textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Severe thunderstorm potential today has lowered except across the Poconos and extreme northern New Jersey.

Increasing potential for fire weather conditions on Thursday.

KEY MESSAGES

1. Marginal Risk (Level 1 of 5) of severe thunderstorms later this afternoon and evening, mainly north of I-80.

2. Record breaking warmth continues through Thursday with very warm and above normal temperatures through the first half of the weekend.

3. Elevated fire weather potential possible on Thursday.

4. There will be a chance of showers later Saturday evening through Sunday.

DISCUSSION

KEY MESSAGE 1...Marginal Risk (Level 1 of 5) of severe thunderstorms later this afternoon and evening, mainly north of I-80.

Similar to Tuesday, there is another chance for isolated severe weather across northeast PA and northern NJ where a Marginal Risk is in place for some isolated damaging winds and small hail. Today's risk will be associated with a remnant MCV that is currently located over the southern Great Lakes region that will track east into the Ohio Valley this afternoon and potentially clip the northern portions of our area this evening. As diurnal heating continues, this should contribute to some reinvigoration of convection in the late afternoon as the complex of thunderstorms advances toward our area this evening. Suppose with the warm and relatively moist airmass and MLCAPE values in excess of 1000 J/kg, some isolated cells could develop, but with bulk shear values generally less than 30 kt, these should not pose a threat. The severe threat will ultimately depend on how upstream convection evolves, but latest guidance trends continue to indicate that the greater potential may be just outside of our area. For this reason, SPC has nudged the greatest potential further north, only keeping areas north of I-80 in the Marginal Risk. In terms of timing, any convective activity looks to occur in the early evening hours, mainly after 7 PM and concluding by or just after midnight.

KEY MESSAGE 2...Record breaking warmth continues through Thursday with very warm and above normal temperatures through the first half of the weekend.

With high pressure situated over the Atlantic Ocean and the warm front well north of the Mid-Atlantic region, continued warmth is expected through Thursday. 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 through the end of the week.

Highs today and Thursday will be in the mid 80s to low 90s, though Thursday's highs could a touch cooler with some high clouds around. However, still expecting several high temperature and warmest low temperature records to fall over the next couple of days. See the Climate Section below for temperature records today and Thursday.

Today is set to be the first 90 degree day of the year for most and first since early September. As is typical in spring though, temperatures along/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 early Friday morning, temps will stay well above normal through Saturday with temps mainly in the mid 70s to mid 80s. Temperatures finally appear to cool back toward seasonable levels on Sunday and into early next week.

KEY MESSAGE 3...Elevated fire weather spread possible on Thursday.

A period of elevated fire weather conditions are possible on Thursday as very warm and dry conditions continue. MinRH values will drop into the 25-35% range for many locales across eastern PA, NJ and the Delmarva. This will be accompanied by southwest winds around 10-15 mph with gusts up to 20 mph in the afternoon. Due to lack of recent rainfall, there is some potential for fire spread. While these conditions do not meet Red Flag Warning criteria, suppose a Special Weather Statement may be warranted. We will be in contact with our fire weather partners later today or tonight to determine if a SPS may be needed depending on how dry 10-hour dead fuel moistures are.

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. While there are a few instances of showers over the next couple of days, any rainfall totals will be minimal.

KEY MESSAGE 4...There will be a chance of showers later Saturday evening through Sunday.

There will be a chance of showers later Saturday evening through Sunday. Any severe activity is expected to subside before reaching the Mid-Atlantic region, leaving just showers and an isolated thunderstorm possibility. Dry weather will return for the first half of the week, while cooler conditions return for the weekend through next week.

AVIATION /18Z WEDNESDAY THROUGH MONDAY/

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

Rest of Today (thru 00Z)...VFR. A stray shower or thunderstorm possible at KRDG/KABE, so have kept mention of VCSH. Elsewhere, dry conditions expected. Southwest winds around 10-15 kt with gusts around 20-23 kt this afternoon. Moderate-high confidence.

Tonight...VFR. Lingering showers or thunderstorms possible at KRDG/KABE through 04Z before diminishing. Southwest winds around 5-10 kt. Moderate-high confidence.

Thursday...VFR with mostly clear skies. Southwest winds around 10-15 kt with gusts around 20 kt. High confidence.

Outlook...

Friday night-Saturday...VFR conditions expected.

Saturday night-Sunday...Mostly VFR conditions expected. There is a chance for showers during the period which could lead to temporary lower conditions.

Sunday night-Monday...VFR conditions expected.

MARINE

No marine headlines are in effect through Thursday. Southwest winds of 10-15 kt with gusts around 20 kt and seas around 2-4 feet. Fair weather.

Outlook...

Friday night-Saturday night...Conditions expected to remain below advisory conditions.

Sunday-Monday...There is a chance for Small Craft Advisory conditions.

CLIMATE

Warm temperatures well above normal are expected for the upcoming week. Today is currently projected to be the warmest day, though Thursday could see some records broken depending on the site.

Below are record highs and record high minimum temperatures for April 15th through April 16th.

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.