


Area Forecast Discussion
Issued by NWS Portland, ME
Issued by NWS Portland, ME
209 FXUS61 KGYX 181205 AFDGYX Area Forecast Discussion National Weather Service Gray ME 805 AM EDT Sat Oct 18 2025 .SYNOPSIS... High pressure settles south of New England today and moves east Sunday as a trough approaches from the west. This trough will send a frontal system into New England Sunday night and Monday, bringing chances for some beneficial rain. Troughing lingers over the Northeast through next week, allowing for additional disturbances, and chances of rain, to enter the region. && .NEAR TERM /THROUGH TODAY/... 800 AM Update...Quick update to issue an SCA for the waters south of Casco Bay. Buoy observations show seas in this area are still hovering around 6ft, but are expected to slowly come down through the day. Update: Previous forecast on track as a chilly quiet morning continues across most of New England. Previously: High pressure will dominate the weather pattern at the surface today as an upper level ridge axis moves into the region. This will mean plenty of sunshine and warmer temperatures, with afternoon highs mainly in the 60s. Some readings in the mid to upper 50s will be possible in the mountains. Winds will generally be light and variable with high pressure in the vicinity. && .SHORT TERM /TONIGHT THROUGH SUNDAY/... Warm air advection will lead to a warmer night than previous nights, with lows ranging from the mid to upper 30s in the mountains to the lower 40s most elsewhere. Some valley fog may be possible overnight. Sunday will be the warmest day of the seven day forecast period as the ridge axis moves east and we transition to southwest flow aloft and a highly amplified trough starts to approach. Forecast highs will mainly be in the lower 60s to lower 70s with some 50s in the mountains. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... Evening Update... Overall no major changes to the long term forecast with this update as next week looks to bring a more active storm track and chances for rain. One adjustment was to bring the rain into the area a little earlier Sunday night and Monday, as the evening model runs have shown a bit more progressive system. Full Discussion... Pattern Overview: The ridge move east, giving way to what looks like an active week. Models are in decent agreement on a train of upper level disturbances moving through the region over the course of the work week. Impacts and Key Messages: * The weather pattern turns active next week, with multiple chances for widespread showers. Rainfall amounts remain uncertain, but significant impacts are not expected at this time. Details: Sunday: The ridge axis moves off to the east by early Sunday evening. The upper low cuts off Sunday night and thicker cloud cover builds in out ahead of it keeping low temperatures on the mild side (mid- to upper 40s areawide). A few showers are possible heading toward sunrise Monday, but the bulk of the precipitation holds off. Monday and Tuesday: The latest developments in regards to the first disturbance early in the week is that confidence in precipitation timing has increased, but rainfall amounts remain uncertain. The GFS has come on board with the Euro, having the low taking the southerly track (The Canadian remains an outlier), but in turn the Euro is starting to follow the GFS in speeding the system up. The GFS is still the fastest, but this increases confidence in seeing a period of drier weather at some point on Tuesday. There has been a notable uptick in QPF in the Euro ensemble suite with probabilities of greater than a half inch now 60-80% (the higher probabilities are in the mountains), but the GFS ensemble suite remains unimpressed and is holding steady with probabilities of 20-40%. As mentioned yesterday, this is likely due to the progressiveness of the system, the GFS wants Tuesday to be mostly dry, while the Euro has showers at least into Tuesday evening. There are a few other considerations that have me leaning toward the Euro solution, the first being that PWATs are going to be modest. The axis of higher PWATs remains offshore, but over our area they are currently modeled around one inch. The second is that it looks like we will have a ~50kt low level jet overhead, so some jet dynamics are bound to come into play here, developing some heavier showers. That being said, we will also have to keep a close eye on the potential for a wind threat to develop. The global models have the tight gradient and low level jet, but their lower resolution is assuming it will be too cloudy to mix any gusts down and can`t resolve a convective wind threat. Don`t be surprised if this becomes a talking point as this system begins to creep into the CAMs, but for now expecting generally 25-30 mph gusts on Monday seems reasonable. Wednesday-Friday: There is decent agreement among the global models that the pattern remains active through the work week, with another upper low swinging in behind the first one Tuesday night/Wednesday morning. This is then followed by a weaker open wave late in the week. I will leave it at that to avoid too much speculation (and writing a tome), but the takeaway should be to keep a close eye on your forecast as we work out the details of each one (and maybe keep a raincoat or umbrella handy next week). && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/... Short Term...VFR conditions are expected through at least this evening, but we could see some valley fog overnight tonight, potentially impacting LEB and HIE. Long Term...Ceilings thicken and lower Sunday night. Monday sees generally MVFR conditions with showers. Some brief IFR restrictions can`t be ruled out if heavier rain materializes. Wind gusts 20-30kts are likely as well, especially at coastal terminals. Some fog may develop after around 06Z Tuesday as rain tapers off and skies clear a bit. Some improvement may be seen for a period on Tuesday, but another system swings in Tuesday night so it will likely be brief. && .MARINE... Short Term...Winds and seas continue to relax. Some 5ft seas may linger today over the fringes of our southern coastal zones but the conditions appear to be marginal enough to hold off on any SCA for now. Long Term...Seas build back to around 5ft Sunday night as a low pressure system approaches the waters. Wind gusts will also increase Sunday night with Monday featuring frequent gusts 25-30kts. Winds calm below 25kts Monday night, with seas slower to subside and likely not falling below 5ft until late in the day Tuesday. An SCA may be needed in the mid-week timeframe as another system passes through. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Small Craft Advisory until 2 AM EDT Sunday for ANZ154. && $$ NEAR TERM...Baron/Hargrove SHORT TERM...Hargrove LONG TERM...Baron/Clair