Area Forecast Discussion
Issued by NWS Portland, ME
Issued by NWS Portland, ME
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928 FXUS61 KGYX 151735 AFDGYX Area Forecast Discussion National Weather Service Gray ME 135 PM EDT Mon Jul 15 2024 .SYNOPSIS... Heat and humidity build for the next few days as high pressure strengthens off the Eastern Seaboard, with chances for scattered afternoon showers and thunderstorms each day. A cold front moves through late Wednesday through Thursday, bringing drier and somewhat cooler conditions for the end of the week and going into the weekend with high pressure building in from the west. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 130 PM Update... Minor changes to reflect latest observational trends. A sea breeze is moving inland across coastal ME and a few isolated showers and storms have developed towards the NH Seacoast and nearby offshore waters. Additional pop-up showers and storms are possible through the remainder of the afternoon. Previously... 950 AM Update... Minor changes to reflect latest observational trends. Clouds associated with earlier showers across the north are now thinning and moving east with just some cirrus in its wake. This is allowing temperatures to warm and this clearing trend will persist through the remainder of the morning and early afternoon before a cu field develops later on with building convective instability. Previously... 6:30am Update... A quick update to account for some isolated showers across northern New Hampshire this morning, and refreshed temps a bit based on latest high res guidance. Also adjusted cloud cover a bit through the morning as the remnants from yesterday`s MCS drifts through. Previous... Heat and humidity build today as high pressure strengthens off the East Coast. A heat advisory remains in effect for today across southern and interior locations outside of the higher terrain, and has been expanded to coastal York county. While the immediate shoreline will not see heat advisory criteria, anywhere west of I-95 and the population centers in Biddeford and Saco are likely too, so the advisory was expanded. Coastal Cumberland has been left out as most of the area will be modified by the wind direction off Casco Bay. In the areas with the heat advisory, heat indices are expected to climb to between 95-100 degrees this afternoon as dew points rise into the low 70s. Within the building ridge, small shortwaves continue to ripple along through the flow. One such shortwave comes in late this afternoon and into the early evening hours, helping to kick off some scattered showers and thunderstorms. Any thunderstorms that do develop have the potential to bring gusty winds, but the best chance looks to be across southern and southwestern New Hampshire today. The SPC has placed this area in a marginal risk for severe weather with their latest update. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... A warm and humid night is in store for tonight as lows only dip into the low 70s in most areas. Northern valleys likely dip into the mid 60s, but elsewhere much of the night will be spent in the 70s. There is also the chance for some scattered showers and storms through the overnight hours as a leftover MCS drifts eastward from the Great Lakes. How organized this system will be by the time it arrives here will depend on how much development there is during the daytime today, but the greatest chance for storms overnight looks to be across northern locations. The HRRR is also indicating further storms developing across Maine toward daybreak as the shortwave propagates into New England. These trends will need to be monitored today, with the potential for a thundery night across much of the area after midnight. Any storms that occur overnight only serve to add to the humidity tomorrow as temps and dew points peak across the area. Heat headlines will likely be needed, and probably with a bigger footprint than today`s, but we continue to approach these headlines one day at a time. Temps warm into the low to mid 90s outside of the higher terrain, with dew points in the 70s making it feel like the upper 90s to low 100s. The seabreeze doesn`t look to bring as much relief to the shoreline tomorrow with a bit more of a southwesterly wind trajectory, but some afternoon moderation is expected. More scattered storms are likely during the afternoon hours, with the best chance across western New Hampshire. These areas also stand the best chance to see some gusty winds with the storms that do develop. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... 