textproduct: Philadelphia/Mt Holly

SYNOPSIS

Cold and dry high pressure will briefly build in through tonight. A low pressure system and associated cold front will approach the region Sunday with the cold front passing through Sunday night. Low pressure will develop over the Southeast Monday night before tracking northeast towards our area Tuesday into Tuesday night. Another cold front will track through the region Thursday night, with high pressure building back in thereafter.

NEAR TERM /THROUGH TODAY/

A mid-level trough currently centered over the Northern Plains will track eastward towards the area tonight. The trough axis will lift northeastward Sunday, passing to the north of our area Sunday afternoon. H5 heights will fall Sunday morning into Sunday afternoon before subtle rises begin as the trough axis lifts away from the region. At the surface, high pressure in control tonight will quickly shift east Sunday morning as a subtle warm front approaches and moves through the area. A cold front trailing a low pressure system moving eastward through southern portions of Ontario and Quebec will track through the region Sunday evening.

A dry night is in store with increasing clouds. With the cold airmass in place, temperatures will still fall into the upper 20s for most, with low-mid 30s for the Coastal Plain and the urban corridor. Temperatures will probably bottom out earlier in the night than typical, with a slow rebound towards sunrise as subtle warm advection begins.

Light precipitation will begin to move into western portions of our area during the morning hours, and spread across the entire area by afternoon. Most locations will see a cold rain. Across the Poconos and perhaps into portions of far northwestern NJ, precipitation is expected to start as light snow, changing to a rain and snow mix during the afternoon. All precipitation will come to an end with the passage of the cold front during the afternoon and evening hours. Rainfall amounts look to generally be in the 0.15-0.25" range. Snow accumulations up to 1" are possible in the Poconos.

Afternoon highs will be in the mid-upper 30s for the Poconos, low- mid 40s elsewhere northwest of I-95, and upper 40s to near 50 southeast of I-95. For the Coastal Plain, temperatures could climb into the low 50s. It will also be breezy, with south- southwesterly winds gusting to 20-25 mph.

SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/

A cold front exits off to the east Sunday night with just the potential for a lingering rain shower mainly near the coastal areas early. Through the night we trend drier with decreasing clouds as a high pressure system builds in from the west. Lows Sunday night will be in the mid 20s to low 30s. It will also be breezy Sunday night with northwest wind gusting to 20-30 mph. This will lead to wind chill values in the teens to low 20s.

On Monday, we are dry with the high pressure system overhead. The high does start to move off to the northeast late Monday into Monday night. As the high departs, we see an increase in clouds by the second half of the day ahead of our next system. Highs on Monday are in the mid 30s to mid 40s. Winds will also gradually lessen through the day Monday and by Monday night winds are 5-10 mph out of the north before turning more out of the east through the night.

Speaking of Monday night, our next system arrives Monday night into Tuesday morning. There will be a low developing over the southeastern US and the high pressure system will retreat off to the northeast. As the high pressure system retreats, the low moves northeast. This low will make its closest approach to the area Tuesday afternoon, and begin departing to the northeast by Tuesday night.

In terms of the details with this system, widespread precipitation is expected. There are chance PoPs (30-40%) starting overnight Monday with the highest PoPs being Tuesday afternoon into the evening at around 80-90%. The precipitation ends from west to east pretty quickly Tuesday night as the low moves off to the northeast.

For the precipitation accumulation, the general QPF has been trending upwards with the system. Also, the system is moving faster which has it coming in earlier. Due to the earlier arrival time, there is the potential for light snow at the onset for much of the area and as far south as parts of Kent county Delaware and Talbot county Maryland. In New Jersey, this could result in some light snow at the onset as far southeast as Cape May. All of that said, this light snow will result in minimal accumulation and not last long as the low draws closer to the area.

