Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 142018 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 318 PM EST Tue Nov 14 2017 .UPDATE... Issued at 1235 PM EST TUE NOV 14 2017 Forecast has been in good shape through the morning with only some minor adjustments to make sure the temps and winds were on track with current conditions. Clouds are starting to erode out of the region over the last couple of hours. Noticing that this is a bit slower than the current grids, by about 2 hours. Will go back and adjust grids to increase clouds and have them eroding through the afternoon. UPDATE Issued at 643 AM EST TUE NOV 14 2017 The biggest issue has been trying to forecast the evolution of the stratus deck and subsequently temperatures. This required some adjustments to the temperature curve this morning. Otherwise little change is needed this update. && .SHORT TERM...
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(Today through Wednesday) Issued at 314 AM EST TUE NOV 14 2017 An area of surface high pressure is just to the north of Kentucky in southern Ohio this morning. We continue to see some northeast to east weak flow around this high pressure. The biggest issue continues to be the persistent area of lower stratus. This low level moisture remains stuck underneath a strong inversion and drier air aloft. The good news is we are starting to see some erosion of this deck of clouds. There are portions of the area that have seen some scattering of the deck and consequently seeing temperatures drop off at a more steady pace this morning. The models remain all over the board on how this deck of clouds behaves, and therefore stuck close to current grids, with a trend toward some of the short term guidance blends. The sky grids will likely have to be adjusted more with satellite trends and newer guidance through the day. The temperatures could be a bit slower to rise in the east, but eventually think most sites will warm into the upper 40s to lower 50s. The warmer spots will be those in the southwest where more sun should be seen overall. This area of surface high pressure will move off to northeast through the day today. While the high pressure does move east think the combination of clearing skies and weak flow will lead to a shot of at least some ridge/valley splits in the eastern valleys. We will also see a surface low take shape across the Upper Midwest as a short wave progresses into the Northern Plains. This low pressure and upper level shortwave will continue to progress into the Great Lakes tonight and Wednesday. The attendant cold front and weak height falls will progress eastward toward the Ohio and Tennessee Valleys through the day on Wednesday. This will bring a shot of rain showers by Wednesday afternoon for most of eastern Kentucky. There were some slight timing differences with the models but trended closer to the shorter term models. Ahead of this, temperatures will warm into the mid to upper 50s under south to southwest flow. .LONG TERM...(Thursday through Tuesday) Issued at 318 PM EST TUE NOV 14 2017 Model agreement appears to be improving just a bit with the morning runs, but differences in timing and strength of a storm system through the region next weekend (our main weather feature of interest for the extended) remains significant resulting in a lower than normal confidence in the forecast overall. However, there has been a consistent run-to-run trend in a generally slower timing. There has also been a more subtle trend towards a slightly weaker system, though the GFS continues to come in much stronger than previous runs of the ECMWF. National guidance suggests the weaker trends, and thus the ECMWF solution is favored as a result of upstream teleconnections. Leaning towards the ECMWF solutions would also suggest a bit warmer temperatures behind next weekend`s system. Progressive pattern has a trough lifting out of the mid and upper Ohio Valley at the start of the period. Brief transiting ridge Friday is quickly followed by next weekend`s storm system. Thereafter model consensus becomes even more muddled but in general models hint at some shortwave energy approaching at or just beyond the end of the forecast window. For now will keep that portion of the forecast dry until a better consensus appears. Sensible weather will see lingering shower activity coming to an end early Thursday morning, restricted to mainly far southeast Kentucky. Only slightly cooler air will filter in behind an exiting cold frontal boundary Thursday. The threat of rain increases again Friday night into Saturday with the approach of the next storm system. Forecast soundings and guidance indicate little if any instability associated with this system. Consequently not expecting any thunder. A surface cold front will move through the area very late Saturday, or more likely Saturday night. Colder air will once again settle down into our area. ECMWF H850 temperatures drop to around -6 C by Sunday. The GFS is about 7 degrees colder. Will stick with the blended guidance for temps through the period but will attempt to tweak temps up slightly for the latter half of the weekend and early next week, closer to the warmer ECMWF. For PoPs, window of most likely PoPs will probably occur late Saturday into Saturday night. With significant differences in the timing of the cold frontal boundary through the area blended PoPs are being averaged down to lower values. Made some minor adjustments to the PoPs in an effort to correct this.
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&& .AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon) ISSUED AT 110 PM EST TUE NOV 14 2017 The low MVFR stratus in place across portions of eastern KY is starting to erode away as a shortwave continues to exit east of the region. Once clouds dissipate over the next few hours, VFR conditions will take hold, and should remain in place through the overnight with high pressure in control. Winds will remain light and generally out of the NE to E through the day, before transitioning to the SE through the overnight. && .JKL WATCHES/WARNINGS/ADVISORIES...NONE. && $$ UPDATE...JMW SHORT TERM...DJ LONG TERM...RAY AVIATION...JMW

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