Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 191815 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 215 PM EDT Wed Oct 19 2016 .UPDATE... Issued at 215 PM EDT WED OCT 19 2016 Based on current sfc observations, temperatures are running several degrees above expected levels. Consequently had to increase afternoon highs. Only increased a couple degrees as expectations are that the developing CU field should help moderate afternoon temps just a bit. Brought grids in line with latest thinking, tweaking sky grids a bit as well. Updated grids and zones have been issued. UPDATE Issued at 1012 AM EDT WED OCT 19 2016 Forecast, including grids are in good shape this morning. Seeing a few showers associated with a frontal boundary that has stalled out along the Ohio River. High res models suggest this boundary along with shower activity will begin to lift back to the north through the day in response to a wave of low pressure that is developing over southern Missouri. Update included bringing grids in line with latest observations and an update to the zones to freshen up wording. UPDATE Issued at 627 AM EDT WED OCT 19 2016 Frontal boundary remains north of the region this AM and showers remain lined up along and near the front. Given very slow advancement south have continued to trend POPs slower and may need to be trended slower int subsequent updates. Trended POPs to blend but many of the short term models remain a bit fast. Otherwise not too many changes needed this hour other than trending to obs and trends. && .SHORT TERM...(Today through Thursday) Issued at 345 AM EDT WED OCT 19 2016 Morning surface analysis showing a surface cold front and weak low pressure to our NW nearing the Ohio River Valley region. This boundary will remain quasi stationary today and we will see clouds and showers ride along and just ahead of the boundary. That said CAMS generally keep best chances of POPs along and north of the I-64 corridor. This seems reasonable given boundary placement and general forecast progs. That said keep best coverage of clouds across the far NW and therefore the lower overall afternoon highs. Now while the high temps may not exceed the records from 2005 particularly at JKL, we will remain well above normal today areawide. Tonight the frontal boundary will begin to start moving toward the eastern KY, as upper level trough begins to deepen across the plains. This will begin to bring additional clouds toward dawn and slight POPs in the western portions of the CWA toward dawn. These additional clouds will aid in limiting the ridge/valley temp splits. Thursday the upper level trough will continue to deepen across the Mid Mississippi River Valley. This will aid in deepening a surface low pressure and swing a frontal boundary toward the eastern KY for Thursday afternoon. This will bring widespread much needed rainfall to the region, as deep layer moisture progresses across the region with PWATs greater than 1 inch. The next issue will be the marginal chance for a strong to severe storm across the region. This as unidirectional bulk shear increases to around 40 knots and modest destabilization occurs through the afternoon. The destabilization is one of the bigger concerns, as cloud cover ahead of this system could limit destabilization. Therefore marginal severe setup with gusty winds being primary threat seems reasonable at this point. Given some mid level dry air and if we can get low level lapse rates approaching 7 to 8 c/km, as seen in some of the model soundings. .LONG TERM...(Thursday night through Tuesday) Issued at 500 AM EDT WED OCT 19 2016 The models are in somewhat better agreement aloft with the main features passing through the area for the extended. The first, and most prominent, of these will be a fairly strong trough plowing through the Ohio and Tennessee Valleys Thursday night into Friday. The CMC has moved significantly toward the others` consensus with now the ECMWF and NAM lagging the GFS - increasing confidence in the consensus solution. The core of the energy with this system will pass through the area midday Friday before moving to the East Coast to fuel an early season Nor`easter. Heights will be slow to rebound in the wake of this wave as it deepens and spins slowly away into the Mid Atlantic States by Saturday. Some trailing energy will stream over East Kentucky to start the weekend, but for the most part the activity will stay north and east of the JKL CWA well into the new work week. This is primarily due to strong ridging reasserting itself to the south and shoving higher heights into the Tennessee Valley and Kentucky through mid week. Given the better model agreement - a blended solution looks to be a good starting point for the forecast. Sensible weather will feature a potent cold front working through eastern Kentucky Thursday night with a sharp change in air mass and the best shot of meaningful rain in weeks. Expect some ongoing thunderstorms at sunset Thursday to quickly diminish as they work east with the front that night. Plenty of light to moderate rain will follow into Friday - slowest to clear the far east due to the moisture and cyclonic flow associated with the East Coast development. A question that remains in the models concerns the absorption of the low pressure and moisture of a potential tropical system off the southeast coast. Should this get sucked in quicker than implied currently, we would look for a bit more in the way of rainfall across the eastern tip of the CWA along with a slower departure late Friday. As it stands, this front and its associated moisture look to be the best bet for much needed soaking rains. High pressure in its wake will make for dry and cool conditions slowly moderating back to normal temperatures through the start of the new week while the storm track stays well north of Kentucky. Cannot rule out some frost patches for the deeper valleys Friday or Saturday night, but will continue to leave mention out of the grids and monitor its threat with subsequent forecasts. Made mainly terrain based adjustments to the CR init starting point T grids each night through the period. Also, fine tuned the highest PoP pattern from 00z Friday through 00z Saturday to better time the actual fropa. && .AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon) ISSUED AT 215 PM EDT WED OCT 19 2016 VFR conditions are expected through the forecast period. However, conditions will be deteriorating fairly rapidly just beyond the end of the forecast window. A low pressure system and its associated cold front will be moving through the region Thursday afternoon into Friday. This system will bring our first opportunity for a substantial widespread rainfall in quite awhile. Current CU field (bases 040 to 050) will expand for a couple more hours, then dissipate again as sunset approaches. Cloud cover will remain more substantial across our north closer to a stalled out surface boundary, affecting mainly SYM. Winds will be generally light around 5 kts or less, then increase again Thursday ahead of the approaching system, generally around 10 kts from the southwest. && .JKL WATCHES/WARNINGS/ADVISORIES...NONE. && $$ UPDATE...RAY SHORT TERM...DJ LONG TERM...GREIF AVIATION...RAY is the U.S. government's official web portal to all federal, state and local government web resources and services.