textproduct: Philadelphia/Mt Holly

SYNOPSIS

A cold front will traverse the region this evening. High pressure will briefly build in through Saturday night. 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 southeastern CONUS 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/

For tonight, low pressure to our north pulls farther away while high pressure approaches as it advances eastward through the Ohio Valley. This will result in a weakening pressure gradient with time and so winds/gusts have diminished, generally around 10 mph or so from the west. Lows tonight will be in the 20s with wind chills in the teens to low 20s with skies generally mostly clear.

For Saturday, high pressure will build eastward setting up pretty much right over our area by late day. As a result, while temperatures will be very similar to Friday (highs mainly in the low 40s) the winds will be much less at around 5-10 mph so the wind chill will not be as significant of a factor compared to Friday. Otherwise expect a mainly sunny and dry day.

SHORT TERM /TONIGHT THROUGH MONDAY/

Subtle ridging aloft Saturday night will quickly give way to mid- level height falls as a trough axis shifts eastward through the Great Lakes on Sunday. The trough axis will pass near or just north of the area Sunday night. Subtle height rises will occur through Monday as the trough departs. At the surface, high pressure will quickly depart to the east by Sunday morning as the next storm system approaches from the west. A surface low will track to our north through the day Sunday and into Sunday evening with a trailing cold front passing through Sunday night.

Saturday night may start out mostly clear, but clouds should fill in from west to east through the night. With the cold airmass already in place, and light winds to start the night, it should be fairly chilly, with lows in the mid-upper 20s across most of the area. With southeasterly wind beginning to increase, temperatures may bottom out relatively early in the night before beginning to increase slightly.

Widespread but mostly light precipitation will overspread the area on Sunday. Along and especially northwest of I-95, precipitation may start as a rain and snow mix, with all snow for the Poconos. As temperatures warm through the day, precipitation should transition to all rain. Some light snow accumulation will be possible for the Poconos. Regarding rainfall, amounts will generally be around 0.25", with isolated areas potentially seeing slightly more or less. Highs on Sunday look to be in the mid 30s for the Poconos, the mid-upper 40s for the remainder of our eastern PA counties and much of NJ, and the low-mid 50s across the Delmarva and the Coastal Plain.

Rain will come to an end across the area Sunday evening from west to east with the passage of the cold front. Lows Sunday night will be in the upper 20s to low 30s. Monday will be dry but chilly, with highs generally in the low 40s. For the Poconos, temperatures may remain near to slightly above freezing. Breezy northwesterly wind can be expected behind the front Sunday night into Monday, with gusts to around 30 mph.

LONG TERM /MONDAY NIGHT THROUGH FRIDAY/

Monday night currently appears mostly dry with high pressure over the area beginning to retreat northeastward. Low temperatures should be in the 20s for most. Low pressure will be developing over the southeastern US, and will begin to approach the area by daybreak Tuesday. It currently appears that the low will make its closest approach to the area Tuesday afternoon, and begin departing to the northeast by Tuesday night.

Widespread precipitation is expected with this system. Right now, have chance PoPs moving into portions of the Delmarva and eastern PA during the pre-dawn hours on Tuesday. PoPs are highest Tuesday afternoon and evening, in the 70-80% realm areawide. Precipitation chances should wind down fairly quickly overnight Tuesday night, with the entire region precipitation- free by Wednesday morning.

Regarding the potential for accumulating snowfall: models are in good agreement this afternoon regarding the track of the low and its associated features. With that said, even subtle shifts could have big impacts given it currently appears likely that the rain to snow line will fall somewhere in our forecast area, with accumulating snowfall increasingly likely for some. In looking at the overall pattern, high pressure looks to retreat northeastward with the approach of the low. This will tend to favor onshore flow and marine influence affecting temperature profiles for many. Initially, snow or a rain and snow mix could be possible as far south as the I-95 corridor, with all snow favored northwest of the fall line, and all rain favored to the southeast of I-95. Through the day Tuesday, the rain snow line will likely shift northwest. At the peak of precipitation coverage and intensity, all snow is possible for the Poconos and into adjacent portions of far northwestern NJ, a rain snow mix will be favored northwest of the fall line, and all rain elsewhere. It is too soon to get overly specific with amounts, but DESI probabilistic guidance suggests around a 50% of snow accumulation exceeding 1" for the Lehigh Valley and points northwest, and around 70% for the Poconos. A cold, soaking rainfall is likely elsewhere. High temperatures could vary widely on Monday, with temperatures mostly in the 30s for the Lehigh Valley and points north and west, the low 40s for most of NJ and the Delmarva, but potentially as high as the low 50s for the Coastal Plain where the marine influence is most felt.

After the low departs Tuesday night, dry conditions are expected through Friday. A cold front looks to bring a reinforcing shot of cold air Thursday night into Friday, but for now it looks like precipitation chances will be quite slim.

AVIATION /06Z SATURDAY THROUGH WEDNESDAY/

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

Tonight...VFR/SKC expected with a few low clouds at times. Westerly winds around 5-10 kt. High confidence.

Saturday...VFR/SKC with a few high clouds late in the day. W-NW winds around 10 kt. High confidence.

Outlook...

Saturday night...Primarily VFR. Sub-MVFR ceilings can't be ruled out in low clouds moving in by daybreak Sunday.

Sunday through Sunday night...Sub-VFR conditions are expected in periods of rain and low clouds. Rain will clear the area Sunday evening, but low clouds could linger through most of the night.

Monday through Monday night...Primarily VFR. Slight chance (20%) of sub-VFR conditions in rain or snow late Monday night.

Tuesday through Tuesday night...Sub-VFR conditions are expected in periods of rain and snow for the northwestern terminals, and in rain elsewhere. Conditions should improve by late Tuesday night.

Wednesday...VFR. No significant weather.

MARINE

Winds have decreased and the Gale Warning has been cancelled as a result. A Small Craft Advisory is now in place through 7 AM for all coastal waters as westerly winds continue to gust up to 30 knots with seas around 3-5 feet. A few gusts up to 35 knots remain possible early this morning for coastal waters north of Manasquan Inlet off the coast of New Jersey.

Winds will continue to decrease into daytime Saturday so following the end of the current SCA, conditions should be sub- SCA criteria through Saturday night. Winds 10-15 knots with a few gusts up to 20 knots, out of the west during the day Saturday, and turning southerly Saturday night. Seas decreasing to 1-3 feet.

Outlook...

Sunday through Monday...SCA conditions are expected beginning Sunday with south winds increasing to 20-25 kt, with gusts near 30 kt. Winds will shift to northwest Sunday night, but remain elevated. Winds should diminish by Monday afternoon. Seas 4-6 feet.

Monday night...No marine headlines anticipated with wind below 25 kt and seas below 5 feet.

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

PHI WATCHES/WARNINGS/ADVISORIES

PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory until 7 AM EST this morning for ANZ430- 431-450>455.