Area Forecast Discussion
Issued by NWS Jackson, KY

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163 FXUS63 KJKL 210855 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 455 AM EDT Fri Apr 21 2017 .SHORT TERM...(Today through Saturday) Issued at 455 AM EDT FRI APR 21 2017 A cold front has dropped south of the Ohio River this morning, stretching from roughly CMH southwest to just northwest of LEX to DYR. This boundary will continue to drift southeastward through the morning. The GFS stalls this boundary out just south of the Kentucky-Tennessee state line by this evening. The ECMWF and NAM are similar but stall the boundary out slightly further north... possibly by as little as 50-75 miles. There is good agreement among model solutions, bringing a wave of low pressure eastward across the TN Valley just south of the Commonwealth through the day Saturday. For sensible weather, and with the frontal boundary draped across the region and more particularly across our southern zones today, had to keep higher PoPs in place across the southern half of our forecast area. We will probably see a lull in activity through the morning, but expect convection to refire along the boundary through the afternoon with the help of diurnal heating. The front drifts slightly further south late this afternoon and evening. Then the wave of low pressure will brings rain back into our area by late tonight. Rain continues to affect the area through the remainder of the short term period. Thunder will generally be restricted to areas along and south of the frontal boundary. There are considerable differences showing up with respect to QPF Saturday, with the ECMWF showing some hefty amounts through the upcoming event. Overall models have not been real consistent with QPF totals. But with the boundary draped from west to east across the region and the potential for some training to take place, we may need to consider some hydro headlines with future updates. Will pass on concerns to upcoming shifts. .LONG TERM...(Saturday night through Thursday) Issued at 455 AM EDT FRI APR 21 2017 The models are in good agreement aloft in the first part of the extended. This entails a developing closed low descending into the Tennessee Valley and through Kentucky. This low tracks slowly across the area this weekend with the GFS reflecting the strongest and furthest south position while ECMWF and CMC are more northerly - closer to eastern Kentucky. By Monday morning the upper low will be passing south and east of the area with the GFS continuing to be the deepest and furthest south solution - though the ECMWF is similar while the CMC weaker and more northerly. In fact, the ECMWF and GFS move the low almost in lock step off the Southeast Coast by Tuesday morning lending support for the GFS`s more aggressive scenario. For this feature, will favor the more extreme and classic closed low solution of the GFS as the ECMWF plays a bit of catch up. Heights will rebound over Kentucky in the wake of the low while the pattern becomes more active to the northwest of Kentucky. As it does so, more energy will brush by the state while broad troughing develops over the northwest quarter of the country into midweek. This mid level trough will sharpen up heading into Thursday with an axis over the desert southwest in the ECMWF and more northerly for the GFS. This will evolve into a closed low for the ECMWF over the High Plains on Thursday while the GFS`s version is much further west. The downstream effects will relate to the strength of a burgeoning ridge through the Southeast and deep into Kentucky. The model disagreements during this latter period lowers confidence in the specifics of the forecast at this time step. Sensible weather will feature a large sfc low pushing through the Southern Appalachians as it moves east toward the Atlantic Coast. This will take its heaviest rains east along with it by Sunday morning. However, plenty of wrap around lighter rains will follow through the rest of the weekend and into Monday morning. This lingering rain, plenty of clouds, and being on the northwest side of spring sfc low will make for a cool end to the weekend and slow a temp rebound on Monday. Warmer weather and more sunshine should arrive in full force Tuesday continuing through the rest of the upcoming week. As part of this rebound, a warm front lifts through and becomes active on Wednesday afternoon and evening for our northern counties with a potential for showers and thunderstorms. By Thursday, very warm conditions will be in control of our weather due to ridging aloft and strong high pressure off to the east resulting in temperatures climbing well into the 80s. Made some low temperature adjustments for ridge to valley distinctions during the latter half of the extended forecast as we dry out and move out of a weak CAA pattern. As for PoPs, mainly just enhanced them through Sunday morning as the core of the low passes through the region. && .AVIATION...(For the 06Z TAFS through 06Z Friday night) ISSUED AT 215 AM EDT FRI APR 21 2017 An approaching cold front will bring an uptick to shower and thunderstorm activity through the remainder of the overnight, generally from west-northwest to east-southeast. Flight conditions are expected to gradually deteriorate through dawn into solid MVFR territory. May see some improvements through the middle portion of the day as the boundary drifts further southward. Northern terminals such as SYM, SJS, and JKL may even see a break in activity for several hours. However, a wave of low pressure to the southwest will ride up into the region later tonight and bring widespread rain into the area, eventually dropping flight conditions into IFR or lower just beyond the end of the forecast period. Generally speaking weather late tonight into Saturday looks less than favorable for general aviation interests. Winds will be generally from the southwest around 10kts or less, with some gusts to about 15kts from time to time. Of course winds could be a bit stronger near any thunderstorms. Winds will veer out of the northwest behind the front as it drops through the area. && .JKL WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...RAY LONG TERM...GREIF AVIATION...RAY

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