textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

No major changes.

KEY MESSAGES

1. Mainly fair and dry weather is expected through this evening.

2. Showers and thunderstorms return Tuesday into Wednesday with the potential for severe weather and flash flooding.

DISCUSSION

KEY MESSAGE 1...Mainly fair and dry weather is expected through this evening.

High pressure remains in control through this evening with temperature and humidity levels remaining similar to Sunday. Generally expect highs ranging from the 70s to near 80 over our northern zones over NE PA into NW NJ with low to mid 80s near the urban corridor over portions of our eastern MD shore counties and southern Delaware. It remains mainly sunny today with light winds.

KEY MESSAGE 2...Showers and thunderstorms return Tuesday into Wednesday with the potential for severe weather and flash flooding.

Unsettled weather returns Tuesday into Wednesday. For Tuesday, a warm front lifts northward throughout the day. As this warm front lifts northward, winds turn more southerly with moisture being transported northward. Temperatures on Tuesday reach the mid 70s to upper 80s with increasing humidity as dew points reach into the 70s for many.

By early Tuesday morning, isolated showers and thunderstorms may already be developing. The coverage of these showers and thunderstorms will be increasing throughout the day and peak during the afternoon/evening hours. Heading into Tuesday night, a cold front will be approaching the region and cross through our area into Wednesday. This will keep the activity going into Tuesday night and Wednesday morning. Beyond Wednesday morning it is a bit more uncertain as it depends on the placement of the cold front. If the cold front takes longer to clear our area, then showers and thunderstorms will linger into the second half of Wednesday. However, the general trend currently looks to be drier as Wednesday progresses, especially by late day.

For Tuesday, there is the risk for severe weather and heavy rain leading to flash flooding. In terms of the set-up, the exact extent of instability that builds remains a bit more uncertain among model guidance with variations. However, the general consensus shows values that are supportive of severe weather. Also, lapse rates will be supportive along with increasing shear values for storm organization. This looks to be another event with multiple rounds. The first being the showers and thunderstorms in the morning, the second being the more widespread coverage in the afternoon and evening, and another round into Tuesday night with the cold front. Activity in the afternoon and evening looks to pose the greatest and most widespread risk for severe weather with the primary hazard being damaging wind gusts. Currently, the Storm Prediction Center has our whole area outlooked in a SLIGHT (2 out of 5) risk for Tuesday. On the heavy rainfall side of things, the moisture transport on Tuesday will result in PWATs getting near or over 2 inches along with warm cloud layer processes. All of this supports showers and thunderstorms being able to produce heavy rain. There is also a SLIGHT (2 out of 4) risk for excessive rainfall outlooked for a large portion of our area Tuesday by the Weather Prediction Center.

On Wednesday, the SPC and WPC have portions of Delmarva and southern NJ outlooked for severe weather and a risk for excessive rainfall, respectively. Part of this set-up will depend on the placement of the front and timing. After Wednesday, we are drier for the end of the week.

AVIATION /07Z MONDAY THROUGH FRIDAY/

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

Thru 12Z this morning...VFR. Winds generally light and variable less than 5 kt though a north/northeast direction may be favored at times. Moderate confidence.

Today...VFR. Light/variable winds become southerly by the afternoon, around 5 to 10 kt. High confidence.

Tonight...VFR. Southeast winds around 5 kt or less. High confidence.

Outlook...

Tuesday through Wednesday...Sub-VFR conditions likely at times in SHRA/TSRA.

Thursday through Friday...VFR. No significant weather.

MARINE

Sub-advisory conditions will prevail through tonight. Winds around 10 to 15 kts or less with seas of 2-3 feet.

Outlook...

Tuesday through Wednesday...Winds and seas likely reach SCA criteria by late day Tuesday and could linger into Wednesday night. SCA now in effect thru Wednesday afternoon for the ocean zones and Tuesday afternoon/evening for the bay.

Thursday through Friday...Conditions are expected to remain below SCA criteria.

Rip Currents...

Today, north winds 5 to 10 mph will turn to the southeast in the afternoon. A light southerly swell with a period of 6 to 8 seconds and breaking waves of 1 to 2 feet will result in a LOW risk for the development of dangerous and life threatening rip currents at the Jersey Shore and at Delaware Beaches.

On Tuesday, south to southeast winds will increase to 15 to 20 mph with gusts up to 25 mph. An easterly swell with a 10 to 12 second period and breaking waves of 2 to 3 feet will result in a LOW risk for the development of dangerous and life threatening rip currents at the Jersey Shore in eastern Monmouth county and Delaware Beaches, and a MODERATE risk for the Jersey Shore in coastal Ocean, coastal Atlantic, and Atlantic coastal Cape May counties.

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 from noon Tuesday to midnight EDT Tuesday night for ANZ430-431. Small Craft Advisory from noon Tuesday to 6 PM EDT Wednesday for ANZ450>455.