Scientific Forecaster Discussion
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Area forecast discussion
National Weather Service Mount Holly New Jersey
715 PM EDT Sat Apr 19 2014
strong high pressure centered near western Quebec will build
southeastward tonight and Sunday. The high should continue to
influence our weather into Monday night. A cold front is forecast to
approach from the west and move through our region late Tuesday.
High pressure is then expected to follow for Wednesday into Friday.
Low pressure and a cold front from the west are anticipated to
arrive on Saturday.
Near term /until 6 am Sunday morning/...
a quiet night with high level clouds gradually thinning and shifting
to the south and east as the upper-level jet across New England
departs. Low temperatures overnight could be a challenge as we have
conflicting forces. As the night progresses, the winds above the
boundary layer are forecast to increase. The predicted speeds are
close to the 50/50 threshold of surface mixing. Our conclusion was
to give the gradient some due east of I-95 where our lows are
predicted to occur earlier and then overall higher than stat
guidance. Northwest of I-95 and the fall line, the radiational
cooling inversion might be too much to overcome and we went closer
to stat guidance. Dew points are so low its going to be tough for
frost to occur anywhere. The more likely places are locales where
the growing season has not been declared started, so no mention in
the grids/zones or headlines.
The hourly grids were adjusted to account for the lower dew points
so far mainly along and north/west of I-95. The sky cover was
increased some especially across the southern zones where the cirrus
is much thicker. Farther north, the cirrus has been trending to thin
out. The winds were tweaked as the sea breeze continues to March
inland across central and southern New Jersey, although further
weakening is expected as the boundary layer continues to cool. No
changes made to the low temperatures.
Short term /6 am Sunday morning through 6 PM Sunday/...
a sunny day is in store as high pressure builds into New England.
The associated air mass is Ohio so dry (no SC over the ocean yet)
that the onshore flow should not produce little if any cloudiness.
The onshore flow should keep locations near the coast and west of
Delaware Bay cooler than today. The late April sun though finds a
way to outperform, especially with the trees well behind schedule.
We went at or above stat guidance from around i95 and Delaware state 1
westward and northwestward. We went closer to stat guidance east
of these roadways. Even without the onshore flow, the antecedent
air mass is predicted to be relatively milder in the northwestern part of
our County Warning Area. We are going to be switching the stronger winds on Sunday
vs today as the windiest locations will be in eastern New Jersey and
Delaware with about the same or less wind speeds (direction east
vs north) in places farther to the west.
Long term /Sunday night through Saturday/...
a ridge of high pressure is forecast to remain over our region
for Sunday night into Monday night as low pressure off the
southeast coast moves farther out to sea. A mainly clear sky is
anticipated for Sunday night and Monday with perhaps an increase
in high clouds from the west on Monday night.
Temperatures are expected to drop into the lower and middle 30s
across our northern counties late on Sunday night where we are not
yet issuing frost and freeze products. Minimum temperatures in our
central and southern counties should be mainly in the 35 to 40
degree range. Spotty frost is possible but it does not seem as
though it will be widespread enough to warrant a mention at this
point. Readings should recover nicely on Monday with plenty of
sunshine. Highs on Monday afternoon are forecast to be well into
the 60s at most locations.
The axis of a middle level trough is expected to pass overhead on
Wednesday morning. A surface cold associated with the feature
should move through our region late on Tuesday. We have maintained
the mention of showers, mainly for Tuesday afternoon and Tuesday
evening. Precipitation totals will likely be less than a quarter
inch in our forecast area.
The middle level pattern should remain progress with a ridge axis
passing overhead on Friday. Surface high pressure from the west is
anticipated to move across our region during the second half of
the work week bringing dry weather and seasonable temperatures.
Surface low pressure is forecast to pass across the Great Lakes
on Friday and Friday night and into the northeast on Saturday. As
a result, we will carry a chance of showers for Friday night and
Aviation /23z Saturday through Thursday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
Tonight...VFR, high level clouds gradually thinning to the south and
east. An earlier sea breeze turned the winds to the southeast at
kmiv and kacy, otherwise north-northeast winds diminishing to 5 to
10 knots. The winds may then increase some toward daybreak
especially for areas closer to the coast.
Sunday...VFR. Northeast to east winds around 10 knots, then locally
turning to the southeast later in the afternoon. Some gusts to around 20
knots are expected from the kphl metropolitan area south and eastward, with
the highest gusts at kacy.
Sunday night through Monday night...mainly VFR.
Tuesday and Tuesday night...mainly VFR with a chance of afternoon
and evening showers.
Wednesday through Thursday...mainly VFR.
the Small Craft Advisory continues for the ocean waters through
the day on Sunday. Seas at buoy 9 are still at 5 feet, so at least
for the southern waters, The Gap of non-Small Craft Advisory winds
is getting smaller all the time. The guidance has been too low
with swells lately.
We are going to be adding Delaware Bay to the Small Craft
Advisory for Sunday day. We have higher confidence about the wind
criteria being met in the Lower Bay than the Upper Bay.
Regardless, winds should start diminishing during Sunday afternoon
and might fall below Small Craft Advisory criteria along the
Monmouth County Atlantic waters and all of Delaware Bay by the end
of the day. Seas on the ocean will take longer to subside below
Small Craft Advisory criteria.
Sunday night...a Small Craft Advisory is in effect for our ocean
waters from Manasquan Inlet southward mainly for seas in the
persistent northeast flow.
Monday...wave heights may remain near 5 feet into Monday on our
ocean waters mainly from Atlantic City southward.
Monday night through Wednesday...no marine headlines are
Wednesday night...northwesterly wind gusts around 25 knots are
Thursday...no marine headlines are anticipated.
we are going to flip our fire weather concern on Sunday to the New Jersey
Pine barrens as they will come closest to the confluence of strong
wind gusts, low afternoon relative humidity levels and continued
dry and drying fine fuels. Closer to the immediate coast, the
relative humidity levels should not be reached. Elsewhere, wind
gusts overall are expected to remain below 20 miles per hour on Sunday
On Monday winds are expected to be lighter in all areas and
relative humidity levels might not drop below 30 percent.
Marine...Small Craft Advisory until 6 am EDT Monday for anz451>455.
Small Craft Advisory until 6 PM EDT Sunday for anz450.
Small Craft Advisory from 6 am to 6 PM EDT Sunday for anz430-