textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Updated aviation discussion.

KEY MESSAGES

1. Damaging winds possible in scattered showers and thunderstorms through this afternoon and evening north and west of the I-95 corridor, with an even higher risk from I-80 on north.

2. Potentially record breaking warmth is possible this week with very warm and above normal temperatures continuing through the upcoming weekend.

DISCUSSION

KEY MESSAGE 1....Scattered showers and isolated thunderstorms, mainly north and west of the I-95 corridor, are anticipated to move in this afternoon and evening. While the severe threat is zero for most of the area, a few strong to severe storms over the northern Lehigh Valley, Poconos, and far northern NJ are possible and could produce damaging wind gusts.

A fairly significant change to the forecast this morning for later today and this evening. An MCS over the Great Lakes will continue to push eastward through today and potentially graze our area this afternoon and evening. Convection associated with the MCS will likely re-develop later this afternoon over southern NY and north- central PA. The question remains how much instability builds with daytime heating as the day goes on. Shear, while present, is not overwhelming either. However, still expecting some thunderstorms developing and potentially clustering as they move into the northern half of our region. Main concern is damaging wind gusts as the line or small clusters of storms move through.

The best chance for strong to severe thunderstorms will be from the I-95 and I-195 corridor on north and west. SPC has expanded the Marginal Risk (1/5) to include these areas. A Slight Risk was even added north of I-80. Showers and thunderstorms begin to move in by the mid afternoon in the Poconos, moving toward I-95 for the late afternoon/early evening. Convection should weaken as it crosses the Delaware River, with a more stable airmass present over New Jersey. Areas south and east of I-95 could still see some showers, but not expecting much in terms of severe weather.

KEY MESSAGE 2...Potentially record breaking warmth is possible this week with very warm and above normal temperatures continuing through the upcoming weekend.

We continue on track with increasing confidence in early season heat with a significant warm up expected through the middle of the week and into the upcoming weekend with the potential for record breaking temperatures.

With high pressure situated over the Atlantic Ocean and the warm front well north of the Mid-Atlantic region, continued warmth is expected. Very warm air aloft coupled with warm air at surface levels will allow temperatures to be as much as 15 to 30 degrees above average this week. As of now, forecast highs are in the low to mid 80s on Tuesday with mid/upper 80s to low 90s on both Wednesday and Thursday, though Thursday may be a touch cooler due to more cloud cover. See Climate Section below regarding potential record breaking temperatures.

At this point, temperatures are expected to reach at least 90 for much urban corridor on Wednesday and a degree or two warmer on Thursday. This would be first 90 degree day of the year and first since early September. As is typical in spring though, temperatures along and near the coast will be significantly cooler due to the colder sea surface temperatures and diurnal sea breeze. While a weak surface front passes through late Thursday night into Friday morning, temperatures will stay well above normal through the weekend with temps mainly in the mid 70s to mid 80s.

Not only will it be very warm over the course of the week, but it will also remain mainly dry. This is of elevated concern for ongoing drought/abnormally dry conditions over much of the area, which will likely only get worse after this week. A few weak disturbances will pass by to the north through Thursday, but other than a stray shower or thunderstorm each afternoon north of the I-78 corridor, no significant rainfall is expected. Flow will generally be out of the southwest, which is more favorable in terms of moisture, which likely will hinder the fire weather concerns this week. Winds will generally be light as well, as another limiting factor. So, even though it will be warm and dry, fire weather concerns are minimal.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

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

Today...Primarily VFR. Scattered showers and isolated thunderstorms potentially develop in the afternoon. Added VCTS to the TAFs between 20-21z to 23-00z for KRDG/KABE and kept the VCSH at all other sites as showers and thunderstorms should be more concentrated over the northern Lehigh Valley and northern NJ. Cannot rule out some storms making it to the I-95 corridor though between 22z-01z. Winds out of the southwest this morning around 5-10 kt, increasing to around 10-15 kt in the afternoon with gusts 20-25 kt. Moderate confidence.

