Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus61 kphi 181331 

Area forecast discussion
National Weather Service Mount Holly New Jersey
931 am EDT Fri Oct 18 2019

strong low pressure centered in New Brunswick, Canada early
this morning will continue to move slowly northeastward. High
pressure located in the Great Lakes and the Ohio River valley
will build to the east. The center of the high is forecast to
pass through or near our region on Saturday morning, before
moving off the coast. Low pressure is expected to progress from
the Carolinas on Saturday night to the waters off the middle
Atlantic coast on Sunday and Monday. A cold front is anticipated
to approach from the west on Tuesday and it should pass through
our region on Tuesday night. High pressure is expected to
follow for Wednesday and Thursday.


Near term /until 6 PM this evening/...
9:30 update...

Going forecast is in good shape. No notable changes with the mid-
morning update. Previous discussion follows.

Yesterday's low pressure system continues to sit and spin over
the Canadian Maritimes as a ridge of high pressure builds into
the Great Lakes region. Still considerable stratus on the back
side of the low but it is gradually retreating northward and at
this point confined mainly to areas from around phl northward. A
fairly tight pressure gradient also persists and is maintaining
breezy conditions across the area.

As we go into the day Friday, aformentioned low slowly weakens
as it drifts northward through Atlantic Canada. At the same
time, high pressure will slowly be advancing eastward towards
the area. As a result, the pressure gradient will relax so while
it will be breezy, it won't be nearly as windy as yesterday.
Also expecting more in the way of sunshine as the column will be
drying with time but still some strato cu around (especially
north) so expecting a mix of sun and clouds. Temperatures will
be a bit on the cool side with highs mainly in the upper 50s to
around 60 but even cooler in the Poconos where some areas won't
get out of the 40s.


Short term /6 PM this evening through 6 am Saturday/...
high pressure at the surface builds eastward into PA through
tonight as the associated upper level ridge moves east through
the Great Lakes. This will result in clearing skies with light
winds so nearly ideal conditions for radiational cooling. For
this reason, our forecast low's for tonight leaned towards the
colder side of guidance and generally expect lows in the mid 30s
or lower from western Montgomery and upper Bucks counties
northward where frost advisories are now in effect. Temperatures
in the Poconos will likely make it down to freezing however
Carbon and Monroe counties have already seen their first freeze
so no frost/freeze headlines were issued for these zones. From
the urban corridor southward, generally expect lows in the upper
30s to low 40s...coolest over Pine barrens of New Jersey.


Long term /Saturday through Thursday/...
high pressure is forecast to be located in our region on
Saturday morning. The center of the high should move off the
coast on Saturday afternoon. We are anticipating a mostly sunny
sky. Temperatures should climb into the upper 50s and lower 60s
at most locations in the afternoon following a chilly start to
the day.

Tropical low pressure is expected to move northeastward across
the Carolinas on Saturday night, before passing off the coast
near Cape Hatteras on Sunday. The low is forecast to meander off
the middle Atlantic coast into the early part of the new week.
Our region should be on the northwestern edge of the clouds and
the precipitation associated with the system from late Saturday
night into Sunday. We will continue to mention a chance of rain
for northeastern Maryland, Delaware and southern New Jersey.
Surface high pressure is expected to nose down from the north
and northeast for Monday as the clouds and rain push out to sea.

Strong low pressure is expected to lift from the upper
Mississippi River valley and the western Great Lakes on Monday
into western Ontario on Tuesday. The feature is anticipated to
pull a cold front through our region on Tuesday night. Based on
the expected upper level flow and the position of the surface
low, we are favoring the slower European model (ecmwf) timing of the front. We
will continue to mention a chance of showers ahead of and with
the boundary.

It appears as though high pressure will build from the
southeastern states on Wednesday to the waters off the middle
Atlantic coast on Thursday. We are expecting dry weather both

Temperatures for the period from Sunday through Thursday should
be near or slightly above normal.


Aviation /14z Friday through Tuesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.

Today...VFR conditions will continue through the day. West to
northwest winds will gust around 15 to 25 knots by mid to late
morning but will diminish through the afternoon. - High

Tonight...VFR with diminishing winds and clear skies. - High

Saturday...mainly VFR. Northwest wind 5 to 10 knots, becoming

Saturday night...mainly VFR. Localized MVFR or IFR conditions
are possible toward morning. South to southeast wind 6 knots or

Sunday...localized MVFR or IFR conditions are possible in the
morning, otherwise mainly VFR. A chance of rain around kphl,
kilg, kmiv and kacy. East wind 5 to 10 knots, becoming

Sunday night...mainly VFR. Northeast wind 5 to 10 knots,
becoming north.

Monday...mainly VFR. Northeast to east wind 5 to 10 knots.

Monday night...conditions may lower to MVFR or IFR. East to
southeast wind 5 to 10 knots.

Tuesday...showers becoming likely with conditions mainly in the
MVFR or IFR range. Southeast to south wind around 10 knots.


today...the Gale Warning has been replaced with a Small Craft
Advisory for all zones and the winds and seas will continue
diminish through today. Conditions should be below Small Craft Advisory levels by
mid afternoon.

Tonight...winds will continue to diminish but could still gust
to near or just above 20 knots into the early part of the

Saturday through Sunday marine headlines are

Sunday afternoon through Monday east to northeast
wind may gust in excess of 25 knots. Waves are expected to build
to 4 to 7 feet on our ocean waters.

Monday afternoon and Monday night...while wind gusts should
drop below 25 knots, waves on our ocean waters are forecast to
remain in the 4 to 6 foot range.

Tuesday...a southeast to south wind may gust in excess of 25
knots. Waves on our ocean waters should be around 5 to 6 feet.


Phi watches/warnings/advisories...
PA...frost advisory from 2 am to 9 am EDT Saturday for paz060>062-
New Jersey...frost advisory from 2 am to 9 am EDT Saturday for njz001-
Marine...Small Craft Advisory until 2 PM EDT this afternoon for anz430-


near term...fitzsimmons/O'Brien

National Weather Service Glossary of Abbreviations