textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Aviation discussion updated.

Increasing confidence in well above normal temperatures next week and a legitimate chance for the first 90 degree of 2026 for Philadelphia.

KEY MESSAGES

1. A mainly dry weather pattern continues through the weekend, continuing an elevated risk for fire spread.

2. Frost possible across portions of southeast Pennsylvania tonight through early Sunday morning.

3. A significant warm up is expected for the early and middle part of next week with temperatures anticipated to reach 90F for the first time this season along portions of the I-95 corridor on Wednesday and Thursday.

DISCUSSION

KEY MESSAGE 1...A mainly dry weather pattern continues through Sunday, continuing an elevated risk for fire spread.

Conditions will be slightly less favorable (compared to Saturday) for fire spread during Sunday, but remain marginal across the region. Minimum RH values around 30-40% with winds turning more S-SE in the afternoon gusting up to around 20 mph.

KEY MESSAGE 2...With high pressure moving overhead tonight into early Monday morning, calm winds and clear skies will give way to the potential for strong radiational cooling. Overnight lows are forecast to fall into the low to mid 30s for areas north and west of the I-95 corridor. Despite a dry airmass in place, dew point depressions will be sufficient to support the potential for patchy frost. A Frost Advisory has been issued for Berks, western Chester, and western Montgomery counties late tonight into early Monday morning where the growing season has begun. For the Lehigh Valley, Poconos, and northern New Jersey, patchy frost is possible, but the growing season there has not begun yet.

KEY MESSAGE 3...A significant warm up is expected for the early and middle part of next week with temperatures anticipated to reach 90F for the first time this season along portions of the I-95 corridor on Wednesday and Thursday.

Strong high pressure will gradually shift offshore Monday allowing for seasonable warm air to push north on southerly flow. This surge of warm air both at the low levels and aloft will push surface temps into the the low 80s Monday, the mid 80s Tuesday and into the upper 80s to low 90s for Wednesday and Thursday. Temperatures toughing 90F in Philadelphia would mark the first 90 degree day of the year and the first since September of last year. As is typical in spring though, temperatures along and near the coast likely will be 15-25 degrees cooler due to the colder sea surface temperatures. In addition to the strong WAA, winds could end up being fairly gusty later in the as the surface inversion starts to erode. A low level jet will bring 35-45 kts close to the surface however with the inversion in place it will take most of the day to erode it and along the coast it will likely not erode. Southerly gusts of 20- 25kts can be expected Monday afternoon.

A series of weak disturbances will result in a slight chance to low- end chance (15-30%) for showers or even an isolated thunderstorm Tuesday through Thursday, primarily in the evening hours and primarily for areas northwest of the I-95 corridor. The bulk of the period will be high and dry however, not good news for the drought.

AVIATION /00Z SUNDAY THROUGH THURSDAY/

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

Tonight...VFR. Winds around 5 kts or less, favoring a northerly direction. High confidence.

Sunday...VFR. Winds east around 5-10 kts in the morning shift to the S-SE and gust to 15-20 kts in the afternoon. High confidence.

Outlook...

Sunday Night...VFR. No significant weather.

Monday through Monday Night...VFR. Slight chance of a shower/thunderstorm (15-20%) at KRDG/KABE in the afternoon. A low level jet will likely cause some issues with LLWS and turbulence with surface wind gusts out of the southwest around 20-25 kt during the day.

Tuesday through Tuesday Night...VFR. Slight chance of a shower/thunderstorm (15-20%) at KRDG/KABE in the afternoon.

Wednesday...VFR. Slight chance of a shower/thunderstorm (15-20%) at KRDG/KABE in the afternoon.

MARINE

Sub-SCA conditions expected through Sunday.

Winds out of the NW to NE around 10 kts shift SE during the day Sunday with gusts around 15-20 kts. Seas 2-4 feet.

Outlook...

Sunday Night through Monday Night...SCA conditions likely (60-70%) as wind gusts out of the southwest near 25 kt and seas of 5 to 7 feet expected.

Tuesday through Wednesday...No marine headlines expected.

PHI WATCHES/WARNINGS/ADVISORIES

PA...Frost Advisory from 2 AM to 8 AM EDT Sunday for PAZ060-101-103. NJ...None. DE...None. MD...None. MARINE...None.