns light northwest.

Friday...becoming VFR early in the day with a gusty northwest wind
to 25 kt in the afternoon.

Saturday...VFR cigs possibly lowering to MVFR conditions in scattered
showers (isolated tstm?). southwest winds may be gusty to 25 kt.


Small Craft Advisory remains in place for tonight and has been
extended into Tuesday as winds are expected to continue to gust
25- 30 knots across the waters tonight into Tuesday. Wind gusts on
the Delaware Bay may drop below 25 knots overnight, but are
expected on increase again on Tuesday.


Tuesday night...Small Craft Advisory lingers in the evening on the Atlantic waters. No
headline after midnight as the northwest wind probably diminishes with
gusts at or below 20 kts after midnight. headline. Northwest wind with gusts under 15 kt
becoming northerly during the afternoon.

Thursday...gusty southerly winds are expected to increase to
25 or 30kt late in the day with an Small Craft Advisory likely.

Friday...northwest winds should gust to 25 kt, especially in the
afternoon when an Small Craft Advisory may still be needed.


will add at 515 PM.


Phi watches/warnings/advisories...
PA...freeze watch from late Tuesday night through Wednesday morning
for paz060>062-101>103-105.
New Jersey...freeze watch from late Tuesday night through Wednesday morning
for njz008>010-012-013-019>022-027.
Delaware...freeze watch from late Tuesday night through Wednesday morning
for dez001.
Maryland...freeze watch from late Tuesday night through Wednesday morning
for mdz008.
Marine...Small Craft Advisory until 11 PM EDT Tuesday for anz450>455.
Small Craft Advisory until 6 PM EDT Tuesday for anz430-431.


near term...Robertson
short term...Robertson
long term...drag 411
aviation...drag/Robertson 411
marine...drag/Robertson 411

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