Scientific Forecaster Discussion

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Area forecast discussion 
National Weather Service Mount Holly New Jersey
612 PM EDT sun Apr 20 2014

Synopsis...
high pressure centered east of New England this afternoon will
move farther out to sea and it should lose its influence over our
region gradually through Monday night. A cold front is forecast to
approach from the west and it is expected to pass through our
region on Tuesday evening. High pressure is anticipated to follow
for Wednesday into Thursday. Low pressure is forecast to move from
the Great Lakes on Friday, across New England on Saturday and over
canada's maritime provinces and the adjacent waters on Sunday.

&&

Near term /until 6 am Monday morning/...
high pressure continues to be the main weather story for our
region. The pressure gradient between the high pressure and the
low pressure area off to our southeast will lessen, allowing for
cooler temperatures than last night. Where growing season has
started, many locations will see patchy frost with temperatures at
or below 36 degrees, so frost advisory will be issued with the
forecast update.

&&

Short term /6 am Monday morning through 6 PM Monday/...
dry conditions and mild weather as ridge axis holds over the
region. Met/mav blend used for temperatures. Winds are
significantly lighter, so cooling marine impact will be
substantially lessened except very close to the coast.

&&

Long term /Monday night through Sunday/...
high pressure will lose its influence over our region gradually
on Monday night. The wind should be light and temperatures are
forecast to fall into the 40s.

A middle level trough is expected to approach from the west on
Tuesday and Tuesday night and its axis should pass overhead early
on Wednesday. A surface cold front associated with the feature is
forecast to arrive in our region late on Tuesday and it will
likely bring rain showers for the afternoon and evening hours. The
front will be progressive and moisture should be somewhat limited.
As a result, rainfall total are expected to be generally less than
a quarter inch. Some very marginal instability is anticipated with
the passage of the cold front. It does not seem as though we will
need to mention thunder.

A push of cold advection is expected for Tuesday night into
Wednesday. Temperatures at 850 hpa are forecast to drop a bit
below zero celsius for Wednesday. As a result, maximum
temperatures should not get much above the lower 60s in much of
our region with highs remaining in the 50s in the elevated
terrain. The cold advection should result in the development of
some stratocumulus. There may be a few showers or sprinkles in our
northern and central counties, mainly through about midday on
Wednesday as a secondary surface trough drops through our region.

The middle level pattern should remain progress with a ridge axis
passing overhead on Thursday night. Surface high pressure from the
west is anticipated to move across our region bringing dry weather
and seasonable temperatures for Wednesday night through Thursday
night.

Surface low pressure is forecast to pass across the Great Lakes
on Friday and into New England on Saturday. It should pull a warm
front through our region on Friday followed by a couple of surface
troughs from the west and northwest on Friday night and Saturday.
We will continue to carry a chance of showers for Friday and
Friday night.

Surface high pressure is expected to nose into our region from
the northwest for Sunday.

&&

Aviation /22z Sunday through Friday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.

Tonight...VFR conditions through the overnight period. No
precipitation. Easterly winds lighten this evening to wind speeds
under 6 knots.

Monday...VFR conditions with winds starting off easterly and
becoming southeast as the day progresses. Winds speeds rise to the
6 to 10 knot range. No precipitation.

Outlook...
Monday night...mainly VFR.

Tuesday and Tuesday night...mainly VFR with a chance of afternoon
and evening showers.

Wednesday through Thursday night...mainly VFR.

Friday...mainly VFR with a chance of showers.

&&

Marine...
6 PM EDT update...winds continue to diminish both on the Bay and
northern New Jersey adjacent ocean waters. Thus...have allowed the Small Craft Advisory to
expire for those locations. The Small Craft Advisory continues for the rest of the
ocean waters as wave heights at buoy 44009 are near 9 feet.

Previous marine discussion...we're in the zone between high
pressure to the north and low pressure passing well south of the
area. Those winds start to diminish, but a persistent North East
fetch will keep seas in the Small Craft Advisory range for most of the ocean zones
through Monday.

Winds will diminish on the Delaware Bay and the Small Craft Advisory will expire
there at 600 PM this evening. Also, the northernmost ocean marine
zone is not as exposed to the northeasterly fetch and the Small Craft Advisory will
also expire there at 600 PM this evening.

No precipitation expected for tonight and Monday.

Outlook...
Monday night...wave heights may remain near 5 feet early Monday
night on our ocean waters mainly from Barnegat Inlet southward. As
a result, a Small Craft Advisory is in effect until midnight on
Monday night.

Tuesday...no marine headlines are anticipated.

Tuesday night through Wednesday night...northwesterly wind gusts
of 25 to 30 knots are possible.

Thursday and Friday...no marine headlines are anticipated.

&&

Fire weather...
relative humidity values near or below 30 percent on Wednesday
afternoon along with a gust northwest wind at 15 to 20 miles per hour may
result in an enhanced threat of wildfire spread at that time.

&&

Phi watches/warnings/advisories...
PA...frost advisory from midnight tonight to 8 am EDT Monday for
paz060-101>104-106.
New Jersey...frost advisory from midnight tonight to 8 am EDT Monday for
njz012-013-015>023-027.
Delaware...frost advisory from midnight tonight to 8 am EDT Monday for
dez001>003.
Maryland...frost advisory from midnight tonight to 8 am EDT Monday for
mdz008-012-015-019-020.
Marine...Small Craft Advisory until midnight EDT Monday night for
anz451>455.

&&

$$
Synopsis...iovino
near term...szatkowski
short term...szatkowski
long term...iovino
aviation...szatkowski/iovino
marine...szatkowski/iovino/Johnson
fire weather...iovino