textproduct: State College

WHAT HAS CHANGED

* The chance for thunderstorms has decreased for the rest of the afternoon. * Added patchy valley fog to the forecast for tonight.

KEY MESSAGES

1) Isolated to scattered showers and thunderstorms possible for the rest of the afternoon, though the chance for additional severe weather has decreased. Scattered storms possible this evening over northwest PA.

2) Mainly dry for Sunday, though daily chances for showers and thunderstorms return to the forecast for next week.

DISCUSSION

KEY MESSAGE 1: Isolated to scattered showers and thunderstorms possible for the rest of the afternoon, though the chance for additional severe weather has decreased. Scattered storms possible this evening over northwest PA.

The line of severe thunderstorms that moved across York and Lancaster Counties earlier this afternoon is now off to the east of our CWA. Satellite shows shallow cu developing behind this line, but with weak upper level support, any additional convection that develops this afternoon is expected to be isolated to scattered in coverage. SPC mesoanalysis shows 1500 to 2000 J/kg of SBCAPE over much of the region along with 25 to 35 knots of shear, so if any storms are able to develop, there is still some potential for them to become strong to severe. Damaging wind gusts would be the main concern.

Some guidance shows additional storms developing over northwest PA later this evening ahead of a cold front. These storms should weaken as they move farther into central PA and will likely struggle to make it south of I-80.

KEY MESSAGE 2: Mainly dry for Sunday, though daily chances for showers and thunderstorms return to the forecast for next week.

Upper level flow becomes more zonal for Sunday which should result in a mainly dry day, outside of an isolated shower or storm that develops on the higher terrain of western PA. The break from the rain will be short-lived, however, as multiple shortwaves moving through will bring daily chances for showers and storms as we head into the coming week.

Machine learning ensembles suggest that there will be some severe weather potential for at least a couple of days next week and SPC has much of the region outlooked in a marginal risk for Monday. There will also be some potential for flash flooding as well, and WPC has placed all of central PA in a marginal risk for both Monday and Tuesday. There is still some uncertainty regarding the severe and flash flood risks, but the details will be worked out over the coming days.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

The main line of showers and storms that tracked near MDT and LNS earlier this afternoon is now well to the east of both sites and any additional storms through the rest of the afternoon will be isolated. MVFR ceilings have developed at JST and AOO, but a return to VFR is expected by 20Z. Elsewhere, VFR conditions will continue through the rest of the afternoon with scattered to broken clouds around 4000 feet and winds out of the west-southwest at 10 to 15 knots. A few gusts to 20 knots will be possible. If any showers or storms happen to move directly over an airfield, brief periods of IFR may occur. The chances for this appear to be low and precip mentions have been kept out of the TAFs.

Scattered showers and thunderstorms may develop over northwest PA later this evening ahead of a cold front. BFD appears to have the best chance of seeing any impacts, so a PROB30 has been introduced there. Most guidance shows the storms struggling to make it much farther south than I-80, so we have held off on including mentions of rain anywhere else.

Low clouds and patchy valley fog should form overnight over northwest PA, leading to a period of IFR conditions at BFD and potentially IPT. Patchy fog is possible farther to the south as well, but impacts at any other airfields appear unlikely. VFR conditions will return by 14Z, continuing through the day on Sunday.

Outlook...

Sun...Mostly dry, some potential for isolated showers across far W PA.

Mon-Thu...Scattered showers/storms. Restrictions possible.

CTP WATCHES/WARNINGS/ADVISORIES

None.