Through the day Tuesday, the onshore flow and warm marine influence will impact the temperature profiles. By daybreak Tuesday, the rain/snow line is near or NW of I-95. As the warmer air continues to filter in, the rain/snow line may get as far NW as the Lehigh Valley by Tuesday afternoon. For perspective on this, the temperatures for highs on Tuesday are near freezing in the Poconos, upper 30s in the Lehigh Valley, near 40 degrees along the I-95 corridor, and in the mid 40s to near 50 in Delmarva and along the coastal areas. Although areas may start as snow, it does not appear that it will last for much of the area. Right now, the Poconos have the best potential at an all snow event from this system.

For the accumulation, the potential is increasing for plowable snow in the Poconos and areas NW of I-78. As you head, south and east of I-78, the potential for plowable snow quickly decreases. Also, outside of mainly the Poconos, the snow that falls will then be melting through the day with the warm air moving further inland. The areas that see all rain or a change to rain will have a good soaking rain.

Once the low departs Tuesday night, a high pressure system will build in from the southwest. This will lead to drier conditions through the night. Lows Tuesday night are in the 20s for most.

LONG TERM /WEDNESDAY THROUGH SATURDAY/

During the long term period, we have a high pressure system in control for the middle and end of the week. It is colder with highs on Wednesday and Thursday in the 30s and 40s. A cold front does look to cross the area Thursday into Thursday night. As the cold front passes through, there is the potential for an isolated snow shower. The main factor with this cold front will be the reinforcement of the cold air. By Friday, highs are in the low 30s to low 40s for most. Our next system looks to arrive late Friday into Saturday bringing another potential for widespread precipitation.

AVIATION /06Z SUNDAY THROUGH THURSDAY/

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

Tonight...VFR with increasing mid-level clouds. Winds light and variable, favoring a southeasterly direction around 3-5 kt after midnight. High confidence.

Sunday...VFR to start. Light rain will move in from southwest to northeast between 14-17Z, with MVFR ceilings accompanying it. Visibility restrictions are possible as well at times, as included PROB30 groups at all terminals. South-southwest winds around 10 kt with gusts up to 20-25 kt. Moderate confidence.

Outlook...

Sunday night...Restrictions possible with low clouds lingering through most of the night. WNW wind gusting 15-20 knots.

Monday through Monday night...Primarily VFR. Chance (30-40%) of sub-VFR conditions in rain or snow late Monday night.

Tuesday through Tuesday night...Restrictions expected in low clouds and periods of rain/snow for the northwestern terminals, and in rain elsewhere. Conditions should improve by late Tuesday night.

Wednesday...VFR. No significant weather.

MARINE

No marine headlines are expected through tonight as west- northwest winds around 5-10 kt slowly become south-southeast after midnight. Winds will begin to increase mid-morning Sunday to around 20-25 kt with gusts to 30 kt. Seas will increase to 4-7 feet. As a result, a Small Craft Advisory has been issued starting at 10 AM Sunday for the Atlantic Coastal Waters.

Outlook...

Sunday night...A Small Craft Advisory has been issued for Sunday night for all marine zones with a NW wind gusting to 25-30 knots and seas 4-6 feet.

Monday...SCA conditions possible in the morning with winds near 25 knots. The winds lessen through the day.

Monday night...No marine hazards anticipated with winds below 25 kt and seas below 5 feet.

Tuesday through Wednesday...SCA conditions likely with east winds increasing to near 25-30 kt and then becoming northwest Tuesday night into Wednesday. Winds look to diminish Wednesday afternoon. Seas 5-7 feet, also diminishing Wednesday afternoon.

Thursday through Thursday night...SCA conditions possible Thursday afternoon into early Thursday night as NW winds increase to near 25 knots and seas reach near 5 feet.

PHI WATCHES/WARNINGS/ADVISORIES

PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory from 10 PM this evening to 6 AM EST Monday for ANZ430-431. Small Craft Advisory from 10 AM this morning to 6 AM EST Monday for ANZ450>455.