textproduct: State College

WHAT HAS CHANGED

* Added discussion about possible snow Sunday night into Monday.

KEY MESSAGES

1) Cold front brings showers to central Pennsylvania into early this morning.

2) Snow possible tonight into Monday as colder air settles in.

3) Freeze potential across northern/western Pennsylvania tonight into Monday morning. Widespread damaging frost/freeze threat extends across all of central Pennsylvania Monday night into Tuesday morning.

4) Drier conditions in the early to middle part of the week may result in a marginal increase in risk of wildfire spread.

DISCUSSION

KEY MESSAGE 1: Cold front brings showers to central Pennsylvania into early this morning.

As of 07z Sun, the cold front has just moved through UNV and is just west of IPT. There is a thin band of light rain along the front, but the primary area of moderate rain is separated to the east and resides within a fairly narrow area of moisture transport with SW flow aloft carrying 1.25" PWAT air.

Looking out over western PA and eastern OH, radar imagery shows showers developing on the back side of the cold front. As the night goes on, additional areas of light rain are expected to develop over Pennsylvania on the back side of the cold front as a midlevel vort max rounds the base of the trough, giving the front more anafrontal characteristics. In total, rainfall amounts associated with the frontal passage will range from 0.20 inches in the southern tier to 0.75-1.00 inch north and east of State College.

If the anafrontal precip is still going steady enough by 8-10 AM in the Endless Mountains region, there could be a brief changeover to wet snow before precip tapers off as colder temperatures pour in. No accumulation expected. Lows by daybreak will range from the mid 30s in the northwest to low 50s in the southeast.

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KEY MESSAGE 2: Snow possible tonight as colder air settles in.

The HRRR and 3km NAM show an area of rain and snow showers moving across western and central PA during the late evening and overnight hours tonight, with potential upslope and lake effect snow persisting longer in the Laurels and northern tier. Primary forcing for this is an upper level vort max nestled in the west side of the trough, and thermodynamics are favorable with steep 0-3 km lapse rates and 2m T falling below freezing. Biggest remaining questions are whether there will be dry air at the sfc, and if the vort max will be as strong as progged by the NAM/HRRR. Most likely scenario is a few tenths of an inch of accum on grassy surfaces in the N/W but it's worth noting that the 90th pctl (1 in 10 chance) amounts are closer to 1 inch, and the 00z RRFS continues to show little to no precip.

On Monday, a trough of -10C 850mb temps will drift across PA and could provide enough instability for scattered light snow showers/squalls. The Snow Squall Parameter lights up in both the NAM and GFS on Monday afternoon and several CAMs depict a broad field of open cellular snow showers. Fortunately, temperatures will rise above freezing areawide on Monday afternoon, but brief reductions in visibility are possible with passing snow showers.

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KEY MESSAGE 3: Freeze potential across northern/western Pennsylvania tonight into Monday morning. Widespread damaging frost/freeze threat extends across all of central Pennsylvania Monday night into Tuesday morning.

Confidence is /very/ high in a widespread freeze Monday night/Tues morning due to a combination of high pressure nearby, light wind, and 8H temps in the -5 to -10C range overhead.

The setup for tonight is a bit less favorable, which means freezing temperatures are unlikely southeast of the I-99/I-80 corridor. Farther west and north, a Freeze Warning is now in effect. Despite lows in the middle 30s for the rest of the CWA, sufficient winds and some cloud cover will limit the potential for frost, thus precluding any Frost Advisory issuance.

The growing season has been activated for all but four zones (Tioga/Sullivan/Potter Counties and Northern Lycoming County) across central Pennsylvania as of 04/18/2026, see the latest Public Info Statement for those details.

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KEY MESSAGE 4: Drier conditions in the early to middle part of the week may result in a marginal increase in risk of wildfire spread.

Looking into the beginning of next week, relative humidities dip down closer to the ~30% critical threshold with Monday outlining the best potential for some post-frontal gusty winds. As of 07z, a wetting rain was observed everywhere northwest of I-81, but steadier rain is moving into southeast PA right now. After all the rain is done falling, we'll touch base with the PA Bureau of Forestry to reassess fuel moistures into the beginning of the week. Despite chilly temperatures (highs 35 to 50F), Monday will be a day to watch due to the combination of gusty winds and marginal RHs. Tuesday will trend warmer with slightly lower RH values, but winds are not expected to be quite as gusty.

AVIATION /10Z SUNDAY THROUGH THURSDAY/

As daybreak approaches, cigs over the western highlands (BFD/JST) and the Lower Susq Valley (MDT/LNS) were flirting with IFR conds. Elsewhere, predominantly MVFR conds were observed.

A cold front will pull east of the Susq Valley this AM, with scattered rain showers persisting beyond sunrise. A few wet snowflakes could even mix in across the NW mtns as colder air returns behind the departing front.

Gradual improvement is expected today, with lingering -SHRA finally pulling east of the region by midday. Cigs should eventually rise to VFR at all TAF sites by aftn as drier air returns.

Models suggest that a quick-moving wave of low pressure could bring a period of -SHSN to primarily N/W PA (BFD/JST) this evening into tonight. A few wet snowflakes or sprinkles could even make it farther to the southeast during the early morning hours on Monday.

Outlook...

Mon...Linger -SHSN possible N/W; otherwise, becoming VFR.

Mon night-Tue...Generally VFR.

Tues night-Wed AM...Scattered -SHRA possible.

Wed PM-Thu...Improving conds.

CTP WATCHES/WARNINGS/ADVISORIES

Freeze Warning from midnight tonight to 9 AM EDT Monday for PAZ004-005-010>012-017>019-024-025-033-034-045-046. Freeze Watch from late Monday night through Tuesday morning for PAZ004-005-010>012-017-018. Freeze Watch from late Monday night through Tuesday morning for PAZ019-024>028-033>036-045-046-049>053-056>059-063>066.