Area Forecast Discussion
Issued by NWS Jackson, KY

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848 FXUS63 KJKL 162359 AAA AFDJKL AREA FORECAST DISCUSSION...UPDATED National Weather Service Jackson KY 659 PM EST Thu Nov 16 2017 .UPDATE...
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Issued at 659 PM EST THU NOV 16 2017 The latest satellite trends reveal lower clouds in the north holding in place, with even a bit more push to the south southwest out of West Virginia, as the low level flow remains north northeast. Subsidence, associated with some height rises into the overnight will likely keep the deck from advancing too much further south, similar to what happened earlier in the day. Forecast lows look on track thus far, and will reassess the numbers more closely later this evening. Did adjust the diurnal curve a bit in the north, allowing for a slower drop off given the cloud cover. Updates will be out shortly.
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&& .SHORT TERM...(This evening through Friday night) Issued at 234 PM EST THU NOV 16 2017 The low cloud deck over the northern part of the forecast area made an advance south early today, but the southern edge of the clouds eroded at the same time. The erosion of cloud on the southern edge of the cloud deck seems to be winning out slowly but surely. As surface high pressure and some weak ridging aloft builds into the area tonight, expect mostly clear skies to end up being the rule across the entire forecast area. Clouds have held temperatures in the upper 30s in the far north today, with temperatures rising into the upper 50s in the south. With clearing expect all areas to fall to near or below freezing tonight. Any fog tonight will be limited to a few valley locations mainly near water sources. On Friday temperatures will warm as surface high pressure shifts east and winds take on a southerly component. With plenty of sunshine temperatures will warm to the mid 50s in the north to the lower 60s in the south. Sheltered valleys should decouple Friday night, allowing a minimal ridge valley temperature difference to develop, especially early and mainly in the east. However as cloud cover increases valley temperatures will rise late in the night. A warm front will also lift into the area Friday night in advance of low pressure moving from the central plains to the mid MS valley. With some lift and increasing moisture, showers will become possible across the northwest half of the forecast area by late Friday night. .LONG TERM...(Saturday through Thursday) Issued at 349 PM EST THU NOV 16 2017 Model solutions are in good agreement through much of the extended diverging more significantly by DY6, Tuesday. Main feature of interest in the long term is a large trough that swings across the eastern CONUS and through the Ohio Valley Saturday into Sunday. Main trough axis is through the Commonwealth by Sunday morning. However, models do hint at some lingering shortwave energy rounding the base of the parent trough Sunday which may help keep some shower activity going in the east Sunday morning. Thereafter the pattern aloft may transition into a bit of a split flow regime as energy digs into the deep south. But details are difficult at best to iron out until models come into better agreement. For now will stay with the blended solutions and model guidance for the remainder of the period. This main system of interest is quite strong and forcing is better than usual with the H850 trough almost aligned (nearly stacked) with the surface front as it passes through our area. Consequently there should be some fairly rapid and strong subsidence behind this system as it exits to the east. Included a mention of isolated thunder for Saturday afternoon and early evening. Instability is very marginal. But thunder can not be totally ruled out and it provides for a better collaborated forecast with neighbors. Winds on Saturday will be the main focus with respect to hazardous weather. Gradient south winds will increase through the day and become gusty. Wind flow aloft will increase to between 35 and 65 kts. With any sunshine and good mixing, and/or any strong showers and thunderstorms, there is the potential to mix down some of those higher winds. For now will maintain inherited gust potentials of up to 40 mph and continue the process of increasing awareness of the wind hazard. Nothing much to add beyond early next week except to say that differences in model solutions show up very well in guidance. In general our weather appears more dry than not. But trends in other elements of sensible weather are very difficult to pin down. For example, 12Z GFS MOS guidance is some 15 to 20 degrees cooler on Thanksgiving than the ECMWF. Take your pick, mid 60s with the ECMWF or mid 40s with the GFS. In the end reality typically winds up being closer to somewhere in the middle that far out in the forecast. ATTM that`s where we will leave the forecast. But it does make for an interesting wait and see moment. && .AVIATION...
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(For the 00Z TAFS through 00Z Friday evening) ISSUED AT 659 PM EST THU NOV 16 2017 Low level clouds will continue to plague SYM through at least 06z. These will invade into SJS between 02 and 06z. Thereafter, the clouds should gradually scatter out. Some patchy IFR or worse fog may form late, but this should be confined to the deeper river valleys. Once the fog burns off, VFR conditions will prevail through the rest of the period. North winds at 5 to 8 kts, will gradually veer to the east and eventually southeast through Friday.
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&& .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GEOGERIAN SHORT TERM...SBH LONG TERM...RAY AVIATION...GEOGERIAN

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