Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 151631 AFDGYX Area Forecast Discussion National Weather Service Gray ME 1231 PM EDT Fri Sep 15 2017 .SYNOPSIS... Moisture associated with the remnants of Hurricane Irma will move through the region today bringing a few showers and possibly a thunderstorm. Beyond this...high pressure will build back into the region for the weekend through early next week bringing dry and mild conditions to the region. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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noon.. minor update. Forecast generally on track with a few showers starting to form across southern NH. 9am update... Shower activity rotating around the upper low continues to extend from IZG down through LCI. These showers are producing some pockets of heavy rain. Morning sounding shows 1000 J/kg of instability and a PWAT of 1.64, which combined with the weak steering flow will mean any storms that do form today will need to be monitored for heavy rain. Currently low cloud cover is limiting surface temperatures which will suppress convection through morning but as the sun breaks through expect shower activity to increase again across southern NH this afternoon. 713 AM Update... Persistent convection this morning along a curving frontal boundary and in the vicinity of a cold pool directly over northern MA and southern NH. Some lightning still occurring off and on with this activity as well as very heavy rainfall. Storms are nearly stationary or moving very slowly north. This will be the main issue today as previously mentioned. Adjusted PoPs slightly as well as cloud cover and temperatures for recent trends. 417 AM Update... A quick update to add lightning back in as a few cells have intensified along a northward moving warm front. Also received a report of very heavy rainfall under one of the cells, so have added this to the forecast update as well. Previous discussion... A moist air mass associated with the remnants of Irma along with a stationary/warm front is supporting showers which are mainly situated across southern NH and SW Maine. Weak lift provided by cyclonic flow at the surface and aloft has kept this convection going. Lightning ended several hours ago...but as forcing increases this morning an isolated strike is not out of the question. Rain is not especially heavy at this time, but PWATs are on the increase with last night KGYX sounding showing 1.22" already. This has undoubtedly increased overnight with south winds encroaching at the coast. Fog and low stratus have developed where other cloud cover is not preventing radiational cooling. Cloud cover will likely prevent the need for a dense fog advisory...but there are areas of dense fog over NH. Temperatures are still quite warm and in the mid 50s north where there are some clear spots to the 70s closer to the coast. Expect skies to be partly sunny across the mountains and foothills during the day with a slight chance of a shower or thunderstorm. Along the coast, skies will remain mostly cloudy near the front with the continued chance of showers and an increasing possibility of isolated thunderstorms with heavy rain as the front shifts north and PWATs push into the +2 sigma range. Have included this wording in the worded forecast as any shower has the potential to cause localized flooding. Highs should reach the mid 70s to lower 80s.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... Ridging builds in farther from the SW and winds will be calm tonight. Cloud cover and showers will linger along the coast and offshore with the trough still over the Gulf of Maine and plenty of moisture around. Moisture will be around 150-175% of normal by mid day, when comparing the NAM to climatology. Therefore expect fog and stratus to be a bigger issue, with areas of dense fog on land and over the water alike. Very likely we may need a dense fog advisory late tonight into Saturday morning. Saturday temperatures will warm into the upper 70s to mid 80s...however it will be humid with almost no wind. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... Weak frontal boundary draped across northern Maine will gradually lift north Saturday night and Sunday as high pressure remains in control over the region. Expect partly cloudy to mostly clear skies through the period. Lows Saturday night will range from the mid 50s to lower 60s. Highs on Sunday will top out in the 70s to near 80. Increasing onshore flow will cap temps in the upper 60s to mid 70s in coastal areas. High pressure will remain nosed in from the east Sunday night and Monday. Increasing onshore flow will likely result in some ocean stratus in coastal areas by Monday evening. Extensive marine layer will hold temperatures down especially in coastal locals where readings will be held in the upper 60s to lower 70s. Inland locations will edge into the mid to upper 70s. Forecast confidence heads downhill at this point as models continue come together on a track for Jose. GFS most aggressive in bringing this system northward into southern New England Tuesday night. ECMWF follows a similar track but is much slower in northward progression staying much farther south by the same period. Have started with SB pops but like surrounding offices have trimmed these numbers back to just chance pops at this point due to the large uncertainty. Chance for precipitation from Jose will extend through Wednesday as both GFS and ECMWF meander this system off the coast before turning it south and west back toward the mid Atlantic coast south of New England. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... Short Term... Areas of LIFR continue this morning are generally confined to southern NH and SW Maine. Elsewhere VFR conditions prevail with mid and high clouds preventing much fog development. Showers have been affecting the PSM/MHT/CON corridor last night and this morning and are moving very slowly. This has added to the low visibilities and clouds. RKD is also reporting -RA this morning but this is more transient in nature. This activity may eventually affect AUG or PWM this morning. Away from the coast expect improvement to VFR by late morning/early afternoon. More widespread shower and isolated thunderstorm activity is expected by this afternoon. Widespread dense fog sets in tonight with even more widespread IFR/LIFR restrictions. Long Term... High pressure builds into the region for the weekend and holds through next week resulting in VFR conditions through the middle of next week. && .MARINE... Short Term... No flags expected through Saturday with waves generally subsiding through tonight. Long Term... Quiet waters as high pressure builds into the region and hold through the start of next week. Tropical Storm Jose may pass through or just east of the Gulf of Maine in the middle of next week. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ SYNOPSIS... NEAR TERM...Curtis SHORT TERM...Hanes LONG TERM...Sinsabaugh AVIATION... MARINE...

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