NWS Philadelphia/Mount Holly wrote its last area forecast discussion before the first event at Jun 7, 2:48 PM EST, 12 minutes earlier.
Area forecast discussion, Jun 7, 2:48 PM EST, 12 minutes before
Area Forecast Discussion
National Weather Service Mount Holly NJ
348 PM EDT Tue Jun 7 2022
.SYNOPSIS...
A cold front will move into our area tonight before stalling just
offshore and also to our south Wednesday. Low pressure will track
along the front and move across our area Wednesday night before
shifting to our northeast Thursday morning. Weak high pressure
builds in Friday, then low pressure moves through Saturday. Weak
high pressure should arrive for late Sunday and into early next
week.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
Clouds and showers will continue to spread across the forecast area
this afternoon as a couple of short wave/vorticity impulses move
across the area. No lightning has occurred yet to our west, and we
do not expect much lightining during the daytime hours. However, as
we move into the evening and overnight hours, a cold front will
approach and move into the area from the wet. Lift and instability
will increase as the front moves into the area, which will increase
the chance for thunderstorms. We do not expect widespread
thunderstorms, only isolated lightning embedded within the showers.
Severe weather is not expected, but locally gusty winds and heavy
rain will be possible with any thunderstorms.
As the front move across, it is expected to stall out right across
the forecast area during the day Wednesday. As the front moves
across the area, moisture begins to diminish temporarily across the
area, so shower chances will drop off after daybreak and be minimal
through the day. Wednesday will be a warmer day than Tuesday, with
temperatures about 5 degrees warmer Wednesday than Tuesday, and
several degrees above normal.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
Summary...Downpours along with some thunderstorms Wednesday night
into early Thursday morning.
As an upper-level trough remains from south-central to eastern
Canada, a stronger shortwave tracks from the Midwest toward the Ohio
Valley Wednesday then across New York State and our area Wednesday
night into early Thursday. The upper-level trough is forecast to
take on some negative tilt as it lifts across the eastern Great
Lakes and into the Northeast. This will support strengthening
surface low pressure from the Ohio Valley to across central
Pennsylvania Wednesday night and then into New England during
Thursday.
As the above takes place, a south to southwest 850 mb jet is
forecast to increase to around 40 knots Wednesday night south and
east of the surface low track. Strong low-level warm air advection
will be maintained due to the low-level jet as will plenty of
moisture (precipitable water values around 2.0 inches). Forcing for
ascent will increase during the course of Wednesday night due to the
incoming upper-level trough, strong low-level warm air advection and
the southerly low-level jet. As a result, showers and some
thunderstorms are expected to develop from the southwest and track
northeastward across much of the area during Wednesday night. The
heaviest should be from about 05z-11z (1AM-7AM) when the nose of the
strong southerly low-level jet slides across our area.
Given the warm air and moisture advections through the night,
instability is forecast to be maintained and potentially even
increase some. The magnitude of this varies among the guidance with
the NAM probably to robust with the instability. There is good
dynamics with this and given the forecast model soundings showing
increasing deep layer shear during the overnight, some strong
thunderstorms may result. Locally strong wind gusts look to be the
primary hazard, especially if a low-level inversion does not
develop. The timing is not ideal for severe thunderstorms given this
occurring during the middle of the night, however the synoptic setup
looks dynamic enough to potentially produce some locally strong
convection. Downpours will also occur, however storm motions should
be pretty quick and while there is some risk of flash flooding it
should remain localized.
For Thursday, strengthening surface low pressure is forecast to be
tracking across portions of eastern New York State to start then it
will continue across New England. Some showers should be ongoing
early but these should quickly move to our northeast and east. A few
additional showers may develop across the northern and far eastern
areas into the early afternoon prior to much drier air arriving.
Stronger low to mid level flow in the wake of this system will
result in a gusty west-northwest wind especially from late morning
through the afternoon. Cold air advection will also increase at 850
mb and this will assist in deeper vertical mixing through the day.
As a result, increased the wind and wind gusts a decent amount. It
will also be turning less humid through the day as dew points drop
into the 50s (some 40s at night). High temperatures are forecast to
be in the 70s to low 80s. The winds then diminish Thursday night
with most places having temperatures dropping into the 50s.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
Summary...Dry to start followed by an unsettled Saturday before
turning drier.
Synoptic Overview...A more amplified flow aloft is forecast with an
upper-level trough across eastern Canada and the eastern U.S. This
will remain in place through the weekend with a stronger shortwave
moving across the East during Saturday. This feature will drive
surface low pressure northeastward near the Ohio Valley and into the
Mid-Atlantic and Northeast Friday and Saturday. There continues to
be some differences in the model guidance regarding the actual track
of the surface low. While the upper-level trough remains in place
into early next week, it may start to shift east of the region
Tuesday.
For Friday...Weak surface high pressure builds in and therefore it
should be dry during the day. A sharpening upper-level trough well
to our west will support a surface low in the vicinity of the Ohio
Valley. Some moisture will be on the increase, mainly in the form of
clouds, with much of the showers holding off until Saturday. Daytime
temperatures are forecast to top out right near average.
