textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Updated aviation section for 12Z TAFs.

KEY MESSAGES

1. Tranquil weather will prevail into the weekend 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 weather will prevail into the weekend with no significant weather hazards anticipated.

Aloft, a closed low will traverse portions of Ontario and the Hudson Bay and into Quebec through Friday, with long wave troughing across much of the northeastern US. Mid-level ridging will briefly build into the region for Saturday. At the surface, a weak cold front will pass through the region today before high pressure returns for Friday and Saturday.

After the cooler temperatures the past couple of days, a brief warmup is anticipated, with highs today in the mid 70s. The cold frontal passage today will usher in drier air and nudge temperatures down a bit for tonight and into the first part of the weekend. Near- normal temperatures are expected tonight through Saturday, with lows in the mid 40s to low 50s and highs in the low to mid 70s for most locations. The cold frontal passage itself is expected to be dry, so tranquil conditions are expected through Saturday.

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 and perhaps 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 into portions of the Ohio Valley through Saturday night, and then northeastward in the direction of our area on Sunday.

Timing discrepancies remain amongst model guidance this afternoon, but there is strong agreement that the remnants of Isaias will bring some impacts to the region Sunday and perhaps 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. WPC has placed most of the region in a Marginal Risk (1 of 4) Excessive Rainfall Outlook for Sunday.

It is too early to specify exact rainfall amounts, but confidence is higher than normal that a large portion of the area could end up with 1 to 2 inches of rain, with higher amounts certainly not out of the question. We will continue to monitor trends over the coming days.

AVIATION /09Z THURSDAY THROUGH MONDAY/

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

Today...VFR. West-southwest winds around 5-10 kt early, become west-northwest around 10-15 kt, with gusts up to 20 kt in the afternoon. High confidence.

Tonight...VFR. Winds west-northwest diminishing to 5-10 kts. High confidence.

Outlook...

Friday through Saturday...VFR. No significant weather expected.

Sunday and Monday...Restrictions likely with the remnants of what is now Hurricane Isaias moving through, accompanied by low stratus and rain.

MARINE

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 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.

PHI WATCHES/WARNINGS/ADVISORIES

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