-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPHI 222259
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
659 PM EDT Mon Apr 22 2024

.SYNOPSIS...
High pressure extending eastward from the Midwest to the Mid-
Atlantic will continue to build eastward toward the East Coast
through Tuesday. A cold front will swing through our region on
Wednesday, followed by another area of high pressure pushing
southeastward from the Great Lakes Thursday and Friday. An
approaching warm front will bring a chance for some rain showers
over the weekend.

&&

.NEAR TERM /THROUGH TUESDAY/...
-- Changed Discussion --
As of 6:45PM...Surface high pressure continues to maintain
influence over the region; conditions are quiet overall. There
is a growing concern for frost/freeze development tonight. Winds
across the region are forecast to go light and variable if not
calm for most of the period. Skies will remain clear throughout
the period with surface high pressure overhead. Strong
radiational cooling will likely take for hold and it is likely
guidance remains too high once again as it was last night
regarding temperatures. Frost Advisory has been extended
southward and a Freeze Warning is now in effect for many of our
counties in our forecast area. Previous discussion remains
below...

High pressure will build out of the southern states tonight and
across the east coast and Mid Atlantic region through Tuesday.

For tonight, mostly clear skies will prevail across the area,
and whatever wind there is early in the evening will become
light and variable if not calm through the overnight hours.
Temperatures are expected to cool off across the area.

On Tuesday, another nice day is expected, but as the high builds
offshore, winds will increase out of the south to southwest and
become gusty 15-25 mph range. Clouds will also begin to increase
across the area later in the day ahead of the next weather system.
Temperatures will be a few degrees warmer than Monday, but remain
near normal.
-- End Changed Discussion --

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
Surface high pressure will shift eastward to the East Coast on
Tuesday, with the high centered off the coast of the Carolinas,
while a ridge extending northward shifts offshore of the mid-
Atlantic coast. Stable atmospheric conditions with an upper-level
shortwave ridge along the East Coast will ensure another dry day
with mostly sunny skies. Expect another frosty start to the day in
areas inland from the coast and away from the urban corridor, but
less so in the Delmarva. Southerly breezes and warm air advection
aloft will result in high temperatures around 5 degrees warmer than
Monday, well into the mid to upper 60s for most areas outside of the
shore and the Poconos.

Clouds will increase Tuesday night as low pressure tracking across
Quebec and northern New England swings a cold front toward our
region. Showers may push southeastward down to the coast by dawn on
Wednesday. That will result in much milder nighttime and early
morning temperatures compared to the previous few nights. Model
guidance has continued to advertise an earlier frontal passage,
pushing offshore Wednesday morning. This system continues to look
quite moisture starved as well, without a tap to moisture from the
Gulf of Mexico. Rainfall amounts should be less than a quarter-inch,
and perhaps less than a tenth of an inch, for most locations through
Wednesday. Following an initial frontal passage early in the
day, a secondary front looks to approach by late day. Models are
indicating conditionally unstable conditions Wednesday
afternoon with this, and with the mid-level trough also
approaching, there may still be some pop up showers with even
some rumbles of thunder in the afternoon, especially northwest
of the Fall Line. And given fairly steep lapse rates in the low
and mid levels, some of these showers/storms could even contain
some hail and gusty winds. Expect warm temperatures for the most
part on Wednesday, at least southeast of the Appalachians, but
accompanied by brisk northwest winds in the afternoon and
evening. Skies will clear as high pressure quickly builds
southeastward from the Great Lakes Wednesday night, across the
Northeast and Mid-Atlantic Thursday morning. If the atmosphere
can decouple and winds calm, that could set the stage for
another frosty morning in spots, especially the more favorable
locations like interior NJ and eastern PA north and west of the
Fall Line.

Thursday is shaping up to be mainly sunny and cooler under the
influence of high pressure with highs in the 50s to around 60.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Expect dry weather and mostly clear skies through Friday as strong
high pressure remains in control along the Mid-Atlantic coast.
Friday morning may see yet another frosty morning inland and outside
perhaps the most urban areas. Afternoon highs should then be in the
50s to low 60s. Models continue to struggle with the forecast
specifics regarding any rain over the weekend, but the general
synoptic set-up looks to be low pressure lifting across the upper
Great Lakes, with a warm front trying to cross the Appalachians.
That may bring some showers in, particularly across eastern PA at
some point over the weekend, but at this point am not expecting a
washout by any means. Sunday may finally see some high temperatures
rising above seasonal averages, possibly into the 70s. This looks to
continue into Monday with increasing shower/storm chances by late
day as a cold front starts to approach.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

Rest of Today...VFR. Northwest winds 5-10 knots, with gusts 15-20
knots. Gusts drop off later this afternoon. High confidence.

