Area Forecast Discussion
Issued by NWS Caribou, ME

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232 FXUS61 KCAR 241923 AFDCAR Area Forecast Discussion National Weather Service Caribou ME 323 PM EDT Sat Sep 24 2016 .SYNOPSIS... Surface high pressure will slowly build toward the region from the west through Monday as an upper level low across the Maritimes continues to move east. Low pressure and an occluded front will approach the area Tuesday. && .NEAR TERM /THROUGH SUNDAY/... The coldest air mass of the season is advecting into the area through the period. High pressure will remain to the west and the pressure gradient will tighten overnight between the high and low pressure near Labrador. This means mixing will continue through the night and reduce the risk of frost except in the normally colder/sheltered locations. Will go with patchy frost in all of the northern zones tonight but will continue to hold off on the advisory. Also expect clouds to increase towards the Crown of Maine late in the night as a shortwave pushes south from Quebec. The trough may set off a few sprinkles Sunday morning...mostly towards the Saint John Valley. This trough will cause mostly cloudy skies for northern Aroostook on Sunday morning. Elsewhere, cumulus fields will cause partly sunny skies. Expect slightly cooler highs on Sunday with lower 50s north and mid to upper 50s for Bangor and the Down East region. Strong low level mixing will generate another windy day as gusts again reach the 20-30 mph range by late Sunday morning. && .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/... High pressure sliding in from the northwest will likely allow for some clearing skies and calming winds Sun night, which may very well be the coldest night of the fall so far for many spots. Will likely need at least a Frost Advisory for the northern zones. Some patchy fog also possible in the clear and calm conditions. Monday will be clear and dry as the center of the sfc High passes over the CWA. Dry conditions will persist into the start of Mon night as the upper ridge crests over the region. However, S`ly winds that are forecast to develop Mon evening will likely keep most spots warm and/or breezy enough overnight to preclude frost. An occlusion racing out ahead of low pressure over the Great Lakes will approach early Tue. Some areas, especially the western CWA, may see rain by sunrise, and rain will spread over the entire state by midday Tue. There remains some disagreement between available guidance on the speed of the rain advance, with the ECMWF and NAM generally about 6 hours ahead of the GFS and CMC. This disagreement precluded putting categorical POPs in at 12z, but felt confident enough to bring them in by late morning. Rain chances persist across the CWA through most of the day, but will begin winding down from west to east later Tue afternoon. && .LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/... An occluding front will be pushing east of the area Tuesday night. Some rain may linger in eastern areas early in the night. Otherwise, dry air circulating in from the southwest ahead of low pressure in the great lakes should bring partial clearing later at night. Wednesday will then be partly sunny and mild as a corridor of dry air between the low to the west and the occlusion off to the east remains over our area. Dry weather will likely last through Thursday. However, we will have to keep watch for a possible secondary low developing off the Mid- Atlantic coast as the upper trough moves east from the Great Lakes. Right now most of the guidance is keeping moisture from this secondary low to our southeast, but if the trough backs the moisture more than is currently indicated it could bring wet weather to parts of the region at the end of the week. A very large and strong ridge of high pressure will then build into the east as the weekend approaches. This will bring dry weather Friday into the weekend. A weak back door cold front may push into the area on Sunday cooling the north off a bit. Ridging should then rebound early next week bringing dry weather and a warming trend. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... NEAR TERM: VFR conditions are expected throughout the period with the possible exception of MVFR cigs at FVE early Sunday morning. The only other concern is the gusty NW winds that will be as strong...or stronger than today. SHORT TERM: Patchy fog, especially in valleys, may cause localized IFR or LIFR conditions Sun night into early Mon morn, especially for KHUL north thru KFVE. Otherwise, no aviation concerns thru Mon evening. As the next system approaches, mid-level cloud deck appears likely to move in between 06z and 12z Tue, with MVFR/IFR CIGs possible in any early areas of rain. As rain spreads over more of the CWA during the day Tue, expect MVFR/IFR CIGs and at least MVFR vsbys to impact all TAF sites thru Tue eve. Improving conditions expected after 06z Wed. Currently expecting good conditions Wed into Thu, but can`t entirely rule out lingering rain and psbl lower CIGS if the previous system does not depart as quickly as expected. && .MARINE... NEAR TERM: Right on the cusp of an SCA with gusts to 25 kts late tonight into Sunday morning accompanied by 4-6 seas. Winds and seas will subside later Sunday. SHORT TERM: At this time, SCA conditions are not expected Sun night thru most of Tue. Wind gusts and seas may be close Sun night before conditions die down, so this will bear watching. Onshore winds developing Mon night into Tue will gradually build seas, and an SCA may be needed by Tue eve, mainly for possible seas of 6ft or more. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...None. && $$ Near Term...MCW Short Term...Kredensor Long Term...Bloomer Aviation...MCW/Kredensor Marine...MCW/Kredensor

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