textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

A Small Craft Advisory was issued for tomorrow morning for all marine zones, continuing through the day on Wednesday.

No significant changes to the snow forecast tonight. 1-3" of snow expected north of I-78, with amounts under an inch expected south of that point.

Potential for some wintry weather Thursday and Thursday night has diminished a bit, while the risk for same early next week has increased a bit.

KEY MESSAGES

1. A clipper system brings light snowfall tomorrow morning, mainly for the northern half of the area.

2. Low pressure slides south of the region, bringing a chance for rain and snow Thursday through Thursday night.

3. Another low pressure may move into the region early next week, producing another chance of wintry weather.

DISCUSSION

KEY MESSAGE 1...A clipper system brings light snowfall tomorrow morning, mainly for the northern half of the area.

An area of low pressure moves through Southern Ontario tomorrow morning, clipping the area and bringing some light snow to the region. The system is relatively moisture starved and fast moving, though the timing of most of the snowfall falling on or just before the morning commute could result in some elevated impacts.

Precipitation will start as snow and overspread the area between 2-4 AM continuing through about 8-10 AM. For South Jersey and Delmarva, QPF amounts are the lowest and any snow will transition to light rain. The remainder of the area should see all snow with this system but the fast moving nature of this system will limit snowfall amounts. Overall, we are expecting 1-3" of snow north of I-78, with a coating up to an inch anticipated south of I-78 to about the Philly metro area. Elected not to issue an Advisory as the HREF probability of 3" or more is less than 10%, even in the Poconos.

Any snow that does fall should melt rather quickly tomorrow as temperatures climb well into the 40s. This should also aid in the snow melt from the most recent winter storm.

KEY MESSAGE 2...Low pressure slides south of the region, bringing a chance for rain and snow Thursday through Thursday night.

A wave of low pressure will pass west-to-east south of the region Thursday into Thursday night. This will provide another opportunity for some wintry weather as we'll have marginally cold air in place behind tomorrow's system. The latest trend, however has been a bit further south with it, lessening the risk of a significant intersection of colder air and precipitation. Thus, for the moment we have mainly chance POPs for snow across our northern tier Thursday into Thursday night, with chance POPs of rain/snow mix across a central slice of the CWA including Philadelphia. Further south, we do have some likely POPs, but at this point temps look warm enough for plain rain across the Delmarva and far southern NJ. We'll continue to monitor, but at this time this mainly looks like a sub advisory event should it occur, and its possible little or no wintry precip occurs.

KEY MESSAGE 3...Another low pressure may move into the region early next week, producing another chance of wintry weather.

Milder weather will prevail over the weekend in the wake of the Thursday night system, with highs in the 40s for much of the region Friday-Sunday and possibly topping 50 in some areas Saturday. This should help melt some of the existing snow pack.

However, a front will send more cold air into the region later Sunday, and hot on its heals some guidance depicts a wave of low pressure riding eastward into the region for Monday. With fresh cold air in place, more wintry weather is certainly possible, though its notable that not all guidance is showing a significant system, some guidance depicting the system much weaker and drier. Thus, while its definitely on our radar, there's not much more to say about it just yet. This could be a bit more substantial than what we're expecting tonight/Wednesday and Thursday/Thursday night, but doesn't currently appear to have potential for a *major* event. More of a run-of-the-mill winter system, if it pans out.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

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

Rest of Today...VFR. A WNW wind 10-15 kt with gusts 20-25 kt. High confidence.

Tonight...VFR conditions to start. Sub-VFR conditions develop around 08Z-10Z with lowering CIGS and VSBY restrictions due to light snow or a rain/snow mix. Winds turn southerly around 5-10 kts. A brief period of LLWS is expected from around 07Z through 12Z. Moderate confidence.

Wednesday...Sub-VFR to start. Light rain/snow moves out by 15Z with the lower ceilings scattering out. Prevailing VFR after around 15Z at all terminals. Moderate confidence.

Outlook...

Wednesday night...VFR. No significant weather.

Thursday through Thursday night...Sub-VFR possible due to rain and snow potential.

Friday through Friday night...Sub-VFR possible in rain and snow potential early in the morning then VFR.

Saturday through Sunday...VFR.

MARINE

The Small Craft Advisory has expired on Delaware Bay and was cancelled on the ocean. Sub-SCA conditions expected through the rest of the day. Winds will be out of the west around 10-20 kt and seas of 3 to 4 feet.

A new Small Craft Advisory was issued for the ocean beginning at 3 AM for coastal waters south of Manasquan Inlet, and beginning at 5 AM for coastal waters north of Manasquan Inlet and Delaware Bay. The SCA on the ocean goes through 6 PM Wednesday as seas of 4 to 7 feet are expected with gusts of 25-30 kt out of the southwest. For Delaware Bay, the SCA goes through 1 PM Wednesday as wind gusts will hover around 25 kt, also out of the southwest.

Regrading river ice, the Delaware Bay is ice free with 10-30% coverage of ice from the Commodore Barry Bridge up to Philadelphia. With warmer temperatures coming this week, the Delaware River up to Philadelphia should be ice-free relatively soon.

Outlook...

Thursday through Thursday night...Mostly sub-SCA conditions. VSBY restrictions in snow and rain.

Friday through Saturday...Sub-SCA conditions now expected.

CLIMATE

Storm total snowfall from the Sunday-Monday storm ranked 16th biggest on record in Philadelphia, 10th biggest in Trenton and 7th biggest in Atlantic City if we include the downtown station data, 6th if we exclude it (typically we exclude downtown because the airport's climate can be notably different 10 miles inland).

Since we are now outside our main big snowstorm window (mid-Jan to mid-Feb), it turns out this was the biggest storm for so late in the year since 1958 in Trenton, 1915 in Philadelphia, and *EVER RECORDED* in Atlantic City, even when we include the downtown station data. For Philadelphia and Trenton, it was the biggest snowstorm since 2016, while in Atlantic City it was the biggest since 2010. For Philadelphia and Trenton, it was the first time a foot or more of snow fell after mid-February since the March 1993 storm.

PHI WATCHES/WARNINGS/ADVISORIES

PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory from 5 AM to 1 PM EST Wednesday for ANZ430-431. Small Craft Advisory from 5 AM to 6 PM EST Wednesday for ANZ450. Small Craft Advisory from 3 AM to 6 PM EST Wednesday for ANZ451>455.