Marine Weather and Tide Forecast for Washington Boro, PA

KEY MESSAGES
1) Isolated to scattered showers and thunderstorms today, mainly south of Interstate 80. Sunday will be mostly dry.

2) Hot and humid pattern set to return for the middle of next week

DISCUSSION
KEY MESSAGE 1: Isolated to scattered showers and thunderstorms today, mainly south of Interstate 80. Sunday will be mostly dry.

Radar trends are verifying earlier forecasts and yield high confidence in CAM projections of isolated to scattered showers and thunderstorms over most of the area with the highest concentration and frequency over the eastern third of the CWA
Latest HRRR/HRRR progs show convection lingering longer than NBM hourlies have them doing. Expect the timing to still be centered between now (2 PM) and sunset. However, we'll add a small amount to PoPs between 00-03Z to bend to the trend.

Previous discussion:

With yesterday's cold front still pushing slowly south across the Commonwealth, we'll likely see another round of showers and thunderstorms fire up late this morning and persist into the early evening hours. However, the threat for torrential downpours does not appear quite as widespread or intense as yesterday. The main area will be south of Interstate 80.

Max SBCAPE is progged in the low 1000s J/kg with fairly weak NW mean flow around 15 kts in the cloud bearing layer. Given the weak flow, initiating boundaries may come from a variety of sources including terrain features, differential heating boundaries (morning fog may create some of those), and the cold front itself. HRRR and REFS members have picked out the higher terrain in Schuylkill County as one such terrain feature that may focus convection initiation, with a swath of locally 1+ inch of rain coming off the high terrain and stretching southeast - a plausible solution that we'll have to watch for. Dry air advection behind the southward moving cold front will gradually bring an end to convection from north to south this evening. Fog may develop in the river valleys tonight as temps fall into the 50s and low 60s.

With drier air in place on Sunday and building high pressure providing a subsidence inversion above the boundary layer, Sunday is still on track to be a mainly dry day. However, a stray shower can not be ruled out particularly over the Laurel Highlands or near the Poconos.

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KEY MESSAGE 2: Hot and humid pattern set to return for the middle of next week

Dry conditions are expected to prevail for the first half of the week with a strong ridge expected to develop over the middle of the country. Increasing heat/humidity is forecast across central Pennsylvania although there remains some uncertainty with respect to how warm temperatures and/or humidity get across the region. Current forecast favors the hottest temps returning Tue to Thu with highs 85-95F and max heat index 90-100F, potentially rising above 100F on Wednesday. Rain chances increase into the latter half of the week.

AVIATION /00Z SUNDAY THROUGH THURSDAY/
00z update... Through this evening, scattered, slow moving showers and thunderstorms will dot Central PA. In all probability, this activity will avoid terminal sites due to their hit and miss nature. However, we will closely monitor developments, and add short-duration TEMPO groups as needed.

Later tonight, most of our guidance is indicating lower cloud development near and just to the east of the Laurel Highlands, with probable development of associated restrictions at KJST and KAOO. For now, we kept restrictions in the MVFR-fuel alternate categories, but some IFR ceiling bases are not out of the question at KJST.

During the predawn hours, due to recent heavy rainfall and resultant wet ground conditions, we feel fog development is likely at KLNS. Restrictions will very likely drop into the IFR category for a time, and could conceivably reach LIFR.

Elsewhere overnight, we anticipate VFR conditions.

On Sunday, once any lower clouds and fog patches lift/dissipate, we should be looking at a restriction-free day. For a change, little to no shower or thunderstorm activity is foreseen during the afternoon.

Generally light winds overnight (5 kt or less), should become easterly at 5-10 kt on Sunday.

Outlook...

Mon-Thu...Mainly VFR, with areas of late night/AM fog.

CTP WATCHES/WARNINGS/ADVISORIES
None.