textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Aviation section updated for the 06Z TAFs.

The Small Craft Advisory was extended through Wednesday for all ocean zones. A new Small Craft Advisory was issued for Delaware Bay for Tuesday and Tuesday Night.

Added a brief discussion on the potential shower threat this weekend.

KEY MESSAGES

1. There is a limited risk for fire weather conditions today.

2. Multiple systems bring rain to the area Wednesday through Thursday. Another weak system could bring some showers on Saturday.

DISCUSSION

KEY MESSAGE 1...There is a limited risk for fire weather conditions today.

High pressure centered off the Mid-Atlantic coast slides out to sea. Zonal flow aloft sets up over the Northeast, and a cold front approaches from the west. Southwest flow increases as the pressure gradient tightens, and winds increase to 10 to 15 mph with 20 to 25 mph gusts. With abundant sunshine, effective mixing will allow dew points to drop into the 30s. With highs in the 70s, MinRH values will be as low as 25 to 30 percent.

Based on coordination with state fire weather partners, a Special Weather Statement will be issued for at least Delaware and the eastern shores of Maryland. Yet to be determined if one will be issued for Pennsylvania and New Jersey, but recent rainfall and greenup are limiting factors. Less rain fell in Delmarva, hence the need for a Special Weather Statement there.

KEY MESSAGE 2...Multiple systems bring rain to the area Wednesday through Thursday. Another weak system could bring some showers on Saturday.

A high pressure system shifts offshore Tuesday, but the continued influence from the high will keep most of the area on the drier side. Also during this timeframe, there will be a low pressure system well to the north in Canada with a cold front sinking southeast from the Great Lakes region. Our NW areas have the potential to see an isolated shower (20-30%) late Tuesday into Tuesday night. The bulk of the rain will move in late Tuesday night into Wednesday morning and continue through the day Wednesday as the cold front sinks southeast into our area. This cold front then stalls across the region into Thursday with a wave of low pressure moving northward along the front leading to more rain on Thursday.

The trend of relatively low instability and limited to zero severe/flooding threat has continued with the latest forecast guidance. Overall, this will be more beneficial rain for the area with an isolated thunderstorm possible.

The NBM Probability of total rainfall from these two systems is about 30-50% for 1 inch or more for ares near and NW of the I-95 corridor. For areas southeast of the I-95 corridor, it is 15 to 30% for 1 inch or more of rainfall. Given how dry we have been, flooding concerns appear to be minimal with this largely being beneficial rainfall for the area.

For Saturday, a weak area of low pressure will move into the region, potentially producing some light showers. This appears to be nothing more than a potential weekend spoiler with no significant impacts expected at this time.

AVIATION /12Z MONDAY THROUGH FRIDAY/

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

Today...VFR. SW winds 10 to 15 kt with 20 to 25 kt gusts most of the day. High confidence.

Tonight...VFR. S winds 5 to 10 kt. High confidence.Outlook...

Outlook...

Tuesday through Tuesday Night...Primarily VFR. Some showers possible north and west of the I-95 terminals on Tuesday Night. South/southwest wind gusts 20-25 kt.

Wednesday through Thursday...MVFR/IFR conditions expected with periods of rain, an isolated thunderstorm, and low clouds. Southerly wind gusts around 20-25 kt on Wednesday.

Thursday Night...Conditions improving but lingering restrictions possible (30-40%).

Friday...VFR. No significant weather.

MARINE

Southwest winds will increase today to 15 to 20 kt with gusts up to 25 kt as the pressure gradient tightens between high pressure over the western Atlantic and an approaching cold front. The strongest wind gusts of 25 kt or higher will be north of Great Egg Inlet, NJ, where a Small Craft Advisory remains in effect. Conditions will remain just below SCA criteria elsewhere.

Winds increase tonight, so the SCA for the ocean waters south of Great Egg Inlet now goes in effect at 6 pm, and an SCA is in effect for all ocean waters tonight.

Outlook...

Tuesday through Wednesday...A Small Craft Advisory is in place for all marine zones. Wind gusts around 20-30 kt out of the south/southwest and seas 4 to 7 feet.

Wednesday Night through Thursday...SCA conditions could linger as winds decline but seas could near 5 feet.

Thursday Night through Friday...No marine headlines expected.

PHI WATCHES/WARNINGS/ADVISORIES

PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory from 2 PM Tuesday to 2 AM EDT Wednesday for ANZ430-431. Small Craft Advisory from 11 AM this morning to 6 PM EDT Wednesday for ANZ450>452. Small Craft Advisory from 6 PM this evening to 6 PM EDT Wednesday for ANZ453>455.