Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 181425 AFDGYX Area Forecast Discussion National Weather Service Gray ME 1025 AM EDT Tue Oct 18 2016 .SYNOPSIS... A warm front will try to slowly lift northeast through the region today. Temperatures will be very warm south of the warm front today, but north of the front it will be cooler with showers expected. As low pressure moves through Quebec, it will drag a weak front into New England tonight and then move offshore. High pressure with dry and very mild temperatures are expected Wednesday. A trough of Low pressure will track across New England Thursday and Friday and will bring some much needed rain to the area. The system exits into the maritimes over the weekend with breezy conditions and much cooler temperatures in its wake. Along with the cool temperatures, clouds and even a few showers possible in the mountains over the weekend. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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1020 AM...Winds have been more NE than SE this morning and this allowing for stronger cold air damming to hold. Have adjusted sky and temps to hold onto the clouds and cooler air longer across the southern zones, and tweak maxes down in this areas as well. Meso models do want to break the inversion in southern NH, the CT valley and SW ME, but it will likely not happen until early to mid afternoon, so highs will be limited to the mid to upper 60s in many spots, with a few spots in the CT valley and maybe the Merrimack valley making it to 70 or so. Also added patchy FG/DZ to the coastal zones and the coastal plain of ME as the will see more in the way of warm moisture advection above the inversion here. 630 AM Update: Only minor changes needed this hour with shower activity essentially over as we find ourselves in a void between activity north of the international border and more showers off the Massachusetts coast...with H8 warm front moving overhead with just a sprinkle or two. Adjusted to current temperatures/dewpoints with very minor PoP tweaks...primarily to lower them in the near term. Previous discussion below... High Impact Weather Potential: Splashover/minor coastal flood potential /see Tides/Coastal Flood section below/. Current Pattern: A look at early morning water vapor imagery reveals decaying area of enhanced moisture associated with earlier MCS whose remnants are now exiting my southern zones. Shortwave ridging is now arriving from the west with next area of deep moisture associated with developing surface low pressure system over northern Michigan. Down at the surface...we can see a high pressure ridge axis aligned over eastern Maine with building SLPs in a cold air damming pattern setting up over coastal Maine into southern NH. South and west of this feature is a stationary boundary separating yesterday/s warmth from cooler air draining south with the high. With aforementioned low pressure system continuing to lift north and east...and shortwave ridging moving east of our longitude... developing deep layer southwesterly flow will begin to nudge the surface front north and east ahead of an approaching cold front that we/ll discuss in the tonight forecast. Thus...forecast concerns center around 1-precipitation potential in the strengthening WAA regime and 2-surface temperatures and how the surface front evolves. Through Daybreak: Backdoor front continues to push south and west...having cleared southern NH with surface pressures continuing to rise. Last remnants of decaying MCS will exit my southern NH zones through 5am...with nothing more than a few sprinkles noted north of this. Expect this trend to continue...with a few light showers/sprinkles along the leading edge of the moisture surge at H8 continuing over northern areas through 8am. Temperatures come down another few degrees under the light northeasterly the upper 40s to mid 50s. Today: Deep southwesterly flow overspreads the region today well ahead of deep low pressure that will reach near James Bay early this afternoon...continuing northeast into this evening. Warm front at H8 will depart my Maine zones this AM...taking any remaining light shower activity with it. With surface low pressure so far removed to our north and west...the surface boundary will struggle to make northward progress today...with most recent renditions of high resolution guidance continuing to bring the warm air to a smaller and smaller portion of our forecast area. Will not go all the way to the HRRR which indicates that the warm front does not arrive during the daylight hours...but will trend afternoon highs back some from inherited forecast. This brings Cheshire/Hillsborough/ Rockingham counties into the lower 70s...with 60s north and east of this except northern Oxford/Franklin/Somerset in Maine where mid 50s will likely be it. Certainly some bust potential vicinity LEB/CON/PSM/SFM...but growing confidence that the warm air fails to reach even southern Maine today.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... High Impact Weather Potential: Minimal. Pattern: Broad southwesterly flow will remain over the area through the short term forecast period with just enough of an angle between this flow and upstream surface front to push it through the region tonight and offshore for Wednesday. Primary forecast concerns center around precipitation potential along the front. Tonight: Surface cold front will be just upstream of New England at 00Z...nearing the coastal plain by daybreak Wednesday. Llevel flow largely veered ahead of the boundary with mid level shortwave energy having bypassed the front to our north and east. Thus...while a +2- 3 sigma PWAT plume will pull overhead through the night...waning instability and llevel convergence suggests a decaying band of showers /embedded thunder?