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Area Forecast Discussion
Issued by NWS Portland, ME
Issued by NWS Portland, ME
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329 FXUS61 KGYX 142311 AFDGYX Area Forecast Discussion National Weather Service Gray ME 711 PM EDT Wed Aug 14 2024 .SYNOPSIS... Isolated showers and storms dissipate this evening. Another round of showers and storms is expected Thursday before some improvement Friday. By this weekend, periods of more unsettled weather are possible through the weekend into early next week. Hurricane Ernesto passes offshore late this weekend and Monday, bringing an increasing swell and dangerous rip currents by Saturday through midweek next week. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... 7 PM Update...One strong/severe storm in southwestern Somerset County ME continues to move southward and is currently weakening. The rest of the region is dry. However, we cannot rule out a few more storms this evening with another short wave trough moving southward in the cyclonic flow regime aloft. Previously... Isolated showers and storms have developed this afternoon. At time of publishing, these are mostly over central and southern Maine. The cu field has been slow to show much deeper growth through the afternoon, perhaps stunted by earlier smokey cast deterring some solar insolation through the first half of the day. There should remain instability off the surface however as upper low stalls over Nova Scotia/New Brunswick. Embedded shortwave will be forcing that taps into this instability into the evening and early overnight to keep showers and some thunder possible. With the low shear and dry low levels, will continue to have some of these storms produce gusty winds through the early evening. This shouldn`t be a widespread impact unless a cluster of storms forms a uniform outflow, but the deeper/stronger storms will be capable of these winds. A few pockets of showers may continue up to midnight, but a general clearing trend is forecast. This will again bring in fog chances for the CT River Valley late. HREF vis and ceiling guidance has also hinted at a low deck of clouds advancing along the coast and interior from the east overnight. Probabilities aren`t the highest, but patchy fog could form over damp areas as the night cools. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/... A similar setup possible for Thursday where a chance for afternoon showers and thunderstorms exists. Shear parameters are again marginal compared to available instability. Theoretically gusty winds and small hail would again be possible in stronger cells. Will continue to assess how this trends, and how this afternoon plays out to increase confidence. HRRR Smoke/RAP models do portray additional high level smoke passing through the region, and this may further impede afternoon convection. Surface temps may be a couple degrees cooler as more morning cloud cover is possible and the upper low retrogrades west. While highs topped out around 80 today, highs may only make it into the mid to upper 70s for ME and the northern half of NH Thursday. A similar evening trend is anticipated as daytime heating wanes and clearing begins. At this time, overnight showers look less likely compared to Wed night. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Overview... A series of troughs affect New England this weekend and into early next week. Generally cool and showery conditions are expected, with some brighter periods in between. Hurricane Ernesto passes offshore late this weekend and early next week, bringing building surf and increasing rip currents. Details... A weak shortwave ridge passes through New England, bringing a relatively drier and brighter day on Friday. Scattered showers are still likely during the afternoon hours across the higher terrain, but don`t look to be as widespread as on Thursday. By Saturday, the ridge passes and a trough begins to deepen through the Great Lakes, with low pressure developing across the Great Lakes as well. The low is very slow to make any eastward progress over the following few days as the ridge stalls and builds across Atlantic Canada through the weekend. With this pattern, showers and scattered thunderstorms likely begin to move into western areas late in the day Saturday, and make slow progress eastward overnight Saturday. The progress mostly stalls by Sunday, with western areas seeing a greater chance for showers than eastern areas. There remains some question as to just how far east it will progress, but at this point the coast stands the best chance to see the driest conditions. By Monday, a shortwave dives in and deepens the trough, while also causing it to become more amplified and help the pattern begin moving along again. With this, the greatest chance for rain and showers in the forecast arrive late Monday as the low progresses east. The trough continues to transit through on Tuesday and possibly into Wednesday, keeping the chance for scattered showers around. While all this is going on, Hurricane Ernesto is expected to pass near Bermuda on Saturday, and making it`s closest pass to Nova Scotia on Monday. Ernesto helps to amplify the ridge across Atlantic Canada, aiding in the slow down of the trough progression, while also bringing it`s own effects. Building surf and increasing rip currents remain the biggest concerns from Ernesto, with a southeasterly swell building by Saturday. The swell builds through Monday, and then will be slow to subside through Wednesday. Rip currents become increasingly more dangerous by Sunday, and continue through at least Tuesday. High astronomical tides are also occuring early next week, so some splashover is also possible. The track is favorable overall for a long duration swell event, with the storm tracking mostly northward for two days around Bermuda. && .AVIATION /23Z WEDNESDAY THROUGH MONDAY/... Short Term...VFR this afternoon, with some SHRA/TS developing this afternoon and early evening. MVFR ceilings may develop late along coastal and interior terminals in ME. This may be accompanied by patchy fog to reduce vis as well. This lifts Thursday, with another round of SHRA/TS in the afternoon. Long Term...Mainly VFR conditions are expected on Friday, with brief showers possible across interior terminals. VFR conditions prevail more often than not Saturday through early next week, 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...Below SCA conditions expected. Stacked upper low over New Brunswick and Nova Scotia will slowly retrograde west over the next few days. This should give little wind at the surface outside of daytime sea breeze that turn onshore in the afternoon. Some marine fog is possible tonight. Long Term...Weak pressure patterns prevail as broad high pressure builds across Atlantic Canada into this weekend. Hurricane Ernesto passes east of the Gulf of Maine late this weekend and early next week, bringing an increasing southeasterly swell starting on Saturday. The swell builds to greater than 5ft by Sunday, and continues through midweek next week. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$