textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

No significant changes to the forecast.

KEY MESSAGES

1. Patchy light drizzle will continue to dissipate through the predawn hours. Patchy fog possible before dawn. A cold front will push offshore today, resulting in breezy and drier conditions.

2. Tranquil weather expected this week and into the weekend with no significant weather hazards anticipated.

DISCUSSION

KEY MESSAGE 1...Patchy light drizzle will continue to dissipate through the predawn hours. Patchy fog possible before dawn. A cold front will push offshore today, resulting in breezy and drier conditions.

Some patchy drizzle across portions of PA and NJ will continue to gradually diminish through dawn as a weak low moves offshore. Clouds and perhaps some patchy fog will also linger before a cold front passes through and high pressure builds in from the west. This will dry things out starting later this morning.

A modest northwest pressure gradient will build as the high pressure builds into the area. This will create breezy conditions, with northwest winds increasing to 10-15 mph with gusts of 20-30 mph through much of the day. Temperatures will remain mild, with highs in the upper 60s to low 70s in most areas as the cooler airmass lags slightly behind the pressure gradient and downsloping gives us an adiabatic warming boost.

Tonight will be by far the coolest so far this season, as temperatures fall into the 40s in many areas by dawn Tuesday. Coastal areas and the Philly urban core will likely stay closer to 50 degrees, and areas north of I-78 will drop into the mid to upper 30s in some spots. There could be some patchy frost in the sheltered valleys of NW NJ and the southern Poconos, but confidence on this is somewhat low give the gradient wind that will still be in place. This should help prevent strong radiational cooling and thus temperatures from bottoming out too much.

KEY MESSAGE 2...Tranquil weather expected this week and into the weekend with no significant weather hazards anticipated.

High pressure will be in control through much of the week resulting in mostly clear/sunny skies and seasonably cool to mild temperatures. The first notably cool Canadian airmass of the season will settle into the area by Tuesday. Highs on Tuesday will only get into the low to mid 60s, with overnight lows Tuesday night/Wednesday morning dropping into the upper 30s and low to mid 40s.

Forecast temperatures are high enough to not need any frost headlines just yet. The radiational cooling setup Tuesday night is not the most ideal. While surface winds will be light to calm, winds not far above the surface will be modest and beginning to advect higher moisture air that is closer to saturation aloft into the area. This combined with rebounding dewpoints should work to suppress strong radiational cooling despite mostly clear skies and light surface winds. Nevertheless, there could certainly be at least some patchy frost in the sheltered valleys of northwest New Jersey and the southern Poconos, where temperatures could locally drop into the mid 30s.

As high pressure shifts offshore by Wednesday, airmass modification will commence. Temperatures return to more seasonable values on Wednesday, and likely go above normal on Thursday with highs in the mid to upper 70s. Temperatures look to return to near normal again for Friday and into the weekend. It should be an extended stretch of pleasant weather days.

AVIATION /07Z MONDAY THROUGH FRIDAY/

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

Through 12Z...Prevailing MVFR and IFR for most sites with some gradual improvement anticipated. As the lower clouds break up overnight, some fog and localized low clouds may redevelop. Light and variable winds settling out of the WNW around 5 kts toward dawn. Low confidence on details regarding restrictions.

Today...VFR. Winds Northwest winds increasing to 10-15 kts with gusts up to 25 kts. High confidence.

Tonight...VFR/SKC. Northwest winds near 10 kts early diminishing to near 5 kts overnight. High confidence.

Outlook...

Tuesday through Friday...VFR. No significant weather expected.

MARINE

The Small Craft Advisory remains for all of the Atlantic coastal waters for 4-6 foot seas. Seas should diminish some overnight as the ENE winds lessen, and some areas may drop below 5 feet for a few hours early this morning. Some patchy drizzle and fog may reduce visibility at times overnight.

The Small Craft Advisory was extended into tonight for all of the Atlantic coastal waters. A new Small Craft Advisory was issued for Delaware Bay starting 10 AM this morning through midnight tonight. Confidence has increased that northwest winds will increase to 15-20 kts with gusts up to 25 kts, especially during the afternoon and evening hours. For the Atlantic coastal waters, gusts up to 25 kts may persist overnight, especially north of Barnegat Light where that advisory was extended through 6 AM Tuesday. Seas lingering near 3-5 feet today. Aside from the breezy northwest winds, fair weather is expected.

Outlook...

Tuesday through Friday...No marine hazards expected.

PHI WATCHES/WARNINGS/ADVISORIES

PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory from 10 AM this morning to midnight EDT tonight for ANZ430-431. Small Craft Advisory until 6 AM EDT Tuesday for ANZ450-451. Small Craft Advisory until midnight EDT tonight for ANZ452>455.