Area Forecast Discussion
Issued by NWS Portland, ME
Issued by NWS Portland, ME
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193 FXUS61 KGYX 100815 AFDGYX Area Forecast Discussion National Weather Service Gray ME 415 AM EDT Fri May 10 2024 .SYNOPSIS... A cool and unsettled weather pattern is expected through the next several days as a longwave trough gradually crosses the area. Although day-to-day details are relatively uncertain, there will be several opportunities for rain showers through this time. No days are expected to be washouts, however. Below- average temperatures are expected through this weekend, then will start to trend warmer next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Low pressure passes well south of the region today, with a rain shield across much of the interior Northeast pivoting east. Meanwhile, high pressure to the NE will continue to feed dry air at the surface across much of northern New England. While much of the CWA will see partly to mostly cloudy skies today, the threat for showers or sprinkles will be limited to mainly the interior. This is where warmer surface temps and moisture in the low levels will combine for some diurnal shower development this afternoon. CAMs depict a lot of this occuring near the mountains and foothills, but could see additional development through the rest of the interior around peak heating. Showers that do develop will be light, with plenty of dry air throughout the column. Kept temperatures roughly in line with NBM guidance, but opted to run lower in places where clouds may be more likely or onshore flow a bit cooler. This should result in many locations seeing highs in the mid to upper 50s today, remaining in the 40s for much of the immediate coast. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... Areal coverage of showers decreases overnight, with clouds persisting. There is uncertainty exactly how overcast it remains tonight, and this could again bring variation to overnight lows amid light winds. With more clouds expected across parts of NH vs. southern ME for much of the night, opted to run slightly cooler temps in ME. However, clouds and moisture arriving from the NE may bring in additional clouds late. Moisture wrapping around passing low to the east will arrive across Maine early Saturday as temperatures again climb in the mid 50s. Showers are again expected to develop as warming begins, initially across portions of southern ME and then into NH. As showers development here will be better forced than Friday, have a wider presentation of PoPs across the interior. However, the limitations of dry air will again be present. A bit more CAPE or instability will be available, however warming aloft will put a lid on just how tall clouds get on the day. Thus, showers may pack a bit more rain than those that develop Friday, but still a low chance of any one location seeing a fulfilling wetting rain. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... A long-wave trough overhead will define the extended forecast period, with embedded shortwaves providing periods of rain showers around the region. Temperatures will fall within seasonal norms, with below-average conditions under more maritime influence this weekend transitioning to near- or above- average as the trough shifts east and allows drier, warmer, continental air to filter in next week. Overall, not expecting any weather impacts besides perhaps some dense fog at times... though there is little confidence in where, when, or if that happens given the nebulous nature of the pattern at this time. Upper level low pressure settles overhead by Sunday with a very weak pressure gradient, which will once again allow a sea breeze to develop amid light background flow. Though low confidence... there is model agreement with deeper moisture building across the region allowing for more cloud development Saturday night into Sunday. Model guidance is mixed for precipitation chances on Sunday, but in general increasing cyclonic flow and mixing should at least contribute a diurnal component to rain shower activity on Sunday. The upper level trough shifts east into Monday with shortwave ridging briefly building to start the coming work week. This should offer a brief period where we actually manage to have minimal precipitation chances... although timing that out may be a challenge in the short-wave driven pattern, especially as it turns a bit more zonal before another trough wanders in around mid-week. All in all, the trough shifting east brings the reasonable expectation for a warming trend, on average, early in the week as a southerly to southwesterly flow regime takes over. Current model consensus brings widespread 60s and 70s, coolest in the mountains where clouds are most likely and along the coast with a southerly component to flow. Though, increasing humidity and ripples in the upper wave pattern continues potential for rain showers... especially as a warm front overtakes the region, followed by potential for a more organized system around mid-week with the next long wave trough. && .AVIATION /08Z FRIDAY THROUGH TUESDAY/... Short Term...VFR for most locations, with SCT or occasionally BKN MVFR decks. These should be limited to Friday morning and again Saturday. SHRA develop for interior terminals today, with coastal locations seeing chances Saturday. Dry overnight, although valley fog may develop. Long Term...Potential for lowered CIGs Sat night through Sun along with -SHRA. The pattern in general from Sun into next week favors periodic restrictions, mainly CIG, and light flow allowing daily sea breezes. But, this is a particularly low- confidence forecast in terms of timing and day- to-day details. && .MARINE... Short Term...Conditions below SCA, but NE winds continue through Saturday 10 to 15 kts. Wave heights 1 to 3 ft through Saturday. Long Term...Light flow and quiet seas are expected over the extended forecast period with SCA conditions unlikely to occur. In general, winds this weekend will be NE, then will turn out of the SW to start the next week however daily sea breezes and a nebulous pressure gradient will muddy this progression a bit. The best chance for 25+ kt winds, right now, comes around Tue with a more organized system potentially crossing the region. && .TIDES/COASTAL FLOODING...High astronomical tides combined with around 0.8 feet of surge may push water levels to around minor flood stage around the time of high tide once more tonight. A Coastal Flood Advisory or Statement may be necessary, however any impacts will be very minor. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ NEAR TERM...Cornwell SHORT TERM...Cornwell LONG TERM...Casey