Area Forecast Discussion
Issued by NWS Jackson, KY

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118 FXUS63 KJKL 211527 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 1027 AM EST Wed Feb 21 2018 .UPDATE... Issued at 1027 AM EST WED FEB 21 2018 Line of showers along the cold front has progressed into our northwest counties a little bit faster than expected, and have updated the forecast with extrapolated movement to reflect this. The line is weakening, so the faster onset of precip may be a temporary trend, and the updated forecast was blended into the existing forecast early this afternoon. Otherwise, changes were minimal. UPDATE Issued at 640 AM EST WED FEB 21 2018 Touched up the grids mainly to reflect the latest T/Td obs and trends. These have been sent to the NDFD and web servers. && .SHORT TERM...(Today through Thursday) Issued at 350 AM EST WED FEB 21 2018 08z sfc analysis shows a well defined front off to the northwest of the area and just now entering western parts of the state. Ahead of this, incredibly warm air is in place over eastern Kentucky this night with readings far more typical of summer. southwest winds of 5 to 10 mph with occasional higher gusts have been supporting these elevated temperatures for much of the area. Even so, there have been enough thin spots and clear patches in the clouds overnight so that an inversion set up and many of the far eastern valleys were able to radiate down into the 50s. Currently readings vary from the upper 60s to near 70 on the ridges and more open areas to the mid 50s in those most sheltered valleys. Dewpoints are more uniform in the mid to upper 50s. Again, fog appears to be non-existent across the area given the warm temperatures. The models are in excellent agreement aloft through the short term portion of the forecast. They all hold an anomalous ridge just off the Southeast Coast with its influence felt deep into the Appalachians. Lower heights and troughing will pass by well to the north tonight into Thursday as deep layer southwest flow persists. This trough will encourage a few stronger mid level impulses to pass through northern Kentucky late tonight and into Thursday morning before the flow aloft settles with time that afternoon. Given the good model agreement will favor a general blend with a strong lean on the higher resolution HRRR and NAM12 for details. Sensible weather will feature very warm conditions continuing through the southeast parts of the area as the front slowly settles into the northwest portion of the JKL CWA. Indications are that this boundary will weaken as it stalls with sfc convergence flagging before it gets too deep into our area this afternoon - likely keeping the heaviest rains off to the north and west through evening. Very mild conditions continue tonight for most locations. Another surge of moisture and lift will then spread northeast along this boundary in association with the compact mid level shortwaves and better 300mb divergence passing by overnight. This surge will bring another round of showers and potential thunderstorms to the area into Thursday morning with the northwest favored for the heavier rains. After a brief lull in its immediate wake the boundary will then remain active into the afternoon Thursday with another sfc wave developing and running east northeast into eastern Kentucky. This latter wave will bring with it PW air in excess of 1.5 inches - or 200 to 300 percent above normal. Will target this wave for heavy precipitation potential and also address this particular anomaly in a forthcoming ESF product in lieu of any flood watch at this time. Do believe that flood watches will eventually be needed for the weekend rounds of rain as this current batch will likely leave the area near saturation - especially outside of far southeast Kentucky. Will maintain the small chance for thunder today and continue that tonight and through Thursday for at least the southeast parts of the CWA where sfc based instability will be maximized. Used the CONSShort and ShortBlend to kick start the grids with only minor temperature adjustments through the short term - outside of this morning`s eastern ridge/valley differences. As for PoPs: have upped them for today as it seems the blend was weakening the front too quickly - though somewhat lighter QPF is now expected for our area today. .LONG TERM...(Thursday night through Tuesday) Issued at 245 AM EST WED FEB 21 2018 The first half of the extended period will feature continued well above normal temperatures and multiple rounds of rainfall. The rainfall could be moderate to heavy at times, especially Saturday and Saturday night. A series of weak areas of low pressure moving along a stalled frontal boundary will be the impetus for the rain. The rain will taper off and finally come to an end on Sunday, as a large area of low pressure aloft finally dislodges the surface front. After that, we can expect a few days of mostly dry weather, as a ridge of high pressure builds across the region. Another bout of rain may occur at the very end of the period, but this is very uncertain at this time. Temperatures during the first 4 days of the extended will be the warmest of the period, with highs on Friday topping out in the 70s, the 60s and 70s on Saturday, the 60s on Sunday. A cool down will be on tap for the end of the period, with daily highs maxing out from the mid 50s to lower 60s on Monday and Tuesday. Nightly lows will generally be in the 50s Thursday night, Friday night, and Saturday night. After that we will see lows in the upper 30s and lower 40s. && .AVIATION...(For the 12Z TAFS through 12Z Thursday morning) ISSUED AT 700 AM EST WED FEB 21 2018 The TAFs will remain VFR through the morning, before lower CIGs advect southeast into the afternoon. Right now will keep this MVFR for most sites during the daytime, but following sunset, expect lower cigs to develop for all the sites from northwest to southeast continuing through the night along with reduced visibility. A stalling front dropping into the area will bring showers into the forecast area starting late this morning and continuing into the afternoon. This could also lead to brief lowering of CIGs and VIS in heavier showers or a stray thunderstorm - kept VCTS out of the TAFs for now owing to limited instability. The winds will also gust 15 to 20 knots from the southwest ahead of the boundary before diminishing and becoming northwesterly through the afternoon from northwest to southeast across the area. Early this morning LLWS will still affect the area with winds off the sfc at 40 to 45 kts from the south southwest until 14z, or so. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...HAL SHORT TERM...GREIF LONG TERM...AR AVIATION...GREIF

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