textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Updated the aviation section for the 00Z TAFs.

KEY MESSAGES

1. Remaining breezy through the rest of the weekend with temperatures moderating some for Sunday.

2. A potentially strong coastal storm/nor'easter late next week.

DISCUSSION

KEY MESSAGE 1...Remaining breezy through the rest of the weekend with temperatures moderating some for Sunday.

For tonight, the winds will remain elevated as the pressure gradient persists but they will diminish a bit compared to earlier today, especially in terms of gustiness. The winds along with some cloud cover moving through overnight will help keep temperatures from really bottoming out. Generally expect lows in the low to mid 40s.

For Sunday, temperatures warm a few degrees compared to today with highs mostly in the low 60s. Some morning clouds will give way to afternoon sun. Expect west winds generally around 10 to 15 gusting at times to around 20 mph due to a pressure gradient persisting between low pressure over eastern Canada and high pressure to our south and west.

KEY MESSAGE 2...A potentially strong coastal storm/nor'easter late next week.

A significant upper-level trough is forecast to evolve across the eastern U.S. later next week. This should support a surface low that initially tracks near the Ohio Valley, however a secondary low should develop in the vicinity of the northern Mid-Atlantic. The model guidance overall is in decent agreement with the development of the strong upper-level trough, however there are some differences on the handling of the embedded shortwaves and thus the surface low. The timing and amplification of the trough will also have an impact on the secondary surface low development and track. This will be important as it will determine where the main forcing for ascent becomes established along with colder air on the west/northwest side of the developing coastal storm/nor'easter.

The strength of the parent upper-level trough would result in a colder air mass moving in with time. This could be sufficiently cold enough for a rain/snow mix of even some snow across our far western to northwestern zones. This would have a greater chance of occurrence if the secondary low develops and takes over instead of the initial low remaining primary and tracking over our area or to our west. Elsewhere, a decent amount of rain is possible. The amount of precipitation (rain and/or snow), and precipitation types for at least portions of our area, will depend on the ultimate development and track of the secondary surface low and the associated thermal profiles that evolve across our region. The coastal impacts, including the potential for stronger winds and also tidal flooding, are less certain because if the surface low tracks over our area that would lessen the residence time of the (stronger) onshore flow. Lots of uncertainty with the details this far out in time (Thursday night through Friday night), therefore this time frame will continue to be monitored.

AVIATION /00Z SUNDAY THROUGH THURSDAY/

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

Tonight...Mainly VFR though there will be some low stratus moving through overnight. Any cigs look to stay mainly in the low VFR range but can't rule out that they briefly go to MVFR, particularly at KRDG and KABE. West winds generally around 10 knots with occasional gusts up to 20 knots remaining possible through around 02Z. Moderate confidence.

Sunday...Low VFR cigs may persist through around 14Z, particularly for KRDG and KABE. CIGs gradually lift and scatter out through the day. West winds generally around 10 to 15 knots gusting up to 20 knots. High confidence overall.

Outlook...

Sunday night and Monday...VFR. West-southwest winds diminishing Sunday evening, then west-northwest to northwest winds Monday increasing with gusts to 25-30 knots probable.

Tuesday and Wednesday...VFR. West-southwest wind gusts to 20 knots possible Tuesday.

Thursday...Sub-VFR conditions possible especially at night along with some rain developing (rain/snow possible near KABE/KRDG late at night).

MARINE

A Small Craft Advisory remains in effect for all waters until 9 AM Sunday. Generally expect winds 15-25 with gusts up to 30 knots and seas 4-5 feet. It will remain on the breezy side for the rest of the day Sunday but the conditions should be just below Small Craft Advisory levels with winds generally around 15-20 knots.

Outlook...

Sunday night and Monday...Small Craft Advisory conditions probable. The conditions should improve Monday night

Tuesday...A period of Small Craft Advisory conditions are possible.

Wednesday...The conditions are anticipated to be below Small Craft Advisory criteria.

Thursday...Small Craft Advisory conditions may start to develop mostly at night.

PHI WATCHES/WARNINGS/ADVISORIES

PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory until 9 AM EST Sunday for ANZ430-431- 450>455.