Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 240256 AAC AFDGYX Area Forecast Discussion...UPDATED National Weather Service Gray ME 1056 PM EDT Sun Jul 23 2017 .SYNOPSIS... A ridge of high pressure will gradually shift offshore into the maritimes tonight into Monday. Low pressure will approach from the southwest later tonight and Monday and will deliver cooler temperatures and the likelihood of rain in an onshore flow. Conditions will gradually improve by Tuesday night and Wednesday as high pressure moves in. A cold front approaches late in the week. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... 1056 PM Update... Have updated the forecast for current radar and observational trends. Precipitation timing was adjusted slightly but is largely unchanged. 838 PM Update... Forecast has been adjusted for temperatures and cloud cover trends. Mix of cirrus and altocumulus moving in from the west as moisture increases throughout the boundary layer. Still looks like it will take most of the night and morning for precipitation to develop over western NH. 6 PM Update... Minor changes to the forecast at this time. Lovely night in progress with temperatures in the 70s and dew points in the 40s and 50s. Any precipitation will remain to the west through at least midnight. Previous Discussion... At 18z a 1019 millibar high was centered near the southern tip of Hudson Bay...while yesterday`s cold front remains stalled from Lake Erie southeastward through the Mid Atlantic region. We enjoyed a brief break today as the Canadian surface high briefly nosed into the forecast area. The surface ridge will gradually retreat offshore tonight with onshore flow and an approaching shortwave impulse spreading increasing and lower cloud into the area overnight. Any precipitation should be confined largely to southern and western New Hampshire tonight. Lows tonight will range from near 50 along the international border with readings in the 50s to around 60 elsewhere. && .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/... A cool damp day in expected Monday as a series of weak lows traverse the surface boundary situated to our south and west. Rain should be lightest and of shortest duration over our far northern and eastern Maine zones as the precipitation has a hard time overcoming the dry air with the surface ridge over the maritimes. Highs will be well below normal for the date and confined to the 60s. Rain tapers to scattered showers Monday night as the first shortwave exits offshore along with an associated surface low. We`re then left with cloudy skies and areas of drizzle and fog for the balance of the overnight period. Lows will be in the 50s. && .LONG TERM /TUESDAY THROUGH SUNDAY/... Low pressure will exit into the Canadian Maritimes on Tuesday as winds switch to the west aloft. However, an upper level trough will remain overhead. Steep lapse rates and low level moisture will allow for mainly diurnally driven scattered showers to pop up across the region during the day. This precipitation will diminish around sunset. There will only be a slow improvement in maximum temperatures, with readings limited to the 60s in most areas. Patchy fog will dominate the region Tuesday night as high pressure parks itself over the region. As the surface ridge exits the region Wednesday, a cold front will approach northern sections, bringing scattered showers and storms to that region by Thursday. On Friday, it appears a surface low will cross Southern New England. This will bring a period of rain to southern areas, with some of it being heavy. The Canadian, and to some extent the Euro model are most aggressive with the cyclogenesis with this system. && .AVIATION /03Z MONDAY THROUGH FRIDAY/... Short Term /through Monday Night/...VFR. MVFR conditions are expected to arrive Monday morning as rain moves into the region...areas of IFR developing Monday night in areas of drizzle and fog. Long Term... Conditions will begin to improve on Tuesday and return to VFR with just some valley fog possible on Tuesday night as high pressure crests over the region. Wednesday will return to VFR. A front will cross the region on Thursday with scattered showers and thunderstorms possible at all locations into Friday. && .MARINE... Short Term /through Monday Night/...the onshore flow will strengthen as we head into Monday afternoon and evening and we may need a small craft for our southern most offshore waters late Monday into Monday night. Long Term... Winds and seas will subside by Tuesday with high pressure building in for Wednesday. Low pressure approaches the waters Thursday and Friday. && .TIDES/COASTAL FLOODING... High astronomical tides tonight and Monday night may contribute to some localized minor coastal flooding right around the times of high tide during the late evening hours. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...Coastal Flood Advisory until 1 AM EDT Monday for MEZ023-024. NH...Coastal Flood Advisory until 1 AM EDT Monday for NHZ014. MARINE...None. && $$ NEAR TERM...Hanes SHORT TERM...Schwibs LONG TERM...Cannon AVIATION...Schwibs MARINE...Cannon/Schwibs is the U.S. government's official web portal to all federal, state and local government web resources and services.