Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 161134 AFDGYX Area Forecast Discussion National Weather Service Gray ME 634 AM EST Tue Jan 16 2018 .SYNOPSIS... Low pressure will develop off the mid atlantic coast today then intensify as it moves northeast through the Gulf of Maine Wednesday. High pressure builds eastward into the region late in the week and into the weekend with a return southwest flow bringing warmer temperatures by the weekend. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 630 AM...Updated grids to better reflect surface conditions, but this was mostly minor stuff. A little bit of light snow was noted in SW ME, but vis was barely being affected, and it looks like its in advance of a weak boundary not far above the surface, which is moving through attm and shutting it down. Previously...Sfc high builds a little across the region today, and will help stave off WAA to our west. It`ll be mostly cloudy, but any precip associated with that WAA will likely be limited to nrn NH and perhaps the CT vly this afternoon, and it will be light. Highs will range from the low 20s in the mtns, to the upper 30s near the coast and in srn NH, as flow shifts to SW. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... SFC low will develop S of Long Island late today and track NE thru the Gulf of ME. This low forms as some energy lifts out the base 500 MB trough to our SE. The 00Z models have shifted the track of the sfc a little further south, and this has shifted highest forecast QPF a little further south as well, with WS warnings for the srn tier of NH counties, and advisories in all the rest of the CWA except the far nrn zones. Expect snow to break out from west to east this evening through the the pre dawn. Snow should be lighter at the outset, but will begin to become moderate to heavy, especially over srn NH toward daybreak. OVernight lows will only fall a few degrees off highs today and generally be in the 15 to 25 range. The bulk of the snow will fall between 09-21Z, arriving earliest in this range in NH and later in ME. There still are some concerns as far as confidence goes with the forecast. First is the wave is stuck in a positively trough, and dynamic forcing is on the weaker side. However, thermal circulations do produce quite the frontogenetical forcing in the mid lvls between 12-18Z Wednesday, and this will likely produce a decent band of heavier snow. The Euro puts the core of that band just S and E of the CWA, and that may leave the heaviest snow out of the CWA, but the best chc will be in srn NH, where 6 inches or so is a good bet at this point. If that bands shifts back to the N and W, then we may have to upgrade to warnings into coastal ME. Also, the sfc low does begin a surge of intensification as it passes to our south, and this may bring some heavier snowfall to the mid-coast. Temps will peak in the mid-upper 20s in the north and into the low 30s in the south. The mid-coast could see some readings near 35, and some rain is possible her, but probably not until after most of the snow has fallen already. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... The deterministic model solutions remain in decent agreement on the long wave pattern through the upcoming weekend and into early next week. Pacific energy breaks down the western CONUS ridge early in the period and eventually the downstream upper trough across the eastern CONUS. This will temporarily cutoff the supply of arctic air to our region and lead to temperatures rebounding above normal for much of the upcoming forecast period. However...there continue to be signs in the models that suggest the western CONUS ridge may begin to rebuild towards D+10. So...this next warmup may be prove to be fleeting in nature. In the dailies...we begin the period with a upper trough axis draped across the Appalachians that weakens and exits the coast by Thursday. At the surface...a weak coastal low exits into the maritimes by early Thursday. A second low develops off the Carolina coast along the trailing cold front and passes well offshore to our east late Thursday and Thursday night. Rising heights and high pressure building to our south will introduce well above normal temperatures into the region for Friday and the upcoming weekend. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/... Short Term...MVFR cigs this morning should improve to VFR, but not by much, today, before conds fall back to IFR in SN late this evening into Wednesday. Long Term... Wed Night...Areas of MVFR in lingering -shsn. Thu...Sct MVFR in mtn -shsn. W Sfc wnd gusting to 25 KT. Fri...Sct MVFR in mtn -shsn. && .MARINE... Short Term...Still seeing swell generated from the coastal storm that passed off shore earlier today, despite winds dropping. Seas would remain in the 5-7 ft range in the open waters this morning before slowly subsiding this afternoon. Long Term... Thu - Fri...Small Craft conditions are possible outside the Bays. Sat...Gales are possible...with Small crafts for the Bays. && .HYDROLOGY... All rivers but the Kennebec at AUG have fallen below flood stage, but ice jams have frozen into place in some areas, and rivers need to be monitored as these jams could move without notice. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...Winter Weather Advisory from 11 PM this evening to 7 PM EST Wednesday for MEZ012>014-018>028. NH...Winter Weather Advisory from 7 PM this evening to 4 PM EST Wednesday for NHZ003>010. Winter Storm Warning from 7 PM this evening to 4 PM EST Wednesday for NHZ011>015. MARINE...Small Craft Advisory for hazardous seas until 8 PM EST this evening for ANZ150-152-154. && $$ SYNOPSIS... NEAR TERM...Cempa SHORT TERM...Cempa LONG TERM...Schwibs AVIATION... MARINE... HYDROLOGY...

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