Area Forecast Discussion
Issued by NWS Portland, ME

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KGYX 230055 AFDGYX Area Forecast Discussion National Weather Service Gray ME 855 PM EDT Tue Aug 22 2017 .SYNOPSIS... A strong cold front will sweep east across the region tonight and early Wednesday accompanied by showers and thunderstorms. High pressure and drier air follows the front late Wednesday through the weekend. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
-- Changed Discussion --
8pm... Thunderstorms are progressing through the area as the cold front approaches from the west. Ahead of the line of storms a very favorable environment with dewpoints near 70 has allowed for a stronger cell to track through central Maine. As the sunsets expect the convection to gradually weaken and transition to a more heavy rain and lightning threat, however the very strong upstream forcing will assist in keeping a few strong to severe storms alive, especially in the southern portion of the CWA which has not yet seen any convection. Looking upstream the convection extends back to near Massena NY. While the individual cells may not be severe the multiple rounds of precipitation will have to be monitored for the potential for flash flooding over the next few hours. Severe Thunderstorm Watch 463 remains in effect through to midnight. 408 PM...Line of convection over eastern New York continues to march eastward into western New England on NWS Doppler mosaic. This activity will reach the Connecticut Valley between 6 and 8 PM then weaken as it moves eastward with loss of daytime heating and a more stable airmass. The primary concern will be wind damage within bowing segments of the line this evening. SPC has issued severe thunderstorm watch #463 until midnight for much of Western New Hampshire and extreme Northwest Maine until midnight. Prev disc... At 18z...a 995 millibar low was over northern Quebec with a trailing cold front through the lower Great Lakes. A shortwave impulse was evident on GOES water vapor over the upper Great Lakes. A broken line of convection was taking shape on NWS Doppler radar mosaic from the Ottawa Valley southward through upstate New York and northwest Pennsylvania in response to strong heating and strengthening wind field ahead of shortwave impulse and strong surface cold front. For this afternoon...a few scattered storms may develop ahead of the line across western and northern New Hampshire and along the international border of Maine with gusty winds and small hail. Otherwise...the line of convection over upstate New York will race eastward and reach the Connecticut Valley towards dusk and western Maine by late evening. The line should weaken as it moves east into forecast area and we lose daytime heating. The primary threat with this line should be damaging wind gusts. The activity will sweep east and offshore in the predawn hours along with the surface cold front. Lows tonight will be in the 60s to around 70 along the coastal plain and in the lower 60s elsewhere.
-- End Changed Discussion --
&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... Clearing Wednesday behind the front as drier and cooler air filters into the area. There could be a morning shower across the higher terrain before the drier air takes hold. It`ll be a warm and noticeably less humid day with highs in the 70s to around 80. For Wednesday night...a few lingering upslope clouds across the higher terrain otherwise mostly clear and seasonably cool with some patchy late night valley fog. Lows in the 50s...with mid and upper 40s across the mountains. && .LONG TERM /THURSDAY THROUGH TUESDAY/... Rather benign weather is expected during the extended period. Mean troughing will be the rule, but with little moisture to work with, we expect the bulk of the period to be dry. Temperatures are expected to be around normal, with perhaps a few chilly nights in the interior. The weekend into early next week is shaping up to be nice as ridging builds at all levels. && .AVIATION /01Z WEDNESDAY THROUGH SUNDAY/... Short term /through Wednesday Night/...Conditions lowering to MVFR and locally IFR in developing late afternoon and evening thunderstorms. Some of the storms could be severe with strong wind gusts and possible hail. The thunderstorms will weaken later in the evening but scattered showers with MVFR conditions will continue until the passage of the cold front by Wednesday morning. Marine stratus and fog may move onshore this evening vcnty of KRKD and result in LIFR conditions for much of tonight. Conditions will improve to VFR throughout following the frontal passage on Wednesday. Long Term...VFR conditions are expected to prevail Thursday through the weekend other than some early morning valley fog. && .MARINE... Short Term /through Wednesday Night/...Winds and seas will increase into tonight ahead of an approaching cold front. SCA conditions will develop by evening and continue overnight and into Wednesday. The cold front will cross the waters early Wednesday allowing a gradually wind shift to the west helping knock down the seas by later in the day. Long Term...Small craft conditions are not expected Thursday through the weekend. && .TIDES/COASTAL FLOODING... We`re in the period of high astronomical tides for the month of August. The remaining high tide of potential concern (referencing Portland Harbor where flood stage is 12.0 ft MLLW) is: 1231 AM Wednesday. 11.1 ft MLLW Tonight`s high tide (1231 AM Wednesday) could see some splashover and minor beach erosion as onshore flow and seas increase ahead of an approaching cold front. Have issued a coastal flood statement for tonight`s high tide. && .GYX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
ME...None. NH...None. MARINE...Small Craft Advisory until 8 AM EDT Wednesday for ANZ150>154.
-- End Changed Discussion --
&& $$ SYNOPSIS... NEAR TERM...Curtis SHORT TERM...Schwibs LONG TERM...Ekster AVIATION...Schwibs MARINE...Ekster/Schwibs TIDES/COASTAL FLOODING...

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.