textproduct: Philadelphia/Mt Holly

SYNOPSIS

Low pressure passes north of the area today and drags a cold front through the region later this afternoon. An upper trough lies over the Northeast as high pressure builds into the Central United States. Several week upper level disturbances will pass through the region later this week, then low pressure may approach the Mid-Atlantic this weekend.

NEAR TERM /THROUGH TONIGHT/

Rapid height falls and intensifying southwesterly wind aloft are overspreading the region early this morning as an upper-low shifts east from the Great Lakes into southern portions of Ontario. Strong shortwave energy embedded within cyclonic flow aloft will pass through the region through late this morning and into early this afternoon as the upper-low continues eastward into southern portions of Quebec. Tonight, winds aloft will veer to more of a westerly direction as the upper-low passes due north of the area. At the surface, a warm front will continue to lift north through the area during the pre-dawn hours. A cold front trailing an occluding surface low will pass through the region from west to east beginning this afternoon, clearing the coast by early evening. Surface pressure will begin to rise slowly tonight as the occluded low meanders over Quebec.

Fog (some dense) has developed early this morning generally along and northwest of I-95. This will continue through sunrise, before fog starts to diminish. Visibilities below a quarter mile are expected to continue at times, and a Dense Fog Advisory is in effect for these areas until 10 AM to account for this.

With strong warm air advection in the wake of the passing warm front, temperatures will rise substantially ahead of the cold front. Temperatures are expected to max out in the mid-upper 40s across the Poconos, Lehigh Valley, and adjacent northern areas of NJ, low-mid 50s across the remainder of eastern PA and most of southern NJ, and perhaps around 60 for southern portions of the Delmarva. A band of showers is expected to pass through the area from west to east ahead of the cold front late this morning into early this afternoon. Rain amounts should be fairly light, ranging from around a tenth of an inch to a quarter inch. Forecast soundings indicate very little, if any, elevated instability accompanying these showers, so thunder is not expected. With that said, the winds aloft will be quite strong, so it is not out of the question that these showers aid in mixing down some of the stronger winds, though likely sub- severe.

After the showers depart and the cold front comes through, some cloud clearing is expected, but temperatures will rapidly drop into the 30s. In addition, strong west winds will develop, with gusts 40-50 mph possible over the entire area. A Wind Advisory will be in effect starting at 10 AM.

Gusty winds will continue through the night tonight with with Wind Advisory remaining in effect. There will be scattered clouds around, but with the strong cold air advection regime in place, expect low temperatures ranging from the upper teens across the higher elevations of eastern PA and northern NJ to the mid 20s elsewhere.

SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/

A tight pressure gradient remains over the Northeast between deepening low pressure near the Gulf of Maine and Canadian Maritimes and high pressure over the Southern Plains and Gulf Coast states. West to northwest winds will range from 20 to 30 mph with 40 to 50 mph gusts through midday or so, then winds diminish in the afternoon. A Wind Advisory remains in effect for the whole area through 1 pm Tuesday, though it may have to be extended by a few hours for the southern Poconos. A cold day on tap with highs mainly in the low to mid 30s. Minimum wind chill values Tuesday morning will be in the single digits in the southern Poconos and otherwise in the teens and low 20s.

Low pressure departs Tuesday night and winds diminish, but still remain somewhat elevated at 10 to 15 mph with gusts up to 20 mph. Skies will be cloudy as shortwave energy passes through the region, so that will keep optimal radiational cooling conditions from developing. Still cold with lows in the low to mid 20s for most of the area, except in the teens for the southern Poconos.

An upper trough remains over the Northeast through the mid-week period and several strong shortwaves will dive into the base of the trough. This will bring some snow to the southern Poconos, Lehigh Valley, and far northwest New Jersey Wednesday afternoon, then another shot of snow down to the I-95 corridor Wednesday night as a stronger shortwave passes through the region. QPF will be minimal, and as a result, minimal snowfall can be expected with an inch or so in the southern Poconos and less than an inch down through the Fall Line.

Highs on Wednesday will be in the mid and upper 30s and lows Wednesday night will be in the teens and low 20s as some colder air filters into the region behind that shortwave.

LONG TERM /THURSDAY THROUGH SUNDAY/

Below normal temperatures will be the rule through the end of the week and next weekend, and precipitation chances will be minimal, at best. Some lingering snow is possible on Thursday, but PoPs will be capped at slight chance. Dry through Friday. Low pressure develops over the Gulf Coast states and looks to take a run at the Mid-Atlantic area next weekend, but it remains to be seen how strong high pressure will be north of the area and if it can keep the low well south of the area. For now, mostly slight chance PoPs with low chance PoPs for southern Delmarva.

Highs through the week will mostly be in the 30s and lows will mostly be in the teens and 20s.

AVIATION /12Z MONDAY THROUGH FRIDAY/

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

Today...IFR/LIFR ceilings at all terminals excluding KMIV to start, which is MVFR and may fluctuate between MVFR and IFR. Visibility restrictions in fog for KPNE northward expected to linger through 12-14Z. Showers will progress eastward across the area through 18-19Z. LLWS will also continue through 17-18Z. After 17Z-18Z, ceilings should lift/scatter to VFR. Southwest wind 10-15 kt gusts around 20 kt initially, turning west this afternoon and increasing to 15-25 kt with gusts generally 35-40 kt. Moderate confidence.

Tonight...VFR. West wind continues around 15-25 kt with gusts 30-35 kt. High confidence.

Outlook...

Tuesday through Tuesday night...VFR. W-NW winds 20 to 30 =kt with 35 to 40 kt gusts during the day, diminishing to 10 to 15 kt with gusts up to 20 kt Tuesday night.

Wednesday through Wednesday night...VFR during the day, then sub-VFR in SN possible at night, mostly at KRDG/KABE/KTTN.

Thursday through Thursday night...VFR. Some SN possible at KRDG/KABE/KTTN during the day.

Friday...VFR.

MARINE

A Gale Warning is in effect until 6 PM Tuesday for all NJ and DE Atlantic Coastal waters as well as the Delaware Bay.

South- southwest wind 15-20 kt with frequent gusts to 25 kt, with seas 4-7 feet this morning. This afternoon, wind will become west at 25-35 kt with gusts upwards of 40 kt. Seas increase to 5-9 feet this afternoon into tonight before beginning to decrease during the pre-dawn hours Tuesday.

Outlook...

Tuesday through Tuesday night...Gale Warnings are in effect for Tuesday for W-NW winds gusting 35 to 45 kt. Winds diminish Tuesday night, and a SCA will be needed for winds gusting 25 to 30 kt.

Wednesday through Wednesday night...An SCA may be needed for winds gusting to 25 kt.

Thursday through Friday...Sub-SCA conditions.

PHI WATCHES/WARNINGS/ADVISORIES

PA...Wind Advisory from 10 AM this morning to 1 PM EST Tuesday for PAZ054-055-060>062-070-071-101>106. Dense Fog Advisory until 10 AM EST this morning for PAZ054-055- 060>062-070-101>106. NJ...Wind Advisory from 10 AM this morning to 1 PM EST Tuesday for NJZ001-007>010-012>027. Dense Fog Advisory until 10 AM EST this morning for NJZ001- 007>010-012-015. DE...Wind Advisory from 10 AM this morning to 1 PM EST Tuesday for DEZ001>004. MD...Wind Advisory from 10 AM this morning to 1 PM EST Tuesday for MDZ012-015-019-020. MARINE...Gale Warning until 6 PM EST Tuesday for ANZ430-431-450>455.