Tonight...VFR. Northwest winds 5-10 knots early, becoming light and
variable this evening and overnight. High confidence.

Tuesday...VFR. Light and variable winds early become south to
southwest 5-10 knots after daybreak, gusting 15-20 knots later in
the morning into the afternoon. High confidence.

Outlook...

Tuesday Night - Wednesday...Potential for MVFR conditions at times,
as a cold front brings showers and a wind shift from southerly to
W/NW.

Thursday - Friday...VFR.

Saturday...Potential for stratus deck with MVFR cigs.

&&

.MARINE...
For tonight, conditions will remain below advisory levels although
winds could gust around 20 knots this evening.

For Tuesday, winds start below advisory levels, but will increase
through the day and likely reach Small Craft Advisory levels on the
northern half of the New Jersey coastal waters, as well as Delaware
Bay. Therefore we have issued a Small Craft Advisory for these areas.

Outlook...

Tuesday night through Wednesday... Small Craft Advisory conditions
expected, at least due to seas. SW winds around 15 kt gusting 20 to
25 kt, shifting to the W/NW later in the day as a cold front swings
through. Seas 5 to 6 ft.

Thursday...SCA possible early in the morning due to lingering
elevated seas. Diminishing NE to E winds. Seas 3 to 5 ft.

Friday...Easterly winds 10-15 kt. Seas 2 to 3 ft.

Saturday...Southeast winds 10 t0 15 knots. Seas 3 to 4 feet.

&&

.FIRE WEATHER...
A dry airmass has engulfed the region today. Northwest winds
will generally be around 10-15 mph, with gusts 15-20 mph this
afternoon. Although these winds are not all that strong, surface
dew points are anticipated to mix down into the low to mid 20s.
This will result in Min RH values in the 20-25% range across E
PA and NJ and 25-30% range across E MD and DE. As such we have
issued a Special Weather Statement for increased fire danger.

Similar conditions are expected for Tuesday, with only slightly
higher winds and RH values. We will likely need another Special
Weather Statement on Tuesday as well.

&&

.TIDES/COASTAL FLOODING...
A prolonged period of southerly flow will develop during the
middle of the week ahead of a cold front that will push offshore
on Thursday. This is forecast to result in surge values rising
to around 1-2 feet above normal along Delaware Bay, the tidal
Delaware River, and Chesapeake Bay. With the full moon
occurring on Tuesday, astronomical tides will be maximized
around this time as well. This should result in some areas of
minor coastal flooding with the Wednesday night high tide,
although the extent and exact areas that may experience the most
impact remains unclear at this time.

Coastal flooding is not currently anticipated along the Atlantic
coast, except for potentially Barnegat Bay.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
PA...Frost Advisory from 2 AM to 9 AM EDT Tuesday for PAZ070-071-
     104-106.
     Freeze Warning from 2 AM to 9 AM EDT Tuesday for PAZ060>062-
     101>103-105.
NJ...Frost Advisory from 2 AM to 9 AM EDT Tuesday for NJZ016>019-
     023.
     Freeze Warning from 2 AM to 9 AM EDT Tuesday for NJZ001-
     007>010-012-013-015-020>022-027.
DE...Frost Advisory from 2 AM to 9 AM EDT Tuesday for DEZ001>003.
MD...Frost Advisory from 2 AM to 9 AM EDT Tuesday for MDZ012-015-
     019-020.
MARINE...Small Craft Advisory from 2 PM to 8 PM EDT Tuesday for ANZ430-
     431.
     Small Craft Advisory from 4 PM Tuesday to 6 PM EDT Wednesday
     for ANZ450-451.
     Small Craft Advisory from midnight Tuesday night to 6 PM EDT
     Wednesday for ANZ452>455.
-- End Changed Discussion --

&&

$$

SYNOPSIS...AKL/Fitzsimmons
NEAR TERM...Robertson/Wunderlin
SHORT TERM...AKL/Dodd/Fitzsimmons
LONG TERM...AKL/Dodd/Fitzsimmons
AVIATION...Fitzsimmons/Robertson/Wunderlin
MARINE...Fitzsimmons/Robertson/Wunderlin
FIRE WEATHER...
TIDES/COASTAL FLOODING...