textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Issued an Extreme Heat Watch for the Philadelphia metropolitan area.

Updated coastal flooding section.

KEY MESSAGES

1. Above normal temperatures take over by Tuesday, likely continuing toward the end of the week. Wednesday will be the hottest day of the stretch, and an Extreme Heat Watch was issued for the Philadelphia metro.

2. Late week could be active and unsettled with a chance for showers and thunderstorms, some of which could be severe.

3. Coastal Flood Advisories have expired. Only spotty minor tidal flooding is expected with tonight's high tide.

DISCUSSION

KEY MESSAGE 1...Above normal temperatures take over by Tuesday, likely continuing toward the end of the week. Wednesday will be the hottest day of the stretch, and an Extreme Heat Watch was issued for the Philadelphia metro.

A more typical summertime pattern sets up beginning on Tuesday. Temperatures are expected to get above normal as ridging extends into the Mid-Atlantic from the west with surface high pressure strengthening offshore. This will set up warm southerly flow, allowing the heat and humidity to return. The heat peaks on Wednesday over the area as temperatures should get well into the 90s with increasing humidity. Its not out of the question PHL and a few other sites tag the century mark again, but nothing like we saw to start July. Humidity will be less as well. However, heat index values are still projected to get near 105F or even higher, potentially up to 108F. As a result, issued an Extreme Heat Watch for the Philadelphia metro area for Wednesday. Further heat headlines (either Advisory or Warning) will be needed across more of the area, but the warmest temperatures and heat indices will be over the urban corridor.

A dry cold front looks to pass sometime late Wednesday which will knock down temperatures a bit, but medium range guidance and ensembles indicate above normal temperatures in the upper 80s/low 90s could remain through the end of the week and potentially into the weekend.

KEY MESSAGE 2...Late week could be active and unsettled with a chance for showers and thunderstorms, some of which could be severe.

We are still several days out but we are monitoring the severe weather setup towards the end of the week and into the weekend. A strong cold front will slide southward to break the heat ridge, putting potential for another round of severe weather in play. The Storm Prediction Center (SPC) has highlighted some of the area in a Slight Risk (15% chance of severe thunderstorms 25 miles from any point) on Friday. Storms look to be driven by a strong cold front swinging in from the northwest and with ample daytime heating and instability, the ingredients are certainly there for strong to severe thunderstorms and damaging wind gusts. Timing is uncertain, as some of the latest guidance is somewhat faster with frontal progression.

In their long term outlook, SPC did mention some small MCS potential during the day 7 to 10 period as some shortwaves are likely to ripple through the northwest flow. Again, still several days out, but we will have to monitor the severe weather potential for the end of the week and possibly next weekend.

KEY MESSAGE 3...Coastal Flood Advisories have expired. Only spotty minor tidal flooding is expected with tonight's high tide.

All Coastal Flood Advisories have expired. While astronomical tides are increasing slightly with the New Moon tomorrow, flow is turning more offshore. Some spotty minor tidal flooding is likely tonight along the Atlantic coast, Delaware Bay, and tidal Delaware River, but water levels should remain below Advisory criteria.

With offshore flow continuing and strenghtening through the middle of the week, no tidal issues are expected after tonight's high tide.

AVIATION /10Z MONDAY THROUGH FRIDAY/

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

Today...VFR. South/Southwest winds around 5 to 10 kt. High confidence.

Monday Night...VFR/SKC. Light southwest winds 5 kt or less. High confidence.

Tuesday...VFR. West/southwest winds around 5 to 10 kt. High confidence.

Outlook...

Tuesday Night through Friday...VFR. Mainly dry though cannot rule out a few thunderstorms towards the end of the week, potentially resulting in brief restrictions.

MARINE

Sub-SCA conditions expected through Tuesday morning. Winds generally 10 kt or less starting out of the east/southeast today and becoming south/southwesterly by tonight. Seas 2 to 3 feet.

Outlook...

Tuesday Afternoon through Tuesday Night...SCA conditions possible (40-50%) for the New Jersey coastal waters as south/southwesterly wind gusts could get near 25 kt at times and seas near 5 feet.

Wednesday through Friday...No marine headlines expected.

Rip Currents...

For today, a single 6 second swell combined with low breaking wave heights (1 to 3 feet) will result in a LOW risk for the development of rip currents for all locations. Southeast flow remains but winds should be light, generally around 10 MPH or less.

For Tuesday, flow turns offshore with a 7 to 9 second period swell. Wave heights remain around 2 feet as well, resulting in a LOW risk for rip currents continuing.

For specific beach forecasts, visit weather.gov/beach/phi

CLIMATE

A brief 1-day spike in temperatures is expected, with highs likely to approach records. Here are the records for Wednesday, July 15:

Allentown/ABE 98 in 1995 AC Airport/ACY 100 in 1995 AC Marina/55N 99 in 1995 Georgetown/GED 96 in 2024 and 1993 Mount Pocono/MPO 92 in 1954 Philadelphia/PHL 103 in 1995 Reading/RDG 100 in 1995 Trenton/TTN 101 in 1995 Wilmington/ILG 99 in 1997 and 1995

PHI WATCHES/WARNINGS/ADVISORIES

PA...Extreme Heat Watch from Wednesday morning through Wednesday evening for PAZ070-071-104-106. NJ...Extreme Heat Watch from Wednesday morning through Wednesday evening for NJZ015-017>019. DE...Extreme Heat Watch from Wednesday morning through Wednesday evening for DEZ001. MD...None. MARINE...None.