Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 230125

Area Forecast Discussion
National Weather Service Mount Holly NJ
925 PM EDT Thu Mar 22 2018

The coastal storm that affected the area will continue to move
into the Canadian Maritimes through tonight where it will linger
into Friday. High pressure briefly affects the area Saturday
while an area of low pressure passes to our south overnight.
High pressure will then build across the northeast later Sunday,
then across much of the east coast through early next week. A
cold front is possible for the later half of the week.


Cirrus over the area has kept temperatures from falling off too
much. That cirrus should scatter out late, and then temps my
fall off fairly dramatically due to the combination of clear
skies, light winds, and fresh snowpack. Lows tonight generally
in the 20s across the region, or about 5 to 10 degrees below
normal. As a result, any water on the roads from snow melt
during the day could freeze leading to slippery conditions on
area roads tonight into early Friday morning.


Friday...A cold core mid level low (-18C at 700MB) and a 90M
12 hr 500mb HFC , digs quickly southeast over the region
through the mid and late aftn. This will result not only in
increasing low clouds, but also scattered rain and snow showers,
especially along and north of the I-78 corridor through the
afternoon. BTV snow squall parameters appear to be met so we`ll
be on the lookout. Most models are dry, and moisture could be
very limited with little chance for moisture advection before
this event. However, lower resolution models tend to underforecast
precip with these types of clipper systems, so we have
mentionable pops basically I78 north. Max temps 30s high terrain
northwest, 40s elsewhere or about 10 to 15 degrees below normal.

Northwest wind gusts 20 MPH.


Any snow showers that affect the area during the daytime are
expected to dissipate by the evening and lead to a dry forecast
overnight. By Saturday, weak high pressure briefly affects the
area, before an area of low pressure passes to our south
overnight. It is expected that this low will pass far enough to
our south that our area avoids another major snow event.
However, several short wave/vorticity impulse are forecast to
move across the area Saturday night through Sunday, while some
enhanced low-mid level moisture and low-mid level lapse rates
increase during the day as well. This could lead to some
isolated snow showers overnight into Sunday, although it is a
small chance at this time. Otherwise, a cool, breezy period is
expected Saturday through Sunday. High pressure builds across
the northeast Sunday, then begins to build down the east coast
Sunday night. Dry conditions will return for late Sunday into
Sunday night.

By Monday, high pressure fully builds across the entire east
coast, and remain in place through Tuesday. This will keep dry
conditions across the area Monday and Tuesday. Temperatures
remain below normal Monday and Tuesday, but a warming trend
begins by Tuesday.

Uncertainty begins to build as we move into Wednesday through
Friday as there is the potential for a cold frontal passage, but
there timing differences among long term models. The Canadian
and ECMWF keep high pressure across the area and the cold front
to our west, until they bring the frontal boundary through late
Thursday into Friday. The GFS brings the cold front toward the
area Wednesday and Wednesday night, then lifts an area of low
pressure across the area with another frontal passage around
Friday. Guidance has been reluctant to come to an agreement on a
solution for the second half of the week. So we will keep a
slight chance of showers in the forecast for Wednesday-Friday
time period. Depending on the thermal profiles, precipitation
would likely fall as rain for most areas, although some snow
can`t be ruled out for some areas.


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

Tonight...VFR with only high clouds (15000 AGL or higher) and
those clear after 09z. Northwesterly winds near or below 10 KT.
High confidence.

Friday...VFR to start. Potential for MVFR or low VFR CIGs and
rain/snow showers, especially vcnty of ABE-TTN during the
afternoon. Northwest winds 5 to 15 kts with potential for gusts
to 20 kts or so. High confidence.


Friday night...Becoming VFR. Slight chance of isolated snow showers
early. Northwest winds gust 15-20 knots.Moderate confidence.

Saturday...VFR. Northwest winds may gust 15-20 knots early in the
day. High confidence.

Saturday night...VFR early, may lower to MVFR overnight. North winds
becoming northeast overnight and may gust 15-20 knots late.
Moderate confidence.

Sunday...Becoming generally VFR.  Slight chance of isolated snow
showers which may temporarily lower conditions. Northeast to
east winds gusting 15 to 20 knots. Moderate confidence.

Sunday night...Generally VFR. East winds gusting 15-20 knots.
High confidence.

Monday-Tuesday...Generally VFR. High confidence.


NW winds 15-20 kt with gusts up to 25 kt tonight. Atlantic seas
will continue to slowly subside. Seas continue to run above the
NWPS forecast by 2 ft. SCA continues through tonight for the
Atlantic waters.

Friday night...Small Craft Advisory conditions possible.

Saturday-Saturday night...Conditions expected to be below advisory

Sunday-Sunday night...Small Craft Advisory conditions possible.

Monday-Tuesday...Conditions expected to be below advisory


RTP water equivalent pcpn: MANY stations were set to missing as
the pcpn amounts were far too low as melted by the system.

What we KNOW.

PHL: today is the 18th consecutive day of below normal temps in
PHL. Looks like we could add 5 more to the string.

There were several record daily maximum snowfalls set yesterday,
March 21st. This occurred at Philadelphia, Wilmington and
Allentown (which smashed their daily record). Atlantic City just
missed the daily snowfall record.

Location        Record for 3/21     Actual Snowfall 3/21/18
--------        ---------------     -----------------------

PHL             4.7" (1932)          6.7"
ACY             5.9" (1889)          5.7"
ILG             5.4" (1964)          6.7"
ABE             4.3" (1964)         13.2"

ACY 1 day snowfall of 5.7" ranks as the 7th highest March,
single day total.

Philly did not place top 10 1 or two day.

Wilmington 6.7 was the 6th highest 1 day total in the historical
database and the two day 8.1 was tied for 7th highest.

Allentown 13.2 was the 4th largest single day total behind the
16.7 3/13/93
16.5 3/20/58
13.8 3/3/60

ABE Monthly 20.7 ranks #4 behind
1958 30.5
1993 21.6
1960 21.3

ACY monthly 9.2 ranks #5 behind
1969 17.6
2014 15.6
1960 13.4
1956 12.7

ILG monthly 20.3 ranks #2 behind
1958 20.3

PHL monthly 15.2 ranks #2 behind
1941 17.2

I tend to remember everything (at least vaguely) after 1950.

Yearly July 1-June 30 snow year ACY 33.7 ranks # 9 well behind
the record of 58.1 in 2010.

What is as yet unconfirmed and may not be for several days...

A new NJ state record for the month of March, may have been set
this morning. This is as yet unconfirmed so we`re not saying
RECORD, but near record works for me...something else may turn
up in the database that was overlooked. Jefferson Township 11.1
inches ydy (1.03 w.e) raised the monthly total to 44.3 inches.
So far the record, as we know it, is 43.0 in 1958 Canistear
Reservoir. UNOFFICIAL but as fyi... but impressive if you like

Finally PHL projection: March avg temp is likely to be less
than Feb (41.9 which was 6.2 abv normal). For now, we`re
projecting 39.6 or 3.9 BELOW the normal of 43.5. We could see
that avg temp rise a degree above where we have it projected.


MARINE...Small Craft Advisory until 6 AM EDT Friday for ANZ450>452.
     Small Craft Advisory until 8 AM EDT Friday for ANZ453>455.


Near Term...Drag/MPS
Short Term...Drag/MPS
Long Term...Robertson
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