textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Small Craft Advisories this evening were cancelled.

Small Craft Advisories were issued for Friday into Saturday.

KEY MESSAGES

1. Lingering rain and/or snow tapers off this evening. Colder tonight through Friday with gusty winds on Friday.

2. Gusty winds and dry conditions Saturday may create some fire weather concerns.

3. A strong cold front moves through Monday bringing precipitation, gusty winds, and a surge of colder air. Some strong thunderstorms will also be possible along and ahead of the front Monday afternoon into Monday evening.

DISCUSSION

KEY MESSAGE 1...Lingering rain and/or snow tapers off this evening. Colder tonight through Friday with gusty winds on Friday.

Cold front is offshore, and northwest winds 15 to 20 mph with gusts up to 25 mph will continue to usher a much colder airmass into the region. Lingering rain with mix with and briefly change to some snow and/or sleet before tapering off this evening. Winds diminish after sunset, and skies clear out. High pressure builds into the Mid- Atlantic, then moves out to sea on Friday.

A much colder night on tap tonight with lows in the 20s to low 30s. Conditions may allow for radiational cooling away from the urban areas late tonight as winds become nearly calm under clear skies, and temperatures may locally be colder than that.

Low pressure will move through the Great Lakes on Friday, and a tight pressure gradient forms between that and high pressure offshore. South winds will increase to 15 to 20 mph with 25 to 30 mph gusts in the afternoon. Highs will be in the upper 40s to low 50s.

Strong shortwave energy associated with that low north of the area may touch off some snow across the southern Poconos with generally less than an inch of snow Friday afternoon.

KEY MESSAGE 2...Gusty winds and dry conditions Saturday may create some fire weather concerns.

Low pressure will depart across northern New England early Saturday while high pressure begins to build in from the Great Lakes area. The pressure gradient between these systems will result in a west to northwest flow across the Middle Atlantic region early this weekend. The air that arrives will also be dry enough by Saturday afternoon to produce minimum relative humidity values in the 20 to 30 percent range. And since winds will be gusting between 25 and 30 mph, this could produce some low-end fire weather concerns. The main limiting factor will be fuel moistures due to the rain from yesterday and today.

KEY MESSAGE 3...A strong cold front moves through Monday bringing precipitation, gusty winds, and a surge of colder air. Some strong thunderstorms will also be possible along and ahead of the front Monday afternoon into Monday evening.

As low pressure tracks 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 will be in place, therefore rain is expected. Thunderstorms are also possible along and ahead of the front Monday afternoon into Monday evening. Instability looks to be fairly limited but the shear and dynamics will be very strong so it's possible there could be some strong to even severe thunderstorms. In fact the setup looks to be not that different than what we had yesterday into last night. As cold air begins to pour in Monday night behind the front a transition to 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. However typically these setups do not bring significant snowfall.

A robust period of cold air advection will follow into the middle of next week resulting in a much colder air mass across our area. This looks to result in high temperatures Tuesday and Wednesday only reaching the upper 30s to low 40s across our region. Winds chills will be in the 20s and 30s much of the time. Quite a difference from the recent spell of warmth.

AVIATION /00Z FRIDAY THROUGH TUESDAY/

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

Tonight...VFR. NW winds 10 to 15 kt with gusts up to 20 kt, becoming LGT/VRB after 06Z.

Friday...VFR. S winds 5 to 10 kt in the morning, increasing to 15 to 20 kt with 25 to 30 kt gusts in the afternoon. High confidence.

Outlook...

Friday night through Saturday...VFR expected with gusty winds for Saturday.

Sunday...Mainly VFR expected.

Sunday night thru Monday night...Sub VFR with IFR probable at times. Rain and chance of tstms. Gusty winds Monday/Monday night.

Tuesday...VFR but with gusty winds continuing.

MARINE

Small Craft Advisories this evening were cancelled with marine conditions falling below advisory criteria.

On Friday, south winds will increase to 15 to 20 kt with 25 to 30 kt gusts. Seas will build to 4 to 6 feet. New SCAs were issued beginning at noon on Friday.

Outlook...

Friday night...SCA conditions expected with gusts 25 to 30 kts and seas 5 to 7 ft on the ocean. Fair weather.

Saturday thru Sunday...SCA conditions early Saturday will diminish by later in the day with relatively tranquil conditions on the waters continuing through most of Sunday.

Sunday night...Building winds and seas with SCA expected. Showers and tstms possible overnight.

Monday thru Tuesday...SCA with Gales possible Monday. Rains and tstms Monday into Monday night before clearing out by Tuesday.

PHI WATCHES/WARNINGS/ADVISORIES

PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory from noon Friday to noon EDT Saturday for ANZ430-431. Small Craft Advisory from noon Friday to 6 PM EDT Saturday for ANZ450>455.