Area Forecast Discussion
Issued by NWS Jackson, KY

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257 FXUS63 KJKL 191757 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 157 PM EDT Sat May 19 2018 .UPDATE... Issued at 1158 AM EDT SAT MAY 19 2018 Showers currently continue to stream northeast across portions of eastern Kentucky, with additional activity expected to both develop and move out of central Kentucky this afternoon along/ahead of an upper trough. Diabatic heating early this afternoon will promote updraft growth, but anemic mid level lapse rates and support from wind fields aloft should negate much in the way of robust development. That being said, storm motions of 30 mph or greater will allow for cells to progress enough to negate a widespread flooding potential. UPDATE Issued at 815 AM EDT SAT MAY 19 2018 Showers have already started to redevelop, mainly over central KY, but will be shifting eastward. For this update, have followed the suggestion of the NAM and HRRR. This initial batch of showers swings through this morning, followed by a bit of a lull at mid day, followed by more development with the trough axis during peak heating this afternoon. && .SHORT TERM...(Today through Sunday) Issued at 505 AM EDT SAT MAY 19 2018 The diurnal precip pattern is continuing, with very few showers remaining early this morning. They will pick up again during the day as destabilization occurs, but will also be aided by a weak trough passing through during peak heating. Low pressure or troughing at all levels was centered over southern IL and southern IN early this morning, and will move slowly east northeast. The combination of instability and upper level support will favor high coverage of precip this afternoon, and likely to categorical POPs were used. The trough axis will depart to our east early this evening, and in combination with loss of heating, will result in the dissipation of convection for the night. No change in air mass will occur, so daytime heating on Sunday will again build instability. However, less favorable conditions for precip aloft (ridging and geopotential height rises) should result in much less coverage, and POPs of only 10-30% were used. Most storms should be garden variety. Modest flow of 20-35 kts aloft today is not impressive. However, with enough instability and perhaps cell interactions, isolated hail or strong wind can`t be ruled out. As in recent days, cell training in the moist atmosphere could again result in isolated heavy rainfall. .LONG TERM...(Sunday night through Friday) Issued at 355 AM EDT SAT MAY 19 2018 The extended portion of the forecast will begin on Sunday night with the first part of the extended featuring a return flow setup into the OH and TN valleys. High pressure over the southeastern CONUS will continue to bring warm and moist air into the region setting up shower and thunderstorm chances each day at least until Thursday. Activity through the middle of next week will also be impacted by impulses tracking along the northern stream. A stronger wave will track into the Great Lakes and Upper OH Valley region for Monday. Increased southerly flow pumping in plenty of moisture with PWATs around 1.50 inches and instability nearing 2500 J/KG will set the stage for a few strong storms with the potential to produce heavy rainfall. The added forcing in place will keep convection going later into the night into early Tuesday morning. Tuesday and Wednesday will be highlighted by a diurnal type pattern. The best chance for shower and thunderstorm development will be in the afternoon and evening each day coinciding with the peak heating. This convection will then dissipate in the overnight hours. By Thursday, a weakening of the ridge over the southeast will allow a shortwave ridge to pass over the region allowing a brief break in the pattern to develop. Thus will go with a slight chance to dry forecast for much of the area. The mentioned ridge shifts east as another shortwave will move into the region for Friday. Lingering high pressure to the east of the Appalachian chain will slow the system moving into the area. Thus will only expect a slight chance of precip in the area for Friday. Will lean to the super blend on this solution as confidence is low on precip chances. Overall temperatures for highs during the extended will still be 5 to 7 degrees above normal. The summer like conditions will continue through the extended it seems. && .AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon) ISSUED AT 157 PM EDT SAT MAY 19 2018 Showers and thunderstorms will continue to develop and spread northeast across eastern Kentucky this afternoon into this evening as an upper level disturbance moves overhead. Have inserted TEMPO groups from this afternoon into early this evening as these storms will be short-lived and transient in nature. May see a brief reduction to MVFR criteria underneath any of these, along with variable and gusty winds up to 30-40 knots or so. Outside of thunderstorms, southwesterly gusts of 15-20 knots will occur this afternoon with mainly low-end VFR ceilings prevailing. Showers and storms will dissipate this evening as VFR conditions largely prevail at all sites. Will see fog in locales that see more rainfall today and in valleys overnight, but not enough certainty at this time to insert any reductions to visibility at any given site. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GUSEMAN SHORT TERM...HAL LONG TERM...SHALLENBERGER AVIATION...GUSEMAN

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