Area Forecast Discussion
Issued by NWS Jackson, KY
Issued by NWS Jackson, KY
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579 FXUS63 KJKL 270400 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 1200 AM EDT Fri Sep 27 2024 .KEY MESSAGES... - The remnants of tropical system Helene will bring a widespread, soaking rain event into Friday. - Flash flooding could result from the remnants of Helene, but the overall potential may be limited by its quick movement. - Wind gusts of generally 40 to 60 mph are expected at times from late tonight into Fri as the remnants of Helene pass by. && .UPDATE... Issued at 1200 AM EDT THU SEP 26 2024 Showers continue across eastern Kentucky at midnight and are still expected to increase in intensity from southeast to northwest through 4 AM EDT. Forecast is on track. UPDATE Issued at 847 PM EDT THU SEP 26 2024 Showers, mainly light, continue to stream northward across eastern Kentucky this evening while Hurricane Helene, now a category 4 hurricane, churns toward the Florida Panhandle. Expect waves of showers to continue drifting across eastern Kentucky. The overall intensity of the rainfall should tick up gradually from the southeast, especially after midnight, as Hurricane Helene lifts across the Florida Panhandle and through Georgia. Overnight PoP/T forecast has been refined with the latest hi-res model solutions. && .SHORT TERM...(This evening through Friday night) Issued at 455 PM EDT THU SEP 26 2024 Late this afternoon, an upper level ridge was centered to the west of Bermuda with another upper level ridge extending from the Southern Rockies to the upper MS Valley. An upper level low was centered near the confluence of the MS and OH Rivers while Major Hurricane Helene continues to move north in the northeastern Gulf of Mexico and headed toward northwest portions of FL. A nearly stationary frontal zone remains from low pressure in Quebec to the upper OH Valley to eastern KY to northwest FL to the northwestern Gulf of Mexico. The upper level low continues to interact with the boundary and moisture transported into the region for a continued precursor rain event (PRE). Rain continues to move from eastern TN north into much of eastern KY at this time. Tonight and Friday, the upper level low is expected to move south to northeastern MS/northwest AL with this upper low and Hurricane Helene more or less moving into Fujiwhara fashion with Helene tracking quickly across northwest and FL and southern and central GA. This will then move across the Southern Appalachian region and then to the Cumberland Plateau through early to mid afternoon on Friday, gradually weakening and becoming extratropical. Bands of rain more closely associated with Helene are expected to cross the region tonight through Friday morning as the pressure gradient also increases between Helene and high pressure north of the eastern Great Lakes vicinity. These winds will have a downslope component a times, but PW will rise near or in excess of 2 inches tonight remain at those levels into the morning before dry slotting works northwest on Friday afternoon. As Helene nears, a general additional soaking rainfall should occur areawide. Some locally more intense rain of 3 or more inches could occur in a band somewhere across eastern KY per some CAM runs, though a general 1 to 2.5 inches of rain expected through Friday evening. Winds and wind gusts are also a concern and in addition to a flood watch in effect generally south of the Mtn Pkwy. Areas generally south of the Mtn Pkwy have either had more rain over the past 3 days and/or are expected to have the highest totals on average. 12Z HREF mean wind gusts increase to 40 mph or higher across the highest terrain along the VA border toward midnight with the stronger gusts progression to the north and northeast through the remainder of the night. Some of this is not expected to be realized in the deeper valleys before sunrise. However, 12Z HREF mean brings wind gusts to near or in some instances than 60 mph northwest across much of the area Friday morning to early Friday afternoon, before gradually slackening. Momentum is likely to mix down as a dry slot moves in behind a morning band of rainfall. Higher elevation locations will experience a longer period where stronger wind gusts are possible from late tonight into early Friday afternoon. A High Wind Warning was issued for Bell, Harlan, and Letcher County from 11 PM tonight to 8 PM on Friday with another tier of High Wind Warnings to the north and west 2 AM on Friday to 8 PM on Friday which generally has elevations of 1500 feet or higher or where soil moisture is highest/heavier rain has fallen over the past 3 days or so. A Wind Advisory was issued for areas further northwest, but gusts to around 60 mph area possible especially in the eastern Bluegrass region and on ridges and further adjustments to headlines may be needed. 12Z HREF probabilties of 60 mph gusts or higher are significant over much of the area at 50 to 100 percent. The 18Z HRRR wind gusts are in general agreement with the HREF values. So in summary, tonight, the strongest wind gusts of 40 mph or more are expected in the High Wind Warning area later tonight, especially on ridges, with wind gusts peaking across the region during Friday morning to mid afternoon on Friday. From late Friday into Friday night, the upper level low and Helene will gradually merge with the combined low meandering over the Lower OH Valley region. Following a relative lull in chances for showers on Friday afternoon and evening with the dry slotting, moisture is progged to increase from west to east late Friday night with an associated increase in shower chances from west to east. .LONG TERM...(Saturday through Thursday) Issued at 225 PM EDT THU SEP 26 2024 The forecast period begins with the area still largely under the impacts of the remnants of Hurricane Helene. At upper-levels, the remnants of Helene will begin to merge with a largely stationary cut- off circulation that`s been situated over western Kentucky through much of this week. As the two systems merge into one circulation, shower and storm chances will persist through the day Saturday and linger through the weekend. Models continue to remain in rather good agreement going into next week with the circulation getting picked up by the mean flow and ejecting out of the area by Monday morning but lingering PoP chances will exist through the end of the period as an upper-level trough, moving through southern Canada, drags a cold front through the region Tuesday afternoon which will then usher in cooler and drier weather for the middle of next week. Overall, the forecast period will be highlighted by multiple rounds showers and storms. Shower and thunderstorm chances drop a little bit with the merging of the closed circulation and the remnants of Helene but chances (40-70%) exist through the weekend. Temperatures through the period will remain rather seasonal as highs are forecast to in the upper-60s to upper-70s. Overnight lows, will be warmer with the insulation of the system overhead but with the approach of a cold front on Tuesday, cooler temperatures and fall-like weather will be in place for the end of the period. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) ISSUED AT 815 PM EDT THU SEP 26 2024 Variable aviation conditions were observed at TAF issuance time as areas of low clouds and showers continued impact eastern Kentucky. Conditions range generally between IFR and VFR on average, but localized LIFR was present at a few terminals closer to the Virginia border. A rumble of thunder is possible overnight, but confidence in any affecting a particular TAF site remains too low the mention. An uptick in the rainfall rates should occur in bands ahead of Helene tonight as well as on Friday morning. Winds will average from the east at 5 to 10 KT to begin the period and then become east and northeast at 10 to 20 KT, with gusts up to around 30KT by 12Z. Winds should increase from the northeast between 12Z to 18Z to as high as 15 to 25KT and begin to trend to the southeast for southern locations to end the with gusts up up into the 35 to 50KT range through at least 19Z. LLWS will also be a threat later tonight into Friday morning, as well, with winds as high as 50 KT a thousand feet off the sfc generally blowing from the east or northeast and then trending toward southeast after 18Z. && .JKL WATCHES/WARNINGS/ADVISORIES... Wind Advisory from 5 AM to 8 PM EDT Friday for KYZ044-050>052- 058>060-068-069-079-083-104-106>109-111-112-114-119. Flood Watch through Friday evening for KYZ058-068-069-079-080- 083>088-107>120. High Wind Warning until 8 PM EDT Friday for KYZ080-084>086-110- 113-115>117-120. High Wind Warning until 8 PM EDT Friday for KYZ087-088-118. && $$ UPDATE...GEERTSON SHORT TERM...JP LONG TERM...VORST AVIATION...GEERTSON/JP