Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 201757 AAA AFDJKL AREA FORECAST DISCUSSION...UPDATED National Weather Service Jackson KY 157 PM EDT Fri Apr 20 2018 .UPDATE...
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Issued at 157 PM EDT FRI APR 20 2018 The forecast remains on track. Temperatures are currently running from the mid to upper 50s, with forecast highs still looking on track. Did adjust dew points down a few more degrees through this afternoon, as some teens and lower 20s are already occurring in places. Updates will be out shortly. UPDATE Issued at 1007 AM EDT FRI APR 20 2018 Temperatures have responded well to full sun this morning, with readings currently running in the mid 40s across eastern Kentucky. Forecast highs in the low to mid 60s for most locations look on target. Have just freshened up the hourly temperatures and dew points through this afternoon to capture the latest trends in observations. UPDATE Issued at 711 AM EDT FRI APR 20 2018 Seeing some valley fog this morning along with the ongoing frost. Both will mix out within the next couple of hours as the sun comes up and temperatures quickly warm.
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&& .SHORT TERM...(Today through Saturday) Issued at 348 AM EDT FRI APR 20 2018 The center of a surface high pressure system near the Corn Belt will migrate across the Great Lakes and upper Ohio Valley today. This has led to temperatures falling to near or below freezing for much of eastern Kentucky this morning, resulting in widespread frost. Shortwave ridging building east of the Great Plains will bring rising heights aloft and subsequent warmer temperatures, with highs warming into the low-mid 60s this afternoon. Light north/northeast winds will be in store tonight as ridging slides eastward and promotes favorable conditions for radiational cooling once again. Areas of mainly valley frost will be in store as temperatures fall into the upper 20s to near 30 degrees. Ridges look to remain in the mid-upper 30s and mostly void of frost given fairly low dewpoints this afternoon. Have elected to hold off on a Frost Advisory for tonight/Saturday morning at this point, but will monitor temperatures/dewpoints through the day to assess the potential for more widespread frost development. Upper ridging cresting overhead Saturday will further warm temperatures into the mid 60s to low 70s. Will see an increase in cirrus cloud cover through the day downstream of a central Great Plains disturbance aloft, but a persistent subsidence inversion and lack of deep layer moisture will keep the first half of the weekend dry. .LONG TERM...(Saturday night through Thursday) Issued at 440 AM EDT FRI APR 20 2018 The extended period is expected to begin with a split flow pattern over the Plains with ridging over the southeast Conus at mid levels and a mid level low/trough moving from the Plains toward the MS valley with mid level ridging extending into the southwest Conus. The northern stream initially will be near the US/Canadian border. At the surface a ridge of high pressure is expected to initially extend from the Great Lakes to the eastern seaboard. The airmass will initially be dry with PW areawide expected to be under a half of an inch. From Saturday night into Sunday, the mid level low will move east southeast and should be centered southwest of Memphis by sunset on Sunday. At the same time surface high pressure should shift northeast of the area while southeast Conus ridging weakens and shifts to the east. Surface low pressure should track from the Southern Plains to MS during that time. Moisture should begin to increase from the top down in this scenario with mainly just some mid level clouds at times by Sunday afternoon, especially across the southwest part of the area. A dry end to the weekend is expected with near normal highs on Sunday after a chilly start especially eastern valleys which should bottom out in the upper 30s on Sunday morning. PW should increase to the two thirds of an inch range in the northeast part of the area by 0Z Monday with PW nearing 0.9 inches near Lake Cumberland by that point. Further increase through Sunday evening will eventually support shower chances first in the far south. Clouds should thicken and lower Sunday night into Monday with a period of unsettled weather to follow. The unsettled weather should continue for the rest of the extended period as the mid and upper level low meanders over the southeast and then moves into the TN and OH Valleys around Monday night and Tuesday. As the system gets closer moisture and lift will increase with the potential for diurnally enhanced chances for showers for spreading north across East Ky by late Sunday night into Monday. This mid and upper level system should then open up and begin to merge or phase with a northern stream system working across Canada and the Great Lakes around midweek. From Tuesday night on, model agreement increases with timing uncertainties along with uncertainties in the details of the upper level pattern. The general consensus is for a trough over the eastern Conus from midweek through the end of the period with at least some weaker embedded disturbances moving through the OH Valley and Appalachians. This pattern would support continued unsettled weather with chances for showers from time to time. Limited diurnal temperature ranges with highs averaging below normal are anticipated from Sunday night on due to the cloud cover and shower chances. && .AVIATION...
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(For the 18Z TAFS through 18Z Saturday afternoon) ISSUED AT 157 PM EDT FRI APR 20 2018 High pressure will keep mostly clear skies in place, with winds averaging around 5 kts or less out of the northeast through the period.
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&& .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GEOGERIAN SHORT TERM...GUSEMAN LONG TERM...JP AVIATION...GEOGERIAN

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