Scientific Forecaster Discussion
fxus61 kphi 270145
Area forecast discussion
National Weather Service Mount Holly New Jersey
945 PM EDT Thu Apr 26 2018
an area of low pressure will move northward across the mid
Atlantic region Friday, before combining with another low as it
moves across New England Saturday. A cold front is expected
Saturday, with additional surface troughs Sunday into Monday.
High pressure across the Great Lakes and Ohio Valley Sunday will
build to our south Monday, before shifting offshore of the
Carolinas Monday night where it remains through Wednesday of
Near term /until 6 am Friday morning/...
As of mid/late evening, an upper low continues to progress
eastward across the southern Appalachians. High to mid-level
clouds and moisture are spreading rapidly northeast ahead of it
over the mid-Atlantic region. However precip remains well to our
southwest over SW VA, and is not expected to reach upper
Delmarva until near sunrise. Clouds overspreading the area
before that should limit overnight cooling, and so overnight
mins have been adjusted upward slightly for most areas.
Otherwise no changes to the current forecast.
Previous discussion below:
low pressure located in northern Maine early this afternoon
will continue to move northeastward and away from our region.
Weak high pressure will influence our weather tonight. Another
area of low pressure approaching from the south is forecast to
move into Virginia toward daybreak.
We are anticipating dry weather for the first half of the night
with just some cirrus overhead. The wind should become light
There will be an increase in mid level clouds from the
southwest late tonight. Light rain is expected to reach
northeastern Maryland, Delaware, and parts of southeastern
Pennsylvania and southern New Jersey very late tonight.
Low temperatures in our region are forecast to range mainly
from the middle 40s to the lower 50s.
Short term /6 am Friday morning through 6 PM Friday/...
a mid level trough is forecast to lift northeastward over our
region between about mid morning and mid afternoon. An area of
rain is expected to precede the trough axis. We should see rain
through most of the morning, with the rain tapering off in the
afternoon from southwest to northeast. Most locations in our
forecast area are expected to receive between a quarter and a
half inch of rainfall.
The surface low is expected to progress slowly northeastward
across the upper Delmarva and southern New Jersey on Friday. The
track makes for a tricky temperature forecast. We've averaged
things out a bit. However, it is likely that some of our maximum
temperatures along and to the northwest of the Interstate 95
corridor may be a little high, and forecast readings may be a
little low on parts of the coastal plain. We will adjust things
when and if the trends in the track become more clear.
A light east to northeast wind is expected to develop on Friday
morning, with the wind becoming southerly to the east and south
of the surface low's center.
Long term /Friday night through Thursday/...
after some possible showers this weekend, and extended period
of dry weather is expected into next week, along with warming
Low pressure that moves across the area during the day Friday
will continue to lift to our north and while another low
pressure moves across the Great Lakes. This low will move into
New England through Saturday, pulling a cold front across the
East Coast before both lows combine into one. There will be a
small chance of showers across the northern third of the area
early Friday night, but most shower activity is expected to be
finished by evening time. The best chance of showers will be
during the day Saturday as the aforementioned cold front moves
across the area. The front will move offshore by Saturday
evening and all associated showers will move offshore with the
front, leaving a dry forecast overnight.
On Sunday high pressure will be moving across the Tennessee
River valley, before shifting across the southern applachians
and offshore of the Carolinas Monday. Meanwhile, low pressure
will remain across northern New England and eastern Canada. This
will keep our area under the influence of a west to northwest
flow, with a couple of weak surface troughs moving across the
area. Most of the area will remain dry with the passage of the
surface troughs. However, an area of enhanced low-mid level
lapse rates and moisture will slide across the far northern
parts of the area during each afternoon, which could lead to
some isolated showers, mainly across northeast Pennsylvania and
northern New Jersey. Gusty conditions could develop both Sunday
and Monday with winds gusting 20-30 mph at times.
The high will remain to our south Tuesday into Wednesday,
keeping dry conditions in the forecast. Winds could remain gusty
at times, but likely not as gusty as Sunday or monday;
generally 15-25 mph.
Late in the week a cold front may begin moving toward the area
from the west. Right now it looks like the front will not make
it into the area Thursday, keeping dry weather in the forecast.
Friday looks like the earliest for it to reach our area.
After an up and down forecast to the temperatures Saturday and
Sunday, a warming trend will begin Monday and continue through
the upcoming week. Temperatures in the low to mid 80s are
forecast for at Wednesday into Thursday.
Aviation /02z Friday through Tuesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
Tonight...mainly VFR with light rain arriving from the
southwest between 09z and 12z. West wind 5 to 10 knots becoming
light and variable.
Friday...conditions dropping to MVFR and IFR in rain between
12z and 15z. East to northeast wind 5 to 10 knots. Some
improvement is possible late in the day.
Friday night...MVFR conditions possible early in the evening
with scattered showers, becoming VFR later in the evening and
Saturday...mostly VFR. A chance of showers which may
temporarily lower conditions.
Saturday night-Tuesday...VFR. Gusty west to northwest winds
20-25 knots Sunday and Monday. Gusty west to southwest winds
15-20 knots Tuesday.
weak high pressure is forecast to influence our weather tonight
and weak low pressure should pass across our region from
southwest to northeast on Friday. Wind speeds are expected to
remain less than 15 knots with gusts not exceeding 20 knots.
A southeasterly swell is anticipated to continue along the
coast. Wave heights on our ocean waters are forecast to favor
the 4 to 6 foot range. As a result, the Small Craft Advisory has
been extended for our ocean waters to include both tonight and
Friday. It has been changed to a Small Craft Advisory for
hazardous seas since wind gusts of 25 knots or greater seem
Friday night...elevated seas may linger into Friday night.
Saturday-Saturday night...conditions expected to remain below
Sunday-Monday...winds may approach Small Craft Advisory levels
Monday night-Tuesday...conditions expected to remain below
Marine...Small Craft Advisory for hazardous seas until 6 PM EDT Friday