textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

No significant changes at this time.

KEY MESSAGES

1. Turning windy and much colder on Thursday in the wake of a strong cold front.

2. Gusty winds continue on Friday and Saturday, increasing the risk for fire weather conditions.

3. A strong cold front moves through during Monday bringing precipitation followed by a surge of colder air.

DISCUSSION

KEY MESSAGE 1...Turning windy and much colder on Thursday in the wake of a strong cold front.

The cold front will be mostly offshore on Thursday, but it may be close enough for clouds and rain to impact most of New Jersey and Delmarva. Farther inland, with strong cold air advection developing behind the cold front, there may be some snow mixing with the rain before ending. Any snow accumulation will be minimal at best. Winds abruptly shift to the northwest and will range from 15 to 20 mph with 25 to 30 mph gusts. The high temperature will likely occur just after midnight, then will fall into the 40s and 50s by daybreak Thursday, before falling further into the upper 30s to low 40s late Thursday afternoon.

KEY MESSAGE 2...Gusty winds continue on Friday and Saturday, increasing the risk for fire weather conditions.

A strengthening low passing to our north across southern Canada Friday into Friday night will keep a strong gradient across our area to end the week and start the weekend.

As a result, southerly winds on Friday will potentially be around 15-25 mph with gusts of 30-40 mph possible. Robust mixing will also allow for RHs to drop to 30-40% across much of the area. On Saturday, winds will turn to the west after the passage of a front and likely remain elevated around 15-20 mph with gusts of 25-30 mph. The westerly winds will also be advecting in more dry air, with minimum RHs on Saturday of 20-30% across the region.

The combination of gusty winds and low RHs will lead to an increased risk of fire weather conditions. The main limiting factor will be fuel moistures. The entire region is expected to receive a wetting rainfall (0.1 inches of rain or more) Wednesday night through Thursday so the threat will be dependent on how quickly the strong winds and low RHs dry out the fuels. The passing front may bring a few showers to our area Friday night but an additional wetting rainfall is not expected with its passage.

KEY MESSAGE 3...A strong cold front moves through during Monday bringing precipitation followed by a surge of colder air.

As low pressure tracks just to our north Sunday night into Monday, a strong cold front will cross our area late Monday into Monday night. A plume of deeper moisture and stronger forcing for ascent should result in a period of rain ahead of the cold front itself later Sunday night and continuing through Monday. A milder air mass should be in place, therefore rain is expected. As some cold air begins to pour in later Monday a transition to some snow before ending is possible if enough moisture remains. The amount of precipitation and any snow will be highly dependent on the timing of the system, how much moisture is with it and how quickly the colder air moves in.

A robust period of cold air advection may follow into the middle of next week, resulting in a much colder air mass across our area. This may result in high temperatures Tuesday and Wednesday struggling to reach 40 degrees across most of our area.

AVIATION /06Z THURSDAY THROUGH MONDAY/

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

Rest of tonight...VFR ceilings with times of MVFR possible. Some showers around which will locally reduce the visibility for a time. Southwesterly winds less than 10 knots, becoming west to northwest 15-20 knots with gusts up to 25 knots toward daybreak. Moderate confidence overall.

Thursday...VFR ceilings with even a period of MVFR ceilings. MVFR visibility with some rain, which then mixes with and potentially changes to snow this afternoon. If all snow occurs and the intensity increases for a time, visibilities can drop to IFR or lower. Northwest winds 15-20 knots with gusts up to 30 knots, diminishing some by late afternoon. Low confidence.

Thursday night...VFR as the sky clears. West-northwest winds diminishing to 10 knots or less. Moderate confidence.

Outlook...

Friday...VFR. South to southwest wind gusts 25-35 knots, diminishing some at night.

Saturday and Sunday...VFR overall.

Sunday night and Monday...Sub-VFR conditions likely with rain expected.

MARINE

Small Craft Advisories remain in effect for all waters through Thursday.

South winds 15 to 20 kt with gusts up to 25 kt will veer to the southwest as the night progresses, then will abruptly shift tot he northwest Thursday morning behind the passage of a strong cold front. 25 to 30 gusts then expected on Thursday. Seas 3 to 5 ft this evening will build to 5 to 7 ft on Thursday.

Showers with isolated thunderstorms possible this evening, then another round of showers with isolated thunderstorms Thursday morning. Showers may persist through the day Thursday.

Outlook...

Thursday night...Sub-SCA conditions expected.

Friday...Small Craft Advisory conditions likely beginning in the afternoon and continuing into the overnight hours.

Saturday...The conditions should be lowering below Small Craft Advisory criteria.

Sunday and Monday...Small Craft Advisory conditions probable, especially from Sunday night onwards.

PHI WATCHES/WARNINGS/ADVISORIES

PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory until 6 PM EDT this evening for ANZ430- 431-450>455.