Area Forecast Discussion

WHAT HAS CHANGED

* Added discussion about possible snow Sunday night into Monday.

KEY MESSAGES

1) A few showers to linger into this afternoon.

2) Snow possible tonight into Monday morning 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: A few showers to linger into this afternoon.

Some showers this afternoon, mainly across the east, just behind the cold front.

Cooling aloft with some afternoon heating has resulted in some showers across the far west over the mountains. Time of day should keep most everything in the form of rain.

In addition, winds not that strong yet, dewpoints still mainly in the 30s. Monday will have a much different feel to it.

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

Cooling aloft and a secondary cold front will result in some late season snow showers across the north and west.

Most of the snow will be over with shortly after sunrise on Monday, as much drier air is advected into cental PA. Amounts will be mainly a dusting to an inch over the higher hilltops.

Cooling aloft could result in a heavier squall early Monday, as we get some heating, but the advection of very dry air will likely offset the cooling aloft, thus think squall potential remains low.

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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.

Monday will see lower dewpoints work into the area, as any showers taper off. Also gusty winds pick up during the day.

Relative humidities dip down closer to the ~30% critical threshold with Monday outlining the best potential for some post-frontal gusty winds. With rainfall and cooler temperatures, this may limit the risk of fire concerns.

Tuesday will trend warmer with slightly lower RH values, but winds are not expected to be quite as gusty.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

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.