textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

The risk of light rain changing to light snow, followed by rapidly falling temperatures and leading to icy roads, has become a greater concern for Wednesday night and Thursday morning.

KEY MESSAGES

1) A storm system will bring light rain which will change to snow before ending Wednesday night, especially north and west of I-95.

2) Rapidly falling temperatures early Thursday morning, combined with the prior light rain/snow, may result in icy roads.

3) The risk of wintry weather through the rest of the period remains low, but cold temperatures mean any changes could result in a return of the chance of snow.

DISCUSSION

KEY MESSAGE 1...A storm system will bring light rain which will change to snow before ending Wednesday night, especially north and west of I-95.

Low pressure will strengthen as it passes northeastward across the region Wednesday night. Light rain is likely to develop as it crosses the region, with guidance currently focusing the majority of precip northwest of I-95. As the low continues strengthening and then starts moving northeast of the region, this will bring the risk of lingering rain changing to snow before ending. This is most likely in the southern Poconos, where around an inch of snow is currently forecast, but enough potential exists further south to include a light accumulation (less than an inch) through most of the remainder of the forecast area, though this is more likely north and west of I-95 than southeast of it. Temps will start warm, but will cool as the system moves through. Precip likely ends before dawn Thursday morning region-wide, though some light snow showers may linger in the Poconos much of the day Thursday.

KEY MESSAGE 2...Rapidly falling temperatures early Thursday morning, combined with the prior light rain/snow, may result in icy roads.

While precip is expected to have ended before dawn Thursday, resulting in a technically dry rush hour, the gusty northwest winds behind the system will likely push temps down into the 20s region-wide by dawn. Thus, anything that doesn't dry out has a shot at becoming icy, and this risk is higher for areas where snow accumulates before precip ends. As mentioned above, this risk is highest in the Poconos, and generally higher anywhere northwest of I-95 than southeast of it, the risk is non-zero across nearly the entire region. For those few who ventured out shortly after dawn on New Years Day, this may not be dissimilar; roads were extremely icy in many areas. The big difference here is that instead of a holiday, Thursday is a standard weekday, so the result could be much more significant from a traffic standpoint. Making matters more complicated will be the likelihood of rain before any changeover, which may wash off any pre-treatment of surfaces. One fortunate aspect is that, unlike before New Years Day, temps will be averaging milder today and Wednesday, so pavement will be a little less inclined to flash freeze, but the rapid air temp drop makes this a risk nonetheless.

KEY MESSAGE 3...The risk of wintry weather through the rest of the period remains low, but cold temperatures mean any changes could result in a return of the chance of snow.

A generally cold pattern looks likely through the weekend into early next week. Pieces of energy which could, theoretically, combine and result in a risk of wintry weather (given conducive temps) are currently progged to remain generally separate, keeping our region in a relative dry slot as they veer either northwest or southeast of us. Currently have just slight chance to low end chance POPs for the weekend period because of this relative separate of energy. We'll need to keep a close eye out given the cold will be present, but at this time the risk of significant wintry weather beyond Thursday through early next week appears low.

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 with high clouds increasing. Southwest winds up to 10 knots. High confid.

Tonight; VFR. High clouds with mid clouds increasing. LLWS developing with 40 to 45 kts at 020. South to Southwest winds 5 to 10 knots. Gusts 15 to 20 kts possible KACY. Medium/high confid.

Wednesday... VFR. Mostly mid-level clouds with lower clouds late, mostly N/W. A small chance for a rain shower KRDG/KABE after 18Z. (Low confid in this however). South to Southwest winds around 10 knots. Medium confid overall.

Outlook...

Wednesday night...Restrictions likely developing Wednesday night in low clouds and periods of light rain/snow. Gusty WNW winds developing late Wednesday night.

Thursday...VFR. Gusty WNW winds.

Friday...VFR. Gusty SW winds possible. LLWS possible Friday night.

Saturday and Sunday...VFR most likely, but small chance of sub- VFR if light rain/snow develop.

MARINE

Winds and seas will increase tonight as low pressure moves by well to the north. Southwest winds will gust 25 to 30 kts tonight and Wednesday morning. The SCA flag is therefore continued. Fair weather tonight and Wednesday.

Outlook...

Wednesday night through Thursday...Small Craft Advisory conditions expected with WNW winds 20-30 kts, and a brief period of gale force wind gusts possible.

Thursday night...Freezing spray possible. Seas may linger near 5 feet across the Atlantic waters.

Friday through Sunday...SCA conditions likely at times. A slight chance of rain and snow Saturday and Sunday.

PHI WATCHES/WARNINGS/ADVISORIES

PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory from 6 PM this evening to 10 AM EST Wednesday for ANZ450>455.