textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Aviation section updated.

KEY MESSAGES

1. Cloudy skies today, but drying out as high pressure builds into the region into tonight. Below normal temperatures will persist. Some areas of frost development forecast tonight for portions of New Jersey and eastern Pennsylvania.

2. Additional chances for much-needed rain arrive during the middle of next week.

DISCUSSION

KEY MESSAGE 1...Cloudy skies today, but drying out as high pressure builds into the region into tonight. Below normal temperatures will persist. Some areas of frost development forecast tonight for portions of New Jersey and eastern Pennsylvania.

Canadian high pressure will build into the region through tonight as low pressure that brought the weekend rain departs out to sea. Dry air will be slow to filter in through the day, so low stratus will persist much of the daytime hours. The stratus should begin to scatter out and dissipate from north to south during the afternoon to early evening hours. So while it'll be a cloudy day overall, most areas outside of far southern New Jersey and Delmarva should see at least a couple hours of sun before sunset this evening.

A northeast breeze will persist today as well, generally around 10-15 mph, strongest near the coast where some gusts near 25-30 mph will remain possible. The cloudy skies will keep temperatures from warming up too much, so temperatures will remain below normal with highs mainly in the 50s. Northern NJ and eastern PA will make a run at 60 degrees though, as skies clearing earlier in the afternoon there should yield more substantial warming before the sunlight wanes. Highs closer to 50 degrees along the coast, where some drizzle may linger during the morning.

As skies quickly clear into the night, radiational cooling will take hold. Winds should become light, favoring a northerly direction around 5 mph or less. Lows will range from the mid 30s to low 40s for most areas. Sheltered valleys of northwestern New Jersey and eastern Pennsylvania should be on the cooler side of this range, with the surface high in the vicinity. Thus, some areas of frost are likely to develop. A Frost Advisory was issued to highlight this threat. Farther south into interior southern NJ and the outer Philly suburbs in PA, lows in the mid to upper 30s could produce some patchy frost, but thinking coverage and temperatures will be a little too marginal to warrant an advisory at the moment. Will keep an eye on this though.

KEY MESSAGE 2...Additional chances for much-needed rain arrive during the middle of next week.

A brief period of high pressure on Monday. A weak frontal boundary then approaches the region late Tuesday, bringing a chance for light rain. This frontal boundary will largely wash out across the region early Wednesday before another stronger low arrives late Wednesday into early Thursday that could bring more widespread showers and perhaps an isolated thunderstorm across the region.

AVIATION /15Z SUNDAY THROUGH THURSDAY/

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

Rest of today...MVFR ceilings improving to VFR by later this afternoon. Northeast winds 10-15 knots, with some gusts to 20 knots mostly at KACY, diminishing to 10 knots or less late. Moderate confidence.

Tonight...VFR. Northerly winds around 5 knots, becoming light and variable to locally calm. High confidence.

Monday...VFR. Northeast winds increasing to 5-10 knots, then becoming east or east-southeast in the afternoon. Moderate confidence.

Outlook...

Monday night...VFR.

Tuesday...VFR ceilings overall. Some afternoon/evening showers possible.

Wednesday...Sub-VFR conditions along with showers likely.

Thursday...VFR overall.

MARINE

A Gale Warning is in effect for coastal waters from Manasquan Inlet NJ south to Fenwick Island DE, out to 60 NM as winds increase during the daytime hours today, ending at 8 PM this evening. The Small Craft Advisory for the Delaware Bay remains in effect through 8 PM as well due to winds in excess of 25 knots. The SCA for coastal waters north of Manasquan Inlet out to 20 NM remains in effect through today to 6 AM Monday, as seas will remain elevated overnight even as winds decrease. Another, SCA will be needed for areas within the Gale Warning as seas remain elevated in that area as well.

In addition to SCA and Gale conditions, visibility restrictions are also expected for all marine areas in rain and fog through this morning.

Outlook...

Monday through Monday night...SCA conditions will linger through Monday with NE winds gusting near 25 kts and seas at 5-7 feet. Winds diminish below SCA criteria Monday night, but seas will remain elevated.

Tuesday through Thursday...SCA conditions possible due to elevated seas around 5 feet.

PHI WATCHES/WARNINGS/ADVISORIES

PA...Frost Advisory from midnight tonight to 8 AM EDT Monday for PAZ054-055-062-105. NJ...Frost Advisory from midnight tonight to 8 AM EDT Monday for NJZ001-007-009. DE...None. MD...None. MARINE...Small Craft Advisory until 8 PM EDT this evening for ANZ430- 431. Small Craft Advisory until 6 AM EDT Monday for ANZ450. Gale Warning until 8 PM EDT this evening for ANZ451>455- 481>483-485.