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 central 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/

VFR conditions prevail as of 18Z with scattered SHRA across much of the forecast area. Any showers over airfields could yield slightly lower ceilings; however, general rule of thumb will be continued VFR conditions through 00Z Monday across all of central Pennsyvlania's airfields based on a combination of GLAMP/NBM model guidance. Increased chances for showers come overnight based on most recent HREF/NBM model guidance with northwesterly flow. Marginally cold temperatures could lead to initial rain showers with some snow mixing in and dropping visibilities lower at BFD/JST overnight where temperatures trend closer to the freezing mark. Highest confidence remains at BFD while PROB30s have been introduced at JST, mainly in the 03-07Z Monday timeframe. Further east at AOO/UNV/IPT, some chances for precipitation remain; however, temperatures are not expected to be as low and there is less of a chance (~30-40%) of snow mixing in with rain so have kept any rain/snow precipitation mentions towards when precipitation is starting to be on a downward trend as opposed to longer durations.

Low-level moisture in place at BFD/JST (highest confidence of precipitation) could lead to extended periods of ceilings below IFR thresholds, as noted on GLAMP/HREF/NBM model guidance after precipitation ends into the mid-morning (~14-15Z Monday) timeframe. Elsewhere, lingering low-level moisture looks a little less likely based on NBM/GLAMP model guidance so have trended back towards VFR thresholds for the 18Z TAF cycle. There does exist a scenario where low-level moisture continues to bring lower ceilings at airfields that receive precipitation overnight; however, confidence is too low to include in the 18Z TAF package at this time. The only airfields with high (~70-80%) confidence in VFR conditions through 18Z Monday will be MDT/LNS which look like they will remain dry through the majority of the TAF package.

Low-level moisture looks less likely to entail longer periods of conditions below IFR thresholds, thus have kept any restrictions

Outlook...

Tue AM...Dry with VFR conditions expected.

Tue PM-Wed AM...Scattered -SHRA possible.

Wed PM-Thu...Drying trend with VFR conditions.

Fri...Dry with VFR early, increasing chances of -SHRA by the afternoon and evening hours.

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.