textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Aviation section updated for the 00Z TAFs.

KEY MESSAGES

1. Tranquil, dry weather will prevail through Saturday with no significant weather hazards anticipated.

2. The remnants of what is now Hurricane Isaias will approach the area late this weekend bringing rain back to the region Sunday into Sunday night.

DISCUSSION

KEY MESSAGE 1...Tranquil, dry weather will prevail through Saturday with no significant weather hazards anticipated.

A diffuse cold front will make its way offshore through early this evening. In its wake, high pressure will build in tonight through Friday bringing continuing mainly clear skies with dry weather. Lows tonight look to generally get down into the 40s for most areas except low 50s for the Wilmington through Philadelphia urban corridor, Delmarva, and coastal NJ. This will be followed by highs Friday generally in the low to mid 70s so not too far off from average for this time of year. Expect that by late in the day there may be some high, thin cirrus over portions of Delmarva and southern NJ but it will otherwise be a mainly sunny day.

Friday evening, the center of high pressure will be centered right over the area but will then start to gradually retreat east and northeastward towards New England heading into Saturday. Expect increasing mid and high level cloudiness through the day Saturday as moisture starts to stream northward in the upper levels. However it remains dry through the day. Most areas will see highs similar to Friday however the winds will be coming around to easterly on the south side of the high to our north so this will keep it a bit cooler near the coast.

KEY MESSAGE 2...The remnants of what is now Hurricane Isaias will approach the area late this weekend bringing rain back to the region Sunday into Sunday night.

The primary forecast concern for the latter part of this weekend into early next week will be the remnants of what is currently Hurricane Isaias in the Gulf. It is expected to intensify further before making landfall somewhere along the northern Gulf coast Friday night as it begins interacting with an upper trough. From there, it is expected to undergo extratropical transition and continue northward towards portions of the Ohio Valley through Saturday night, and then northeastward in the direction of our area on Sunday.

Some timing discrepancies of several hours remain amongst model guidance this afternoon, but there is strong agreement that the remnants of Isaias will bring some impacts to the region beginning During the day Sunday and perhaps lingering into early Monday. At this point in time, it appears that widespread rain will be the primary impact. It should be noted that PWATs are modeled to be in the 1.5-2+ inch range, so some periods of heavy rainfall will be possible. Our current forecast is for .50 to 1.00 inches of rainfall with the system through early Sunday evening but with more rain falling Sunday night into early Monday, storm totals in the 1.0 to 2.0 inch range will be quite possible. It's even still possible some areas could see over 2.0 inches but confidence regarding this is low. WPC has placed most of the region in a Marginal Risk (1 of 4) Excessive Rainfall Outlook for Sunday meaning at least isolated instances of flooding will be possible. We will continue to monitor trends over the coming days.

AVIATION /00Z FRIDAY THROUGH TUESDAY/

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

Tonight...VFR. W-NW winds 5 kt or less. High confidence.

Friday...VFR. W-NW winds 5 to 10 kt in the morning, then 10 to 15 kt with gusts up to 20 kt in the afternoon. High confidence.

Friday night...VFR. NW winds 5 kt or less, veering to the N-NE late. High confidence.

Outlook...

Saturday through Saturday night...VFR. No significant weather.

Sunday through Monday...Sub-VFR conditions are likely in rain and low clouds.

Monday night through Tuesday...Primarily VFR. Isolated showers are possible Tuesday afternoon, which could lead to brief periods of sub-VFR conditions.

MARINE

Westerly winds around 10 knots by later this evening into the overnight. Winds continue mainly out of the west for Friday at around 5-10 knots. Seas 2-3 feet this afternoon diminishing to around 1-2 feet by later tonight through Friday.

Southwest winds of 10-20 kts will shift to westerly in wake of a cold front today, before beginning to diminish by this evening. Seas 2 to 4 feet. Fair weather.

Outlook...

Friday night through Saturday night...No marine headlines currently anticipated with winds under 25 kts and seas below 5 feet.

Sunday through Monday...Advisory conditions are possible with wind gusts in excess of 25 kts and seas in excess of 5 feet as the remnants of Hurricane Isaias move through. Visibility restrictions are possible in rain and perhaps spray.

Tuesday...Conditions return to below Small Craft Advisory levels with west to southwest winds around 10-15 knots and seas 2-4 feet.

PHI WATCHES/WARNINGS/ADVISORIES

PA...None. NJ...None. DE...None. MD...None. MARINE...None.