Area Forecast Discussion
Issued by NWS Portland, ME
Issued by NWS Portland, ME
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611 FXUS61 KGYX 252254 AFDGYX Area Forecast Discussion National Weather Service Gray ME 654 PM EDT Wed Sep 25 2024 .SYNOPSIS... High pressure retreats northward as moisture works its way into the region tonight. Low pressure keeps north as a triple point of fronts moves through the area Thursday. This brings much needed rainfall to the area, albeit heavy at times. Dry weather returns in time for the weekend as high pressure moves overhead. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... 645 PM Update...PoPs and temperatures look to be on track early this Wednesday evening as much of the forecast area is dry except for a few batch of rain moving into southwestern NH. This area of rain will gradually overspread the rest of the region this evening, with the heaviest rain holding off until about 12z Thu morning or so. Previously... Impacts *No significant weather impacts expected. The first round of light rain showers is moving through western Maine at this hour. Most of the area will see a decent break between these and the system tonight. The only exception may be an additional light shower along the Vermont- New Hampshire border in the next few hours. Otherwise, the bulk of the rain begins to arrive in Western New Hampshire after 10PM, overspreading the region by day break Thursday. Deeper moisture will be moving into the area during this time as well with the 12Z GYX RAOB observing PWATs around 0.83" already in place this morning. Overcast skies will keep us well insulated tonight with temperatures bottoming out in the upper 40s and low 50s. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/... Impacts *A convective fine line containing heavy rain may develop in the population corridor around the evening commute. Ponding water on the roads may lead to minor travel impacts. Widespread rain will be ongoing Thursday morning with some embedded heavier showers possible during this portion of the forecast period as well. PWATs will be up around 1.25" in Northern zones and closer to 1.50" in southern zones and along the coast. This, combined with warm cloud depths up around 12kft, will promote efficient and locally heavy rainfall. To this point many areas were making a run for their driest September on record, so 1hr and 3hr flash flood guidance is 2" and 3" respectively. HREF ensemble probability of just 1"/hr rain rates is near zero, so any flooding should be limited to ponding on road ways or around storm drains that may be clogged with leaves. As the day progresses CAMs continue to develop a fine line of convection during the late afternoon. This would be the focus for heavy rain in southern New Hampshire and southern Maine. Instability is limited as we will be pretty thickly overcast through the day, but an isolated rumble of thunder is not out of the realm of possibility. For this reason, any impactful wind gusts look likely as well, except for when it gets closer to the coast and out over the water where mixing will be better, then a stray gust 25-30 mph is more likely. Daytime highs will again be limited to the upper 50s and low 60s. The bulk of the rain will be exiting the area after midnight with just lingering showers overnight. When all is said and done rainfall amounts will generally be around 1.50" with locally higher amounts up around 2.5". With clouds clearing, patchy fog may be pretty widespread heading toward daybreak Friday. Nighttime lows will again bottom out in the upper 40s and low 50s. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... As low pressure exits the region, increasing sunshine will be the theme across much of the forecast area. Most breaks in the cloud cover will be over downslope region where temperatures will be reaching the upper 60s to lower 70s. Across the northern higher terrain, expect a few widely scattered rain showers to develop in the west to northwesterly flow. A cyclonic flow will continue aloft on Saturday. Therefore, despite being dry across the region, expect a mix of sun and clouds, especially during the midday and afternoon hours with the added diurnal warming. Similar conditions will continue on Sunday with highs mainly in the upper 60s to near 70 over the weekend. Next week will begin as dry conditions as a ridge of high pressure builds over the region. It won`t be until a potential pattern change on Wednesday with a strong cold front bringing a few showers to the region midweek. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... Short Term...Rain moving in will keep the area MVFR tonight. Overnight and during the day Thursday there may be some localized IFR restrictions as the rain will be heavy at times and low stratus develops. This will continue right through Thursday night as ceilings lift and fog likely develops in the systems wake. A fine line of convection may develop affecting CON, MHT, PSM and PWM. HIE is likely see down slope wind gusts of 15-20 kts during this time period with all other sites staying calmer outside of convection. Long Term...Friday morning may feature some fog but afterward VFR should be the prevailing condition right through the weekend. Winds will be light with gusts generally 10-15kts. && .MARINE... Short Term...SCA conditions continue as swell increases once again during the day tomorrow. Seas will be generally 4-6ft, with 3-5 ft in the waters outside of Penobscot Bay. Offshore winds may also gust 25-30kts as a front moves offshore Thursday night. Long Term...Max wave heights of 5ft remain through at least Friday morning before finally dropping below 5 ft later in the day and remaining below SCA criteria through the weekend. Winds will be gusting 15-20 kts on Friday before high pressure begins to move over the waters and the gradient relaxes over the weekend. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Small Craft Advisory from 11 PM this evening to 8 AM EDT Friday for ANZ150. Small Craft Advisory until 8 AM EDT Friday for ANZ152>154. && $$ SYNOPSIS... NEAR TERM...Baron/Ekster SHORT TERM...Baron/Combs/Cornwell LONG TERM...Cannon AVIATION... MARINE...