Area Forecast Discussion
Issued by NWS Portland, ME

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146 FXUS61 KGYX 211745 AFDGYX Area Forecast Discussion National Weather Service Gray ME 1245 PM EST Sat Jan 21 2017 .SYNOPSIS... Expect warm temperatures today as an upper level ridge crosses the region. A cold front will drop south out of Canada Saturday night into Sunday morning, bringing cooler weather again. A storm system tracking up the coast will bring wintry precipitation to the area late Monday and Tuesday. A cold upper trough will remain over the area through the latter part of the week with a return to colder temperatures. Scattered snow showers in the mountains and foothills can be expected through the latter part of the week. && .NEAR TERM /UNTIL 5 PM THIS AFTERNOON/... 1244 AM...Minor ESTF update to reflect satellite trends and latest mesonet in near term grids. Prev disc... 930 AM...A mostly cloudy but mild day across the forecast area as ample moisture remains trapped below the strong subsidence inversion evident on 12z KGYX RAOB. For this ESTF update...I adjusted sky grids to reflect satellite trends and ingested the 14z mesonet into near term grids. On the waters...raised wave forecast slightly based on GOMOOS and C-Man observations...but kept seas just below SCA threshold. Prev Disc... Update... Have updated the forecast based on current trends and latest set of mesoscale models. Very mild conditions persist for this time of the year and this time in the early morning hours. Have adjusted temperatures upwards based on latest trends. Plenty of low cloud cover will remain in place in the forecast area with patchy fog dissipating over the next hour or two. Models continue to bring a slight chance for mixed precip over far northern areas today. This is a low confidence forecast for any measurable precip. Prev Disc... High pressure will remain over the forecast area today. However, low clouds will continue to dominate the region. A weak impulse shearing into the upper level ridge may bring some very light precipitation to northern New Hampshire today as well as areas in adjacent northern Oxford County. Most areas will start the day warm and climb through the 40s during the afternoon. However, it will be cool enough at the onset early today to allow for a least the chance for light icing in the far north. This is a low confidence, low probability event and will need to be monitored over the next several hours. && .SHORT TERM /5 PM THIS AFTERNOON THROUGH 6 PM SUNDAY/... There is still a chance of a light mix across the far north tonight in close proximity to the weak shearing short wave. This is also the area where cold air advection will begin during the late night hours. Cold air advection will continue on Sunday as a backdoor front sweeps towards southern New England. Canadian high pressure will begin to nose southwards into the region. The best chance for precipitation, albeit low, will be over western New Hampshire where there could be a period of light rain or light rain and snow. This sets the stage for the extended forecast and cyclogenesis along the Mid Atlantic coastline. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... A slow moving upper low currently tracking along the southern gulf states will be kicked northeast toward the mid atlantic coast Monday and reaching the Gulf of Maine by Monday night. The system will come from a source region with plenty of moisture so total qpf amounts from the system look to be in a range from a half inch in the mountains to over 2 inches over southern coastal areas. PTYPE will become a major issue with this system. Initially high pressure stacked to the north allows a dome of cold air to be in place allowing the precipitation to start as snow but with the strong low/mid level southeast jet in advance of the negatively tilted trof approaching, temps aloft and in the low levels will quickly warm allowing the snow to change to rain along the coast and a mixed bag inland. Models indicate depth of cold air will be enough well inland to allow moderate of amounts of snow before the changeover. Problems with this forecast will also be the boundary layer temps well inland after the warm air works inland aloft allowing for some pockets of freezing rain or sleet to develop. Along the coast some gusty winds are possible Mon night. Models generally agree the bulk of the precipitation will be over by Tue morning but still some scattered snow showers to continue in the mountains and foothills. Mid to late week generally a broad cyclonic flow develops over the northeast allowing snow showers in the mountains and foothills with a return to a colder air mass for the rest of the week. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... Short Term...Mainly MVFR conditions in low clouds. Any patchy fog will dissipate quickly this morning. Long Term...IFR to LIFR conditions expected with mixed precipitation to develop Mon afternoon and continue Mon night into Tue. Conditions improve to VFR over southern areas by late Tue while in the mountains MVFR conditions will continue Tue night into Wed with scattered snow showers. && .MARINE... Short Term...Mainly quite conditions ahead of the next storm. Winds and seas will remain below Small Craft Advisory thresholds. Long Term...A strong east flow will develop ahead of an approaching coastal low. High confidence of Storm force winds developing over the outer waters Mon afternoon through Mon night. In the bays gale force winds are likely. Seas will likely build to 15-20 over the outer waters. Winds diminish Tue as the surface low moves overhead and then into the Canadian maritimes by Tue night. High pressure and a light westerly flow will move across the waters Wed. && .SPLASH-OVER... Despite being in the low portion of our tide cycle...large building waves may product some erosion and splash-over near the times of high tide Monday night and Tuesday. Preliminary storm surge values appear to be around 1.5 to 2 feet with a persistent...strong easterly wind developing. .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Gale Watch from Monday afternoon through late Monday night for ANZ151-153. Storm Watch from Monday afternoon through late Monday night for ANZ150-152-154. && $$ SYNOPSIS... NEAR TERM...Cannon SHORT TERM...Cannon LONG TERM...Marine AVIATION... MARINE... TIDES/COASTAL FLOODING...

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