Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 180100 AAA AFDJKL AREA FORECAST DISCUSSION...UPDATED National Weather Service Jackson KY 900 PM EDT Sat Mar 17 2018 .UPDATE...
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Issued at 900 PM EDT SAT MAR 17 2018 Now that the severe weather threat has ended across the area, the severe thunderstorm watch has been cancelled. The forecast and the hazardous weather outlook products have both been updated to reflect this changes. Also updated the precipitation forecast for the rest of tonight based on current radar trends and the latest run of the HRRR model. Now have thunderstorms moving out of the area between 2 and 3Z and precipitation overall moving out of eastern Kentucky between 4 and 5Z. Will need to issue another update toward the end of the shift to get rid of any remaining evening wording and for areas where the ongoing precipitation will have already ended for the night. UPDATE Issued at 735 PM EDT SAT MAR 17 2018 Have updated the grids with the latest obs to establish new trends. Will leave the severe thunderstorm watch and zone forecast text product as is until we cancel the watch this evening after the severe threat has finally ended. It does appear that the severe weather threat will end across our area well before the midnight EDT expiration time of the watch. It also appears that we may be able to take precipitation out of the area a bit faster than the inherited forecast has been indicating, but will continue to monitor current radar trends and the latest model data to before making that determination.
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&& .SHORT TERM...(This evening through Sunday night) Issued at 520 PM EDT SAT MAR 17 2018 A cold front was bisecting the forecast area from east to west late this afternoon, with a low pressure system tracking along the front from central into eastern KY. Showers and thunderstorms have quickly developed along the front. The regime will shift southward this evening. There is good speed shear in place, and dry mid levels with steep lapse rates. The severe weather parameter which is looking puny is the moisture. Strong heating has mixed drier air to the surface with dew points only in the 30s and 40s over most of the southern portion of the area late this afternoon. Can not rule out severe weather in places where higher dew points linger or redevelop, but for much of the area late afternoon conditions don`t look all that favorable. Freezing level and wet bulb zero height are quite low, which favors large amounts of small hail. Any large hail would probably need to come from storms with significant rotation. Storms should taper off from northwest to southeast this evening after cold fropa. Surface high pressure passing to our north will provide fair weather Sunday into Sunday night. Another low pressure system heading east from the southern plains will pull the front back north toward KY as a warm Sunday night. Showers could make a return to our southwest counties by dawn, but will more likely hold off until the daytime on Monday. .LONG TERM...(Monday through Saturday) Issued at 520 PM EDT SAT MAR 17 2018 Model solutions are in decent agreement, sufficient enough to pick out the main features of concern through the extended. Flow aloft amplifies with time but remains fairly progressive, with implications that our generally unsettled pattern will continue with only one relatively short period of fair weather from Thursday through at least part of Friday. Consequently our weather is active straight out of the gate as a mid level low, upper level wave moves into the region Monday. Additional shortwave disturbances follow Tuesday into Wednesday before exiting to our east by Thursday. Solutions differ on timing another shortwave disturbance into the region by the end of the period, with the 12Z GFS bringing our next weather maker into the area by late Friday into Saturday. The 0Z ECMWF and 12Z Canadian hold off on this system until beyond the end of the period, and seem to suggest a deeper, more organized storm system. Closer to the surface, a low pressure system will pass through the Tennessee Valley Region Monday/Monday night. Instability is marginal but may be enough to kick of a thunderstorm or two late Monday into Monday night. Shortwave disturbances following in the wake of the initial low will be responsible for the redevelopment of another surface low or two over the southern Appalachians through Tuesday and Wednesday. If enough cold air manages to be drawn southward into the region from the north, sensible weather may feature a wintry mix of rain and snow showers for a period of time late Tuesday night into Wednesday morning, particularly across the higher terrain. However, details remain a bit too sketchy to provide any specifics for now. Drier conditions will work into the area by Wednesday night and Thursday as ridging moves in from the west. Fair weather should continue through much of Friday before the next potential weather maker moves in from the west by late week or early into the weekend. Comparing models favored a slower arrival of the precipitation for the end of the extended and would not be surprised if Friday winds up dry in the end. But should not discount the GFS solution totally based on its recent very good performance with the last few systems to affect our area. Otherwise, near normal temperatures initially will cool to well below normal for the mid week time frame. Temps then rebound for the end of the week and following weekend. | && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) ISSUED AT 735 PM EDT SAT MAR 17 2018 Showers and a number of thunderstorms will continue to move across eastern Kentucky this evening. Based on the latest upstream radar trends, it appears that the showers and storms will be ending at LOZ, SME, and SYM by 1Z or so this evening, by 2 or 3Z at JKL, and between 4 and 6Z at SJS. Any storms may produce MVFR conditions at any given airport this evening. It appears that SJS and JKL will have the best chance of seeing a shower or storm to begin the TAF period. Will continue to monitor the ongoing showers and storms and will update the TAFs as necessary as the rain moves off to our east. Conditions should begin to improve VFR at the TAF sites between 13 and 17Z on Sunday. Cloud cover should progress from OVC to BKN to SCT during that time as well, with clear to mostly clear skies expected by Sunday afternoon. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...AR SHORT TERM...HAL LONG TERM...RAY AVIATION...AR is the U.S. government's official web portal to all federal, state and local government web resources and services.