textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Aviation section updated for the 06Z TAF issuance.

Other sections updated as needed.

KEY MESSAGES

1. Low pressure south of the area will push a warm front north through the region tonight through Wednesday.

2. For the later half of the week, we will have a hot, humid, and at times stormy pattern in place.

DISCUSSION

KEY MESSAGE 1...Low pressure south of the area will push a warm front north through the region tonight through Wednesday.

After a pleasant day (Tuesday), A warm front lifts north through the region tonight, allowing showers and isolated thunderstorms to develop late tonight and into Wednesday morning. Low pressure developing over the Southeast lifts north along the Eastern Seaboard, but there is considerable uncertainty as to its track.

The overall system is weak with low pressure and upper short wave energy moving across our area Wed-Thu. The recent hot/humid airmass will return and even minor lifting will create the potential for more drenching downpours. Severe weather is not expected with weak winds fields across the area.

The Weather Prediction Center has a Marginal Risk for Excessive Rainfall, which is a 1 out of 4. for Wednesday and Thursday. For now, will follow the NBM and carry high chance to low end likely PoPs for most of the region Wednesday. There is the potential for another 1/2 inch to 1 inch of rain Wednesday afternoon and evening. The higher totals are presently forecasted to occur across the southern Poconos and perhaps into the Lehigh Valley.

KEY MESSAGE 2...For the later half of the week, we will have a hot, humid, and at times stormy pattern in place.

Expect a prolonged period of southwesterly flow as our region will be in between a Bermuda High well to our east, and a mid level long wave trough that will be slowly sliding east over the northern tier of the U.S./southern Canada. As such, heat and humidity will be building throughout the later half of the week. At this point, Friday and Saturday appear to be the warmest days, with highs ranging from the low 80s (Poconos) to the low 90s (metro). That in and of itself is pretty close to normal. However, with dewpoints in the mid 70s possible, we could get heat index values at or above 100 degrees for much of the area. All that being said, this still doesn't look nearly as impactful an extreme heat setup as what we saw earlier this summer during the first week of July.

The other aspect of this are the daily storm chances, primarily confined to the afternoon and evening with a typical diurnal pattern. Given the hot and humid conditions that will be in place, we can't rule out the more common thunderstorm hazards of damaging winds and heavy rain/flooding, but in general, I don't see any one day that has an especially high threat of any of these at this time. If an embedded short wave trough crosses our region as the larger trough axis approaches, that could increase the risk, particularly for severe threats, but trying to time that out at this point would be very difficult, given that we are still seeing some differences between the models with the larger pattern.

AVIATION /06Z TUESDAY THROUGH SATURDAY/

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

Today...VFR. Northeast winds early, gradually becoming more east or east-southeast in the afternoon around 10 kts. High confidence.

Tonight...VFR most of the time but MVFR or lower possible late as lower CIGS and showers arrive from the South towards dawn. Medium confid.

Outlook...

Wednesday through Wednesday night...MVFR or lower possible in SHRA and TSRA.

Thursday through Saturday...Periods of MVFR or lower in afternoon and evening SHRA/TSRA.

MARINE

The Small Craft Advisory was cancelled with winds and seas continuing to decrease over the waters. Winds have turned NE to E as high pressure to the west builds in. Winds speeds will remain mostly 10 to 15 kts today and closer to 5 knots tonight. Fair weather today and most of tonight. A few showers are expected after midnight across Delaware Bay and the southern coastal waters.

Outlook...

Wednesday through Saturday...Overall, a prolonged period of sub-SCA conditions, however there is a chance for 25+ kt wind gusts Thursday night. Afternoon and evening showers and thunderstorms possible as well.

Rip Currents...

For Today, surf heights should decrease some. However, there will be a northeast (onshore) breeze and southeasterly swells with breaking waves of 2-3 feet in most areas. This will result in a MODERATE risk for the formation of dangerous rip currents along the NJ Shore and Delaware Beaches.

For Wednesday, surf heights and swells will continue to lessen some, and surface winds will shift south to southeasterly. This will result in a MODERATE risk for the formation of dangerous rip currents along the NJ Shore, and a LOW Risk for the Delaware Beaches.

PHI WATCHES/WARNINGS/ADVISORIES

PA...None. NJ...None. DE...None. MD...None. MARINE...None.