Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 211140 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 740 AM EDT Fri Apr 21 2017 .UPDATE...
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Issued at 740 AM EDT FRI APR 21 2017 Overnight convection is dissipating and it appears this lull in activity will continue for the next couple of hours or so. However, upstream convection is currently moving through western Kentucky and should be pushing back into our area by mid to late morning. Frontal boundary has made it as far south as the I-64 and I-75 corridor to our northwest and continues its slow drift to the southeast. Main update was to adjust PoPs for the aforementioned lull. Tweaked Ts and Tds to bring in line with latest hourly observations. Updated the zone package accordingly.
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&& .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...
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(For the 12Z TAFS through 12Z Saturday morning) ISSUED AT 740 AM EDT FRI APR 21 2017 Overnight convection is dissipating and it appears this lull in activity will continue for the next couple of hours or so. MVFR CIGS have developed across the area. These will likely linger until the next wave of showers and thunderstorms, currently moving through western Kentucky gets into our area by mid to late this morning. Kept potential for thunder generally along and south of the front for the remainder of the day with SME and LOZ being the two main terminals affected. A wave of low pressure to our southwest will ride up into the region later tonight and bring more widespread rain into the area, eventually dropping flight conditions into IFR territory or lower just beyond the end of the forecast window. Generally speaking weather late tonight into Saturday looks less than favorable for general aviation interests. Winds will be generally from the west-southwest around 10kts or less, with some gusts to about 15kts from time to time. Expect winds to be a bit stronger in the vicinity of any thunderstorms. Otherwise winds will veer out of the northwest at about 10kts behind the front as it drops through the area by late tonight.
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&& .JKL WATCHES/WARNINGS/ADVISORIES...NONE. && $$ UPDATE...RAY SHORT TERM...RAY LONG TERM...GREIF AVIATION...RAY

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