Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 262228 AFDGYX Area Forecast Discussion National Weather Service Gray ME 628 PM EDT THU MAY 26 2016 .SYNOPSIS... High pressure to our east will allow a southerly wind to bring warm and humid conditions into New England. Some afternoon thunderstorms will be possible on Friday afternoon as the heat and humidity generate instability in the atmosphere. The hottest day will be Saturday when much of the area will warm into the 80s and 90s. A cold front will drop southward across the region late Saturday into Saturday night. An onshore easterly flow will keep temperatures cooler on Sunday especially east of the mountains. Warm air builds in again from the southwest on Monday and Tuesday before another cold front crosses the area from the northwest Tuesday night. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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625 pm update: a few convective cells have developed over southern NH so added pops in the area of the cells. Minor tweaks to temps based on latest mesonet data. No other changes at this time. Previous Discussion: Mainly clear skies will be replaced by clouds that will continue to spill east ahead of an approaching warm front. This front will become hung up across far Western Interior Maine and southern/central New Hampshire. Scattered showers and thunderstorms will gradually move eastward through New Hampshire tonight. Expect these storms to move east into more stable conditions across Maine, where elevated convection is a possibility over night. Dew points will remain in the lower to mid 50s overnight, with readings climbing to near 60 over southern New Hampshire. This will be close to the forecast overnight mins. Patchy fog may occur in the CT River Valley.
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&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... With warm air advection and the front in the vicinity on Friday, expect showers and thunderstorms to develop once again, mainly in the afternoon hours. Sufficient CAPE with ~1000 J/KG forecast, mainly over New Hampshire. There will be a significant west to east gradient in max temperatures and therefore instability. At this time, have limited enhanced wording for the possibility of damaging winds and hail to New Hampshire. Have included this possibility in the HWO as well. Greatest threat would be for high wind gusts. Dew point values will climb into the lower to mid 60s over southern New Hampshire during the day. With air temperatures forecast in the mid 80s, expect heat indices to further be on the rise. There is a possibility of patchy drizzle and fog along the coast due to onshore winds developing once again. This may linger into Friday night as convection gradually weakens with the loss of solar radiation. && .LONG TERM /SATURDAY THROUGH THURSDAY/... Weak low pressure moving through the Gulf of Saint Lawrence will cause winds to shift to the northwest on Saturday. This will help to keep the influence from the seabreeze minimized to the immediate coastal areas in the afternoon. Meanwhile the heat continues to build with high temperatures reaching the mid 80s to low 90s. With dewpoints remaining in the 60s, it will also be humid. Heat index values will likely approach 95 degrees in urban New Hampshire. Cannot rule out an afternoon thunderstorm either though this should be fairly isolated. Saturday night another front drops southward across the area... helping to push out the warm/humid air mass. By Sunday morning high pressure will be centered over eastern Maine with an easterly wind flow across much of the area. This onshore flow will keep temperatures cooler on Sunday, especially east of the mountains. Went just a few degrees below the blend of guidance values to account for the wind off the cold waters. Meanwhile, the heat and humidity continue to build further to the west over New York state. By Monday this heat and humidity will shift eastward as high pressure moves east and a shortwave trough drives a cold front toward the area from the northwest. This will bring a chance for some thunderstorms on Monday. If all the ingredients come together just right then there could be a chance of severe thunderstorms. Right now the biggest question is whether the instability will be able to spread into our area or whether the southerly low level flow will keep enough of a marine influence in place to limit instability especially across Maine. A cold front crosses the area Monday night into Tuesday. The air mass behind the front is not that much cooler than the one ahead of it so temperatures remain in the 70s to low 80s for highs. A better shot of cooler air arrives Wednesday into Thursday. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... Short Term...Areas of MVFR developing tonight in showers and thunderstorms with local IFR near the coast in drizzle and fog. Showers and thunderstorms will be possible again on Friday. Long Term...Generally expect VFR conditions Saturday. Cannot rule out an isolated thunderstorm Saturday afternoon. An onshore flow develops by Sunday morning and it is possible that low clouds could move in off the water bringing IFR conditions east of the mountains. Showers and storms are possible again on Monday in advance of the next cold front coming in from the northwest. && .MARINE... Short Term...Quiet on the waters with winds and seas remaining below Small Craft thresholds. Long Term...A cold front drops south into the Gulf of Maine and pushes westward Saturday night. Winds become easterly which could increase the wave heights in the western Gulf of Maine, but still expect winds and waves below advisory levels. High pressure shifts east with a southwest flow returning by Monday with gusts possibly approaching advisory levels as the front approaches Monday night into Tuesday. && .FIRE WEATHER... Moderate to high humidity levels return for tonight through the start of the holiday weekend. We are forecasting all areas to receive rainfall for the end of the week into the upcoming weekend...although amounts should be relatively light. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$

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