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Area Forecast Discussion
Issued by NWS Portland, ME
Issued by NWS Portland, ME
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592 FXUS61 KGYX 140245 AFDGYX Area Forecast Discussion National Weather Service Gray ME 1045 PM EDT Tue Aug 13 2024 .SYNOPSIS... A tranquil evening is expected tonight as high pressure holds over the area. Mostly clear skies are expected across NH and ME tonight before some valley fog develops across portions of western NH tomorrow morning. Scattered thunderstorms develop tomorrow and Thursday afternoon. Some storms tomorrow may contain small hail and gusty winds. Friday looks to be more pleasant with storms mainly staying contained in N NH and NW ME. After Friday, more unsettled weather is possible through this weekend and potentially even into early next week as well. 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 6 AM WEDNESDAY MORNING/... 946 PM Update... The last of the isolated showers will continue to dissipate over the northern mountains late this evening. This will leave the region with dry condition, albeit, patchy fog will develop, especially in the Connecticut River Valley. 822 PM Update... Quick update to raise pops over northern areas. A few showers may make its way across the international border and into Maine over the next hour or two before dissipating. This is supported by the latest HRRR and NamNest solution. Update... Mainly clear skies continue this evening across the region with with some cloudiness lingering across the northern higher terrain. Patchy fog will develop once again tonight, mainly in the Connecticut River Valley and mainly after midnight. Otherwise, little in the way of changes to the near term portion of the forecast. Prev Disc... Skies generally clear out of the region this evening, allowing for a tranquil evening ahead. With a crisp and calm night ahead, the CT river valley could see some valley fog tomorrow morning. Some lighter patchy fog is possible elsewhere but light winds will likely keep western and central Maine mixed, preventing the formation of fog out there. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY/... Tomorrow, an upper-level low positioned over eastern Maine may bring some scattered thunderstorms tomorrow afternoon. Chances of seeing a thunderstorm are higher across central ME and the Midcoast, but everyone has a chance of seeing a storm. These will likely be garden variety thunderstorms, with heavy downpours, small hail, and perhaps a few strong wind gusts as well. Storms will move from north to south tomorrow afternoon. Tomorrow night, storms clear the area before fog possibly develops early Thursday morning. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... 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 cutoff low deepens across Atlantic Canada on Thursday, with multiple shortwave troughs rotating around it starting on Thursday. With this feature, increasing clouds, showers, and storms develop during the afternoon on Thursday, with the greatest coverage across the higher terrain. These gradually die off after dark. 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 /03Z WEDNESDAY THROUGH SUNDAY/... Short Term... VFR expected the remainder of this evening. Some fog is expected along the CT river, lower CIGs at LEB and HIE. Confidence is high in LIFR CIGs due to fog at LEB. Low stratus likely at HIE, lowering HIE to IFR early tomorrow morning. Otherwise tomorrow starts as a VFR day, but thunderstorms could bring restrictions tomorrow afternoon with higher confidence in these lower CIGs at AUG and RKD. More patchy fog is possible Thursday morning with low CIGs possible across all TAF sites. Long Term...Mainly VFR conditions are expected, but periods of MVFR ceilings and showers are likely at times from Thursday 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... Southwesterly flow at 7-12kts with 1-3 ft seas expected this afternoon. Winds shift to the northwest at 7-12kts by tomorrow morning with no change in seas. Scattered thunderstorms possible tomorrow afternoon, especially in Penobscot Bay. Outside of convectively driven wind gusts, wind speeds should generally calm through the afternoon. No SCAs are expected through Thursday morning. 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. && $$ Cannon/Clair