Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 250722 AAD AFDJKL AREA FORECAST DISCUSSION...UPDATED National Weather Service Jackson KY 222 AM EST Sat Feb 25 2017 .UPDATE... Issued at 210 AM EST SAT FEB 25 2017 Grids were updated based on recent radar, observation and short term model trends. This led to only minor adjustments to pops, but did fine tune the wetbulb cooling as the showers and thunderstorms arrive. Many of the thunderstorms have been containing pea sized hail and this trend should continue for the next hour or two across the far southeast part of the area before storms exit the area. UPDATE Issued at 949 PM EST FRI FEB 24 2017 Current conditions feature the area of showers and storms at the CWA doorstep along the I-75 corridor. It seems that no dominant cold pool or organization of the cells in central Kentucky, or Tennessee for that matter has occurred. Thus, with the cap still in place over eastern Kentucky, will be hard pressed to see any severe convection tonight. So have updated to pull the severe wording from the forecast but have left in the mention of strong storms with the potential to produce gusty winds and small hail. Have updated the HWO as well to take out the severe wording and input the mention of strong storms. UPDATE Issued at 713 PM EST FRI FEB 24 2017 Current conditions feature a line of showers and segments of strong to severe thunderstorms in central Kentucky to the west tracking northeast. Fine tuned the pops to account for a more timely arrival into eastern Kentucky. Decided to keep the severe mention in the forecast though, with heating lost and instability becoming more elevated, the cap in place more and more hints at any severe weather in eastern Kentucky will be dependent on what develops in central Kentucky and advects in. Mainly in the form of a squall line or bowing segments. As well, the main threat continues to be damaging winds. Onset into Kentucky may be as soon as 9pm. A new ZFP was sent out to account for these changes. && .SHORT TERM...(This evening through Saturday night) Issued at 517 PM EST FRI FEB 24 2017 South-southwest flow aloft will become more westerly through the short term as a potent storm system plows through the Great Lakes, pulling a trough through the Commonwealth over the next 24 hours. Surface low pressure over Lake Michigan will continue to move off to the northeast, pulling a cold front eastward through the region, and into eastern Kentucky during the overnight. A line of thunderstorms currently developing across the Midwest will move into our forecast area through the overnight period. HRRR timing of the main line of convection has been fairly consistent and generally agrees with what has been advertised. Some thunderstorms could produce severe weather with the main threat being damaging winds. Hail will be a secondary threat and a brief, isolated tornado can not be ruled out. Moisture, or the lack thereof will be the primary limiting factor to severe weather as dew points will top out in the mid 50s ahead of the front. Timing of the cold front through eastern Kentucky will also be a limiting factor. Regardless bulk shear is very impressive with this system, 40-70 kts, with the majority of the shear realized in the lowest 3 km. Thus the potential for bowing cells and line segments will be favored. Surface based instability to support this storm mode is not ideal but does appear to be sufficient. Consequently damaging winds are the primary severe weather threat. This has a distinctive QLCS flavor to it and considering the environment as a whole feel an isolated tornado can not be ruled out, though features of this type tend to be weaker than most and short lived. Low wet bulb temperatures and freezing levels suggest hail will be a possibility as well. Colder air invades the coal fields on Saturday and will set things up for a rather chilly weekend in general. Gusty winds will combine with strong cold air advection to make for a less than optimal day for outdoor activities. .LONG TERM...(Sunday through Friday) Issued at 315 PM EST FRI FEB 24 2017 The extended portion of the forecast will be fairly active, with alternating periods of wet and dry weather and warm and cooler conditions. The period will likely start off dry, with slightly above normal temperatures Sunday and Sunday night. The pattern is then expected to shift on Monday, as a weak warm front moves through the area, bringing persistent southerly flow and warmer air into the region. Rain showers should begin to move into the area from the southwest and west late Sunday night into early Monday morning. The rain will overspread the entire area by late Monday afternoon and early Monday evening, as an area of low pressure moves along what will become a nearly stalled out frontal boundary. This pattern is tentatively expected to persist through late in the day on Tuesday. A wave of low pressure is then forecast to form along the western end of the stalled front Tuesday night. This second area of low pressure is then expected to push eastward on Wednesday, and will drag another cold front across the lower Ohio valley and Tennessee valley regions. This boundary may be just strong enough, and just enough moisture an instability available, for a few thunderstorms to form along and just ahead of the front, as it moves across the region. Once the front moves past us Wednesday night, any thunderstorms should give way to all rain showers. We may even see enough cold air filter in behind the system to allow some snow to mix in with whatever rain is left. The last of this precipitation should be out of the area by late Thursday morning. Thursday and Thursday night should be mostly dry. There is an outside chance that a few rain and snow showers will move across the area along and north of I64 to end the period, with due to uncertainty, this should be taken with a grain of salt. Temperatures in the extended on average will be above average each day, with the warmest days being Monday, Tuesday, and Wednesday, when the highs will be in the 50s and 60s. Closer to normal values should be experienced on Thursday, when the mercury is forecast to max out lower 50s. Nightly lows should be in 30s, 40s, and 50s. && .AVIATION...(For the 06Z TAFS through 06Z Saturday night) ISSUED AT 139 AM EST SAT FEB 25 2017 The first few hours of the TAFs were adjusted to account for timing of the broken line of convection moving across the area. A period of MVFR to possible brief IFR visibility is anticipated due to moderate to briefly heavy rainfall with CIGS possibly also falling briefly into the MVFR range as showers and thunderstorms pass. Winds will initially be southwesterly ahead of the front with some gusts of 20 to 30 KT with initial shower and thunderstorm activity. As the cold front moves across the area during the first 3 hours of the period, winds will become more west to northwesterly averaging around 10KT with some gusts up to 20KT possible. Low end MVFR to VFR conditions are then anticipated for a couple hours behind the front before CIGS return to VFR on average. Winds should increase again on o then increase again tomorrow afternoon with westerly winds gusting up to 25 knots as well. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JP SHORT TERM...RAY LONG TERM...AR AVIATION...JP is the U.S. government's official web portal to all federal, state and local government web resources and services.