Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 210901 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 401 AM EST Tue Feb 21 2017 .SHORT TERM...
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(Today through Wednesday) Issued at 401 AM EST TUE FEB 21 2017 Abundant cirrus will continue to stream in from the Gulf of Mexico downstream of a narrow upper trough stretching from the Northwest Territories into Mexico. The northern portion of this feature, extending through the Ohio into the Tennessee Valley, will dampen and shear out through the day as the southern stream cuts off across the lower Mississippi Valley and Gulf of Mexico. South to southeast surface winds will remain in place as surface ridging moves off the Atlantic coast with low pressure following a similar course to that of the southern U.S. upper low. Height falls coupled with arrival of decaying energy aloft will lead to developing rain shower chances by late this afternoon across eastern Kentucky. The lack of any notable surface features nearby, due to a decaying cool front in the Ohio Valley associated with a low moving through Ontario, raises some question as to the extent of precipitation development. Additionally, a downsloping component to the low level flow raises uncertainty as to how much rain will fall, especially across southeastern Kentucky nearer the higher terrain. Nonetheless, the presence of energy aloft in tandem with a moist warm sector airmass spells showers becoming scattered to numerous through the evening and tonight. Deeper mixing today, owing to the recent subsidence inversion lifting, should allow for similar temperatures despite a relatively cooler pocket of 850 mb temperatures to tap into. Highs look to top out in the upper 60s to near 70 degrees. Far southeastern Kentucky will stand a better chance for widespread rainfall as the southern stream cutoff low pushes east/southeast into the northern Gulf later tonight into early Wednesday. Precipitation amounts may again be cut into with weak downslope flow in place, but the probability of measurable precipitation is certainly high. Weak shortwave upper ridging will follow departure of the weakening trough Wednesday, but it will not take much forcing to kick off a few showers through the day given the degree of moisture in place. Showers lingering from the morning will also be slow to exit east of the Commonwealth as westerly steering flow weakens into the afternoon. Although still well above normal, high temperatures should cool off a tad from Tuesday with readings in the mid 60s. .LONG TERM...(Wednesday night through Monday) Issued at 401 AM EST TUE FEB 21 2017 Extended period features potential for record high temperatures, then turning much cooler but remaining near normal. The period begins with a weak upper level and surface feature that introduces a chance of showers for Thursday morning into Thursday afternoon. These features here are quite subtle and therefore think the chance POPs seem robust enough at this point. Overall think the NAM seems most overdone QPF wise, but this will depend on any convection that could develop. Based on the instability the best chances for storms would be across the Bluegrass, but only went slight at this point given the cloud cover and before mentioned very subtle features. Then all eyes turn toward a upper level trough and surface low developing across the Northern Plains Thursday night. First thing this will do is bring warm southerly flow and temperatures will soar into the low to mid 70s for all on Friday. This system will deepen as the upper level closed low takes on a negative tilt and ejects the surface low into the Great Lakes by Friday afternoon and evening. The feature we will be watching is the trailing cold front combined with height falls that will bring a good shot of showers and thunderstorms to the region. Given the dynamics of this system with strong shear and decent CAPE we could see a isolated strong storm Friday evening. Overall based on the upper level dynamics would think the better chances for stronger storms would be west of the CWA across Western KY and into portions of the Midwest. This front will cross the region overnight Friday into early Saturday morning ushering in much cooler air compared to what we have become accustom. These near normal temperatures will remain the story for the remainder of the long term period. The model guidance becomes more divergent with the GFS wanting to bring a clipper type system through, but little support is rendered from the ensemble mean of the GFS or other long term synoptic guidance. Therefore stuck with the slight to chance POPs for Sunday night into early Monday. Some of this could be more in the way of snow Sunday night into Monday morning, but given low confidence not going to put this in HWO at this point.
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&& .AVIATION...(For the 06Z TAFS through 06Z Tuesday night) ISSUED AT 1253 AM EST TUE FEB 21 2017 VFR conditions will continue through Tuesday afternoon and likely through the evening. Cloud bases will lower through the day, but any MVFR ceilings should hold off until late in the evening toward 06Z Wednesday. Rain showers will increase in coverage this evening and tonight through 12Z Wednesday as south to southeast winds generally range between 5 and 10 knots. Pilots flying toward LEX/SDF/CVG should be cautious of the potential for some 30-35 knot southwesterly wind shear within the lowest 2000 feet late tonight into early Tuesday morning. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...GUSEMAN LONG TERM...DJ AVIATION...GUSEMAN

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