Area Forecast Discussion
Issued by NWS Jackson, KY

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606 FXUS63 KJKL 180521 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 1221 AM EST Sat Feb 18 2017 .UPDATE...
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Issued at 1221 AM EST SAT FEB 18 2017 The forecast in track tonight. The latest obs were ingested into the hourly forecast grids to establish new trends. No update was needed. UPDATE Issued at 1015 PM EST FRI FEB 17 2017 As of 10 AM, some of the generally more sheltered valley locations have decoupled with some of those locations having dropped into the 30s while other more open terrain locations and other not as sheltered valley locations were in the 50s. The forecast has been updated to include a much wider range between valley and ridgetop min T by cooling off min T for the deeper valley locations. UPDATE Issued at 713 PM EST FRI FEB 17 2017 Dewpoints and relative humidities continue to gradually increase across the area this evening with most observations now above 30 percent. Hourly grids have been freshened up based on recent observations and trends. Some of the valley locations have already decoupled and with the Breathitt Mesonet already at 47, a wider ridge/valley temperature difference has been included with this update. Otherwise, high clouds should gradually increase from the south and southwest overnight as a shortwave begins to approach. At the same time, the pressure gradient is expected to be sufficient enough to keep the atmosphere a bit mixed. Even so, some more sheltered valley locations may reach the upper 30s.
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&& .SHORT TERM...(This evening through Saturday night) Issued at 339 PM EST FRI FEB 17 2017 Current conditions across eastern Kentucky feature some gusty southwest winds caused from some decent mixing this afternoon. In addition to the dry air in place and what has mixed to the surface, some RH values have dropped into the 20 percent range along with some decent southwest winds. This in addition to the very warm air advecting into the area has resulted in some fire weather concerns which should be coming to an end by 00Z this evening as RH values recover into the 40 percent range by this evening. Tonight, with a ridge passing through, clear skies will remain for much of the night before some cloud cover ahead of a disturbance shifting northeast out of the lower MS valley area. Model trends and observations might suggest a bit drier heading into this feature than expected so lower pops below likely through Saturday night. NAM and GFS trends significantly lessened QPF amounts with this system and Superblend values confirmed this. Therefore, what measurable precip does fall, will likely be less than a quarter of an inch across much of the area. In addition, the origin of this wave being from the southern stream will be lacking any baroclinicity and so will be looking at very little instability. As well, the warm trends will continue with high temps in southwest flow tomorrow rising to well above normal values again. .LONG TERM...(Sunday through Friday) Issued at 400 PM EST FRI FEB 17 2017 The models are in pretty good agreement aloft through the first part of the extended as they all depict the departure of a relatively weak trough from the southern Appalachians early Sunday followed by strong ridging through the start of the new week. The apex of this ridge passes through Kentucky on Monday ahead of a full latitude trough sweeping east through the Northern and High Plains down to the Rio Grande Valley. However, its forward/eastward momentum is slowed on Tuesday as the southern portion drags and starts to close off while the north part whips into the Great Lakes but also weakens. The models are not handling this development very well with the ECMWF the strongest and furthest east with its new Gulf Coast closed low. The Canadian is slowest while the GFS weakest and furthest south with its core. Nevertheless the mass of these lower heights stay in the Gulf - allowing zonal flow to take over to the north and through Kentucky - with our state dodging a direct impact from either parts of this system. The bulk of the energy in this pattern will then be contained north of the Ohio Valley through the end of the week. However, a strengthening low - especially from the ECMWF will head for the Upper Midwest with more ridging for the area ahead of this. Given the model agreement early and some issues later on will favor a general model blend for the bulk of this forecast. Sensible weather will feature a continuation of the very warm conditions through the entire extended portion of the forecast. Generally highs will be in the mid to upper 60s with lows in the upper 40s to lower 50s. As seems appropriate for this spate of spring-like weather we will have a few periods of showers mixed in the forecast this week - mainly from Tuesday night through Wednesday and again later Friday. Best chances for significant rain appears to hold off until next weekend depending on how the Midwest system develops and moves into the area. Thunder does not look like a good bet this week, though, as the best upper support stays well away from the CWA. The main concern through next week looks to be one of fire weather where limited rainfall and very warm temperatures appear to be giving eastern Kentucky a jump start on the season. Made some small to moderate adjustments, early on, to the temperatures at night for minor ridge to valley distinctions before we see a brief CAA pattern midweek. As for PoPs, basically tightened them up a bit with the dying cold front passing through Tuesday night. && .AVIATION...
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(For the 06Z TAFS through 06Z Saturday night) ISSUED AT 1221 AM EST SAT FEB 18 2017 Mainly high clouds will increase across the region through 12Z ahead of an approaching mid level shortwave. However, before 12Z, the mid clouds should encroach on the Lake Cumberland Region with clouds thickening and lowering further, with low level clouds moving in from southwest to northeast from then until the end of the period. Scattered showers are possible mainly from 16Z onward and enough saturation may occur for a few periods of MVFR CIGS and or VIS by the end of the period. Confidence in that occurring was not high enough to include at this time. Southwest winds will average 10KT or less through the period.
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&& .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...AR SHORT TERM...SHALLENBERGER LONG TERM...GREIF AVIATION...AR is the U.S. government's official web portal to all federal, state and local government web resources and services.