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WHAT HAS CHANGED

* Issued Freeze Watches for Mon and Tue mornings

KEY MESSAGES

1) Cold front brings showers and thunderstorms to central Pennsylvania into early Sunday morning. Some storms could be severe across western Pennsylvania through the evening. Flash flooding possible across northern Pennsylvania.

2) Frost/freeze potential across northern/western Pennsylvania Sunday night into Monday morning. Widespread damaging frost/freeze threat extends across all of central Pennsylvania Monday night into Tuesday morning.

3) Marginal fire weather concerns this afternoon ahead of the cold front. Drier conditions early this week into the middle of the week will fuel multiple days of marginal fire weather risk.

DISCUSSION

KEY MESSAGE 1: Cold front brings showers and thunderstorms to central Pennsylvania into early Sunday morning. Some storms could be severe across western Pennsylvania through the evening. Flash flooding possible across northern Pennsylvania.

Radar is back to normal.

No significant changes from the previous thinking on both severe and flash flooding. Threat is mainly wind, but early cells in advance of a main line of showers/storms are spinning. Some pre-storm gusts in NW PA were into the 30s and 40s. Meadville G49KT.

Prime time for severe weather will be between 4 pm and 9 pm. After sunset, the system slows down and training of cells may occur, but mainly behind the (ana)front. They will be grabbing moisture from 1.2" PWATs, though.

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KEY MESSAGE 2: Frost/freeze potential across northern/western Pennsylvania Sunday night 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. High pressure, light wind and 8H temps in the -5 to -10C range overhead.

Not quite so high confidence for the night before. Also, the freeze Sun night- Mon morning would mainly be from AOO-UNV-IPT north. Frost worries are low for the other half of the CWA, mainly because of the wind, but also some cloud cover.

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 3: Marginal fire weather concerns this afternoon ahead of the cold front. Drier conditions early this week into the middle of the week will fuel multiple days of marginal fire weather risk.

Sneaky fire weather day across the southwestern zones of central Pennsylvania (Somerset, Bedford, Fulton) with marginal minimum relative humidities and gusty winds ahead of a cold frontal passage. The rain moving in should allow a rise in dewpoints and RH.

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. We'll likely need to see where wetting rain falls over the next 24 hours and reassess fuel moistures into the beginning of next week; however, Monday will be a day to watch going forward due to gusty winds and marginal RHs. Tuesday will also be a notable day to watch in the fire weather realm with current forecast outlining RHs dipping below 30% in spots; however, less wind to contend with so that's where further evaluation of fuels will become increasingly important after rainfall exits the area.

AVIATION /00Z SUNDAY THROUGH THURSDAY/

A cold front will track across central PA tonight, with periods of showers through the night as precipitation rides along the front. LAMP guidance suggests a moderate/high likelihood (50-70% chance) of prevailing MVFR as the front moves across our terminals, with prevailing IFR moderately likely (30-50% chance) at KBFD/KJST where upslope and lake enhancement may increase low-level moisture and lower ceilings. A brief period of IFR may also occur in the heavier showers associated with this front, which is being handled by TEMPO groups. Moreover, LLWS mentions were added to KMDT/KLNS between 03Z-09Z Sunday as a southerly 40-50 kt LLJ develops ahead of the front.

Cold air advection in the wake of this front will drop freezing levels below 1500 ft across the Northern Tier (KBFD) and Allegheny Mountains (KJST/KAOO) overnight, allowing for snow to mix in the light rain showers after 09Z-10Z Sunday. Afternoon rain/snow showers will also be possible, driven by shortwaves embedded within a longwave trough moving overhead, along with steep low-level lapse rates (8-9 C/km) and upslope/offshore WNW winds.

Otherwise, prevailing VFR is likely (70-80% chance) after 18Z Sunday across our terminals as drier air enters the region, with northwesterly winds gusting between 25-30 kts across central PA.

Outlook...

Mon...Lingering -SHSN possible early N/W; otherwise, dry conditions with VFR prevailing.

Tue...Dry with VFR conditions prevailing early, rain showers possible during the afternoon and evening hours.

Wed...NW flow with potential restrictions and a chc of -SHRA N/W.

Thu...Clearing.

CTP WATCHES/WARNINGS/ADVISORIES

Freeze Watch from late Sunday night through Monday morning for PAZ004-005-010>012-017>019-024-025-033-045-046. 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.