textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Updated the aviation section for the 12Z TAFs.

KEY MESSAGES

1. A slow moving cold front crosses the area Friday with the heaviest rain possible during the morning rush hour.

DISCUSSION

KEY MESSAGE 1...A slow moving cold front crosses the area Friday with the heaviest rain possible during the morning rush hour.

An upper-level trough pivoting over the Great Lakes region will continue to slowly track eastward today before the upper low moves overhead on Saturday. At the surface, this translates to a slow moving cold front crawling across parts of our area today.

Isolated to widely scattered showers early this morning will become more widespread by daybreak, making for a wet morning rush hour. Since there has been a lack of rain for our area the past 2 to 3 weeks, the showers are rather beneficial. Rainfall amounts will vary across the area with lower amounts N/W (a tenth to three- quarters of an inch) while southern NJ and Delmarva will have higher totals of 1 to 2 inches with locally heavier amounts possible. Along the I-95 corridor, the latest runs of hi res guidance has increased slightly, up to 1.5 inches with locally higher amounts of up to 2 inches possible. The rain is expected to occur over a long enough period to preclude any widespread flooding concerns, but some localized poor drainage flooding is possible. The WPC has added a Marginal Risk for Excessive Rainfall along the I-95 corridor and southeast today. A few thunderstorms may develop in the morning, but the chances of this are lower, around 20-40%. The front stalls for a period around or just southeast of the I-95 corridor during the morning before resuming a SE push during the afternoon. This will promote the higher QPF totals for those areas with moderately heavy showers and perhaps an isolated thunderstorm possible during the morning rush hour. Conditions will gradually improve throughout the day with mostly fair weather for areas N/W. There will be slower improvement for S/E areas. For the I-95 corridor, conditions are forecast to improve during the afternoon. The SE areas may not see any substantial improvement until the evening hours.

The cold front departs offshore Friday night, with dry conditions returning for much of the area. However, guidance indicates an upper- low will track eastward across northern portions of the area on Saturday. This will lead to a lingering chance for some light rain north of I-78, with the highest chances (40-50%) across the Poconos and far northern NJ. By Sunday morning, the upper-low will be east of the area bringing a return of dry conditions to the region along with cooler temperatures.

AVIATION /12Z FRIDAY THROUGH TUESDAY/

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

Today...IFR to LIFR in light showers and fog for KRDG/KABE, a mix of MVFR and VFR for the I-95 terminals as the heaviest rain and storms depart, and MVFR to IFR for KMIV/KACY in continued rain and storms this morning. Conditions will gradually improve from NW to SE. For KRDG/KABE, VFR is probable by late morning. The I-95 terminals are forecast to become VFR during the afternoon around 19Z. KACY/KMIV will be the slowest to improve with MVFR to IFR conditions lingering into the evening. Northwest to north winds around 5 to 10 knots. Medium confidence.

Tonight...Prevailing VFR conditions for most terminals. Restrictions will remain possible during the early evening at the near- coast terminals, but improvement to VFR is possibly overnight. Cannot rule out patchy fog development if skies clear out quick enough with light and variable winds. Low confidence.

Outlook...

Saturday through Saturday night...Primarily VFR. Brief restrictions will be possible for the Lehigh Valley terminals in rain or low clouds.

Sunday through Tuesday...VFR. No significant weather.

MARINE

Small Craft Advisory extended through the afternoon, mainly for seas 3 to 5 feet. SSW winds around 15-20 kts with gusts near 25 kts possible in the afternoon with rain. Winds and seas subside below SCA criteria after the frontal passage in the evening. Visibility restrictions possible in periods of rain.

Outlook...

Saturday through Tuesday...Advisory conditions will be likely at times with west-northwest winds 15-20 kt gusting to 25-30 kt. Highest confidence in advisory conditions is currently late Saturday into early portions of Sunday and again on Monday. Seas generally 4- 6 feet through the period.

PHI WATCHES/WARNINGS/ADVISORIES

PA...Dense Fog Advisory until 8 AM EST this morning for PAZ054-055- 061-062. NJ...Dense Fog Advisory until 8 AM EST this morning for NJZ001-007. DE...None. MD...None. MARINE...Small Craft Advisory until 5 PM EST this afternoon for ANZ450>455.