textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

No significant forecast changes.

KEY MESSAGES

1. A significant warming trend will continue into this week. High temperatures will generally be upward of 10 to 20 degrees above normal, with low to mid 90s expected for many areas Monday through Wednesday.

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

DISCUSSION

KEY MESSAGE 1...A significant warming trend will continue into this week. High temperatures will generally be upward of 10 to 20 degrees above normal, with low to mid 90s expected for many areas Monday through Wednesday.

An upper level ridge will continue to build into the eastern US this week, bringing a period of well above normal and summer- like temperatures. At the surface, high pressure over the western Atlantic will anchor and strengthen off the coast of the Mid Atlantic. This will result in a very warm south to southwesterly flow for several days bringing the warming trend.

Temperatures this afternoon will continue to climb through the 80s to near 90 inland as SW warm advection continues. However the immediate coast will be cooler with highs near 80 before the sea breeze starts pushing inland. In fact these coastal areas are likely near or at their highs as of early this afternoon. Earlier there had been some thinking that we could see an isolated shower or storm this afternoon but this looks unlikely at this time with our POPs generally around just 10 percent.

The southerly flow continues tonight and it will be relatively mild as a result with lows in the 60s. Coastal areas as well as our N/W zones should get down into the low 60s while the urban corridor will struggle to get below the middle to upper 60s.

Temperatures continue to climb into Monday for inland areas with highs generally in the 89 to 94 degree range for 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 today. This will keep these areas near the coast mainly in the 70s to low 80s.

Confidence continues to increase that temperatures on Tuesday will get into the low-mid 90s across most of the region, outside of the immediate coastal areas and higher elevations. This is increasing the chance that areas within the I-95 urban corridor will flirt with heat advisory criteria. Diurnal mixing will likely keep higher dew points at bay during the peak of the heat in the afternoon. Overall, this is still not a high confidence setup. However, with warmer air temperatures, it will not take as much moisture to push heat indicies a few degrees higher and exceed the early season criteria in the urban areas.

The heat forecast remains a bit more uncertain for Wednesday, as a faster progression of an approaching front may bring more clouds ahead of the showers and storms, and cap temps and heat indices a bit lower. Regardless, this will still be a period of abnormally warm conditions and getting the area close to record high temperature territory Monday through Wednesday this week.

The heat looks to break by Thursday following the cold frontal passage late Wednesday. Temperatures will moderate closer to normal for the remainder of the week and into next weekend.

KEY MESSAGE 2...A cold front will bring some showers and thunderstorms to the region Wednesday through Thursday, along with moderating temperatures closer to normal by the end of next week.

As mentioned above, a cold front will approach the area Wednesday and bring an end to the stretch of above normal temperatures by Thursday. Showers and thunderstorms will accompany this front as it passes through the region. Recent guidance trends show the front moving through during the second half of Wednesday into Wednesday night. At this range there is still uncertainties in timing, but if the front moves through during the day Wednesday, then the potential for stronger storms increases as there will be plenty of instability present. Currently, the better forcing looks to be displaced to the north of the front. All of this said, it remains still a bit early to get very specific on the details and extent of the convection, impacts, and hazards. The front then looks to linger nearby or just south of the area on Thursday leading to more potential for showers. By the end of the week and into next weekend, the trend continues to show a more unsettled pattern.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

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

Rest of this afternoon...VFR with winds generally WSW around 5 to 10 knots. Very slight chance (10%) of a shower or storm. High confidence.

Tonight...VFR. Southwest winds diminishing to 5 kts or less to locally calm. High confidence.

Monday...VFR. SW winds generally around 10 knots except winds shifting to SSE by the afternoon at ACY.

Outlook...

Tuesday...VFR prevailing with no significant weather expected.

Wednesday through Thursday...Sub-VFR with rain showers and thunderstorms Wednesday afternoon and evening. Rain showers may continue into Thursday.

Friday...Sub-VFR possible with the chance for rain showers.

MARINE

Generally fair weather through tonight except very slight chance (10%) of a shower or storm nearshore through early this evening.

For Monday, southerly winds increase to around 10 to 15 gusting up to 20 knots by afternoon but the conditions are expected to stay below Small Craft Advisory levels. Seas around 3 feet.

Outlook...

Tuesday through Wednesday...Southwest winds increase through the day Tuesday with Small Craft Advisory conditions possible by Tuesday afternoon as wind gusts reach near 25 kt. Seas look to start to reach near 5 feet as well Tuesday evening. Seas lessen by Wednesday morning but elevated winds out of the southwest remain through the day Wednesday with gusts near 25 kt. Showers and potentially some isolated thunderstorms move through Wednesday afternoon into early Wednesday night.

Thursday...Conditions expected to be below Small Craft Advisory criteria by this time but showers may linger.

Friday...Conditions are expected to be below Small Craft Advisory criteria. There is the chance for some rain showers.

Rip Currents...

Today, southwest winds will average 10 to 15 mph, but will turn south in the afternoon behind sea breezes. There will also be breaking waves of 2 to 3 feet with a 9 to 10 second period swell. As a result, there is a MODERATE risk for the development of dangerous and life threatening rip currents at the Jersey Shore and at Delaware Beaches.

On Monday, winds will be more south to southeast at 10 to 15 mph with breaking waves of 1 to 2 feet with a 7 to 8 second period swell. As a result, there is a MODERATE risk for the development of dangerous and life threatening rip currents at the Jersey Shore and a LOW risk at Delaware Beaches.

Important to note that while surface temperatures inland will be in the upper 80s today and in the upper 80s to low 90s on Monday, temperatures along the coasts will mainly be in the 70s to near 80 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...None. DE...None. MD...None. MARINE...None.