NWS Philadelphia/Mount Holly wrote its last area forecast discussion before the first event at Mar 19, 3:39 PM EST, 1 hour 51 minutes earlier.
Area forecast discussion, Mar 19, 3:39 PM EST, 1 hour 51 minutes before
Area Forecast Discussion
National Weather Service Mount Holly NJ
439 PM EDT Sat Mar 19 2022
.SYNOPSIS...
A cold front will cross the Middle Atlantic region tonight. High
pressure will move across the Southeast through Monday then move
offshore Tuesday. A weak cold front will move southward through the
area Monday. Another low pressure and frontal system will move to
our northwest Wednesday night into Thursday followed by high pressure
into next weekend.
&&
.NEAR TERM /THROUGH SUNDAY/...
Unseasonably mild conditions continue across the region early this
evening. There has been little change regarding the forecast for the
remainder of the day. A potent mid-level shortwave is now making its
closest approach to the region, a couple hundred miles to our
northwest. Strong downstream lift from this disturbance has
initiated convection in a weakly unstable air mass over central
Pennsylvania. These storms will continue moving northeastward into
portions of our area this evening, mainly from 6 to 10 PM. Our
eastern Pennsylvania zones, especially north of Philadelphia, as
well as our northern New Jersey zones continue to have the best
chance for severe weather.
The parameter space for this event remains somewhat marginal.
Instability is respectable for early season standards at around 1000
J/kg, but definitely not a high instability case. And dry air
remains a concern and will serve to greatly limit convective
potential from around Philadelphia southward due to weaker lift in
southern areas being unable to overcome the subsidence. However,
deep layer shear is very strong, 60 kt or greater, and lift is much
better over the northern zones. Damaging winds appear to be the main
threat, with the dry air in the column contributing to high DCAPE
values and plenty of wind aloft also which stands to be transported
downward by convection. Hail is also possible thanks to the good mid-
level lapse rates, potentially up to about low end severe (1 inch
diameter) criteria. Tornado potential appears quite low owing to
increasingly linear storm mode and fairly high LCLs, but with shear
this strong even if fairly unidirectional, can't rule one out
entirely. The threat should wane by around 10 PM due to loss of
instability and the eventual passage of the cold front.
Once the cold front passes this evening, partial clearing is
anticipated. The wind is expected to shift to the west. Temperatures
will likely fall into the 40s at most locations by daybreak on
Sunday.
On Sunday, cooler but drier weather is expected behind the front. As
the main trough axis moves through, considerable cloud cover
(stratocumulus) is likely to develop due to the cold pool of air
aloft. There is a slight chance of a shower flurry in some of the
northern zones by late in the day. With only modest cold advection
behind Saturday's cold front, highs will be cooler but still fairly
mild, mainly mid to upper 50s with some cooler values north.
Finally, as the trough axis passes, low level winds increase, and it
could be quite breezy during the afternoon and evening, with
west-northwesterly gusts of around 30 mph likely.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
A period of quiet weather as high pressure settles in a weak
cold front settles down from the north, but except for some
clouds, a insignificant feature. Temperatures Monday well above
normal with low to mid 60s most areas for highs and mid/upper
50s for the NW areas. Overall, a pleasant day.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
The upper trough that was over the East during the weekend heads out
to sea and will be replaced by mean ridging aloft. This will lead
to a week of mild spring temperatures. Our present forecast features
high temps above normal each day, except Wednesday, with maxs in
the 60s for most areas. On Wednesday, highs will be only normal
which for this time of year is mid 50s for PHL and metro areas
nearby and upper 40s/low 50s across the NW areas. Overnight lows
will be mild too with mostly 40s and 30s NW.
Much of the long range will be dry, continuing a dry month for our
area. The one exception will be the Wed/Wed night/Thu periods when a
stronger low well to the west (IN/IL) sends a few shortwaves/fronts
across our region. Going along with the NBM pops and neighboring
offices, Likely and some Categorical pops are in the forecast attm.
Looking ahead into next weekend, the ridge across the East relaxes a
bit, so temperatures will probably be closer to normal. An
approaching trough may create the opportunity for some spring
showers too. Way too early to be specific.
&&
.AVIATION /21Z SATURDAY THROUGH THURSDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.
Through this evening... Prevailing VFR. There remains a chance for
scattered showers and tstms late this afternoon and especially early
to mid evening, mainly from PHL north. Have covered this with TEMPO
groups at several of the TAF sites. The threat looks to wane by the
time you get as far south as PHL, and still think the thunder
potential there is too low to warrant a TAF mention, but it is a non-
zero possibility. Showers and storms should generally last less than
an hour, and not all areas will be affected. Southwest wind 10 to 15
kt with gusts to 20 kt or a little higher. Gusty and erratic winds
possible in any tstms. Moderate confidence.
Rest of tonight... Mainly VFR with any lingering showers or storms
having dissipated or moved offshore by about 03z. Am slightly
concerned about fog potential once scattered showers and storms
depart. None of the guidance shows anything, but if winds end up
lighter than expected, at least some patchy MVFR vsbys would be
possible. Something to keep an eye on but not a big risk. Winds
mainly from the west at 5 to 8 kt, but may be more west-northwest
early in the night then more west-southwest later. Moderate
confidence.
Sunday... Mainly VFR. However, increasing cloud cover is expected,
and we will probably see some CIGs of 2000 to 4000 ft develop by
afternoon especially from PHL west. Westerly winds increasing to 10
to 15 kt with gusts to 25 kt by afternoon and evening, locally a
little stronger. Moderate confidence.
Outlook...
Sun night/Mon/Tue...VFR. W or NW Winds from 5 to 10 knots
gusting to 15 knots into the afternoon.
Wed/Thu...Mostly VFR but scattered showers may produce MVFR/IFR
at times.
&&
.MARINE...
Through tonight... A Small Craft Advisory remains in effect for the
Atlantic coastal waters, with seas around 5 ft expected through the
night.
Sunday... The SCA has been extended through Sunday for the Atlantic
coastal waters of New Jersey and off the mouth of Delaware Bay. A
lull in conditions is possible during the morning, but seas will
remain close to 5 ft. By afternoon, westerly wind gusts of 25 to 30
kt will likely develop. The SCA may also need to be extended for the
Delaware coastal waters, and one may need to be issued for Delaware
Bay due to the wind potential. Those areas should be sub-SCA during
the morning, however.
Outlook...
Sunday night...SCA conditions likely with northwest winds
gusting from 25 to 30 knots and seas ranging from 3 to 5 feet.
Mon/Tue...Sub-SCA conditions expected.
Wed...Sub-SCA conditions expected during the day, then SE winds
gusting around 25 knots and seas nearing 5 feet into the
overnight.
Thu...SCA possible. Showers.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory until 6 AM EDT Monday for ANZ450>454.
Small Craft Advisory until 6 AM EDT Sunday for ANZ455.
&&
Synopsis...O'Hara
Near Term...O'Brien
Short Term...Davis/O'Hara
Long Term...O'Hara
Aviation...O'Brien/O'Hara
Marine...O'Brien/O'Hara