textproduct: State College

WHAT HAS CHANGED

* Have dropped the wind and winter weather advisories * Discussing timing and precip type for Tues night

KEY MESSAGES

1) Turning warmer to start the week with precip arriving Tuesday night over the NW.

2) The potential remains for a storm system to develop over the Mid-Atlantic and impact Pennsylvania later in the week, with snow or a wintry mix. However, a wide range of outcomes are still on the table, including that the storm will fail to form at all. Stay tuned for later forecasts.

DISCUSSION

KEY MESSAGE 1...

Upper trough moving away, and only a weak wave aloft will generate clouds across the nrn tier on Monday. If any flakes drop from the clouds over nrn PA, they won't be worth a mention. So, the quieter/mainly dry forecast for Monday and Tuesday is looking fine as is. A wave rolling to our north on Tuesday will also make some clouds across the north during the daylight hours. The wave will turn the advection sign and 8H temps will rise through the day, and bump sfc temps to highs in the U30s N to near 50F S. Any precip that would hit the ground will hold off until sunset or later in Warren County. This has been a highly continuous and therefore high-confidence forecast for quite a few days. Diffluence aloft and good southerly flow at the sfc from the western Gulf to our backyard should help moisture increase Tuesday evening and through the night. Precip will start to drop in from the NW. Temps will be marginal for rain or snow on the higher/cooler elevations. Forecast soundings keep column temp within a deg or two of -3C below 10kft at BFD with temp at sfc 30-32F with no overt warm nose. So, that would be snow. Elsewhere, it should be warm enough at the sfc for either a mix of RA/SN or just plain rain Tues night.

KEY MESSAGE 2...

The potential remains for a storm system to develop over the Mid-Atlantic and impact Pennsylvania later in the week, with snow or a wintry mix. However, a wide range of outcomes are still on the table, including that the storm will fail to form at all. Stay tuned for later forecasts.

An initial mid-week cold frontal passage, accompanied by rain showers, could turn more interesting Wednesday night and Thursday, as the front stalls just east and south of the Commonwealth. Some model projections bring a surface wave northeast along the front, with wintry precipitation developing back into at least parts of central PA. Latest NBM suggests roughly a 20 pct chance of at least Winter Weather Advisory level snowfall, with a large spread in potential accumulation.

Key model differences remain, and sensible weather during this period will be driven by small-scale sensitivities in the upper- level pattern, which are inherently hard to pin down this far out. Please stay tuned for later forecast updates.

AVIATION /03Z MONDAY THROUGH FRIDAY/

Snowfall across central Pennsylvania has largely dwindled with remaining mentions at BFD possible through ~03Z Monday before tapering off area wide. Recent RAP model guidance keeps low-end MVFR to high-end IFR conditions at BFD/JST, which continues to seem plausible based on a consensus of HREF/GLAMP model guidance so have continued mentions through ~14Z Monday before improvement before all model guidance points towards a brief period of MVFR. Elsewhere, borderline MVFR/VFR ceilings are expected at AOO/UNV over the next couple of hours based on a NBM/HREF/RAP model blend through ~15Z Monday. VFR conditions are expected to prevail elsewhere in the near term with fair agreement in all model guidance. Widespread VFR conditions are expected across central Pennsylvania after 18Z Monday.

Wind gusts will be the main concern in the near term with gusts upwards of 30 to 40 kts possible across the western highlands through ~06Z Monday. Some underperformance could be possible across JST/AOO as a subsidence inversion limits wind gusts; however gusts over 20 kts are expected overnight. Breezy winds continue throughout much of the 00Z TAF package, with all model guidance pointing towards wind gusts decreasing towards the end of this TAF cycle.

Outlook...

Tue-Wed...Mainly VFR.

Thu-Fri...Chance of snow showers, perhaps mixing with rain in the southeast.

CTP WATCHES/WARNINGS/ADVISORIES

None.