textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Snowfall potential Tuesday night has decreased with best chance for snow shifting south.

KEY MESSAGES

1. Below normal temperatures will continue this week with many areas remaining below freezing. Dangerously cold wind chills return for the weekend.

2. Two opportunities for light snow to occur across the region this week. The first is Tuesday night and the second on Friday.

DISCUSSION

KEY MESSAGE 1...Below normal temperatures will continue this week with many areas remaining below freezing. Dangerously cold wind chills return for the weekend.

Outside of today, temperatures for the rest of the week will remain seasonably cool where highs will generally be in the mid 20s to low to mid 30s. Another Arctic front arrives by Friday night and highs over the weekend and into early next week look to be in the teens and 20s once again.

In terms of low temperatures, anticipate mainly the single digits and teens with the exception of Tuesday night. By the weekend, lows will range from the single digits to as low as 5 below zero. Wind chills will once again return to dangerously cold levels over the weekend, where another round of cold weather headlines may be warranted towards the end of the week.

KEY MESSAGE 2...Two opportunities for light snow to occur across the region this week. The first is Tuesday night and the second on Friday.

Surface high pressure remains over the Southeast coast Tuesday before moving out into the western Atlantic Tuesday night. A broad upper trough digs down into the Southern Plains and into the Gulf Coast states while a closed mid-level low tracks across Ontario and Quebec. Associated strong shortwave energy passes across the Northeast as a weak surface low originating from the Midwest approaches the Middle-Atlantic late Tuesday. These features then pass through the area overnight on Tuesday into Wednesday morning. This system is quite weak in nature and moisture starved. Latest model consensus has decreased the overall snowfall potential across the region, showing drier air likely dominating across the northern half while the southern half of the area could still see some light accumulations. In terms of snowfall amounts, expecting a coating to an inch of snow in most places, especially south of the PA Turnpike and I-195. For areas further north, perhaps some flurries but no accumulations expected. Overall, minimal impacts are expected with snow ending by Wednesday morning.

The next chance for snow arrives on Friday and possibly into Friday evening. A strong clipper system moves by to the north and an associated Arctic front will cross the region. It's too early for any specifics on this system, but a period of light snow and/or snow squalls are probable.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

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

Tuesday...Prevailing VFR. Light and variable winds during the morning becoming west to southwest in the afternoon. SCT/BKN 050-080 deck in the afternoon. Moderate confidence.

Tuesday night...Prevailing VFR with sub-VFR cigs and light snow possible for terminals PHL and south. Low confidence overall, but greatest potential for -SN at MIV/ACY.

Outlook...

Wednesday through Thursday night...VFR. No significant weather expected.

Friday...Prevailing VFR with sub-VFR conditions possible with a period of light snow and/or snow squalls.

Friday night through Saturday...VFR. Gusty winds up to 30-35 kt possible. Otherwise, no significant weather expected.

MARINE

Sub-SCA conditions expected through Tuesday night.

Regarding the river ice threat...Ice has formed across area bay waters and inland estuaries. This includes, but is not limited to the Delaware estuary. On rivers, the ice has grown in thickness enough to start causing restrictions in flow. An example of this can be seen at the Trenton River gauge. Per satellite imagery, the Delaware River is pretty much ice covered from just south of Trenton upstream to about Washington Crossing.

The most common ways river ice can break up is either through a thermal or mechanical means. We would like to see temperatures rise into the 40s for a few days, but that's not expected this week into the weekend. Rainfall, producing river rises, can also break up ice. But again, that's not in the forecast either this coming week.

As a result, we expect the ice we're seeing to expand before it contracts. Even though there may be a pause in the growth during the daylight hours this coming week, temperatures at night will support expansion.

Outlook...

Wednesday through Friday...No marine headlines expected. Winds mainly remain less than 20 kt with seas around 2-3 feet. Periods of light snow possible on Friday, otherwise fair weather expected.

Friday night through Saturday...Gale force conditions probable with seas up to 8 feet. Freezing spray likely.

PHI WATCHES/WARNINGS/ADVISORIES

PA...None. NJ...None. DE...None. MD...None. MARINE...None.