Tonight...Primarily VFR. Slight chance (15-20%) of a shower through 03z at KACY/KMIV. Added some patchy fog to the KABE/KRDG TAF which could reduce visibilities down to IFR/MVFR. Higher chance for fog depending on if rain impacts any terminals this afternoon and evening. Light southwest winds 5 kt or less. Low confidence.

Outlook...

Wednesday through Thursday night...Prevailing VFR. A chance of showers and thunderstorms (~20-40%) in the afternoon and evening hours each day for the Lehigh Valley and I-95 terminals.

Friday through Saturday...VFR. A few showers possible, otherwise no significant weather.

MARINE

Tranquil conditions expected on the waters today and tonight with no headlines in place. Southwest winds around 10-15 kt with gusts up to 20 kt and seas 2 to 4 feet. Outlook...

Wednesday through Saturday...No marine headlines expected. Winds will generally remain below 20 kt with seas around 2-4 feet. A few showers possible, otherwise fair weather.

CLIMATE

Warm temperatures well above normal are expected for the upcoming week. Wednesday is currently projected to be the warmest day, though Tuesday through Thursday could see some records broken depending on the site. Below are record highs and record high minimum temperatures for April 14th through April 16th.

Record High Temperatures April 14 Site Record/Year Allentown (ABE) 88/2023 AC Airport (ACY) 86/1945 AC Marina (55N) 90/1941 Georgetown (GED) 87/1977 Mount Pocono (MPO) 84/2023 Philadelphia (PHL) 91/1941 Reading (RDG) 90/1941 Trenton (TTN) 89/1941 Wilmington (ILG) 87/1941

Record Warmest Low Temperatures April 14 Site Record/Year Allentown (ABE) 61/2014 AC Airport (ACY) 63/2023 AC Marina (55N) 60/2023 Georgetown (GED) 65/2019 Mount Pocono (MPO) 56/2014 Philadelphia (PHL) 62/2014 Reading (RDG) 64/2014 Trenton (TTN) 62/2014 Wilmington (ILG) 60/2014

Record High Temperatures April 15 Site Record/Year Allentown (ABE) 86/1941 & 1994 AC Airport (ACY) 90/1967 AC Marina (55N) 86/1941 Georgetown (GED) 86/1960 & 2024 Mount Pocono (MPO) 82/1941 Philadelphia (PHL) 88/1941 Reading (RDG) 86/1941 & 1994 Trenton (TTN) 87/1994 Wilmington (ILG) 86/1896

Record Warmest Low Temperatures April 15 Site Record/Year Allentown (ABE) 59/2002 AC Airport (ACY) 61/2002 AC Marina (55N) 59/2006 Georgetown (GED) 65/2002 Mount Pocono (MPO) 58/2002 Philadelphia (PHL) 64/2002 Reading (RDG) 64/1938 Trenton (TTN) 63/2002 Wilmington (ILG) 62/2002

Record High Temperatures April 16 Site Record/Year Allentown (ABE) 90/2012 AC Airport (ACY) 89/2002 AC Marina (55N) 88/2002 Georgetown (GED) 89/2002 Mount Pocono (MPO) 85/2002 Philadelphia (PHL) 90/2002 Reading (RDG) 90/2012 Trenton (TTN) 91/2012 Wilmington (ILG) 92/1896

Record Warmest Low Temperatures April 16 Site Record/Year Allentown (ABE) 60/1941 AC Airport (ACY) 62/2002 AC Marina (55N) 64/2002 Georgetown (GED) 65/2012 Mount Pocono (MPO) 56/2002 Philadelphia (PHL) 62/2002 Reading (RDG) 65/1941 Trenton (TTN) 62/2002 Wilmington (ILG) 63/2002

PHI WATCHES/WARNINGS/ADVISORIES

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