textproduct: Philadelphia/Mt Holly

SYNOPSIS

High pressure will weaken across the area today. Meanwhile, low pressure will approach from the west on later today, bringing the start of unsettled weather. The low will cross north of the area while its associated cold front will pass across the Middle Altantic area Wednesday. Another high pressure system will build in to end the week and for the start of the weekend.

NEAR TERM /THROUGH WEDNESDAY/

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. Broad low pressure will lie over the northern Great Lakes as that secondary low will track over eastern Pennsylvania and New Jersey this evening. 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 develops late this afternoon and becomes more steady and persistent into 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 /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/

The cold front continues to move away Wednesday night as high pressure from the Ohio Valley begins to build towards our area. A cold West wind will bring decent cold air advection to the region. Showers will diminish Wednesday evening and clearing skies follow for Thursday. Temperatures will drop into the 30s Wednesday night, but then only rise into the 40s for Thursday. Temps for Thursday will be around 5 degrees below normal for late November. Winds will gust between 20 and 25 mph much of the day.

LONG TERM /FRIDAY THROUGH TUESDAY/

As we head into the end of the week and early weekend period, we'll get a preview of early winter temperatures and gusty winds across the area as strong low pressure pulls away across Quebec while high pressure moves into the Ohio Valley. We are not expecting any widespread precipitation for the area, but a few snow showers across the southern Poconos or north NJ are possible Friday.

Highs Fri/Sat will be in the low/mid 40s most areas with mid/upper 30s for NW most spots. Lows will be in the 20s Fri and Sat mornings. These temperatures will generally be 4 to 6 degrees below normal. The gusty winds, especially Friday, will produce wind chills 5 to 10 degrees cooler than the air temps.

The high will crest over the area later Sat and then move offshore Sunday. This will result in milder conditions with a return to more normal temps Sun/Mon. The milder air arrives with an increased chance for rains with slight chances for Sunday (20%) then a chance for Monday (around 30%)

AVIATION /18Z TUESDAY THROUGH SUNDAY/

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

Rest of today...CIGs and VSBYs will lower to MVFR from west to east from 20Z to 22Z as RA develops. S to SE winds less than 10 kt. 40 KT of SW LLWS will develop along and southeast of the I-95 corridor terminals after 22Z. High confidence on MVFR conds developing, low confidence on timing.

Tonight...IFR CIGs/VSBYs with CIGs as low as LIFR tonight in RA and stratus. Although rain ends by 05Z, VSBYs will be restricted in BR. Another round of SHRA will develop after 09Z. Light S winds. 40 to 45 KT of SW LLWS through around 06Z. Moderate confidence overall.

Wednesday...IFR CIGs with MVFR VSBYs through the morning. Some SHRA will pass through the terminals through 15Z or so. Conds should lift to VFR after 18Z. S to SW winds 5 to 10 kt, increasing to 10 to 15 kt with gusts up to 20 kt late in the day. High confidence overall, low confidence on timing.

Outlook...

Wed night... Isolated showers for the northern sites (TTN) for the evening, otherwise VFR expected with gusty West winds continuing.

Thu/Friday... VFR gusty West to Northwest winds.

Saturday... VFR expected.

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...

Gales will continue across the waters Friday/Friday evening before winds and seas begin to diminish, slowly. SCA conditions will be across the waters after that into Saturday. No significant weather is expected.

After that, winds and seas will remain below SCA levels for the rest of the weekend. On Monday, low-end SCA gusts may develop on the waters. Fair weather Sat night/early Sunday then slight chances (20%) for rain later Sunday. A chance for rain Monday (30%).

PHI WATCHES/WARNINGS/ADVISORIES

PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory from 10 PM Wednesday to 6 PM EST Thursday for ANZ430-431. Small Craft Advisory from 7 PM this evening to 6 PM EST Thursday for ANZ450>455.