textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

No significant changes were made as the cold front continues to track offshore. A Wind Advisory remains in effect for Carbon and Monroe counties for tonight. Some snow showers remain possible for the next few hours, but the threat of snow squalls is diminishing.

KEY MESSAGES

1) Snow showers/squalls possible into early evening. Gusty winds develop tonight.

2) Unsettled wintry weather with impacts possible mid to late this upcoming week.

DISCUSSION

KEY MESSAGE 1...Snow showers/squalls possible into early evening. Gusty winds develop tonight.

A strong, nearly vertically stacked, low pressure system over the Province of Quebec will continue to track east. A trailing cold front has shifted offshore. Strong shortwave energy with the trough has produced snow showers across our County Warning Area (north and west), and even some snow squalls, over western New York and western Pennsylvania. NAM BUFKIT soundings showed pretty steep low level lapse rates, along with a 40 kt or so low level jet. There was even be some modest instability with CAPE values of 100 to 200 J/kg.

Precipitation is currently drying up on radar, but the best chances the next few hours remain across the southern Poconos, far northwest New Jersey, and the Lehigh Valley. Temperatures have crashed in the cold air advection behind the front.

A tight pressure gradient develops over the area tonight between that aforementioned low pressure over the Canadian Maritimes and high pressure building into the Tennessee Valley and Mid- Atlantic. West to northwest winds will increase to 15 to 25 mph with 30 to 40 mph gusts across the majority of the area, and 20 to 30 mph with gusts up to 50 mph in the southern Poconos. A Wind Advisory is now in effect for Carbon and Monroe counties. for most of tonight. Winds diminish late. Wind chills tonight will generally be in the teens to low 20s, and in the single digits in the southern Poconos.

KEY MESSAGE 2...Unsettled wintry weather with impacts possible mid to late this upcoming week.

A few longer range models continue to show that low pressure and associated fronts may arrive over the Middle Atlantic region for the middle and late parts of the upcoming week. There is ample uncertainty with regards to the details presently to offer any specific details. We will continue with chance PoPs in the forecast for rains and snows during the Wednesday through Thursday night periods. Our temperatures forecast for these times would support snow for the, climatologically favored, N/W counties and mostly rain and perhaps some snow for S/E areas.

AVIATION /00Z MONDAY THROUGH FRIDAY/

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

Tonight...Any SHRA/SHSN will end by 02Z. VFR otherwise. W-NW winds 15 to 20 kt with 25 to 35 kt gusts, diminishing after 06Z, and eventually down to 5 to 10 kt after 09Z. High confidence.

Monday...VFR. W-NW winds 10 to 15 kt with 20 to 25 kt gusts in the morning, backing to the SW at 5 to 10 kt late in the afternoon. High confidence.

Outlook...

Monday night thru Tuesday night: VFR expected.

Wednesday thru Thursday: sub-VFR at times with lower CIGS and rains (S/E) and snows possible N/W.

MARINE

Gale Warning in effect. A cold front passes across the waters this evening. Brief VSBY restrictions are possible in snow showers, but coverage will be limited. NW winds ramp up to 20 to 30 kt with 35 to 40 kt gusts.

Winds diminish late tonight, and then a SCA will likely be needed for the waters into Monday morning.

After conditions subside to sub-SCA levels Monday morning, west to northwest winds will gust to 20 kt or so with 2 to 4 ft seas.

Outlook...

Winds and seas will remain below SCA levels Monday night and Tuesday with Fair weather expected. Beyond that, low-end SCA conditions for the ocean (mainly) are expected for Tue night and Wednesday and again for Thursday. Gales are possible for Thursday night and Friday. Rains and snows possible Wed thru Thursday night.

PHI WATCHES/WARNINGS/ADVISORIES

PA...Wind Advisory until 4 AM EST Monday for PAZ054-055. NJ...None. DE...None. MD...None. MARINE...Gale Warning until 6 AM EST Monday for ANZ430-431-450>455.