Area Forecast Discussion
Issued by NWS Portland, ME

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KGYX 080258 AFDGYX Area Forecast Discussion National Weather Service Gray ME 958 PM EST Thu Dec 7 2017 .SYNOPSIS... Weak high pressure will continue to slowly build into the region Friday with generally fair weather expected for most of the area. A pattern change begins to take hold this a coastal low will develop offshore Saturday. This looks like it will deliver light snow to the coastal plain through Saturday night or early Sunday. Beyond the weekend we will have to watch for another coastal low developing offshore...especially midweek...that could deliver some snow to the region but confidence is currently low. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
-- Changed Discussion --
955 pm Update: Continued cloud cover over southern and central areas for the rest of the night. Snow showers continue in the mountains so POPs look good there. Extended the POPs a little further southward as radar is showing some light flurries in areas further south away from the mountains. 645 pm Update: Made some adjustments to the sky grids for the evening across southern and central areas to reflect widespread clouds across most of the area as per current satellite imagery shows. Otherwise, only minor tweaks to temps based on latest obs data for next few hours. No other changes. Previous Discussion: CAA continues...with air mass picking up additional moisture from the Great Lakes in Wly flow. Snow showers continue in the mtns in upslope flow...enhanced by this lake moisture. Will keep PoP high chance to likely/categorical...with light accumulations. A subtle S/WV...evidence by cooler WV brightness approaching from near Lake Superior. This will act to enhance snow shower activity I have a secondary max of PoP around 03z to 06z. Froude numbers looking to stabilize near 1 snow showers should focus near the peaks and not so much we have seen today. Gradually flow becomes more SW towards morning...and snow showers will begin to lift N into Canada.
-- End Changed Discussion --
&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... Fri the forecast area will be between a S/WV trof approaches from the W and the baroclinic zone remains offshore. Expect cool temps...and increasing clouds from the S and W. The increasing clouds and light SW flow will also help to keep overnight temps relatively mild Fri into Sat. && .LONG TERM /SATURDAY THROUGH THURSDAY/... The deterministic solutions are in good agreement on the long wave pattern through late next week. The well advertised pattern change to a high amplitude western ridge and eastern trough across the CONUS should remain in place for the foreseeable future. This pattern will result in an extended period of below normal temperatures as the door remains open for reinforcing shots of arctic air into the Great Lakes and northeast CONUS. We begin the period with the trough axis stretching from the Great Lakes southward into the Gulf of Mexico. We`ll be in south-southwest flow aloft and under weak surface ridging as we`re sandwiched between an offshore baroclinic zone and a weak disturbance over the Great Lakes. The flow aloft will back on Saturday with the offshore baroclinic zone retrograding closer to the coast. The western edge of the cloud shield will move onshore as well. Over the past 24 hours...the model trend has favored a pronounced westward shift and if this trend continues we may in fact see several inches of measurable snow mainly along the I-95 corridor and points east. There will be a tight east-to-west gradient and abrupt cutoff to where measurable snow will fall. Snow amounts will be highly sensitive to slight shifts in track as evidenced by the earlier CMC solution with a zero QPF for the entire area versus the more robust ECMWF and GFS solutions. During the day Sunday...the baroclinic zone is finally kicked well offshore by exiting shortwave impulse. In the wake of this system...the close proximity of the upper trough and upslope flow will produce clouds and a few snow showers...especially across the higher terrain. Weak ridging briefly takes hold for Sunday night and early Monday. Digging shortwave energy over the western Great Lakes will carve out a full latitude trough over the eastern seaboard by Tuesday. A cold front will approach the area by late Monday then slow down in response to the upper trough and falling heights. The front will crawl across the region on Tuesday with cold air injection leading to significant cyclogenesis near the mid Atlantic coast. The deepening surface low will then track northeast into the Gulf of Maine as trough goes negative tilt. Over the past 24 hours...the models have come into better agreement with regards to the timing and evolution of this storm system. All-in-all...a decidedly active and wintry pattern can be expected over the next week to ten days across the region. && .AVIATION /03Z FRIDAY THROUGH TUESDAY/... Short Term...Widespread VFR conditions thru Fri night. Low level moisture trapped in the Wly flow will bring scattered MVFR CIGs to areas N of the mtns tonight. HIE may see VCSH or TEMPO SHSN...though confidence is too low to put into the TAF at this time. Long Term... Sat Night - Sun AM...MVFR with areas of IFR vcnty of the coast in -sn. Sun PM...Sct MVFR in mtn -shsn. Tue...MVFR psb with areas of IFR in -sn. && .MARINE... Short Term...Wly flow continues over the waters into Fri. Winds will remain near 25 kts...with seas near 5 ft thru the night. A passing S/WV trof may allow winds to briefly increase again SCA remains in effect. As winds become more SW Fri into Fri night...winds and seas will gradually diminish. Long Term... Sun - Tue...Small Craft conditions are likely. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Small Craft Advisory until 6 AM EST Friday for ANZ150-152-154. && $$ Near Term...Marine is the U.S. government's official web portal to all federal, state and local government web resources and services.