Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 270130
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
930 PM EDT Sun Sep 26 2021

.SYNOPSIS...
High pressure will build northward from the Southeast states
tonight and Monday. A cold front will move through the region
Tuesday. A broad surface high will move southeastward towards
New England for the remainder of the week. An area of low
pressure may move into the region into next weekend.

&&

.NEAR TERM /THROUGH MONDAY/...
No significant changes with the late evening update. Surface
high pressure is expected to remain in the southeastern states
tonight before sliding off the coast on Monday. The air mass
will continue to bring dry weather conditions to our region.

Through much of tonight, we should have mostly clear conditions.
However, a deck of mid level clouds associated with warm
advection aloft is expected to pass over eastern Pennsylvania,
and northern and central New Jersey from very late tonight into
early Monday morning. Scattered clouds are then anticipated for
the balance of Monday.

The gusty northwest wind will likely diminish this evening. A
westerly wind less than 10 MPH is anticipated for tonight. A
southwest wind is expected to increase to 10 to 15 MPH on
Monday.

Lows tonight should favor the 50s. Warming in the southwest
flow on the back side of the surface high is expected to cause
temperatures to approach 80 degrees in much of our region on
Monday afternoon.

&&

.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
A progressive short wave trough will move over the Great Lakes
Monday night with an attendant surface low and cold front moving
towards our region out of southern Canada. While moisture is
still limited, there is still weak instability forecast along
and ahead of the front, so will keep scattered showers and
thunderstorms in the forecast on Tuesday. Steep lapse rates and
the slightly drier mid- level profile could lead to some small
hail with the stronger of these thunderstorms.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
The forecast in the longer term remains on track with a
blocking pattern developing from the Plains to the Northeast and
Mid- Atlantic.

At the surface, a surface low will undergo cyclogenesis over
the Canadian Maritime Provinces Wednesday beneath a further
amplifying and negatively tilted trough over the Northeast.
Several pieces of shortwave energy will ride around the Plains
ridge and into the Northeast upper-level low into the end of the
workweek. At the surface, high pressure will slowly move across
the Great Lakes Thursday and Friday, with a cool northerly flow
filtering into the region.

It should be rain-free Wednesday through Friday amidst the
blocked pattern. There is low confidence in the forecast for
Saturday and Sunday as model guidance waivers on whether the
blocking pattern breaks down or remains intact. Kept the
forecast dry on Saturday with a slight chance showers holding
off until Sunday.

&&

.AVIATION /02Z MONDAY THROUGH FRIDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Tonight...VFR conditions expected. Mostly clear, with an
increase in clouds after 08Z. Northwest wind 10 to 15 knots,
becoming west 8 knots or less this evening. High confidence.

Monday...VFR. Decreasing cloud cover in the morning, with only
scattered clouds in the afternoon. Southwest wind increasing to
10 to 15 knots with gusts around 20 knots. High confidence.

Outlook...

Tuesday...Mainly VFR. Scattered mid-level clouds as a cold
front traverses the region may lead to some restrictions.
Southwest winds turning west-northwest from 10 to 15 knots.
Moderate confidence.

Wednesday through Friday...VFR with northerly winds from 10 to
15 knots. High confidence.

&&

.MARINE...
Conditions are expected to be below Small Craft Advisory
criteria through the day on Monday as high pressure passes off
the Southeast coast.

Outlook...

Monday night...Southwesterly winds from 15 to 20 knots with
gusts to 25 knots will likely require an SCA. Seas from 2 to 4
feet.

Tuesday...Sub-advisory conditions expected with southwesterly
winds turning northwesterly from 10 to 15 knots and gusting to
20 knots. Seas from 2 to 3 feet.

Wednesday through Friday...Sub-advisory conditions expected
with northerly winds from 10 to 15 knots with gusts to 20 knots.
Seas from 2 to 4 feet.

Rip currents...

A MODERATE risk of rip currents is anticipated for the NJ coast
on Monday, with a LOW risk expected for the Delaware Beaches.
By Tuesday, with the medium period swell diminishing, and off
shore flow continuing, a LOW risk is currently forecast for the
coast of both NJ and DE.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...None.

&&

$$
Synopsis...Davis
Near Term...Iovino/Johnson
Short Term...Franklin
Long Term...Franklin
Aviation...Franklin/Iovino/Johnson
Marine...Franklin/Iovino/Johnson


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