textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

All Key messages updated. Overnight thunderstorms may be a bit later than previously expected.

Updated rip current discussion.

KEY MESSAGES

1. Showers and thunderstorms are expected again tonight and Friday.

2. Hot and humid conditions are forecast across the region into the evening.

3. The Labor Day Weekend will feature mostly dry weather with at or below normal temperatures and lower humidity.

DISCUSSION

KEY MESSAGE 1... Showers and thunderstorms are expected again tonight and Friday.

As short waves continue to move across the Great Lakes then then turn southeast across the northern Middle Atlantic region, we will see more rounds of showers and thunderstorms accompany them. We had this setup last night with the showers diminishing this morning across Pennsylvania by mid-morning. Another shot of energy is moving across Michigan and Lake Erie as of this afternoon and this will affect our areas later tonight and into Friday morning. The latest SPC outlook has much of the region in a SLIGHT risk for severe weather tonight. Damaging winds and large hail are the primary threats with severe weather.

In addition, local flash flooding is possible with the thunderstorms. There is limited confidence in which areas will receive any flooding, and also with greater storm motion, it's probable that flooding may be limited. For these reasons, we have not considered any flood watches attm.

KEY MESSAGE 2...Hot and humid conditions are forecast across the region into the evening.

We'll continue the ongoing Heat Advisory for the remaining part of the day although in some areas we may come up a bit low of the Advisory numbers. The morning clouds kept temps from rising earlier today, but the ongoing period of sunshine will create increasingly uncomfortable readings into the evening.

3. The Labor Day Weekend will feature mostly dry weather with at or below normal temperatures and lower humidity.

By Saturday, the trend among model guidance shows the frontal boundary south of our region, with Canadian high pressure building in across the Northeast and Mid-Atlantic. This will largely end any shower and thunderstorm potential. Thus, Labor Day Weekend is still shaping up to feature nice weather, with temperatures trending at or slightly below normal and lower humidity.

AVIATION /20Z THURSDAY THROUGH TUESDAY/

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

Tonight... VFR early with mostly high clouds. Overnight, showers and tstms arrive from NW and move SE across the terminals with MVFR and perhaps a period of IFR conditions. Timing will be around 02Z/03Z for the NW terminals and 04Z/05Z for Delaware Valley sites. Further SE, KMIV/KACY will have their TSTMS around 05Z/06Z. Fog is possible after the TSTMs and rains end. High confid early then lower confid around TSTM timing.

Friday... Patchy fog early then VFR expected. Scattered showers and TSTMs possible later in the morning and early afternoon, but limited confid for inclusion in 18Z TAFS. Low confid overall.

Outlook...

Friday night... VFR expected. Patchy rural fog possible. Saturday through Tuesday...Primarily VFR conditions expected.

MARINE

Winds and seas are expected to stay below Small Craft Advisory conditions. A prevailing West to Southwest wind expected. Later today and into the overnight periods winds will be light and somewhat variable. TSTMs will create locally hazardous winds and seas overnight. Scattered showers/TSTMs for Friday.

Outlook...

Saturday through Tuesday...Sub-SCA conditions are expected through the period.

Rip Currents...

For Friday, winds turn offshore, with west/northwest winds 10 MPH or less. Breaking waves also around 2 feet or less expected with a dominant period of 8 seconds. With relatively tranquil conditions in the surf zone, a LOW risk for rip currents is expected at all beaches.

For Saturday, winds turn more northerly, though still light. Similar surf zone conditions expected at all beaches will result in another LOW risk for all shore points to start the holiday weekend.

PHI WATCHES/WARNINGS/ADVISORIES

PA...Heat Advisory until 8 PM EDT this evening for PAZ060-070-071- 101>104-106. NJ...Heat Advisory until 8 PM EDT this evening for NJZ013>015- 017>020-027. DE...Heat Advisory until 8 PM EDT this evening for DEZ001>003. MD...Heat Advisory until 8 PM EDT this evening for MDZ012-015-019- 020. MARINE...None.