Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 201321 AFDGYX Area Forecast Discussion National Weather Service Gray ME 921 AM EDT Thu Apr 20 2017 .SYNOPSIS... A cold front will remain just off the coast today with lingering showers in the mountains. Clouds will increase tonight ahead of a low pressure system moving out of the great lakes. Rain will move in on Friday and continue through Friday night. The mountains will see a change over to snow overnight Friday before ending as a cold front sweeps through Saturday morning. Weak high pressure builds in for Sunday before another period of unsettled weather to start next week. && .NEAR TERM /UNTIL 7 PM THIS EVENING/...
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920 AM...At 13z a west-east frontal boundary was stalled to our south with a 1019 millibar low situated along it over southeastern New York State. A surface trough extended northward through eastern New England. A 1032 millibar high was situated over the southern tip of Hudson Bay. For today...the weak wave will ripple along the boundary and turn the flow onshore along the coast by mid day. The 1032 millibar high will briefly nose into the region from the north and there may be some short lived breaks in the overcast over northern and interior sections of the forecast area. Otherwise...lingering low level moisture and a predominantly onshore flow will make for a mostly cloudy day. Temperatures will struggle to reach the 50s today with 40s along the international border. Prev Disc... 650 am...Just a few minor changes to POPs/T/Td based on current trends, but otherwise forecast unchanged for today, with a lot of clouds, but mainly dry weather. Previously...Weak cold front moving SE of the CWA early this AM, which will slow and become stationary across southern New England today. Will see weak flow develop this morning, which may mix some drier air down and produce a few breaks sun inland areas from mid-morning thru early afternoon, but for the most part there will be more clouds than sun. Coastal areas will likely get stuck in the clouds, as the N flow is too weak to overcome any onshore density current that gets going once things start warming up. Temps will be warmer given at least a morning of no onshore flow, so highs will range from around 50 in the mountains and on the mid-coast to near 60 in interior srn NH. Might see some spotty DZ late this afternoon in the upslope areas of the foothills as SE flow begins to increase ahead of the next approaching system.
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&& .SHORT TERM /7 PM THIS EVENING THROUGH 6 PM FRIDAY/... Compact 500 mb closed wave crosses the Great LAkes tonight, and gets a shot of energy, showing some negative tilt there before it lifts NE across srn Quebec FRi and Fri night as it fills. This will allow for one sfc low to track with the wave aloft to our N, and another to develop along the stalled front to our south. HEaviest precip will generally and north, but will see rain moving in from the SW tomorrow night and continue into Friday. The more significant QPF, and this is only on the the order of a half inch will be late tonight into Friday morning when remnant convection and best dynamics passes just to our NW. Lighter rain will persist through the day Friday as we remain between the weakening system to the north and the developing system to ours south. For the most part this will fall as rain, although higher elevations could see some snow, this will mostly above 4K ft in this timeframe, although the elevation for snowfall will lower Fri night. It will be cool through the period as the developing low to our south cuts any hope of warmer air moving in and we remain in E-NE flow. Overnight lows tonight will be in the mid-upper 30s in the mtns, and in the 40-45 range on the coastal plain and in srn NH. Highs Friday will be lucky to see temps rise by about 5 degrees, maybe reaching 40-45 in the mountains, and 45-50 in the south. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... A short wave aloft currently over Montana will move east through the end of the week bringing low pressure into northern New England for the start of the weekend. Rain will be widespread on Friday and continue overnight before coming to an end on Saturday morning. While initially on Friday everywhere will start as rain expect to see a transition to snow at the higher elevations overnight as the cold air aloft moves in. This will result in up to an inch of accumulation, mostly above 2500ft. Neither sleet nor freezing rain is a concern here as there is minimal warm air aloft and surfaces are too warm to freeze on contact. Rather expect wet snow or snow mixing with rain in the overnight hours. Weak high pressure begins to build in on Saturday night and crests over the region on Sunday. This high will simply trap any remaining moisture at the surface giving cloudy skies and some possible fog along the coast. There is a low chance for the area to break out of the clouds, in which case a sea breeze could develop but overall feel the cold damp option is more likely and have stuck with overcast skies. On Monday the forecast area is further squeezed between two systems as a cold front passes to the north and a low moves south of the area. Again look for widespread clouds with showers possible in southern New Hampshire. On Tuesday the cold front in the north tries to combine with the low off shore to bring more widespread precipitation across especially the eastern portion of the forecast area. This is a possibility but a rather low confidence forecast at this point and have just stuck with a mild mannered blend of options for the rest of the forecast package at this point. && .AVIATION /13Z THURSDAY THROUGH MONDAY/... Short Term...For the most part IFR or lower will prevalent through Friday. Will see some improvement to MVFR today, especially away from the coast, and may see some VFR late morning into the afternoon at interior NH terminals, but all locations can expect to return to IFR or lower tonight in rain/fog and low cigs. These conditions will persist into Friday, and coastal terminals could see E-NE winds gusting to 20-25 kt at times on Friday. Long Term... Widespread IFR in rain will continue Friday night into Saturday morning. Conditions will then improve to MVFR region wide for Sunday, with a chance for IFR creeping crud during the overnight in coastal locations. && .MARINE... Short Term...SCA seas persisting, but subsiding through early morning, as are winds. So the 10Z expiration time of the SCA looks reasonable. Will get a break today , but developing low pressure to our south will begin to produce strengthening E-NE flow tonight with SCA conds returning late tonight and on Friday. Long Term... Small crafts will again be needed Friday overnight into Saturday morning. && .FIRE WEATHER... Moist onshore flow will persist into Saturday, with below normal temps precluding any fire weather threat thru the weekend. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ ES

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