Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 131409 AFDGYX Area Forecast Discussion National Weather Service Gray ME 1009 AM EDT Thu May 13 2021 .SYNOPSIS... Much of today will feature mostly sunny skies and warmer temperatures. Late in the day, a weak cold front will drop in from the north and deliver a band of showers and perhaps an isolated thunderstorm to the mountains and foothills. Thereafter, warming weather will continue but we`ll likely have to dodge a few afternoon and evening showers and isolated thunderstorms over the weekend as the morning sunshine provides some instability. A cold front looks to approach from the north around Tuesday of next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Update... Have updated the forecast for the rest of today. Have added more cloud cover as latest satellite imagery continues to show the growth of Cu over the region. Have upped the forecast highs for this afternoon as well. Winds have already begun to gust in the 10 to 20 mph range and that will continue for the rest of the day. Tweaked wind forecast upwards. Prev Disc... 625 AM Update...Have adjusted temperatures and sky cover a little bit for the next few hours based on observational data but otherwise the going forecast remains largely untouched. Previously... Mid level clouds have been been a bit stubborn early this morning across southern zones but are gradually doing so. However, as a result of the cloud cover lasting well into the night, will cancel the frost advisory in one or two zones early this morning. Today should be quite a nice day with partly to mostly sunny skies and temperatures warming well into the 60s to around 70 degrees at many locations which is right around average for this time of year. Later on in the afternoon, a short wave trough and attendant weak SFC cold front will approach from the north. They will aid in the development of scattered showers and isolated thunder in the mountains, which will then move into the foothills by early evening before weakening. A few of these may contain brief wind gusts from the north of up to 35 MPH due to inverted-V low level thermodynamic profiles. The HRRR has been pretty consistent with this scenario over the last 24 to 30 hours and it`s not out of the question that a special weather statement or two may be required after about 4 pm. A few of these may make it as far south as central NH and southern ME early in the evening, but would likely be more isolated in coverage and exhibit a weakening trend due to loss of daytime heating.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/... Any showers will dissipate during the early evening hours with the loss of daytime heating. At this time, overnight lows do not look to be as low tonight due to lingering clouds and occasional boundary layer mixing. Have therefore not planned any sort frost/freeze products at this time. A good amount of sunshine on Friday with continue to lead to warming temperatures. Highs are expected to get to a few degrees above normal, with readings 70 or higher at many locales. Again, an isolated shower or thunderstorm will be possible during the afternoon hours, especially across southwestern NH. Marginal red flag conditions may be met Friday afternoon across portions of central ME as well as the western ME mountains as RH values dip to the 20 to 30 percent range with winds gusting between 18 and 25 MPH. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... A series of upper level disturbances will promote the development of afternoon showers and thunderstorms this weekend. Temperatures will be near to just above normal with 70s across the interior, 60s to the north and low to mid 60s near the coast where afternoon sea breezes will develop. Going into the next work week there are not many signals for a persistent dry pattern nor any signs of a widespread precipitation event. There will continued chances for afternoon showers Monday with similar temperatures experienced over the weekend. A northern stream wave will cross southeastern Canada towards the middle of the week that has the potential to push a cold front through the area sometime between Tuesday and Wednesday. The current thinking with regards to the shower and thunderstorm potential this weekend has not changed much since previous forecast packages. A short wave at H5 will approach Saturday afternoon with morning sunshine leading to few hundred J/kg of CAPE developing by afternoon. This will lead to scattered showers and a slight chance for thunderstorms Saturday afternoon and evening with activity diminishing towards sunset. Another shortwave will cross the area Sunday closer to peak heating leading to greater chances for showers and thunderstorms. There will again be a few hundred J/kg of CAPE to work with, but effective shear will be weak both days this weekend minimizing the potential for organized cells with sustained updrafts. However, low level lapse rates will be steep with inverted-V soundings that will enhance gusty outflow winds with stronger cells. PWATs will generally be around 0.5 to 0.75 inches, which is slightly below normal for this time of year minimizing the potential for torrential rain and hydrologic concerns. Chances for afternoon showers will continue Monday as another weak upper level wave crosses southern New England. Temperatures will generally be in the 70s with cooler conditions near the coast. Global models continue to vary on the timing and placement of a northern stream wave crossing southern Canada Tuesday leading to low confidence towards the end of the forecast period. At this time this wave looks to push a cold front through the region Tuesday into Wednesday have have keep chance PoPs in the forecast through the middle of the week. && .AVIATION /14Z THURSDAY THROUGH MONDAY/... Short Term...Mainly VFR expected through Friday. The exception may be later this afternoon and early evening in the mountains and foothills as well as portions of central ME. A band of showers and isolated thunderstorms may move from north to south with brief lower conditions and SFC wind gusts to 30 kt. This would mainly be from 20z through 01z today. At this time the seabreeze looks to remain offshore today and Friday but it`s possible it could sneak in for an hour or two late this afternoon. Long Term...There will chances for afternoon showers and thunderstorms each day Saturday through Monday that have the potential to bring brief periods of MVFR/IFR with VFR prevailing during the mornings. && .MARINE... Short Term...Winds/seas stay below SCA criteria through Friday. A gusty shower not out of the question late this afternoon and early evening with a brief 25 kt gust from the north possible. Long Term...Winds and seas will remain below SCA thresholds into early next week. There will be chances for afternoon showers and an isolated thunderstorm during the afternoons Saturday and Sunday that may bring some gusty winds. && .GYX WATCHES/WARNINGS/ADVISORIES...
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ME...None. NH...None. MARINE...None.
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&& $$ NEAR/SHORT TERM...Cannon LONG TERM...Schroeter

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