textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Dense fog advisory for Carbon and Monroe has been allowed to expire.

KEY MESSAGES

1. Occasional light rain, drizzle and mist will linger across the area this morning.

2. Periods of rain Thursday night and Friday. Light wintry precipitation may cause travel hazards tonight and Friday morning, mostly near and north of the I-80 corridor.

3. The region will be on the northwestern edge of a potential coastal storm forecast to be just offshore on Sunday and Monday.

DISCUSSION

KEY MESSAGE 1...Occasional light rain, drizzle and mist will linger across the area this morning.

Stalled frontal boundary remains straddled across southern Delmarva. Warm advection overhead has resulted in plenty of clouds, and lingering snow on the ground has helped keep it murky and misty as it cools and condenses out the low-level moisture most efficiently. Dense fog, however, has now dissipated so the dense fog advisory has been allowed to expire in the Poconos.

KEY MESSAGE 2...Periods of rain Thursday night and Friday. Light wintry precipitation may cause travel hazards tonight and Friday morning, mostly near and north of the I-80 corridor.

Low pressure moving into the western Great Lakes region will cause a surface warm front to move towards the area tonight. A round of rains and higher elevation wintry precipitation is expected overnight. The start timing looks to be generally after 7PM/8PM for the wintry precip. Both light snow and freezing rain are possible. A Winter Weather Advisory was be issued for tonight and early to cover this event. Snow accums will be in the less an inch with ice of 0.1 to 0.2 inches possible.

A zone of warm air advection ahead of this system and associated front will result in some overrunning precipitation. It looks like a quick moving system, and it is possible that the energy with this becomes elongated with time. Periods of rain will occur, with the bulk of it falling tonight through Friday morning. Precip looks to come in two main rounds, one late this afternoon and evening across Delmarva and southern NJ, then a second round overnight through Friday morning focused on the northern half of the forecast area (though eventually spreading south). Rainfall amounts look to range from around 0.3" to 0.5" across the region, with some locally higher amounts possible. Some fog will be possible as the milder and more moist air overruns some lingering chilly near- surface air, especially in areas that still have a snowpack along and north of the I-78 corridor.

There looks to be a south to north temperature gradient across our area Friday due to the placement of a warm front. Milder air then arrives for Saturday as the low-level flow turns from northeasterly to westerly. Most places in the coastal plain Saturday should get into the upper 40s to low 50s as cloud cover breaks some. A boundary may linger longer very close to our far northern zones Saturday with just a slight chance (20 percent) for some light precipitation.

KEY MESSAGE 3...The region will be on the northwestern edge of a potential coastal storm forecast to be just offshore on Sunday and Monday.

Model guidance continues to show low pressure moving off the Southeast or Mid-atlantic coast Saturday night, and then deepening a few hundred miles off the Mid-atlantic coast Sunday into early Monday before moving eastward on Monday and out to sea. There remains a large amount of uncertainty as to how impactful this system will be to the local region, with some guidance suggesting light to moderate snowfall in the New Jersey- Philadelphia metro-Delaware regions, and other guidance showing no snow at all over the entire local area. That being said, areas south and east of Philadelphia still have the greatest potential for impacts from any snow and wind Sunday afternoon into early Monday.

In the wake of this storm, a colder air mass looks to settle into our region early next week. High temperatures in the mid 30s to near 40 degrees both Monday and Tuesday (colder in the Poconos), with lows in the mid teens and 20s.

AVIATION /14Z THURSDAY THROUGH MONDAY/

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

Today... Lower CIGS are continuing to lower across the terminals as of the and should remain mostly IFR into the morning before slow improvement back to MVFR. A longer period of MVFR into the afternoon is expected at most sites. IFR possible late with rains arriving from the S/W. Low confid overall.

Tonight... Low CIGS and low vsbys in rains/fog. Freezing rain/snow are expected for the MPO vcnty. Low confid with regards to how low conditions will get or if it'll persist long after precip ends.

Outlook...

Friday through Friday night...Mostly IFR conditions, along with periods of rain during the daytime Friday.

Saturday...Conditions likely improve to VFR.

Sunday and Monday...Rain and snow likely (50-70%) that will result in restrictions. North/northeasterly winds up to 25 kts Sunday becoming Northwest on Monday.

MARINE

Winds and seas generally remaining below SCA levels today and tonight. Seas will be mostly to 5 ft on the ocean and 1 to 2 ft for Delaware Bay. There will be some fog on the waters early this morning, but then fair weather for the day. Showers are expected tonight along with more areas of fog.

Regarding the river/marine ice, Delaware Bay continues to be mainly ice free outside of shallow near-shore areas. Ice coverage remains around 10-30% from the the Delaware Memorial Bridge up to the Commodore Barry Bridge. North of that up through Philadelphia, ice coverage is around 30-70%.

Ice coverage will continue to decline with warmer temperatures for the rest of the week.

Outlook...

Friday through Saturday night...The conditions are anticipated to be below Small Craft Advisory criteria.

Sunday and Monday...Small Craft Advisory conditions expected. A period of gale or even storm force winds/gusts possible, depending on the track and strength of a coastal storm moving offshore.

EQUIPMENT

The KDIX radar is back in service, however some additional work will be required through the end of the week.

PHI WATCHES/WARNINGS/ADVISORIES

PA...Winter Weather Advisory from 7 PM this evening to noon EST Friday for PAZ054-055. NJ...Winter Weather Advisory from 7 PM this evening to noon EST Friday for NJZ001. DE...None. MD...None. MARINE...None.