Area Forecast Discussion
Issued by NWS Caribou, ME

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000 FXUS61 KCAR 210753 AFDCAR Area Forecast Discussion National Weather Service Caribou ME 353 AM EDT Fri Sep 21 2018 .SYNOPSIS... Strong low pressure will track north of the region this afternoon into tonight. A strong cold front will move through late tonight. && .NEAR TERM /THROUGH TONIGHT/... Two significant concerns: dense fog Northern Maine this morning, then strong winds late today into tonight. Fog has become quite dense over much of Northern Maine. Expanded the dense fog advisory south a bit to cover areas from Patten to Houlton. Fog shouldn`t last too long thankfully, as winds pick up fast this morning as the strong weather system approaches. Winds with the weather system are by far the main concern late today into tonight, as rain will be rather modest with generally less than one quarter inch Downeast and up to one half inch in the St John Valley. Winds aloft are exceptionally strong for the warm season, which is concerning because leaves are on the trees making them much more susceptible to damage. 850mb winds reach 70 knots from the southwest this evening over Northern Maine. SPC sounding climatology for Caribou doesn`t have any soundings with 850mb winds over 60 knots for the month of September, and only a handful of times does it reach 70 knots at 850mb at Caribou in the winter. Winds aren`t quite as impressive aloft Downeast, but significant enough to be of concern. The prefrontal airmass is fairly stable at least initially this afternoon into early evening, so the brunt of the winds will have trouble mixing down to the surface except over higher terrain. However, convective showers move through around mid-evening into the overnight hours as the cold front approaches, and any of these showers (or possibly isolated storms) could bring the strong winds to the surface. And certainly, with the cold front passage after midnight, strong winds will mix down to the surface. At least winds aloft won`t be quite as strong when the cold front arrives, but still strong enough to cause tree damage considering leaves are still on the trees. Generally expect peak gusts 45 to 50 mph most places, with a better shot of the highest gusts Northern Maine, as well as higher terrain. While gusts 45 to 50 mph may not sound like much, again, we need to reiterate that we don`t see winds like this often when leaves are still on the trees, other than local warm season thunderstorm winds or the rare tropical system. Leaves on the trees leads to much greater impact than when there are no leaves. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... The cold front will be off the coast first thing Saturday morning. Any lingering early morning clouds and showers will give way to a mainly sunny day with gusty northwest winds continuing into midday. The winds will begin to diminish as high pressure builds into the region. Highs on Saturday will range from the mid 50s to near 60 degrees north and low to mid 60s central and downeast, which is close to seasonal for this time of year. The stage will be set for areas of frost to develop Saturday night, especially across northern and central areas. An approaching cold front from the northwest brings some increasing clouds across the north by Sunday morning. The cold front crosses the region Sunday but the front is expected to cross the region dry. Even cooler air is expected to follow the passage of this front. Sunday night will be a very chilly night as a large Canadian high pressure system settles across the region. Widespread frost with freezing temperatures are possible by Monday morning across the far north with areas of frost possible central and downeast. && .LONG TERM /MONDAY THROUGH THURSDAY/... Monday morning starts off very chilly with frost before afternoon temperatures moderate into the 50s by afternoon along with abundant sunshine. Monday night is another cold night with more frost possible. After a dry day Tuesday, a bit of a moderating temperature trend is expected by mid week but along with the milder temperatures will come the chance for showers. && .AVIATION /07Z FRIDAY THROUGH TUESDAY/... NEAR TERM: Dense fog northern TAF sites early this morning should end by mid-morning as south winds begin to increase ahead of the weather system. Generally low VFR to MVFR conditions during the day today, with greater chance of MVFR in the north. Winds steadily increasing through the day and into the evening. Tonight, ceilings lowering to IFR or low MVFR. Of larger concern tonight is the gusty winds, plus low level wind shear (primarily speed shear). SHORT TERM: VFR conditions through middle of next week. The exception will be patchy late night and early morning river valley fog which could bring local IFR conditions in reduced visibilities. && .MARINE... NEAR TERM: Gale force winds tonight, with rough seas building to 6 to 10 feet as well. Delayed onset of gale a few hours to 6 PM. SHORT TERM: The Gale Warning will likely need to be replaced with a Small Craft Advisory Saturday morning with gusty Northwest winds expected to continue into the afternoon. The could be another opportunity for Small Craft conditions Sunday afternoon and into Sunday night in the cold advection behind a departing cold front. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...Dense Fog Advisory until 8 AM EDT this morning for MEZ001-002- 005-006. Wind Advisory from 2 PM this afternoon to 8 AM EDT Saturday for MEZ001>006-010-011-015>017-029>032. MARINE...Gale Warning from 6 PM this evening to 8 AM EDT Saturday for ANZ050>052. && $$ Near Term...Foisy Short Term...Duda Long Term...Duda Aviation...Foisy/Duda Marine...Foisy/Duda

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