Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 100520 AFDGYX Area Forecast Discussion National Weather Service Gray ME 1220 AM EST Sun Dec 10 2017 .SYNOPSIS... Low pressure developing south of Nantucket will move northeast staying east of the Gulf of Maine. This low will produce a plowable snowfall for a good portion of the forecast area. A few upslope snow showers can be expected across the mountains, otherwise dry weather is expected Sunday through Monday in the wake of the low. The next low pressure system will affect Maine and New Hampshire Tuesday with another round of wintry precipitation. Cold and windy conditions are then expected midweek. Another low pressure system could affect the region at the end of the week. && .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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1220 AM Update...Have adjusted pops and final snowfall forecast based on latest trends in observational data. Overall, the event is winding down from sw to ne now, with vsbys improving. 920 PM Update... Latest snow fall reports are on the order of 3 to 5 inches...with the higher amounts solidly underneath mesoscale banding. Visibility is improving already in VT and parts of NH with snow tapering off from the west. Have adjusted temperatures once again as well as QPF and snow totals for the evening. Also bumped up the start time for the Small Craft in Casco Bay as they are already at criteria. Overnight lows will range from the low 20s north with readings near their lows already elsewhere. 635 PM Update... A couple of persistent synoptic scale bands of precipitation are affecting northern New England this evening and will continue before coming to an end around 9-11 PM for many areas with the Mid Coast of Maine seeing additional accumulations through 1 AM. Largely advertised snowfall amounts are on track with most locations reporting between 1-3" of snow...a minor snow event for the region. However this being the first event, please use caution on snow slicked roads which may or may not have been treated. Now that the sun is down accumulations are increasing on roadways as surface temperatures decrease. Minor changes to the forecast for temperatures and QPF/snowfall amounts for this update. At 19z...a 999 millibar low was developing offshore of the DELMARVA with three hour pressure falls on the order of 5 millibars southeast of New England into the Gulf of Maine. NWS Doppler Radar mosaic continues to show banded precipitation spreading northward into the forecast area. We`ll see light to moderate snow...with a few brief bursts of heavy snow with the stronger reflectivity bands this afternoon into the evening hours. Northern and southern stream energy will continue to phase through early evening with offshore low continuing to intensify. The GFS has shifted the axis of precipitation further east while the NAM, CMC and ECMWF maintain the axis of heavier precipitation further west similar to last night`s solutions. Based on the current model suite and radar/satellite trends the current forecast amounts remain in place along with existing winter headlines. Steadier snow will taper to snow showers from west to east tonight as the surface low races across the Gulf of Maine and into the maritimes by morning.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH 6 AM MONDAY/... Cold cyclonic flow and upslope flow will produce clouds tomorrow mainly across the higher terrain along with a few snow showers and light additional accumulations. Elsewhere...we`ll see a partly to mostly sunny day. Temperatures will top out in the 30s...but a gusty westerly wind will make it feel several degrees colder. Clouds will increase in coverage Sunday night ahead of the next shortwave impulse...with snow showers continuing overnight across the higher terrain. Lows will range from near 10 above along the international border with teens and lower 20s elsewhere. && .LONG TERM /MONDAY THROUGH SUNDAY/... 12Z operational and ensemble models suggest an active winter weather pattern will continue through next week. Monday begins with the passing of an upper level trough and a reinforcing shot of cold air with another cold frontal passage. A weak wave may form along this front, potentially bringing a period of steady light snow to the mountains. A large and vigorous upper level low pressure system for this time of the year will dig south and eastward from the Great Lakes region late Monday night into Tuesday. While a primary surface low remains over the Great Lakes region, a secondary area of low pressure will develop along or near the New Jersey coastline. This system will take over and move northeastward, along or just off the coast near the proximity of a coastal front. Warm air will likely be pinched off and not make it to the coastline, keeping most if not all the precipitation in the form of snow. Several inches accumulation is possible with this next system. Thereafter, the complex area of low pressure slowly exits the region Tuesday night and Wednesday. However, the vigorous upper level feature will remain to our west, keeping the chance for snow showers in the region. In fact, this is the type of system that can produce relatively persistent snow shower activity over the higher terrain, resulting in additional snowfall accumulations in the mountains and foothills. Breezy and cold conditions will continue into Thursday. Temperatures will remain below normal for this time of the year, especially considering a fresh snowpack. Models are in disagreement during the Thursday night into Friday time period. The Euro maintains a more zonal flow aloft, while other models suggest a sharpening to the upper level trough and a passage of low pressure over southern New England. && .AVIATION /05Z SUNDAY THROUGH THURSDAY/... Short Term /through Sunday Night/...MVFR in snow with areas of IFR. Improving conditions are expected after midnight as the snowstorm moves away. Mainly VFR Sunday and Sunday night except for lingering MVFR in mtn -shsn. Long Term...Mainly VFR conditions Monday lowering to IFR and LIFR conditions Monday night into Tuesday. IFR conditions likely over northern areas remaining right into Wednesday. Improving conditions thereafter. Possible MVFR/IFR conditions on Friday. && .MARINE... Short Term /through Sunday Night/...Offshore Low pressure will bring SCA conditions through Sunday night as gusty NW winds develop. Long Term...Possible winds reaching SCA thresholds Tuesday into Tuesday night. A strong west to northwest flow on Wednesday into early Thursday may result in winds approaching gale force. Another system may bring gusty winds on Friday. && .GYX WATCHES/WARNINGS/ADVISORIES...
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ME...Winter Weather Advisory until 5 AM EST early this morning for MEZ018-019-023-024. Winter Weather Advisory until 7 AM EST this morning for MEZ007>009-012>014-020>022-025>028. NH...Winter Weather Advisory until 5 AM EST early this morning for NHZ002>010. Winter Weather Advisory until 3 AM EST early this morning for NHZ011>015. MARINE...Small Craft Advisory until 6 AM EST Monday for ANZ150>154.
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