textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

The Rip Current Risk for today has been increased to HIGH for the New Jersey coast.

KEY MESSAGES

1. A High Risk for Rip Currents and cold ocean water temperatures will create dangerous conditions today at the New Jersey coast.

2. A significant warming trend will take place this weekend and continuing into next week. High temperatures will climb into the mid 80s to near 90 degrees by Sunday, with low 90s expected for many areas Monday through Wednesday.

3. A cold front will bring chances of showers and thunderstorms to the region late Wednesday through Thursday, along with moderating temperatures closer to normal by the end of next week.

DISCUSSION

KEY MESSAGE 1...A High Risk for Rip Currents and cold ocean water temperatures will create dangerous conditions today at the New Jersey coast.

Southerly winds today will increase to around 15-20 MPH with gusts up to 30 MPH. Seas of 4-5 feet offshore with a medium 9-10 second period swell will result in breaking waves of 2-4 feet in the surf zone. The combination of these factors will result in a HIGH Risk for the development of dangerous rip currents along the Jersey Shore today.

Additionally, ocean water temperatures across the near shore waters remain in the 50s, increasing the risk for hypothermia for any who enter the water. The combination of cold water temps and risk for rip current development will make conditions dangerous, even for the best swimmers.

KEY MESSAGE 2...A significant warming trend will take place this weekend and continuing into next week. High temperatures will climb into the mid 80s to near 90 degrees by Sunday, with low 90s expected for many areas Monday through Wednesday.

An upper level ridge will build into the eastern US this weekend and into next week, bringing a period of above normal and summer-like temperatures. At the surface, high pressure over the western Atlantic will anchor off the coast of the Mid Atlantic. This will result in a warm south to southwesterly flow for several days and gradually warming temperatures beginning today through Tuesday or Wednesday.

Following a seasonably cool start this morning with temperatures in the mid 40s to low 50s, southwesterly warm advection flow will ramp up as high pressure strengthens offshore. Highs this afternoon are forecast to be mainly in the low 80s, and in the mid 70s in the usual cooler high elevation and coastal locations. Skies will be nearly cloud free during the daytime hours. The southwest breeze today will become a bit gusty this afternoon, with gusts up to 25 mph possible.

A shortwave trough will pass across the region tonight, bringing and increase in cloud cover and low end potential (10-20% chance) for showers this evening for our western areas. Elsewhere, there will be a chance of sprinkles as the weak system passes through. With the cloud cover and persistent southwest flow, temperatures will be slow to fall tonight. Lows are forecast to range from the upper 50s to mid 60s.

Highs Sunday will climb into the mid to upper 80s inland as southwest warm advection continues. Along the immediate coast, it will generally be a good 5-10 degrees cooler.

Temperatures continue to climb into Monday for inland areas with mid to upper 80s for many areas, and low 90s over portions of eastern PA, inland southern NJ, and Delmarva. However the flow be more out of the south to even southeast so they'll be more of cooling influence near the coast and even extending a bit farther inland compared to Sunday. This will keep these areas near the coast mainly in the 70s to low 80s. Tuesday and potentially Wednesday could see some areas inland getting into the mid 90s but confidence on specific details becomes a bit lower by this time. The heat looks to break by Thursday. In terms of overall heat impacts, the current forecast has the urban corridor flirting with heat advisory criteria by next Tuesday into Wednesday, but that said, this particular setup doesn't look exceptionally favorable for both very high heat and humidity. Through Tuesday, mixing should keep dewpoints from getting too high. Evapotranspiration will be limited due to ongoing drought and ocean temperatures remain cool. Long story short, it is still quite early in the season for high dewpoints to combine with high heat. By the time these numbers creep up by Wednesday, clouds and showers/storms may help knock temperatures down some. In any case, we'll be getting close to record high temperature territory Monday through Wednesday of next week.

Temperatures will moderate closer to normal by late next week following a cold frontal passage late Wednesday.

KEY MESSAGE 3...A cold front will bring chances of showers and thunderstorms to the region late Wednesday through Thursday, along with moderating temperatures closer to normal by the end of next week.

Overall, the next 4 days look mostly dry, but can't rule out some diurnally driven showers/thunderstorms, mainly on Sunday. As the CAM guidance has started to come into range for Sunday, the area of focus looks to be for the southern third of the area, from the southern Philadelphia suburbs southwards into Delmarva. Forecast soundings indicate that for areas further north, there will simply be too much mid-level dry air. Overall, though PoPs for Sunday remain rather low even in Delmarva, around 10-20% at best as forcing looks weak. Could see some isolated convection focused near surface forcing mechanisms, such as the sea breeze. Surface flow will be westerly inland, but southerly near the coast, so this convergence zone could be something to help convection initiate.

As mentioned earlier, a cold front will approach and likely bring an end to the stretch of above normal temperatures late next Wednesday. Convective activity will likely accompany that front in some form or fashion, but it's too early to speculate on specific impacts or hazards. The front looks to linger nearby or just south of the area late next week and this could keep some showers around at least into Thursday but perhaps even Friday.

AVIATION /12Z SATURDAY THROUGH WEDNESDAY/

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

Saturday...VFR/SKC. Southwest winds increasing to around 10-12 kts, gusting near 20 kts by 16Z. High confidence.

Saturday night...VFR conditions. Mid level clouds will push into the region early in the night, with a low chance of a brief shower or sprinkle at all terminals through 06Z. No restrictions expected. High confidence.

Outlook...

Sunday through Tuesday...VFR prevailing with no significant weather expected. 10-20% chance of a shower or storm on Sunday.

Wednesday...Potential for sub VFR conditions with afternoon/evening showers and storms likely.

MARINE

Southerly winds will increase through the day, reaching 15-20 kts with gusts up to 25 kts expected by late afternoon into the evening. Seas will also be increasing to around 5 feet. A Small Craft Advisory remains in effect for our coastal ocean zones from 4 PM today to 10 AM Sunday.

Outlook...

Monday...No marine hazards expected. Fair weather.

Tuesday through Wednesday...Southwest winds increase and could reach Small Craft Advisory levels by late Tuesday into Wednesday.

Rip Currents...

The risk for the development of dangerous and life threatening rip currents for the Jersey Shore today has been increased to HIGH. For the Delware Beaches, the risk for today remains MODERATE.

South winds will increase to 15 to 20 mph with 25 to 30 mph along with breaking waves of 2 to 4 feet with a 3 to 4 feet/9 to 10 period swell along the coast of New Jersey. Along the coast of Delaware, winds will be more shore-parallel, resulting in lower breaking waves in the surf zone of 2 to 3.

On Sunday, winds shift to more of a west to southwest flow at 10 to 15 mph for all coastal areas. Breaking waves of 2 to 3 feet with a 3 to 4 feet/9 to 10 period swell are expected. Therefore, the risk for rip currents for all beaches on Sunday is MODERATE.

Important to note that while surface temperatures inland will be in the low 80s today and in the upper 80s on Sunday, temperatures along the coasts will mainly be in the 70s due to ocean temperatures in the 50s. These cold water temperatures can quickly cause hypothermia and physical incapacitation to anyone suddenly immersed in the water.

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

PHI WATCHES/WARNINGS/ADVISORIES

PA...None. NJ...High Risk for Rip Currents through this evening for NJZ014-024>026. DE...None. MD...None. MARINE...Small Craft Advisory from 4 PM this afternoon to 10 AM EDT Sunday for ANZ450>455.