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Area Forecast Discussion
Issued by NWS Portland, ME
Issued by NWS Portland, ME
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513 FXUS61 KGYX 140753 AFDGYX Area Forecast Discussion National Weather Service Gray ME 353 AM EDT Wed Aug 14 2024 .SYNOPSIS... Comfortable temperatures and valley fog this morning will give way to increasing clouds and showers and thunderstorms this afternoon. Especially across western Maine, a few of these storms could be strong and contain small hail and gusty winds. Another round of showers and storms is expected Thursday before some improvement Friday. After Friday, more unsettled weather is possible through this weekend and potentially even into early next week. Hurricane Ernesto passes offshore late this weekend and early next week, bringing an increasing swell and dangerous rip currents by late this weekend and early next week. && .NEAR TERM /UNTIL 7 PM THIS EVENING/... Valley fog this morning will lift shortly after sunrise with daytime mixing. It will be another warm day with sun early. An approaching S/WV trof will help increase clouds and convection by this afternoon. Storms will develop along the higher terrain and drift south with the S/WV. Forecast soundings still show decent lapse rates aloft and ample CAPE for stronger storms. Lack of shear will preclude a widespread severe weather threat...but an isolated storm with small hail and gusty winds will be possible. I have not included that wording in the forecast grids at this time since the coverage of severe weather threat is not anticipated to be that great. Subsequent updates may put that wording in...mainly from the mtns into most of western ME. && .SHORT TERM /7 PM THIS EVENING THROUGH 6 PM THURSDAY/... CLearing skies will allow for radiational cooling and valley fog once again. Given the increased chances of rain today I do have more widespread coverage of fog tonight. Thu will also remain under the influence of the upper trof...giving us another afternoon of increasing convection. Showers and storms should focus midday to early afternoon in the mtns...and drift south thru the afternoon and evening. Still cannot rule out a stronger storm or two...with machine learning guidance showing a low probability of small hail. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... Overview... A series of troughs move through the Northeast late this week and through the weekend, bringing multiple chances for showers and storms, as well as near average to seasonably cool temperatures. Tropical storm Ernesto is expected to strengthen into a Hurricane and pass offshore this weekend and early next week, bringing an increasing swell and dangerous rip currents starting this weekend. Details... A weak shortwave ridge moves through on Friday, bringing a brighter and relatively drier day. However, with the cutoff low and cold pool aloft still nearby, some scattered showers are still possible Friday afternoon, especially across northern and eastern areas. By Saturday, the next trough begins to dig in through the Great Lakes. This brings an increasing chance of showers late in the day, especially across western and northern areas. These continue to spread eastward overnight as low pressure develops through the Great Lakes and slowly drifts eastward. A ridge develops and remains nearly stationary across Atlantic Canada over the weekend. This slows and nearly stalls the system in the Great Lakes from making much eastward progress, allowing eastern areas to stand a better chance at remaining drier. This pattern continues through Monday, with another reinforcing shortwave transiting the trough going into Tuesday. While all this is going on across the Northeast, Ernesto is expected to become a hurricane and pass offshore this weekend and early next week, likely passing close to Bermuda this weekend. An increasing swell from the system is expected to begin arriving by Saturday, with waves gradually building through Monday, and then slowly lowering from Tuesday through midweek next week. There remains some question as to how much the trough across the Northeast will interact with Ernesto and affect its track. While it`s expected to remain offshore, this interaction will determine how close Ernesto will pass by to New England, and the angle that it will be tracking while offshore. These factors impact how large the waves will build to, and the strength of the rip currents. Regardless, the long period swell begins to arrive by Saturday, likely starting as a 2ft swell with a 16 second period, and then gradually build through Monday. To how large remains in question and dependent on the track distance and direction, which will be the main question to solve over the next few days. Regardless, rip currents begin to strengthen by Saturday and remain a concern through at least midweek next week. && .AVIATION /08Z WEDNESDAY THROUGH SUNDAY/... Short Term...Local LIFR conditions in the CT River Valley will linger until just after sunrise then VFR. SHRA/TSRA develop by mid afternoon and drift south thru the evening hours. Local MVFR or lower conditions are possible in any convection, and some may contain gusty winds and small hail. After showers dissipate local LIFR conditions will once again by possible in valley fog tonight. Another round of local MVFR or lower conditions will be possible Thu in SHRA/TSRA. Long Term...Mainly VFR conditions are expected, but periods of MVFR ceilings and showers are likely at times through early next week, especially across interior terminals during the afternoon and evening. Nighttime valley fog is also likely at LEB and HIE each night. && .MARINE... Short Term...Winds and seas are expected to remain below SCA thresholds. Later this evening showers and storms may drift over the coastal waters with locally gusty winds possible. Long Term...Weak pressure patterns prevail as broad high pressure gives way to broad low pressure late this week through the weekend. Hurricane Ernesto likely passes east of the Gulf of Maine late this weekend and early next week, bringing an increasing southeasterly swell starting by Saturday. The swell may build to greater than 5ft by Sunday. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ SHORT TERM...Legro