textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Aviation section updated for 6Z TAFs.

KEY MESSAGES

1. A system moves in Monday bringing the threat for heavy rainfall and associated flooding along with at least some risk for severe weather.

DISCUSSION

KEY MESSAGE 1...A system moves in Monday bringing the threat for heavy rainfall and associated flooding along with at least some risk for severe weather.

Medium range guidance continues to hint at a stretch of unsettled weather to start next week. The main question will be the track of the low pressure as it moves through the region, which will have notable consequence in specific impacts.

The main takeaway though is that Monday is currently looking wet, with some thunderstorms likely mixed in as the area of low pressure moves through, mainly in the afternoon. Consensus guidance shows PWAT values (1.75- 2.00") near the climatological maxima, setting up the risk for heavy rainfall. NBM Probability of 1" or more from this system has around 30-50% from Philadelphia on north and around a 10- 30% south of Philadelphia. These numbers have come down some since the previous forecast cycle but it's worth stressing the continuing uncertainty in the forecast. If the low track trends farther north, this would tend to reduce the heavy rainfall and flash flooding threat but increase the severe weather threat...especially over southern parts of our forecast area (Delmarva, southern NJ). In fact this could end up being a system that brings mainly a heavy rainfall/ flooding threat to northern parts of our forecast area with more of a severe threat to southern areas. Again, a lot of uncertainty still remains, but the overarching synoptic setup will be favorable for an impactful system. One final note regarding the flooding, We're still in a region-wide drought so that could mitigate the flood threat some.

Showers/storms may linger into Monday evening but should be cleared of the area by Tuesday morning as a cold front sweeps offshore.

AVIATION /06Z SATURDAY THROUGH WEDNESDAY/

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

Thru 12Z this morning...VFR. West-northwest winds less than 10 knots. High confidence.

Today and tonight...Mainly VFR. Isolated shower not impossible in the afternoon/evening, but odds less than 25 percent, even less a chance of any restrictions with said shower. West- northwest winds increasing to 10-15 knots with gusts up to 25 knots in the afternoon, then diminishing again after sunset. High confidence.

Outlook...

Sunday...VFR. No significant weather likely.

Sunday night...Mainly VFR. Some showers possible late.

Monday and Monday night...Sub-VFR conditions with showers and some thunderstorms likely.

Tuesday and Wednesday...VFR. No significant weather.

MARINE

A weak trough will traverse the waters this evening and will result in a period of increased westerly winds overnight and Saturday morning. The strongest wind gusts (25 knots) looks to be across the northern to central New Jersey Atlantic coastal waters, and this is where a Small Craft Advisory has been issued/expanded for late tonight and Saturday morning. Seas on the ocean are forecast to remain below 5 feet however.

Outlook...

Saturday night through Sunday night...No marine headlines expected.

Monday through Monday night...SCA conditions expected with southerly wind gusts increasing to around 30 kt with seas 4 to 7 feet.

Tuesday...SCA conditions could linger early.

Wednesday...Sub SCA conditions.

Rip Currents...

For Saturday, westerly winds around 10-15 mph are expected. However, the onshore swells begin to weaken, decreasing to around 2 to 4 feet at around a 7 second period. Breaking waves in the surf zone should be around 2 feet or less as a result. Therefore, a LOW risk for the development of dangerous rip currents is forecast for all beaches on Saturday.

For Sunday, westerly winds diminish to around 10 mph. Onshore swells will remain weak around 1 to 2 feet with a 7 second period. Breaking waves in the surf zone will be around 1 foot or less. Therefore, a LOW risk for the development of dangerous rip currents is forecast for all beaches on Sunday.

For specific beach forecasts, visit weather.gov/beach/phi

PHI WATCHES/WARNINGS/ADVISORIES

PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory until 2 PM EDT this afternoon for ANZ450- 451.