Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 230117 AAC AFDGYX Area Forecast Discussion...UPDATED National Weather Service Gray ME 917 PM EDT FRI JUL 22 2016 .SYNOPSIS... Warm and humid air continues to stream into the region this afternoon and evening ahead of an approaching cold front. The front will generate showers and thunderstorms across the area this evening before stalling. It will also provide the focus for some additional showers and thunderstorms tomorrow. High pressure builds from the west on Sunday before moving offshore Sunday night. Another cold front will move across the region on Monday giving us another chance for showers and thunderstorms. High pressure returns on Tuesday for the remainder of the forecast period. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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915pm Update: Boosted temperatures overnight based on evening trends as well as GFS LAMP data for the overnight. Additionally...given inverted V profiles in the low levels... see some potential for damaging winds at least for the next few hours /as seen in current severe storms to the west of the radar/...but coverage of activity should remain isolated to scattered. 701pm Update: Continue to pull back on PoPs based on early evening radar trends...as well as recent runs of the HRRR...which suggest a weakening trend to southwestern Quebec convection as it pushes in from the north and west. Current environment proving too hostile for anything but isolated activity...except over parts of northern Oxford/Franklin and central Somerset counties. No other significant changes at this time. 528pm Update: Primary changes this hour are to boost late afternoon temperatures and lower dewpoints over southern areas where a hot late afternoon continues. Also...have boosted PoPs in northern Franklin/central Somerset counties along line of showers/thunderstorms that have gradually been increasing in coverage in this area over the past 2 hours. Isolated activity further south is struggling to compete against dry airmass evidenced by late afternoon water vapor imagery. Of interest is next area of moistening /and attendant H5 speed max/ over southwestern Quebec with associated convection north and west of Ottawa. Latest renditions of both the operational/experimental HRRR indicate that as this area reaches northern New England later this evening...there is some potential for a round of organized potential over northern zones. Thus...will maintain highest PoPs in this area...noting however...that instability may become more of a question by the time this feature arrives. Previous below... A warm and humid airmass has taken control of the weather over northern New England today. While there is currently significant instability across the region...there remains the absence of any type of triggering mechanism. That appears as though it will change as the evening progresses. A disturbance currently moving through southern Canada is expected to arrive this evening and give us the convective focus that seem to be lacking. Models have been doing a good job of handling this. They have done a good job of picking up on the mid level dry air that has been suppressing convection. They have also done a good job of picking up on the convection moving out of southern Canada and into northern Maine. Once the short wave gets here there should be in the neighborhood of 2000j/kg of Cape to tap into. The primary threats remain damaging winds and large hail. With abundant low level moisture in place...expect to see some valley fog forming tonight in favored valley locations.
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&& .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... Weak frontal boundary from today will stall across the region tonight and will provide some low level convergence to get storms started tomorrow. While it does not appear that there will be as much energy to work with tomorrow...the storms could be more widespread simply because there is a focus area to get them started. With low level moisture remaining in place...expect to see some valley fog again in favored locations. && .LONG TERM /SUNDAY THROUGH FRIDAY/... High pressure will build in on Sunday allowing for a fair and drier day across the region. A warm frontal boundary will approach from the west on Monday and should allow for the development of at least scattered showers and thunderstorms during the afternoon and evening hours. These may continue Monday night into Tuesday before a frontal boundary moves offshore. Thereafter, there are some signals in model guidance that low pressure and a decent rainfall may arrive sometime Friday or Saturday. Low confidence on that at this time, however we will continue to watch for some much needed rainfall. && .AVIATION /01Z SATURDAY THROUGH WEDNESDAY/... Short Term... Summary: A series of cold fronts will drop south through the region through Saturday night...bringing the potential for showers and thunderstorms...particularly on Saturday afternoon. Restrictions: VFR all locations attm. HIE has the greatest potential to see shra/tsra activity this evening...but expect that most of the terminals will remain dry through the night. There is the potential for LIFR/IFR fog RKD/LEB/HIE after midnight...with confidence in this occurrence now a bit lower given the lack of much rainfall this afternoon. For the day on Saturday...expect scattered showers/thunderstorms to develop over the mountains by late morning and through the afternoon...with activity spreading south and east during the afternoon. This will have the potential to bring localized IFR/MVFR restrictions. Fog will again be possible Saturday night...particularly at LEB/HIE. Winds: Westerly winds will become southwest and diminish to 5kts or less for the overnight before becoming west northwesterly and increasing to 10g18kts for the day on Saturday. Winds will increasingly become northwesterly Saturday night and diminish to less than 10kts. LLWS: No threat through Saturday night. Thunder: Isolated thunderstorms will be possible for LEB/HIE and possibly points south and east overnight...but recent trends suggest that south of HIE...activity will be very limited through tonight. More widespread shower and thunderstorm activity is expected for the afternoon on Saturday...but confidence in coverage is too low to include in this 24 hour TAF package. This activity will end Saturday night. Long Term...Mainly VFR expected Sunday through Monday. However, showers and thunderstorms may bring scattered lower conditions Monday afternoon and night. Low probability of some stratus and fog Monday night into early Tuesday as well. && .MARINE... Short Term...Onshore swell will keep seas at or above Small Craft Advisory criteria through tonight. Seas begin to subside enough tomorrow that an SCA may not be needed. Otherwise...no other flags expected. Long Term...Prevailing conditions Sunday through Tuesday should feature conditions below small craft thresholds. A few thunderstorms may affect the waters Monday afternoon and night. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Small Craft Advisory for hazardous seas until 8 AM EDT Saturday for ANZ150-152-154. && $$ SYNOPSIS... NEAR TERM...Arnott SHORT TERM... LONG TERM... AVIATION...Arnott MARINE...

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