Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 090326 AFDGYX Area Forecast Discussion National Weather Service Gray ME 1026 PM EST Sun Dec 8 2019 .SYNOPSIS... A milder and increasingly moist southerly flow will precede a low pressure system approaching from the Great Lakes. This system will bring mainly rain to the area Monday and Tuesday along with unseasonably mild air. The mild weather and snow melt combined with the rain could push a few rivers to near bankfull by late Tuesday. Much colder air follows this system for the remainder of the week with an active weather pattern to continue. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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1020 PM...Overall, forecast seems in decent shape. I think mins are happening now or have in some spots along the coast, here the Sw flow is starting to mix down warmer temps. Otherwise expect a slow rise in temps overnight. POPs were just tweaked a little, but other than SHSN over the mtns /and maybe a steadier snow here just before daybreak/, expect it stay dry overnight. 605 PM...Did some tweaking to POPS and temps overnight. This keeps the overnight dry in all but the nrn zones, and even backs off arrival of steadier rain in all but the far srn coastal zones until mid morning. Looks for snow in the mtns, accumulating after midnight, but generally light. I think temps may see a slight dip this evening, es[especially away from the coast, before rising slowly thru the night. Previously...At 19z a 1036 millibar high was centered southeast of Cape Cod. GOES imagery showed an area of warm air advection clouds gradually spreading eastward into the area. Temperatures had warmed into the upper 20s and lower 30s in the milder return flow. NWS Doppler Radar mosaic showed an area of light precipitation upstream across southeast Quebec. For tonight...light warm air advection precipitation will break out mainly across northern and mountain sections. The airmass is cold and dry to start so we should see light snow with some sleet possible towards morning with a shallow elevated warm layer across the north. Further south...primarily some light rain or spotty drizzle late...although it could start as a light snow/rain mix in a few spots. The forecast soundings suggest we should see little if any freezing rain as we transition from frozen to liquid late tonight and Monday morning.
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&& .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/... On monday...steadier and a bit heavier precipitation breaks out across the area as low pressure intensifies over the Great lakes and southerly flow increases across the area. Temperatures will warm into the lower 40s near the international border while we see mid 40s to lower 50s elsewhere. There will be some light snow/sleet across the mountains early transitioning to rain. Given the frigid temperatures the past few nights...we could see a few pockets of light glaze in the mountains even with temperatures a few degrees above freezing during the morning hours. The mild air mass over the snow pack will make for areas of fog by afternoon. Unseasonably mild Tomorrow night in the continued southerly flow with steadier rain tapering off overnight. We`ll be left with areas of drizzle and fog that may be locally dense. The mild temperatures and fog will contribute to snow melt. By Tuesday morning...the first round of rain and snow melt will be pushing a few rivers and streams towards bankfull. && .LONG TERM /TUESDAY THROUGH SUNDAY/... The dry slot and some partial clearing will likely push into the forecast area by midday Tue. Any precip will be tied to the terrain forcing as WNW flow begins to pick up. Tricky forecast late Tue into early Wed for coastal zones as the next S/WV trof approaches. The baroclinic zone will be offshore at that time...but a strong S/WV trof moving thru the Great Lakes will help to try and lift it back Nwd. Flow never quite backs enough for return flow...but it does look like we will try and advect a little higher moisture into what is overall a dry air mass. There should be strong moisture transport along the boundary...but forcing will be rather narrow. Given the dry air to the NW...I can see a sharp cutoff to any snowfall that occurs NW of the front. Right now I have light accumulations in the coastal zones...but not much outside of that. It will take more amplified flow to get anything more than that out of this fast moving event. High pressure builds in for the remainder of the work week...with below normal temps expected. Next chance of widespread precip will be over the weekend as a stronger S/WV trof induces a wave along the leftover baroclinic zone. There is a lot of uncertainty regarding the track and intensity of the resulting low pressure...so the multi-model consensus blend was used for the forecast in that period. I did go with a non- diurnal temp trend Fri night...as increasing clouds and approaching precip should keep temps from cooling off thru morning. && .AVIATION /04Z MONDAY THROUGH FRIDAY/... Short Term /Through Monday Night/...Ceilings begin to lower tonight, mainly over northern areas in -SN. Areas of RA/-SN enter the region from southwest to northeast early Mon with widespread IFR developing in precipitation and areas of fog. IFR/LIFR then continues for the remainder of the period. Southerly winds will gust to 35 kt at coastal TAF sites Monday night. Long Term...With flow turning NW much of the area will see conditions improving back to VFR. Upslope flow will keep MVFR CIGs and local IFR in SHSN around HIE thru the day. Tue night some -SN looks like it will try and developing behind the front and bring areas of IFR or lower to coastal terminals into Wed morning. Otherwise high pressure builds in for the rest of the work week and VFR conditions prevail. && .MARINE... Short Term /THrough Monday Night/...Strengthening southerly flow between an offshore high and approaching frontal system will bring two strong surges of wind to the waters this period. The first will be tonight when Gales are likely all waters with a few gusts to Gale possible in Casco Bay. The second will be late Monday and Monday night with an 80+ kt low level jet. We should see strong Gales all waters with storms possible over the eastern two-thirds of our outer waters...where a storm watch has been posted. Long Term...CAA continues thru Tue with winds and seas only gradually diminishing...and SCA conditions lingering into Wed. High pressure builds in for the remainder of the week with winds and seas falling below SCA thresholds. && .HYDROLOGY... Mild temperatures, high dew points, and periods of rain will impact the area Monday and Tuesday and erode snow cover across the region, particularly over southern New Hampshire and coastal western Maine. While the fresh snow will initially absorb rainfall, the snow will likely ripen and begin melting. This will lead to an influx of water into local waterways. At this time, southern New Hampshire has over a foot of snow in places with liquid equivalent likely exceeding 1", with some areas possibly closer to 2". Should moderate rainfall occur in areas with high snow water equivalent, instances of localized flooding will be possible in poor drainage areas, as well as some main stem rivers and tributaries rising above action stage and approaching bankfull by Tuesday. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Gale Warning until 5 AM EST Tuesday for ANZ151-153-154. Storm Watch from Monday evening through late Monday night for ANZ150-152. Gale Warning until 6 PM EST Monday for ANZ150-152. && $$ SYNOPSIS... NEAR TERM...Cempa/Schwibs SHORT TERM...Schwibs LONG TERM...Legro AVIATION... MARINE... HYDROLOGY...

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