textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Updated aviation section for 12z TAFs.

KEY MESSAGES

1) Additional showers and thunderstorms through today could lead to further instances of flash flooding. However the threat for widespread significant flash flooding has diminished.

2) High pressure builds in for Wednesday with the chance of showers and storms returning again for Thursday and Friday.

DISCUSSION

KEY MESSAGE 1... Additional showers and thunderstorms through today could lead to further instances of flash flooding. However the threat for widespread significant flash flooding has diminished.

For the day today, a broad area of low pressure will linger to our south over eastern Virginia while high pressure remains near eastern New England. This will allow for a continuing east to northeast low level flow and further rounds of showers and thunderstorms developing especially by the afternoon. However the best low level convergence as well as upper level right jet entrance dynamics will be shifted slightly east compared to Sunday. The result of this will be that the heaviest of the rainfall will be favored near NYC east through Long Island and north into parts of southern New England. This is the area now in a MODERATE risk of excessive rainfall from the Weather Prediction Center while most of our forecast area is in A SLIGHT risk. This still means that scattered instances of flash flooding will be possible and the Flood Watch that was issued yesterday remains in effect until 8 PM this evening. Expect a generally lull in showers this morning before showers and storms become more widespread again by the afternoon. Rain rates of over 2 inches per hour will be possible with urban, low lying areas, and areas that were hit hard with rainfall this past evening seeing the best chance for flash flooding. Otherwise, it's also worth noting that it will not be getting quite as unstable this afternoon due to much of the area being "worked over" by previous convection and mainly cloudy skies. This will limit the risk of severe weather. The Storm Prediction Center has our Delmarva zones in a MARGINAL risk for severe weather (meaning any severe weather should be isolated) with the remainder of our CWA in a general risk (non severe thunderstorms). Damaging winds will be the biggest threat with any severe storms.

For tonight through Tuesday, low pressure will slowly move off to the north and east as several additional weak impulses of energy aloft move through. Showers/storms should diminish in coverage through this evening with rates diminishing as well. Some additional showers are likely for Tuesday but they are not expected to be heavy so no further flooding is expected.

KEY MESSAGE 2...High pressure builds in for Wednesday with the chance of showers and storms returning again for Thursday and Friday.

High pressure builds in for Wednesday with seasonable temperatures and partly to mostly sunny skies expected.

As we head towards the end of the week into next weekend, a new frontal boundary and associated upper level trough will move in from the west bringing a return to chances of showers and storms. POPs increase to 30-40 percent by Thursday and then 40-60 percent by Friday. It's possible that the front and associated showers/storms linger for the start of next weekend however forecast confidence is low by this time.

AVIATION /10Z MONDAY THROUGH FRIDAY/

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

Today...A few showers around this morning with cigs mainly IFR to low MVFR. Most sites should see cigs lift to MVFR this afternoon but there will once again be some thunderstorms around that could affect TAF sites after 18z. Best chances for storms will near the I-95 corridor and points southward. East-northeast winds at 5-10 kt. Moderate confidence.

Tonight...Showers/storms diminishing through the evening but cigs likely lowering through the evening to IFR. Northeast winds 5-10 knots. Moderate confidence.

Outlook...

Tuesday...Some isolated to scattered showers around with generally MVFR cigs.

Wednesday...Mainly VFR.

Thursday through Friday...Chances for showers return by late Thursday into Friday and this could result in sub VFR conditions at times.

MARINE

No marine headlines are anticipated through tonight. East winds generally 10-20 knots for Monday shifting to north/northeast Monday night. Seas generally 2-3 feet except up to 4 feet by later Monday into Monday night off the coast of Monmouth and Ocean Counties. Expect additional rounds of showers over the waters through Monday night.

Outlook...

No marine headlines are currently anticipated through the rest of the week.

Rip Currents...

Through Tuesday...Winds remain east to southeast around 10 kt, with gusts to 20 kt in the afternoon. Resulting increasing NE wind wave will return an elevated MODERATE Rip Current Risk along much of the Jersey Shore Monday and Tuesday, with LOW risk persisting over Cape May/Atlantic Counties and the Delaware Beaches, where winds remain lighter and more SSE through Tuesday afternoon.

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

PHI WATCHES/WARNINGS/ADVISORIES

PA...Flood Watch through this evening for PAZ054-055-060>062-070- 071-101>106. NJ...Flood Watch through this evening for NJZ001-007>010-012>027. DE...Flood Watch through this evening for DEZ001. MD...None. MARINE...None.