NEAR TERM /UNTIL 6 PM THIS EVENING/
Early morning satellite imagery shows a dendritic pattern of valley fog across Northern PA. Expect the fog to dissipate by 12Z-13Z, then fair and seasonably warm mid-summer conditions with low humidity are anticipated later today under surface high pressure and rising heights aloft. Mixing down progged 850mb temps of around 15C yields expected highs in the 80s.
Dry air above a weak inversion in the model soundings supports undercutting NBM dewpoints this afternoon by a few degrees.

SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/
Another cool night is in store for the region under the surface ridge, with favorable conditions for radiational cooling and late night valley fog across Northern PA. A modest increase in temps/humidity appears likely Sunday/Monday, as the surface high drifts off the East Coast and a return southerly flow develops.
Ensemble mean 2m/850mb plumes support highs mainly in mid 80s to low 90s.

A closed upper low off of the Mid Atlantic coast is progged by all guidance to track north into New England Monday, as a shortwave lifts up the Ohio Valley toward PA. Large scale subsidence and a ribbon of lower pwats in between these features will likely result in fair weather over Central PA Monday. The best chance of a late day shower/tsra appears to be over the Laurel Highlands associated with the approaching Ohio Valley shortwave.

LONG TERM /MONDAY NIGHT THROUGH FRIDAY/
In conjunction with the retrograding low moving westward into PA and the upper level trough pushing through the region from the east, the best odds for rain will be Tue and Wed across central PA. These two system interacting will provide plenty of lift and moisture for shower and thunderstorm development. PoPs will be highest on Tuesday night and Wednesday afternoon as the cutoff low gets ingested into the main wave of the trough as it digs across the Ohio Valley and Mid-Atlantic regions.

There remains some uncertainty with how the upper level pattern will progress after Wednesday, but building high pressure over the western and central US will bring an increasing threat for excessive heat as the calendar flips from July to August. As the ridge builds, it seems we could be in a favorable ring of fire pattern with daily chances for diurnally driven showers and thunderstorms through the end of next week.

AVIATION /12Z SATURDAY THROUGH WEDNESDAY/
For the 12Z TAF package, so far clear and VFR.

No real change from earlier. VFR conditions will prevail across the region today into Sunday. Localized mainly MVFR fog is possible at KBFD. Similar conditions expected for Sunday, as high pressure remains over the area.

There could be some fog at other sites, but for now will go with what earlier fcst had. Dewpoints not real high and the sun is out for much of the time over the last few days, so the soil has dried out some since Monday.

Outlook...

Sun-Mon...Dry weather with predominantly VFR conds expected.

Tue-Wed...Increasing chances for showers and thunderstorms.

CLIMATE
The average temperature from July 1 to July 25, 2024 at Harrisburg is 80.7F, which is tied for the 3rd warmest July 1-25 period on record (81.8F in 2020, 81.5F in 1999, 80.7 in 1955).

The average temperature from June 1 to July 25, 2024 at Harrisburg was 78.2F, which is the warmest meteorological summer-to-date on record.

The average temperature from January 1 to July 25, 2024 at Harrisburg is 56.3F, which is the warmest year-to-date on record.

CTP WATCHES/WARNINGS/ADVISORIES
None.