Area Forecast Discussion
Issued by NWS Caribou, ME

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000 FXUS61 KCAR 222359 AFDCAR Area Forecast Discussion National Weather Service Caribou ME 759 PM EDT Sat Jul 22 2017 .SYNOPSIS... High pressure will dominate the weather through Sunday with below seasonal temperatures expected. Low pressure will track south of the region Monday into Tuesday. High pressure will build across the region Wednesday. && .NEAR TERM /THROUGH SUNDAY/... 755 PM Update: Only chg was to expire paddle risk headline along the coast with no weather element chgs since the 635 PM update. 635 PM Update: Just minor chgs to fcst hrly cld cvr into the ovrngt based on latest sat imagery which does show some hi cld cvr apchg Downeast areas of the Rgn and fcst hrly temps/dwpts based on latest sfc obs with only minor chgs to fcst ovrngt lows msly to accentuate broad vly fcst lows ovr the far N. The last chg was to hi trrn temps arnd Mt Katahdin from late this aftn into Sun to increase diurnal/nocturnal range closer to climo values of 10 to 12 deg for this tm of season plus a small warm advcn factor on Sun. Orgnl Disc: A weak surface trough along the coast will move offshore this evening and the high will build southeastward from the James Bay region of Canada. This is a very cool and dry air mass with dew points dropping to the 40s across the entire forecast area by later tonight. H850 temps will be less than 5C for much of the forecast area by Sunday morning. With light winds and clear skies tonight, lows will dip into the upper 30s in some of the normally colder valleys of Aroostook County. Elsewhere in northern zones, lows will be in the lower 40s. Further south, the cold air won`t be quite as firmly entrenched and some mid- level clouds will move through late in the night. As a result, lows will only drop to the upper 40s to lower 50s. The clear skies continue Sunday and temperatures will be a bit cooler in the southern half of the forecast area than today with high temperatures forecast to reach the upper 70s. A slack pressure gradient will permit a sea breeze circulation to develop along the coast in the afternoon. && .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/... Surface high pressure will be ridged north and east of the region Sunday night through Monday night. At the same time, surface low pressure will track to the south while an upper level trof slowly crosses the region. Cloud cover will increase across the region Sunday night through early Monday. The surface high will impede and slow the progress of rain across the forecast area, particularly northern areas. Uncertainty still exists regarding the placement of precipitation and rain totals Monday through Monday night. Showers will then diminish Tuesday with high pressure building across the region during the afternoon. Temperatures will be at below normal levels Monday/Tuesday. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... High pressure will allow for a clear, calm, and cool Tues night, with lows ranging from the lower 50s Downeast to the upper 40s in the North Woods. Pleasant weather will continue through Wed. Clouds will begin to overspread the CWA Wed night as an upper trough and surface cold front approach from the west, but both the CMC and ECMWF have backed off onset of precip until after 12z Thu, bringing them more in line with the GFS. There remains some disagreement between models on how much moisture and thus precip will be associated with this front, with the ECMWF and CMC both on the wet side, and the GFS decidely on the dry side. For what it`s worth, the GFS has been much more consistent than the other two models on both frontal timing/speed and the QPF forecast. Between 12z Thu and 12z Fri, generally kept POPs to Chance levels under 50%, but did go for Likely POPs around 60% for the western border and St. John Valley between 18z Thu and 00z Fri, with Chance POPs elsewhere. Also put in chance of thunder for those areas Thu afternoon and evening. There is a chance that the front could stall out near the coast Thu night into Fri, and keep showers and a few storms possible there, as per the 12z GFS and 00z ECMWF. Or as the 12z CMC and 12z ECMWF point toward, the front may be slower moving and perhaps a stronger upper-level trough or even cut-off low could cause increased POPs to persist across a broader swath of the CWA for Friday and even into the weekend. Given the uncertainty, and the significant flip between the 00z and 12z ECMWF runs, POPs were kept low and the time frame later next week will need to be monitored for possibly significant changes to the forecast. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/... NEAR TERM: VFR conditions are expected through the period with no cigs and excellent vis. Winds will be light tonight through Sunday. SHORT TERM: VFR conditions are expected across the region Sunday night. Generally expect VFR conditions Monday, though occasional MVFR conditions are possible across central and Downeast areas during the afternoon. Occasional MVFR/IFR conditions are possible Monday night into early Tuesday mostly across central and Downeast areas. Conditions will improve to VFR levels later Tuesday. VFR conditions are expected Tuesday night through Wednesday night. Occasional MVFR conditions are possible Thursday, particularly across northern areas. && .MARINE... NEAR TERM: No significant weather is expected under high pressure. Seas will remain around 2 feet or less. SHORT TERM: Winds/seas will remain below small craft advisory levels Sunday night through Tuesday. Visibilities could be reduced in rain later Monday into Monday night, with a chance of showers Tuesday. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...None. && $$ Near Term...VJN Short Term...Norcross Long Term...Kredensor Aviation...VJN/Norcross Marine...VJN/Norcross

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