FXUS61 KPHI 210542

Area Forecast Discussion
National Weather Service Mount Holly NJ
142 AM EDT Fri Jul 21 2017

A cold front will approach the area tonight and cross through by
Friday morning. Weak high pressure will then prevail through
Saturday. Another front and associated low pressure will be across
the area Saturday night through Monday. High pressure will then move
in next Tuesday and remain into the middle of next week.


The sky over our region should become clear to partly cloudy. A
surface trough trailing the convective complex is expected to
pass through our forecast area late tonight.

The wind is anticipated to become light and variable overnight. Low
temperatures should be mostly in the 70s.


Maximum temperatures on Friday will be similar to those of today.
However, the humidity is forecast to be slightly lower. We will
leave the Excessive Heat Warning in place for the urban corridor.
However, other areas should fall a bit short of their criteria for a
Heat Advisory.

The sky is expected to be mostly sunny on Friday. We will not
mention any precipitation due to the lack of any significant
triggering mechanism along with the continued existence of a capping
inversion aloft.

The wind should favor the west and southwest on Friday around 5 to
10 MPH.


The heat wave will continue on into the weekend, but it will gradually
weaken with temperatures more in line with normal after Monday. A
few recent model runs are showing that high temperatures around
90 degrees readings are possible Monday, something which has
changed since yesterday, but for now we will continue with upper
80s across the Philadelphia metro area and for Delmarva too.
Dew point temperatures will be lower over the area Saturday, but
then climb back to steamy values Sunday and early Monday. A
front will cross the area Monday and drier and cooler air will
arrive behind that for the middle of next week.

Shower and tstm chances will be rather low Friday night and into
Saturday morning, but then increase from w to e through the afternoon
as the the front and humid air return to the area. High chance
to low likely pops will be over the area Sunday into Monday as
the system passes the region. Lower pops will be over the area
Tuesday and Wednesday with high pressure settling over the


The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

For the 06Z TAFs...Mostly VFR through the period, though there
may be some patchy/transient visibility restrictions through
early morning in favored more rural valley locations and where
rain fell today. Expecting FEW-SCT cumulus around 5000-8000 feet
tomorrow with winds transitioning from northwest to west or
southwest as the day wears on. Speeds should remain around or
below 10 kts. No storms are expected through the TAF period.

Fri night thru Saturday morning...VFR expected.
Saturday afternoon thru Monday...Mostly VFR. Sct showers and
tstms with lower conditions possible. Tue...Mostly VFR.


High pressure over the Atlantic will continue to influence the
coastal waters of Delaware and New Jersey for tonight. A weak
frontal boundary from the northwest is forecast to arrive early on
Friday. The wind should favor the south and southwest at less than
15 knots tonight, becoming west to southwest on Friday. Wave heights
on our ocean waters will remain around 2 to 4 feet and waves on
Delaware Bay should be 1 to 2 feet.

Sub-SCA conditions overall. The main hazard will be sct tstms
mainly between Saturday afternoon and Monday. Locally higher
winds and seas with tstms. Bring your NOAA weather radio along
to get alerts.


The underlying 10 second southeasterly swell is forecast to
persist into Friday. However, this is expected to be weaker than
yesterday so conditions may be more in the low category.


The KDOV dew point readings are unrepresentative of the area
and should not be used when diagnosing humidity/heat indices and
meteorological analysis of meteorological items which use
dewpoint in a calculation.


PA...Excessive Heat Warning until 8 PM EDT this evening for PAZ070-
NJ...Excessive Heat Warning until 8 PM EDT this evening for NJZ015-
DE...Excessive Heat Warning until 8 PM EDT this evening for DEZ001.


Near Term...Gaines/Iovino
Short Term...Iovino
Long Term...O'Hara
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