Area Forecast Discussion
Issued by NWS Portland, ME
Issued by NWS Portland, ME
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359 FXUS61 KGYX 261426 AFDGYX Area Forecast Discussion National Weather Service Gray ME 1026 AM EDT Thu Sep 26 2024 .SYNOPSIS... Much needed rainfall continues today, heavy at times this afternoon. Dry weather returns tomorrow into the weekend as high pressure moves overhead. The next chance for rainfall comes into mid week next week. && .NEAR TERM /TODAY/... 1025am Update...Refined PoPs as current radar and observations show southern New Hampshire and even far southern Maine are getting a break from the rain and will likely only see on and off shower activity through the rest of the morning. The rest of the area continues to see a steady rain, with some heavier showers already being observed. The 12Z GYX RAOB observed a PWAT value of 1.47 so a juicy air mass is in place and heavier showers are expected to be more common this afternoon with better forcing. Only other update was to bring in latest temperature and dewpoint observations. 630am Update...Quick update this morning to go ahead with a High Surf Advisory along the southern ME and NH coast. Buoy observations this morning already satisfy the criteria, and increasing onshore wind will promote slightly higher wave heights through the afternoon. Previous Discussion... Rounds of rainfall set for today. Morning WV imagery depicts an expansive stream of moisture moving up the eastern CONUS. Blocking upper low across the Ozarks has connected a conveyor belt of moisture advection from the tropics into the Northeast. This moisture feed will become focused later today as a triple point travels through the CWA. Steady rain will tend to favor interior areas through the first half of the day, with showers towards the coast. Steady rain will trend east into the mid afternoon hours, with some elevated instability bringing the chance for a couple rumbles of thunder. These will mainly be across southern NH and ME. Intense upper jet flattens this afternoon, aligning with lower levels to form a concentrated flow draped across southern NH into interior and coastal ME. The result will be training moderate rainfall through the afternoon supported by 2 sigma PWAT anomaly and the jet dynamics. HREF members depict a stripe of enhanced rainfall amounts between 1.5 and 2 inches total up to midnight tonight. This is roughly along a line from Lebanon, NH to the Midcoast of ME. Some isolated higher amounts are likely within the Whites and Upper Valley. Peak rainfall rates will be associated with consolidated triple point low passing mid to late afternoon. The concern with this will be these rates coinciding with the afternoon commute through the population corridor. Urban nuisance flooding and ponding will be possible during this time period which could lead to a hydroplaning hazard. Overall, the threat for more in the way of flash flooding continues to be mute. Flash flood guidance remains quite high due to our dry stretch, and would need this whole storm to happen in little over an hour to increase this concern. As the low tries to spin up this afternoon and evening, there may be a rather sharp back edge of the rain. Behind may be a brief period of drizzle, followed by fog formation into the evening. For the immediate coast, will evaluate the need for a high surf advisory today given increasing wave heights and long period swell along the southern coasts. && .SHORT TERM /TONIGHT THROUGH FRIDAY/... Cold front will be exiting the coast this evening. Not much wind to filter at the surface to begin. This should promote areas of fog to develop through the night for much of the CWA. Friday will be warmer and breezy, especially for the coast and interior where mid 70s will be possible. To the north, may see some upslope showers continuing in the mountains during the day. Otherwise, after a day or so of dreary weather, we pick up right where we left off with dry weather into the weekend. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... 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 /15Z THURSDAY THROUGH MONDAY/... Short Term...MVFR becomes IFR for most terminals this morning through the afternoon. Widespread SHRA will trend more steady RA today with vis restrictions down to 2 or 3 miles in heavier rainfall. Onshore winds pick up, gusting to 25 kts along the coast as a front moves through late afternoon. No real wind shift with this, more a drop in overall wind speeds. Drizzle/fog follow this front passage this evening and overnight. This could bring IFR to LIFR conditions into early Friday morning. Friday trends VFR after sunrise. Long Term...VFR should be the prevailing condition right through the weekend. Winds will be light with gusts generally 10-15kts. && .MARINE... Short Term...Long period swell peaks today with building wave heights. Onshore winds will aid in pushing waves 5 to 6 ft through the afternoon, with periods approaching 12 seconds. Passing low pressure this evening will put an end to these onshore winds, with slackening wave heights overnight and into Friday. Long Term...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...High Surf Advisory until 8 PM EDT this evening for MEZ023-024. NH...High Surf Advisory until 8 PM EDT this evening for NHZ014. MARINE...Small Craft Advisory until 8 AM EDT Friday for ANZ150-152-154. Small Craft Advisory until 8 AM EDT Friday for ANZ153. && $$ NEAR TERM...Baron/Cornwell SHORT TERM...Cornwell LONG TERM...Cannon