textproduct: Philadelphia/Mt Holly

SYNOPSIS

A low pressure system is approaching from the west today bringing rain to the area into tonight. The low will cross north of the area while its associated cold front will pass across region Wednesday into Wednesday night. A high pressure system will then build in to end the week and for the start of the weekend.

NEAR TERM /THROUGH TODAY/

Broad low pressure lies over the Great Lakes while a weak secondary low lies over the Tennessee Valleys. Both systems will lift to the northeast tonight, pushing a warm front north through the region. The warm front is struggling to lift north, especially over the terrain west of the Fall Line as cold air damming has been a bit stronger than forecast. As a result, some dense fog has developed. A Dense Fog Advisory is now in effect for portions of the Lehigh Valley and Poconos as visibility as low as a quarter mile is expected in some spots. Another weak area of low pressure will lift through the region Wednesday morning as a stronger warm front lifts north through the region. A cold front then approaches Wednesday afternoon.

In terms of sensible weather, rain continues to become more steady and persistent through this evening with that first low and warm front. Around midnight or so, rain tapers off, and then it will be warm and muggy for the overnight hours with fog and low stratus.

A second round of showers will impact the area in the pre-dawn hours into Wednesday morning as that second warm front with weak low pressure lifts north through the region. There should be enough elevated instability across Delmarva and southeast New Jersey as ML MUCAPE values will be up to 300 J/kg along with 0-6 km of Bulk Shear to allow a few rumbles of thunder.

Low clouds and patchy fog will persist through the morning and into early Wednesday afternoon. There should be enough breaks in the clouds in the afternoon to allow for some sunshine to develop.

As that cold front approaches Wednesday afternoon, some showers and possible thunderstorms may move into far western portions of the forecast area.

Lows tonight will generally be in the mid to upper 40s north and west of the I-95 corridor and in the low to mid 50s south and east of a line from Philadelphia to Wilmington. Lows will be in the upper 50s in southern Delmarva.

Highs on Wednesday will be quite mild, generally in the mid to upper 60s.

Rainfall amounts will range from around 1/2 inch to 3/4 inch.

SHORT TERM /TONIGHT THROUGH FRIDAY/

A cold front passes through the area Wednesday night and we see strong cold air advection with winds also increasing out of the west. Wind gusts will start to increase to 30-35 mph across the area with upwards of 40 mph in the Poconos. Lows Wednesday night will be in the upper 20s to mid 30s. Wind chill values will be in the 20s and potentially the teens in the Poconos. A few showers may linger early across our eastern zones Wednesday night as the cold front continues to clear the area.

Winds continue to increase for Thursday and Friday with cold air continuing to filter in. For Thanksgiving, the day looks dry but cold and windy. Highs are in the mid 30s to mid 40s. Gusty winds out of the west at 30-40 mph. Lows Thursday night are in the 20s. Wind chills will be in the teens when you factor in the windy conditions.

Friday looks to be the windiest day with gusts out of the west- northwest at 35-45 mph. In this set-up, with all the cold air filtering in across the region, there will be ongoing lake-effect snow showers upstream of our area. Due to the wind shift to have a more NW component, we have the potential to see some snow showers in the Poconos and northern NJ on Friday. Highs on Friday are in the mid 30s to mid 40s.

LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/

Our winds do start to decrease Friday night as a surface high builds in and moves overhead into Saturday. This will keep us dry Friday night into Saturday.

For the weekend, it is a colder start with highs on Saturday in the mid 30s to low 40s. By Sunday, temperatures start to climb back into the upper 40s to upper 50s for highs. On Monday, highs reach into the 40s for most. There is also the signal for another system to bring increasing precipitation chances on Sunday into Monday.

AVIATION /06Z WEDNESDAY THROUGH SUNDAY/

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

Through 12z...IFR/LIFR conditions at the Lehigh Valley as the warm front is struggling to move through, resulting in patchy fog and low conditions. KRDG has been in and out of fog. KABE should stay IFR though cannot rule out periods of LIFR there. For the I-95 terminals, IFR expected through the rest of tonight with low CIGs but cannot rule out periods of IFR VSBYs as well. For the South Jersey terminals, the warm front lifting through has resulted in VFR, which should continue for the next few hours. Conditions lower back to MVFR and then IFR as another round of rain moves through around daybreak and through the mid to late morning. The low-level jet is still positioned over South Jersey, so some low-level wind shear is possible at these terminals through 09z-10z. Light southwest winds around 5 kt. Low confidence in timing and extent of restrictions.

Today...IFR through the morning, improving to MVFR and quickly up to VFR by the early to mid afternoon. Moderate confidence in timing and extent of restrictions. Winds southwest around 5-10 kt.

Tonight...VFR. Gusty westerly winds pick up with the passage of a cold front with 10-20 kt sustained and 20-30 kt gusts between 23z and 01z. High confidence in prevailing VFR. Moderate confidence in timing of frontal passage.

Outlook...

Wednesday night through Friday...VFR. Gusty west to northwest winds, especially Thursday and Friday.

Saturday...VFR. West-northwest winds 5-10 knots.

Sunday...Sub-VFR possible in rain. South wind 5-10 knots.

MARINE

Small Craft Advisory conditions develop on the ocean waters tonight. South winds 10 to 15 kt with gusts up to 20 kt through this evening, then winds increase to 15 to 20 kt with gusts up to 25 kt. Though there may be a lull in 25 kt gusts Wednesday morning, winds ramp back up in the afternoon. Will keep the SCA in effect. Winds on Delaware Bay will be a bit lower, hence no SCA for those waters for tonight through Wednesday.

Seas 2 to 3 ft, building to 3 to 5 ft Wednesday afternoon.

Visibility restrictions in rain and fog tonight through late Wednesday morning. A few thunderstorms are possible on the southern ocean waters late tonight through Wednesday morning.

Outlook...

Wednesday night through Thursday...A Small Craft Advisory is in effect with a west-northwest wind 25-30 kt and seas 4-6 feet.

Thursday night through Friday...A Gale Watch has been issued for all marine zones with a west wind of 35-40 kt and seas of 5-7 feet.

Friday night...SCA conditions expected with 25-30 knot winds and seas near 5 feet.

Saturday...SCA conditions possible early but winds and seas quickly subsided through the day.

Sunday...Conditions are expected to be below SCA criteria.

PHI WATCHES/WARNINGS/ADVISORIES

PA...Dense Fog Advisory until 10 AM EST this morning for PAZ054-055- 060>062-101-105. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory from 10 PM this evening to 6 PM EST Thursday for ANZ430-431. Gale Watch from Thursday evening through Friday afternoon for ANZ430-431-450>455. Small Craft Advisory until 6 PM EST Thursday for ANZ450>455.