Scientific Forecaster Discussion
fxus61 kphi 221933
Area forecast discussion
National Weather Service Mount Holly New Jersey
333 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.
Near term /until 6 am Friday morning/...
storm over... and probably final pns is posted. Map to Post 330
PM and is our best presentation today for the reality that
occurred Tue aftn-Wed night. Dual Nor'easter Imo performed, on
a scale 1 to 5 scale, not quite what I expected which was a 5.0
for late March. It came in ~4 (winds down 5 kts from expected,
cflooding was down 1 category from expected and snowfall
probably about 4" less than expected). Still, this was a major
winter storm for our area.
On the map, you may want to take a close look in the rural
hinterland of Sussex County New Jersey where elevations vary from
roughly 400 ft to ~1800 ft. The elevated northwest corner was
spared...less than an inch. The se part of the County up to 10
inches. The gradient between Sussex and Newton New Jersey...about 7
inches in 12 miles (similar elevation),a 20 minute drive at
most. The gradient to elevated Highland Lakes, even greater.
Models had a sharp northern cut off...we just were never
sure where it would be. While this storm produced... it was
never completely organized as one Mammoth storm that we
sometimes see spin up just south of Li.
A nice afternoon is in progress for cleaning up. Gusty northwest
winds to 25 mph with variable amts of cirrus. Visible imagery
shows the extent of the snowcover from ydys storm.
Tonight...cirrus early then clear late. Temperatures tonight
are expected to be lower than what we saw this morning, with
lows tonight forecast to be 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
Short term /6 am Friday morning through 6 PM Friday/...
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 miles per hour.
Long term /Friday night through Thursday/...
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
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 European model (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.
Aviation /20z Thursday through Tuesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
Remainder of this afternoon...VFR cirrus. Northwest winds 10-15 kt
with gusts up to 30kt. High confidence.
Tonight...VFR with only high clouds (15000 above ground level or higher) and
those clear after 09z. Northwesterly winds near or below 10 knots.
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.
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.
Monday-Tuesday...generally VFR. High confidence.
today and tonight...NW winds gusty 20-30 kt this afternoon and
15-25 kt tonight. Atlantic seas will continue to slowly subside.
Seas continue to run above the nwps forecast by 2 ft. So its
mainly an Small Craft Advisory this aftn all waters, then into tonight for the
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
Abe monthly 20.7 ranks #4 behind
Acy monthly 9.2 ranks #5 behind\
Ilg monthly 20.3 ranks #2 behind
Phl monthly 15.2 ranks #2 behind
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 New Jersey 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
Marine...Small Craft Advisory until 6 am EDT Friday for anz450>452.
Small Craft Advisory until 8 am EDT Friday for anz431-453>455.
Small Craft Advisory until 8 PM EDT this evening for anz430.