/ and forecast PoPs will follow this trend with measurable precipitation rather unlikely along the coastal plain. Clouds and warm airmass aloft will allow for another night of mild low temperatures...with consensus lows in the 50s/lower 60s looking good. Wednesday: Nice day expected on Wednesday with high pressure building in behind departing cold front. Deep moisture plume will be pushed offshore during the day...with very modest cold advection behind this feature. Could see some residual clouds in the mountains under modest northwesterly flow...but mostly sunny south south and east of this. T8s remain around +10C with T9s +12-17C north to south during the afternoon. Thus...expect highs to be well above normal...60s north of the mountains with mid/upper 70s in the foothills and points south. Enjoy significant changes are in store in the long term period below! && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... A progressive digging upper trough will move across the Ohio Valley and Great Lakes region Thursday and in advance first spreading clouds and then the chance of rain in the afternoon from west to east. The upper trough will continue to develop over the eastern Great Lakes Thursday night and Friday becoming vertically stacked and spawning surface cyclogenesis across the St Lawrence Valley and upstate New York. A broad area of rain will gradually develop by Friday afternoon. The upper trough will continue to develop as it becomes negatively tilted and then becomes a closed low by Friday night. As the system develops, models are indicating a strong southeast flow will develop to its east and will likely pick up some tropical moisture from a system off the southeast coast of the U.S. This may bring some soaking rains to the area late Friday and Friday night. Models indicate the closed upper low is expected to move slowly north and east into the maritimes Saturday and Sunday possibly allowing some lingering showers mainly in the mountains due to the unstable cyclonic flow. Much cooler temperatures will arrive behind the system Saturday into Sunday. Cool and dry weather is expected Monday as Canadian high pressure builds across the region. && .AVIATION /14Z TUESDAY THROUGH SATURDAY/... Short Term /through Wednesday/... Summary: A warm front will slowly lift north through the area today before a cold front moves in from the northwest tonight with high pressure arriving for the day on Wednesday. Restrictions: Conditions deteriorating attm with MVFR /and some IFR/ cigs developing north of warm front. This trend will continue through the morning before gradual improvement this afternoon and evening. A few isolated showers are possible for ME terminals this morning with dry conditions this afternoon. Tonight...a band of showers will impact HIE/LEB before falling apart as it moves south and east. Conditions overnight generally VFR except fog development HIE/LEB and potentially CON/AUG. VFR for the day Wednesday. Winds: Generally from the northeast 5-10kts today...shifting south 10 kts this afternoon into this evening as the warm front moves north. Southwesterly winds shift northwesterly for the day on Wednesday 10-15kts. LLWS: Impressive LLWS setup this evening as southwesterly flow strengthens atop strong llevel inversion. Expecting 30-40kt winds at 1-2kft all sites through the overnight. Thunder: Very remote chance of a rumble this evening HIE/LEB...otherwise no threat. Long Term...Conditions deteriorate Thursday in an onshore flow with increasing clouds and showers. IFR or LIFR conditions are possible Thursday through Friday night. Could see an improvement to VFR this weekend. && .MARINE... Short Term...Winds nearing SCA levels this morning...but bona-fide SCA conditions hold off until tonight with strengthening southerly winds/building seas. Winds/seas diminish behind departing cold front Wednesday. Long Term...An increasing south to southeast flow Friday and Friday night may develop SCA conditions. Winds behind the system over the weekend may be gusty from the west and northwest so SCA conditions may continue. && .TIDES/COASTAL FLOODING... Have issued coastal flood statement for this afternoon/s 1pm EDT high tide given surge forecast of up to one half foot...which would put both Portland and Fort Point right at FS early this afternoon. Wave action does not look that impactful...only 2-3 feet at the coast. Will monitor the surge/winds this morning and see if advisory is warranted. Tides remain high for the next few days...but winds look to remain light beyond today/s high tide. Will continue to monitor. Tides at Portland the next few days follow below: 108 PM Tue 11.7 ft mllw 200 PM Wed 11.5 ft mllw 256 PM Thu 11.1 ft mllw && .GYX WATCHES/WARNINGS/ADVISORIES...
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ME...None. NH...None. MARINE...Small Craft Advisory until 8 AM EDT Wednesday for ANZ150>152- 154.
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&& $$ SYNOPSIS...Arnott/Marine NEAR TERM...Arnott/Cempa SHORT TERM...Arnott LONG TERM...Marine AVIATION...Arnott MARINE...Arnott/Marine TIDES/COASTAL FLOODING... is the U.S. government's official web portal to all federal, state and local government web resources and services.