Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 200341 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 1041 PM EST Mon Feb 19 2018 .UPDATE...
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Issued at 1041 PM EST MON FEB 19 2018 The latest satellite data and obs suggest we continue to see mostly mid to high level clouds streaming across eastern Kentucky from time to time this evening. Despite the clouds, some of the deeper valley locations have found a way to decouple based on the Kentucky Mesonet observations, but this was handle reasonably in the grids already. Only minor adjustments were made to blend in the latest obs and trends. UPDATE Issued at 727 PM EST MON FEB 19 2018 The evening surface analysis shows the warm front is now across the northern Ohio Valley and Lower Great Lakes regions. An area of low pressure to our northwest and high pressure to our east is providing south to southwest flow in the gradient across eastern Kentucky. This southerly flow will keep at least mid to high level clouds streaming across the region tonight based on the latest satellite trends. Did slow the temperature drop off in the valleys given some remaining mixing, but otherwise think the grids are in reasonable shape this evening.
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&& .SHORT TERM...(This evening through Tuesday night) Issued at 405 PM EST MON FEB 19 2018 As of mid to late afternoon, a mid and upper level ridge was centered south of Bermuda with another ridge over parts of the eastern Pacific. A trough was located over the western Conus and Rockies with southwest flow aloft. Meanwhile, a baroclinic zone extended from Quebec into the Great Lakes to mid MS Valley to the southern Plains. Despite some passing mid and high clouds and cumulus having developed, with south to southwest flow warmer air has advected into the region behind a warm front. Temperatures have reached the low to mid 70s in all but the VA border counties where clouds have been more extensive. Record highs have been at least tied so far at both JKL and LOZ. The ridge located south of Bermuda should build west into the southeast and eastern seaboard tonight and into Tuesday as a trough continues to work across the west with a series of shortwaves moving from the Rockies and Plains to the Great Lakes and into Ontario. At the surface, the region will remain in the warm sector during the period, with a sfc wave of low pressure and an initial shortwave moving into the Great Lakes tonight and weakening. Another wave of low pressure should develop in the Lee of the Rockies in advance of the next shortwave tonight and track into the Western Great Lakes on Tuesday. A more potent shortwave will move across the Rockies and into the Plains from Tuesday into Tuesday night, combined with the mid and upper level ridge building north off of the eastern seaboard, should begin to push the baroclinic zone/cold front into the Lower OH Valley by the end of the period. However, with weak forcing at best during the period, a considerable amount of clouds are expected through the period though it should remain rain free. However, there have been breaks in the low clouds today and there may be some breaks at times through the period. Cumulus clouds should dissipate tonight with breaks in clouds expected. Deeper sheltered valleys should decouple this evening with eastern valleys dropping off well into the 50s with ridgetop and more open terrain only dropping to around 60. Continued southerly flow and 850 mb temperatures climbing a coupe of degrees C should bring record highs for the 20th to both JKL and LOZ. Depending on the amount of sunshine, the all time February record high of 79 at JKL from 1996 will likely be broken as the forecast high is currently 80. LOZ will likely set a record daily high for the 20th, but fall short of the all time February record high. Deeper and more sheltered eastern valleys should again fall well into the mid 50s on Tuesday night. .LONG TERM...(Wednesday through Monday) Issued at 254 PM EST MON FEB 19 2018 Model solutions for the extended are in good agreement through Thursday. There is general agreement in the overall mid/upper level pattern thereafter but a few more significant differences show up that will influence any details of sensible weather. The extended will remain under the influence of southwest flow until the end of the period when stronger systems riding out of the southwest CONUS begin to wear down high pressure just off the Atlantic Coast, causing steering winds aloft to veer more westerly. At the surface we find a semi-stationary baroclinic zone has set up across the Ohio Valley. An associated surface frontal boundary will drop down across our area late Wednesday or Wednesday night. This boundary then stalls in the vicinity of our area as dynamics driving the surface system lift northeast into eastern Canada. This boundary quickly shifts back to the north during the day Friday as a wave of surface low pressure passes through the lower Ohio Valley and into the Great Lakes. Several minor waves of low pressure continue to traverse the region along this baroclinic zone until a final more significant wave sweeps everything out to our east by late Sunday or early Monday. Sensible weather features generally unsettled and warmer than normal weather through the extended. There will be some threat of rain just about anytime through the extended. Temperatures will run some 10 to 20 degrees above normal through the period. The main exception will be Thursday when the surface frontal boundary stalls and produces a large temperatures gradient across the area with low to mid 50s in the north and near 70 across the south. Otherwise high temperatures will run in the mid 60s to mid 70s on average. Overnight lows will run generally in the 50s. Temperatures do drop back down much closer to normal by the end of the period. There does appear to be enough surface based instability in place across the area to maintain the mention of thunderstorms on Wednesday with the arrival of the surface front. There is also a short period of elevated instability across the area early Friday north of the surface boundary as it lifts northward. Is it possible meteorological spring arrived a bit early this year? && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) ISSUED AT 630 PM EST MON FEB 19 2018 We will start the TAF period VFR and that will remain the story for the remainder of the TAF period. However, under warm southerly flow we will keep at least some high clouds streaming across the Ohio Valley for the TAF period. The models are in good agreement on a increasing LLJ across the Tennessee and Ohio Valley and with an inversion setting up this evening have added LLWS to the TAF later this evening into early Tuesday. The previously mentioned LLJ will lead to gusty winds Tuesday afternoon as we see more mixing. Overall we will be looking at 15 to 20 knot gusts, but higher gusts are not out of the question. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...DJ SHORT TERM...JP LONG TERM...RAY AVIATION...DJ

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