textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Adjusted timing of Small Craft Advisories on the Atlantic Coastal Waters. Otherwise, no significant changes to the forecast.

KEY MESSAGES

1. Weak low pressure will cross through the area late tonight into Wednesday bringing the chance for some light showers.

2. High pressure builds into the region for the end of the work week with above normal temperatures.

3. Low pressure will bring widespread rainfall to the region this weekend.

DISCUSSION

KEY MESSAGE 1...Weak low pressure will cross through the area late tonight into Wednesday bringing the chance for some light showers.

Low pressure currently over the upper Midwest will dive south across the Great Lakes tonight and across the northern Mid- Atlantic on Wednesday. Some light showers may develop this evening as forcing for ascent increases ahead of a warm front, mainly to the north and west of I-95. Some light showers may continue overnight, but the greater chances for showers will occur in the morning hours on Wednesday as low pressure itself tracks through the area. Any rainfall will be rather light in nature however, as total QPF will generally range from a few hundredths to perhaps a tenth or two. Shower activity will wane through Wednesday afternoon with some breaks of sun possible late. Highs will mainly be in the upper 50s to upper 60s on Wednesday with lows in the upper 30s to upper 40s.

KEY MESSAGE 2...High pressure builds into the region for the end of the work week with above normal temperatures.

A warm front lifts north through the region Wednesday night, then high pressure builds over the area on Thursday. High pressure slides offshore on Friday, and then a back door cold front slides through the region Friday afternoon.

Conditions will be dry with temperatures warming to above normal levels. Highs on Thursday will top off in the low to mid 70s throughout, though on the warmer side across interior portions of southern New Jersey and Delmarva.

High pressure slides offshore on Friday and a back door cold front will slide south through the region. A few showers may develop, but conditions will otherwise be mostly dry and cooler with highs closer to normal levels. Highs will top off in the low to mid 60s.

KEY MESSAGE 3...Low pressure will bring widespread rainfall to the region this weekend.

Low pressure organizes and develops over the Great Lakes Friday night and dives towards the Northeast and Mid-Atlantic on Saturday. Showers are likely throughout the day, providing what looks to be a beneficial rainfall with around 1/2 inch or so of rain. It will, however, be outright chilly with highs in the 40s to around 50. Most showers taper off Saturday night with lingering showers into Sunday. Highs will still only be in the 50s on Sunday.

Dry and warmer on Monday with highs in the 60s.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

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

Rest of Today...VFR with mostly clear skies. South-southwest around 5-10 kt. High confidence.

Tonight...Prevailing VFR. Increasing clouds in the evening will give way to BKN/OVC skies overnight. A slight chance of rain showers early in the evening (between 00-03Z), before increasing again after 06-10Z. A slight chance of MVFR ceilings with showers, but expect VFR conditions to remain. South-southeast winds around 10 kt, locally higher near KMIV/KACY. Moderate confidence overall.

Wednesday...Prevailing VFR for most terminals, with MVFR ceilings likely at KABE and possibly KRDG/KTTN. Rain showers continue through the morning and end from northwest to southeast between 15-18Z. Skies should begin to scatter out after 18Z. South-southeast winds will gradually become north-northwest in the afternoon around 5-10 kt. Low-moderate confidence.

Outlook...

Wednesday night through Thursday night...VFR.

Friday...VFR. Cannot rule out a few light SHRA with minimal restrictions.

Friday night through Sunday...Sub-VFR in SHRA. Improving conds on Sunday.

MARINE

A Small Craft Advisory is in effect for the Delaware Bay from 2 AM to 8 AM Wednesday. A Small Craft Advisory is in effect for the Atlantic Coastal Waters from Great Egg Inlet to Fenwick Island from 2 AM to 11 AM Wednesday. A Small Craft Advisory is in effect for the Atlantic Coastal Waters from Sandy Hook to Great Egg Inlet from 2 AM to 1 PM Wednesday.

South-southeast winds around 10-15 kt will increase tonight to around 15-20 kt with gusts up to 25-30 kt. Wind will gradually diminish through Wednesday morning and become southwest around 10-15 kt by Wednesday afternoon. Seas around 3-5 feet. A chance for rain showers late tonight through Wednesday.

Outlook...

Wednesday night through Friday...Sub-SCA conditions.

Friday night through Sunday...SCA conditions develop on Saturday and persist through the weekend. VSBY restrictions in showers Saturday through early Sunday with improving VSBYs on Sunday.

CLIMATE

Record low temperatures are possible at some climate sites for this morning, April 21st. Below are the daily low temperature records for 4/21:

Daily Record Low Temperatures April 21 Site Record/Year Allentown (ABE) 28/1925 & 1956 & 2018 AC Airport (ACY) 25/1981 AC Marina (55N) 26/1875 Georgetown (GED) 27/1961 Mount Pocono (MPO) 11/1908 Philadelphia (PHL) 27/1875 Reading (RDG) 26/1982 Trenton (TTN) 30/1907 & 1925 Wilmington (ILG) 28/1925

PHI WATCHES/WARNINGS/ADVISORIES

PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory from 2 AM to 8 AM EDT Wednesday for ANZ430-431. Small Craft Advisory from 2 AM to 1 PM EDT Wednesday for ANZ450>452. Small Craft Advisory from 2 AM to 11 AM EDT Wednesday for ANZ453>455.