500 MB pattern cross NOAM moves from a zonal to become more amplified by late in the week, with ridging over the inter- mountain west and troughing in the east. But before things become less warm, we still have several days of heat to go, as the ridge over the east gets a poleward push from the digging trough over the Great Lakes and Midwest. The trough will linger into next weekend, and while it will be cooler, temps will still be running on the warm edge of the normal envelope. On Tuesday it looks sunny enough with decent SW flow to mix the hot air aloft down to the sfc, and this will allow for highs of 90-95 everywhere but the mtns and the mid coast, with mostly mid 90s in S NH and interior SW ME. The SW flow and mixing should keep Tds limited to around 70 F, so while it will be hot and humid Heat indices are expected to top at out a little over 100, and not reach the 105 warning criteria. Still it will be a day where staying cool and hydrated will be important. It will be unstable enough to pop a few isolated convective cells almost anywhere, and with a weak passing well to the N, there will be a better chance in the mtns. But more areas will stay dry than see any SHRA/TSRA. Tuesday night mins will mostly be 70-75, but upper 60s in the mtns and the mid-coast, perhaps warmer in the more populated areas of S NH. SCT showers and convection could linger in the mtns through the evening as well. Given the highs Tds some fog is possible ins sheltered areas, but the SW flow should remain strong enough, that it will only be patchy. Wed will be another hot day, but probably not quite as bead as Tuesday, as we see more in the way of clouds through the day, and the chance of SHRA/TSRA ahead oi the cold front to our NW. Could also see some turning of the flow onshore, with a better sea breeze in the afternoon, as the storms develop further inland. However, will probably need a heat advisory for one more day, although maybe with less coverage than Tuesday. The sfc front pushes offshore in the evening, but is expected to stall S of the CWA, so while the mtns and foothills may see the benefit of cooler temps and lowers Tds Wed night, it is unlike closer to the coast and in S NH, although it will be cooler than previous night with lows ranging from around 60 in the N to the mid to upper 60s in the S. 12Z Euro has stalled that front further S than some previous runs, but could still see a lot of clouds around in the S on Thu, with a chance of showers, and a chance of showers in the N Thu afternoon as the upper level trough approaches. Highs will be in upper 70s to mid 80s. The trough stays well to our N Friday and Saturday, and will usher in more seasonable mid level air, and highs both days look to be 75-80 in the mtns and in the low to mid 80s S of there, with over night lows ranging from the mid 50s N to the low to mid 60s in the S. && .AVIATION /18Z MONDAY THROUGH SATURDAY/... Short Term...Brief MVFR conditions are possible at HIE around sunrise, but otherwise mainly VFR conditions prevail through this evening at all terminals. Scattered showers and storms may bring brief restrictions to southern and western terminals this afternoon, but probs remain too low to include in the TAFS. Marine fog likely moves into RKD tonight. Some valley fog is possible at LEB and HIE tonight. Showers and storms are possible after midnight through daybreak at most terminals. Mainly VFR prevails tomorrow outside of isolated afternoon storms, and any lingering fog at RKD. Long Term...Tuesday and Wednesday will be hot days with high humidity and warm lows Tue night. A few SCT TSRA are possible on Tue afternoon as well. Fog will likely be limited to the KHIE/KLEB Tue night as SW flow does keep it a bit overnight. A better chance for TSRA is expected Wed aft/eve, as if overnight fog Wed night. A few isol TSRA remain possible on Thu, but Friday looks dry attm, with VFR. and the threat of fog each night. Also SCT TSRA are possible both afternoons. The next chance of more widespread flight restrictions will be Wed night into Thu morning as the cold front pushes through and may stall just off shore. && .MARINE... Short Term...A building high east of the waters brings south- southwesterly flow across the waters for the next couple of days. A few gusts in the afternoon may reach 25kt near the sea breeze front along the coast. Locally dense fog is possible after midnight tonight through tomorrow. Long Term...Generally winds/seas stay below SCA levels through the coming week, but could approach SCA gusts late Wed or Wed night in advance of a cold front. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...Heat Advisory until 8 PM EDT this evening for MEZ012-018>020- 023-033. NH...Heat Advisory until 8 PM EDT this evening for NHZ004-006- 008>010-012>015. MARINE...None. && $$ NEAR TERM...Tubbs