647 FXUS61 KGYX 102345 AFDGYX Area Forecast Discussion National Weather Service Gray ME 745 PM EDT Wed Oct 10 2018 .SYNOPSIS... A backdoor cold front will drop south and west across the area late this afternoon and tonight, bringing an end to the unseasonably warm weather of the last couple of days. Another cold front approaching from the west will bring a steady rain to the region Thursday. It will sweep through the region Thursday night bringing an end to the rain. After a quiet weekend another low pressure system may once again bring our area some rain early next week. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... 700 PM Update... Backdoor cold front currently pushing southwest through southwestern Maine and will be edging into southeastern New Hampshire around midnight. Showers kicked off by this boundary are diminishing in intensity and coverage in central and far eastern zones and should push east of the forecast area over the next several hours. At the same time expect showers north of the border to gradually drop south into far northern zones through midnight. Ocean stratus behind the front is pushing southwest through central and coastal areas of Maine and will likely see areas of drizzle developing in these areas after midnight. Have adusted area temp/tds based on current obs. Have also tweaked pops to reflect latest radar trends. No other changes planned to current forecast attm. Prev Disc... Backdoor cold front is working its way SWwd down the coast at this hour. Along with a sharp wind shift to NE flow...temps have dropped quickly 5 to 10 degrees before leveling off behind it. So for Wrn ME I have tried to work this into the forecast temps. Across NH...diurnal cooling will also begin to take place before the front arrives. Behind the front low clouds will gradually fill in and continue to lower overnight. WAA aloft will allow some weak lift and possible showers...though areas of drizzle are more likely. Fog may also move in off the Gulf of ME...but the hi-res guidance was bearish on that...so I did not hit it too hard with rain and drizzle already in the grids. If it did form it looks most likely from PWM down to PSM. Non-diurnal temp trend tonight as the front and cold air damming setting up will be largely responsible for trends. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/... Main trof approaches Thu and begins to entrain some of the moisture from Michael. The largest areas of showers or steady rain will work into Wrn zones around daybreak...and progress Ewd to cover the whole forecast area by late morning. It looks like there may be a brief break in precip...before the true tropical moisture moves in for the afternoon. Hi-res guidance is showing quite a bit of convection after 2 PM or so...some of which could have heavy rain at times. Any convection looks elevated...with cold air damming keeping temps cool outside of the farthest W zones in the CT Valley. I again went with a non- diurnal temp trend to show this. PWATs will be quite high for this time of year...but the juxtaposition of forcing is a little off to really concentrate that heavy rain potential. HREF probability matched mean QPF around 0.75 to 1.25 inches across the area seems pretty reasonable. With max QPF amounts in the 2 to 2.5 inch range...I feel like a flash flood watch would be overkill...with better forcing and moisture S and W of the area. Michael will be moving quickly which helps reduce max QPF potential...but it also could lead to modeling errors as small track changes will be exacerbated by the forward speed. So it is still worth keeping a close eye on heavy rain potential even though I am not adding wording to the wx grids at this time. Rain will quickly come to an end from NW to SE as the upper trof axis crosses the area Thu night. That will eventually mix out the low level damming...but again temp trend will be largely non-diurnal. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... The upper air pattern is beginning to change, with Hurricane Michael and an advancing upper level trough finally suppressing the East Coast ridge which has brought frequent warmth. The first sign of this is the cold front that pushes through on Thursday. It will have cleared the coast by Thursday night with drier air moving in behind it. The remnants of Hurricane Michael will be tracking along the frontal zone to our south on Friday. Offshore winds will bring the warmest conditions to the coast, where temperatures may reach the low 60s. Cool high pressure builds slowly out of the plains and toward the East Coast this weekend. This will be a typical fall air mass with relatively drier air and temperatures only topping out in the 50s in the afternoon. The coldest night is expected to be Saturday night when the axis of high pressure crosses the area. This will be our best chance of seeing a widespread frost or freeze, though it's certainly not a slam dunk. When comparing this to last weekend's attempted frost, we will see less cloud cover and thus more cooling potential. However, this air mass is not quite as dry as last weekend's air mass, so it's possible that once we drop into the low to mid 30s fog may form and prevent extensive frost or a freeze. This potential is worth watching and is mentioned in the Hazardous Weather Outlook for areas that have not yet had a freeze. High pressure slides offshore on Sunday and we see a slight increase in temperatures before the next front moves through on Monday. The first driving wave moves to our north in Canada, so the majority of the precipitation may fall up there. But after the front moves through, a secondary wave moves along it to our south Monday night. This one may generate another surface low and more widespread precipitation for southern and central New England. With colder air to the north of the front, it's possible that we see some snow especially in the mountains on the northern end of the precipitation area. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... Short Term /through Thursday Night/...Up first will be an abrupt wind shift to NE flow behind the backdoor front. Low clouds will lag that wind shift some...but eventually expecting all terminals except the farthest W HIE and LEB to drop to IFR CIGs. Those should gradually lower even more...especially along the coast to LIFR. There is the chance for a SHRA or more likely DZ S of the mtns as well. Starting around daybreak Thu and expanding Ewd into the late morning...RA will overspread the area. Some could be heavy at times...but overall conditions should remain IFR. There is the chance for some isolated TSRA...but not high enough to include in the TAFs. Will have to keep an eye on some marginal LLWS conditions Thu...as sharp inversion will keep strongest winds just above the surface. Long Term...Should see VFR conditions Friday. May see a brief period of lower ceilings moves across on Saturday. The next frontal system moves through on Monday and may bring lower ceilings and some rainfall. && .MARINE... Short Term /through Thursday/...SCA remains in effect as winds will kick up behind the backdoor cold front. The abrupt wind shift is about to pass MISM1...and will continue to move quickly down the coast late this afternoon and early this evening. Winds will decrease Thu...but seas may linger around 5 ft outside of the bays into Fri. Long Term...As the remnants of Michael pass offshore along the departing front, the added pressure gradient may increase winds into the advisory range on Friday. Otherwise expect high pressure to slowly approach from the west and crest over the East Coast on Sunday. && .TIDES/COASTAL FLOODING... Upcoming tides tonight at 101 AM of 10.5 ft and Thu at 117 PM of 10.8 ft along with NE flow will allow for a very minor tide anomaly around 0.5 ft. This could lead to some splash over S of Cape Elizabeth...and some high water in the Hampton Beach area. && .CLIMATE... Record high temps for today Oct 10... Portland Jetport...81 set in 2011 and 1949...this has been broken with a high of at least 84 so far. Concord...86 set in 1939...high temp so far of at least 82. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Small Craft Advisory until 5 PM EDT Thursday for ANZ150>152- 154. && $$