Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 242020

Area Forecast Discussion
National Weather Service Mount Holly NJ
420 PM EDT Sat Mar 24 2018

Strong high pressure over southeast Canada will control the weather
over the northeast United States into early next week while a big
ocean storm develops in the western Atlantic. A cold front
approaches from the west Wednesday, then stalls awaiting the
development of low pressure in the mid Atlantic states late Thursday
or Friday. High pressure builds into our area next Saturday.


As of mid-afternoon, a sunny day is in progress across the area with
temps in the mid to upper 40s, but feeling a bit cooler in the NW
breeze. A few diurnal cu are streaming down from the north and some
ci blowoff from the midwest storm are noted on our SW fringe, but
otherwise mostly sunny conditions prevail.

For tonight, surface high pressure will build in from the north with
an accompanying surge of cooler air. This high will push the midwest
storm track well to our south. However there should be some increase
in mid clouds over the northern mid-Atlantic as an upper low/trof
system approaches from the north with some UVV developing ahead of
it toward morning. Over night lows look to be a couple of degrees
cooler than last night with some cold advection occurring.


For Sunday, surface high pressure continues to build in from the
north. The above mentioned upper trof will rotate around an offshore
low center and through the forecast area during the day. There is
apparently enough low-level moisture with this system to support
scattered showers, although precip amount reaching the ground should
be quite light. Highest PoPs (though still only about 25%) are over
coastal sections of NJ. Temperatures rising from the 30s into the
40s will result in snow mostly changing to rain for most areas.
Precip should end by mid to late afternoon as the upper trof moves
S/E of the area.


**Winter over?? Probably not**

The first week or two of baseball season has to occur with its
seemingly usual amount of consideration for cold or snow
postponements. The cold air will be developing across the
northern border of the United states next weekend. And around
here, I`m not ruling anything out for the end of this coming
workweek in the Poconos.

500 MB: A big ridge builds overhead while tomorrow mornings
southward diving short wave cuts off into a strong and large
western Atlantic storm early this week. But the ridge may be
wasted. Another amplifying large scale trough will be digging
southeastward from the northwest Territories during midweek and
scoop up a southwest USA short wave to result in a negative
tilt trough sweeping through our area at the end of the workweek.

Temperatures: Calendar day averages will be 5 to 10 degrees
below normaL Monday and Tuesday, warming closer to normal
Wednesday and for sure above normal Thursday or Friday but to
what extent we`re not sure. The 00z-12z/24 op GFS still is
decidedly warmer than the the 00z-12z/24 ECMWF.

Forecast basis:  A 50 50 blend of the 12z/24 GFS/NAM MOS was used
for Sunday night-Monday night, the 12z GFSMEX MOS for  Tuesday and
the 15z WPC 12 hr max/min/temps/pop and the 6hrly sky, wind,
dewpoint were used for the period Wednesday-Saturday. I did
modify downward the max T on Wednesday and Friday per the op EC
and for now we are not using the 12z/24 GFS MEXMOS 72F warmth
for PHL on Thursday.

The dailies...

Confidence all days: Generally ABOVE average unless otherwise

Sunday night...any leftover cloudiness early becomes clear.
northeast gusty 15-25 MPH (at night!).

Monday...Sunny! Northeast gusty 15 MPH.

Monday night...Clear. light northeast or calm wind.

Tuesday...Increasing high clouds from west to east (diffluent
500MB-400 MB ridge cirrus).  Light mostly east wind.

Wednesday...Showers possible ahead of the next cold front. It
may be freezing rain or even sleet in the Poconos and far
northwest NJ. Confidence: Below avg on precipitation occurrence
and Max temps due to expected heavy cloud cover.

Thursday...Variable cloudiness and probably warmer. Should be
our first above average day of temps in over 3 weeks. Small
chance of showers. Confidence: average.

Friday...Should have low pressure developing on the stalled
front in our area or along the APPS as it appears the southern
stream short wave phases a bit with the northern stream and cuts
across our area. Slight chc pcpn ends as snow in the Poconos.

Saturday...Breezy and dry with sunshine returning.


The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Tonight...Mainly VFR conditions should prevail through tonight,
although some mid-level cigs may develop towards morning. NW winds
will shift to the north as stronger high pressure begins to build in
overnight. Moderately high confidence.

Sunday...VFR conditions should again prevail, however brief periods
of MVFR cigs are possible at times during the day as an upper trof
moves through, triggering a few light rain or snow showers. Any
precip should not be enough to limit vsbys significantly. Winds will
veer from N to NE at 10 to 15 kt with a few higher gusts
possible. Confidence generally high, but low for timing of any

Sunday night...Becoming VFR CLEAR but a good chance of northeast
winds gusting 15-20kt (lowest west vcnty RDG/ABE), highest east
vcnty ACY). High confidence.

Monday...VFR Clear or few clouds near 4000 ft.  Northeast wind gust
15 kt.  High confidence.

Monday night through Tuesday night...VFR, gradually increasing
cirrus. Light mostly north to northeast wind. High confidence.

Wednesday...VFR to start may deteriorate to MVFR conds in showers
late in the day. south wind. Low confidence.

Thursday...Uncertainty, but probably VFR, Light wind. Average


Winds and seas are currently sub-SCA with a relatively light NW
wind. However, high pressure building in tonight and Sunday will
increase the pressure gradient and resulting NE winds will increase.
Gusts will increase to 25 kt Sunday morning and higher in the
afternoon. The SCA start time was left at 14z. Seas will lag a bit
but are expected to reach 5 ft by midday and continue to build
through the afternoon.

Confidence all days below: WELL ABOVE average.

Please see the MWW statement for details.

Sunday night...A Small Craft Advisory is in effect.  Northeast wind
15 to 25 knots with gusts around 30 knots. Waves on our ocean waters
building to 5 to 9 feet.

Monday and Monday evening...SCA seas Atlantic coastal waters.
Northeast wind 10 to 20 knots with gusts around 25 knots. Waves on
our ocean waters 5 to 8 feet.

Late Monday night through Tuesday night...SCA seas Atlantic coastal
waters. Northeast wind 10 to 15 knots. Waves on our ocean waters 5
to 8 feet, except possibly 10 ft with a period of 15 seconds s
NJ and DE coastal waters.

Wednesday...SCA seas expected Atlantic coastal waters. Northeast
to southeast wind around 10 knots. Waves on our ocean waters 5
to 8 feet with a 15 second period.

Thursday...SCA seas possible Atlantic coastal waters. Residual
swell from the big ocean storm of earlier in the week.


Through yesterday...

MPO 21 consecutive days below normal

PHL, RDG, ILG, GED 55N 19 consec days below normal.

ACY 18 consecutive days below normal

TTN 17 Consecutive day below normal

We may yet be revisiting month of March snowfall totals.  Dont put
the shovel away yet.

We should add at least 4 more days to the current stretch of


MARINE...Small Craft Advisory from 10 AM Sunday to 6 AM EDT Tuesday for
     Small Craft Advisory from 10 AM Sunday to 10 AM EDT Monday for
     Small Craft Advisory from 10 AM Sunday to 6 AM EDT Monday for


Near Term...AMC
Short Term...AMC
Long Term...Drag
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