For Saturday and Sunday...A sharpening upper-level trough arrives
from the west Saturday which will support a surface low tracking
across the region. There continues to be some differences in the
model guidance regarding the track, with some solutions showing a
strengthening surface low farther north from about central PA to
southeastern NY while some other solutions are weaker and farther
south near Delmarva. The actual track will determine whether we get
a more showery outcome or a period of steady rain. Given the
uncertainty, went with more of a middle of the road track which
basically brings the surface low right over our area. We maintained
showers in the forecast instead of rain to avoid flip-flopping and
given the differences in the model tracks of the surface feature.
Increasing large scale forcing for ascent overspreads our area and
this will result in showers/rain Saturday. If the surface low tracks
farther north, then at least some of the warm sector will lift more
northward and therefore included a slight chance of thunderstorms
everywhere Saturday. Some heavy rain is possible given decent
forcing and especially if there is some convective contribution
along the surface low track. Some showers may persist Sunday
especially as the upper-level trough axis swings across our area. A
few low-topped thunderstorms cannot be ruled out Sunday afternoon
given colder air aloft. More pronounced drying should occur Sunday
night. Temperatures will be cooler Saturday given the expected cloud
cover and precipitation, with even Sunday tending to be just below
average.
For Monday and Tuesday...An upper-level trough is forecast to be in
place across the East, although it may start to shift to our east
during Tuesday. This will maintain northwesterly flow, however
surface high pressure should be building into our area from the
west. At this point, went with a dry forecast with daytime
temperatures topping out around average.
&&
.AVIATION /20Z TUESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.
Rest of Today...VFR conditions will continue much of this afternoon,
although as showers move into the area, MVFR ceilings will drop for
ABE and RDG. Even as showers affect the rest of the sites today,
their ceilings are expected to remain VFR.
Winds remain gusty our of a southerly direction, with gusts reaching
around 20 knots through this afternoon. Moderate-High confidence.
Tonight...Showers will continue to affect the TAF sites this evening
and overnight. Conditions will lower to MVFR this evening, before
lowering to IFR later in the overnight. There is a slight chance of
thunderstorms, but confidence is low enough to keep out of the TAFs
at this time. Wind gusts will drop off this evening and overnight,
but a steady south to southwest flow will continue 5-10 knots, then
shift to westerly direction as the front moves into the area.
Moderate confidence.
Wednesday...IFR/MVFR conditions early will lift to VFR through the
mid to late morning hours. VFR conditions are then expected to
persist through the afternoon. There is a chance of showers or
thunderstorms in the afternoon. Winds will shift to the west and
northwest as the front moves across the area.
Outlook...
Wednesday night...VFR ceilings lower to MVFR/IFR due to low clouds
and showers and some thunderstorms moving through. Visibilities will
be reduced at times due to the precipitation. South to southeast
winds 5-10 knots. Low confidence.
Thursday...Sub-VFR conditions with lingering showers possible early,
otherwise VFR. West to west-northwest winds increasing to 15-20
knots with gusts to around 25 knots, then diminishing to 10 knots or
less at night. Moderate confidence.
Friday...VFR during the day, then conditions may lower to MVFR or
IFR at night with some showers arriving late. West winds 5-10 knots,
becoming southwest 5 knots or less or light and variable. Low
confidence.
Saturday...MVFR/IFR conditions probable with showers and perhaps a
thunderstorm. East to southeast winds 5-10 knots, becoming west to
northwest near 5 knots at night. Low confidence.
Sunday...Mostly VFR. A few showers possible especially in the
afternoon. West-northwest winds around 10 knots. Moderate
confidence.
&&
.MARINE...
Rest of today through tonight...Small Craft Advisory remains in
place as waves will linger around 5 feet and winds will gust up to
25 knots at times tonight.
Wednesday...The Small Craft Advisory was extended for a few hours
Wednesday to account for lingering 5 foot seas, before conditions
drop below advisory levels for the afternoon.
Outlook...
Wednesday night and Thursday....Small Craft Advisory conditions
should occur for a time as low pressure tracks near and north of the
area.
Friday...The conditions are anticipated to be below Small Craft
Advisory criteria.
Saturday...A period of Small Craft Advisory conditions may occur,
especially seas on the Atlantic coastal waters, depending on the
track and strength of low pressure.
Sunday...The conditions should be mostly below Small Craft Advisory
criteria.
Rip currents...
Due to both some stronger winds locally and a longer period swell
contribution from the remnants of Alex far offshore, the rip
current risk will be elevated for a few days. Currently, we are
expecting a MODERATE risk for the formation of dangerous rip
currents through Wednesday.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory until 11 AM EDT Wednesday for ANZ431-
450>455.
&&
Synopsis...Fitzsimmons/Gorse
Near Term...Robertson
Short Term...Gorse
Long Term...Gorse
Aviation...Gorse/Robertson
Marine...Gorse/Robertson