Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
637 am EDT Sat Oct 25 2014
a cold front over the Midwest this morning will move eastward today
and through the area tonight. The middle-Atlantic region will be
situated between low pressure over eastern Canada and high pressure
building in from the Tennessee Valley on Sunday. High pressure ridges
into the area Sunday night and Monday. A warm front will lift north
of the area Tuesday before a cold front moves through late
Wednesday. High pressure briefly returns Thursday. Low pressure may
develop over the eastern United States Friday.
Near term /until 6 PM this evening/...
had to adjust the hourly temperatures down quite a bit as most
points now have completely lost their winds and radiated pretty
well. Upstream observations indicate that the surface ridge axis
is just to our west at this hour and will be moving overhead by late
this morning. Light and variable flow will become more westerly by
the afternoon with a tightening surface pressure gradient. Ample
sunshine will allow for decent vertical mixing today, though not
as strong as in past days...gusts upwards of 20 miles per hour are possible
this afternoon. A deck of stratocu is possible but given the lack
of moisture and just reaching convective temperatures not
expecting anything widespread or thick.
Temperatures look to have another chance to clip 70f across the
southern half of the County Warning Area. The westerly downsloping winds and 925mb
temperatures climbing to around 12c will make this possible. Went a
couple degrees above guidance for today given the above.
Short term /6 PM this evening through 6 am Sunday/...
gusts should drop off by later this evening and winds back towards
the southwest just a bit ahead of an approaching weak cold front.
The front should blast through the region by Sunday morning with just
a few passing clouds expected. The column will remain dry enough and
there is not much forcing associated with the front over our region,
so we keep it dry. Good cold air advection aloft will allow for
better mixing tonight and coupled with the tighter pressure gradient
we keep stronger westerly winds through the overnight hours. With
that being said, used the warmer mav guidance for lows tonight.
Long term /Sunday through Friday/...
a vertically-stacked low will be positioned over eastern Canada
while high pressure is centered just west of the central
Appalachians. A tight pressure gradient between these two systems
will reside over the middle-Atlantic region, thus Sunday will be a
breezy day. 00z NAM/GFS BUFKIT soundings show the potential for
frequent gusts 25 to 30 miles per hour with occasionally higher gusts to 35
miles per hour. Post-frontal cold air advection expected to be transient, becoming neutral
during the afternoon. Therefore, temperatures should be able to reach climatology
(mid 60s) in most places.
The pressure gradient will weaken Sunday night as the low lifts into
the Canadian maritime while high pressure builds toward the middle
Atlantic. Still not certain on full decoupling, so went conservative
with min temperatures in the middle/upper 30s northeast PA/northwest New Jersey and
low/middle 40s from I-95 east.
High pressure shifts off the southeast coast early in the week.
South-southwest return flow around the high on late Monday will
strengthen Tuesday as a warm front advances northward through the
region and a cold front approaches from the Midwest states. Tuesday
and Wednesday looks to be the warmest days of the period (max temperatures
near 70f) with the warm sector established in the region.
Low pressure will cut well to our northwest as it tracks from the
Great Lakes toward Hudson Bay midweek. The attendant cold front will
progress into the area during this time. Differences in timing of
frontal passage have narrowed with the latest model guidance. The cold front
will most likely move through Wednesday afternoon into Wednesday evening.
Showers are possible with the front. Went slightly higher with probability of precipitation
than previous forecast but still limited to around 30 percent with
limit moisture/lift along the front.
Dry conditions and seasonable temperatures expected behind the front
Thursday with weak high pressure building in from the Tennessee Valley.
The details for the end of the week still need to be determined but
models signaling toward the amplification of a longwave trough over
the eastern Continental U.S. On Friday. Increasing clouds are likely with
perhaps showers returning to our area.
Aviation /12z Saturday through Wednesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
No change with the 12z tafs, added an extra group for phl to bring
in the strong northwest gusts Sunday morning.
Today - tonight...VFR. Westerly winds gusting to 20 knots this
afternoon decrease this evening. Winds back towards the southwest
ahead of approaching dry cold front. Winds veer to the west again
behind the front. High confidence.
Sunday...VFR. Breezy west-northwest winds 15-20 knots will gust up to 30 knots.
Sunday night through Tuesday night...VFR. Light northwest winds generally
at or below 10 knots through Monday, becoming southerly Tuesday.
Wednesday and Wednesday night...generally VFR although a brief
period of MVFR and rain showers possible with cold frontal passage.
today...sub-sca expected. Gusts across our southern waters may come
close to Small Craft Advisory this morning but drop off through the day. Seas will
remain 3 to 4 feet and decrease by this evening. High confidence.
Tonight...Small Craft Advisory conditions expected, possible brief gales right behind
cold front passage...mainly southern waters. Westerly winds increase
to 20 to 25 knots later tonight as a cold front moves through the
waters. There is a low-end chance of a few gale gusts but not
confident...high end Small Craft Advisory gusts expected. High confidence on sca, low
Sunday and Sunday night...high end Small Craft Advisory Sunday with west-northwest gusting to
30 knots. Still cannot rule out the possibility for gales but setup not
particularly favorable for deep mixing as cold air advection aloft ceases rather
quickly in the morning. Small Craft Advisory extended into Sunday evening for the waters,
ending south to north overnight for the coastal Atlantic zones as
the pressure gradient gradually weakens.
Monday and Monday night...light winds and calm seas.
Tuesday and Wednesday...southwest winds increase ahead of a cold
front. Have capped gusts at 20 knots owing to stable mixing profiles.
breezy and dry conditions expected on Sunday behind a cold front.
Sustained northwest winds near 20 miles per hour are expected. 00z NAM/GFS BUFKIT
soundings show the potential for frequent gusts of 25 to 30 miles per hour with
occasionally higher gusts to 35 miles per hour. The Post-frontal cold air advection pattern is
brief, becoming neutral during the afternoon. Current forecast
reflects min rhs Sunday afternoon in the low to middle 30s even after
leaning toward a drier (i.E., Lower dewpoints) solution with
downsloping west-northwest flow off the higher terrain. Additionally, heating
may be limited somewhat by stratocu off the Great Lakes, especially
over the northwest half of the County Warning Area which may prevent rhs from
falling critical thresholds. An enhanced threat for the spread of
wildfires may exist on Sunday with the above meteorological factors
and with forecast fuel moisture below 10 percent but confidence not
nearly high enough to issue a Fire Weather Watch.
Marine...Small Craft Advisory from 8 PM this evening to 2 am EDT Monday
Small Craft Advisory from 8 PM this evening to 6 am EDT Monday
Small Craft Advisory from 8 am to 9 PM EDT Sunday for anz430-