Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 270221 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 1021 PM EDT Fri May 26 2017 .UPDATE...
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Issued at 1021 PM EDT FRI MAY 26 2017 Updated the forecast this hour to adjust the hourly trends for temperatures and dew points. Some of the more sheltered valleys in the east have dropped off a bit. Have adjusted the temps for this. As well, adjusted the pops as some showers may cross the area later tonight as the MCS tracks by to the north. Any thunder should hold off till after dawn. By 15Z tomorrow, convection should refire over the area south of the boundary as it begins to slide south through the morning hours. Adjusted pops to address this change. Strong convection should still hold off till later in the day after max heating. A new zfp has been sent out with this update. UPDATE Issued at 720 PM EDT FRI MAY 26 2017 Issued an update to adjust for the hourly trends over the area. Temperatures in the far eastern valleys appear to decouple later tonight before the extensive cloud cover and showers move in. Adjusted for these updates.
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&& .SHORT TERM...(This evening through Saturday night) Issued at 400 PM EDT FRI MAY 26 2017 The latest surface map features a modest ridge of high pressure aligned from the Ohio Valley down through Florida. Broad low pressure is located across Missouri and Oklahoma, with a warm front aligned to the east into central Indiana. Aloft, the flow is fairly zonal across the southern half of the CONUS. Further north, a short wave trough is pulling away from southern New England, with another deeper trough aligned from south central Canada down into California. Eastern Kentucky has enjoyed a welcomed dry day, with dew points down into the mid 50s, and temperatures in the mid to upper 70s. Unfortunately, this tranquility will be short-lived, as a return to stormy conditions across the area is anticipated into the Holiday Weekend. Tonight, an MCV, currently located in northern Illinois, will track east. Organized convection will track east and southeast, with most of the model guidance showing activity mainly staying just north of our area. Will allow for some slight to chance POPs after midnight; however, given a stout cap in place, will keep out the mention of thunder. Temperatures will drop off into the low to mid 60s for most, although there may be a few sheltered valleys that dip into the upper 50s, given the early clearing and drier dew points in place. On Saturday, the leftover convection to our north will likely bring a surface boundary closer to the I-64 corridor. Another instability axis may also develop closer to the TN/KY border. The model guidance is erratic with timing and placement of the convection for tomorrow afternoon. As such, have stuck with mainly a persistence forecast, keeping chance POPs, peaking in the afternoon. Model soundings remain supportive of a few storms possibly approaching severe limits. Saturday night, a short wave trough will be moving into the Ohio Valley, with organized convection likely approaching the area after midnight. There is still some uncertainty on the timing and to some degree the placement of the MCS. Have continued with likely POPs across the western half of the area, with somewhat of a weakening trend to the complex towards dawn as it heads further east into our area, as is more typical with these types of systems as they move further away from the main forcing. The greatest threat with this complex will be damaging wind gusts and also isolated flash flooding given the recent wet conditions. .LONG TERM...(Sunday through Friday) Issued at 416 PM EDT FRI MAY 26 2017 A low pressure system will be traveling NE across the Mid- Mississippi Valley Sunday morning, with KY in the warm sector (warm front to our north and cold front approaching from the west with strong southerly flow). Models are all still pointing at a MCS initiating in this unstable atmosphere to our west Saturday/Saturday night and traveling eastward into our region. However still a large amount of uncertainty to start out the period on Sunday morning as a MCS is expected to be somewhere in the area. Models are still very inconclusive as to where the MCS will actually be located, or if it will even be impacting our CWA at all. The CAMs are not much help, with the ARW pegging all convection to our south Sunday morning, the Hi-res NMM is much slower and much farther north over central Kentucky by 12Z, and the NAM12 has a line spreading across our CWA during this time frame. As such, ended up sticking more with the model blend during the day Sunday given the high uncertainty. This keeps chance to likely pops across the CWA into the afternoon as well, at which point the unstable atmosphere is likely to produce more convection across the region just ahead of the cold front. Based on latest forecast soundings, instability is quite impressive, as are lapse rates, with large hail and high wind gusts still looking to be the primary threat. CAPE values are ranging from 3,500 j/kg to 4,000 j/kg Sunday afternoon, with LI`s between -9 and -11, with good drying aloft to help aid in hail growth. The cold front is expected to pass eastward across our CWA Sunday night into Monday morning, with best pops and convection expected over the far SE portion of the state just ahead of the frontal passage. Rain should move out of far eastern KY during the day Monday with a drier airmass moving in behind, allowing skies to clear out and temperatures to rise to near 80 under westerly flow. Dry weather will persist into the day Tuesday as well. SW return flow will return for Wednesday with some precip expected to make it back into the CWA. Based on the latest GFS20 soundings, a strong cap will be in place Wednesday morning, so did not include thunder until the afternoon. Instability then increases nicely through the afternoon. Models are in good agreement that pops will remain in place, at least over our southern CWA to round out the forecast period. Temperatures will be fairly stead through the period, generally in the upper 70s to around 80 during the afternoon. Sunday night will remain relatively warm with the clouds and ongoing rain ahead of the cold front, with lows in the low to mid 60s. After that point, lows will generally be in the mid and upper 50s. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) ISSUED AT 720 PM EDT FRI MAY 26 2017 Expect mainly VFR conditions to hold on through the overnight period, as high pressure gradually retreats off to our east and southeast. Towards dawn and just after, cigs will begin to fall as a round of showers and thunderstorms develops and moves through the area especially in SYM and SJS. In the afternoon, more extensive areas of showers and thunderstorms will develop and thus will put in MVFR to IFR cigs in the TAFs to account for the afternoon development. Winds will mainly remain light outside of thunderstorms. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...SHALLENBERGER SHORT TERM...GEOGERIAN LONG TERM...JMW AVIATION...SHALLENBERGER

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