Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 242015 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 315 PM EST Fri Feb 24 2017 .UPDATE... Issued at 140 PM EST FRI FEB 24 2017 Ample sun is helping to heat things up nicely this afternoon. Based on hourly trends increased afternoon highs just a tad. Winds have increased as well. From all appearances winds may peak out at or just under Lake Wind Advisory criteria in our Blue Grass counties. This appears less likely in our southwest but will keep an eye on just in case. Models have generally trended a bit slower with the cold front into the area tonight. However, based on the HRRR timing still looks fairly decent for storms into the area. So not expecting too much of a change form the current forecast for the potential of severe weather tonight. Updated zones and grids have already been issued. UPDATE Issued at 1012 AM EST FRI FEB 24 2017 Updated temperatures with the morning update. Temps are slow out of the gate in the east, due to a bit of valley fog and rising faster than expected in the western valleys where gradient winds have already mixed out the morning inversion. Also seeing a brief jump in winds to announce the breaking of that inversion. Expect they will die back down a bit over the next hour or so before increasing again later this afternoon. No updates to the zones at this time. UPDATE Issued at 657 AM EST FRI FEB 24 2017 Mostly clear skies with a few high clouds is the story this morning for most. Surface analysis shows surface low is strengthening across NE MO this morning as it continues NE. Overall forecast grids remain in good shape this morning. In terms of the severe weather, The HRRR is aligning close to the other CAMs at this point in terms of overall trends. Overall looking at the newest data think the current forecast is on track and will be looked at in subsequent updates. && .SHORT TERM...
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(Today through Saturday) Issued at 340 AM EST FRI FEB 24 2017 Early morning surface analysis shows an area of surface low pressure continues to track NE out of the Central Plains into Missouri and a warm front is now well north across the Upper Ohio Valley region. WV imagery this morning showing plenty of upper level moisture streaming into the region and this is leading to scattered high clouds across eastern KY. Given these have only been high clouds and the valleys have decoupled leading to decent temp splits from some of the cooler valley locales. A mix of high clouds and possible some diurnally driven CU will remain the story through the day. LLJ will continue to move east in response to strengthening system to our west. This will begin to mix down as we move into the afternoon hours with gust of 25 to 30 possible across the Bluegrass and Lake Cumberland region. The other issue will be downsloping flow across the far east could also mix down drier air, with RH values in the mid 30s to lower 40s possible. This will have to be monitored today given the gusty winds, but it will help that the gustier winds will be west of the drier downsloped air. All the focus shifts to strengthening system to the west as we move into the late evening and overnight period. Models remain in good agreement with trailing cold front approaching from the west through the day. Initially convection will fire out ahead of the front and track across portions of the Midwest. Some of these will be single cell type storms, but as the system progresses east storm mode will become more multicell/QLCS. Given the strength of the cold front, lapse rates will remain steep through the evening and into the overnight. Also models, specifically CAMS, are in good agreement with the trailing cold front catching up to the initial convection possibly providing further lift as it moves into the region. One issue will be how much instability remains in place at that point given the time of day and year. However, if we are able to maintain this, the speed shear environment will be substantial through a deep layer and low level shear is rather impressive with some directional shear possible. This seem to be picked up well by the SHERBE (that deals with high shear low CAPE environments) with values near 1 or higher. Overall storm mode will remain more QLCS in nature and therefore the tornado threat will be very isolated. Think the better threat for tornado will exist further north across the Ohio Valley where more boundary interactions will take place. The main threat across eastern KY will be damaging winds given the storm mode and strong jet, and an outside threat of marginal hail given the airmass cooling aloft causing freezing levels to drop to near 10 KFT. In terms of grids, did opt to slow the progression of POPs to better align with the CAMs and also added enhanced wording for damaging winds given the greater threat. Behind this front will be progressively cooler temperatures from west to east early Saturday into Saturday afternoon. That said, higher terrain locations could hit the freezing mark by the end of the period. Given some wrap around moisture is possible did keep some sprinkles and perhaps flurries across the higher terrain into the afternoon. Given the high temperature will occur at midnight the temp curve will be quite unorthodox, and therefore leaned away from blended diurnally driven curve. .LONG TERM...(Sunday through Friday) Issued at 315 PM EST FRI FEB 24 2017 The extended portion of the forecast will be fairly active, with alternating periods of wet and dry weather and warm and cooler conditions. The period will likely start off dry, with slightly above normal temperatures Sunday and Sunday night. The pattern is then expected to shift on Monday, as a weak warm front moves through the area, bringing persistent southerly flow and warmer air into the region. Rain showers should begin to move into the area from the southwest and west late Sunday night into early Monday morning. The rain will overspread the entire area by late Monday afternoon and early Monday evening, as an area of low pressure moves along what will become a nearly stalled out frontal boundary. This pattern is tentatively expected to persist through late in the day on Tuesday. A wave of low pressure is then forecast to form along the western end of the stalled front Tuesday night. This second area of low pressure is then expected to push eastward on Wednesday, and will drag another cold front across the lower Ohio valley and Tennessee valley regions. This boundary may be just strong enough, and just enough moisture an instability available, for a few thunderstorms to form along and just ahead of the front, as it moves across the region. Once the front moves past us Wednesday night, any thunderstorms should give way to all rain showers. We may even see enough cold air filter in behind the system to allow some snow to mix in with whatever rain is left. The last of this precipitation should be out of the area by late Thursday morning. Thursday and Thursday night should be mostly dry. There is an outside chance that a few rain and snow showers will move across the area along and north of I64 to end the period, with due to uncertainty, this should be taken with a grain of salt. Temperatures in the extended on average will be above average each day, with the warmest days being Monday, Tuesday, and Wednesday, when the highs will be in the 50s and 60s. Closer to normal values should be experienced on Thursday, when the mercury is forecast to max out lower 50s. Nightly lows should be in 30s, 40s, and 50s.
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&& .AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon) ISSUED AT 140 PM EST FRI FEB 24 2017 Generally high clouds out there this afternoon with a little Cu mixed in for good measure. Southerly winds have kicked up nicely at around 10 kts with gusts to about 20 kts. Gusts are a bit higher to our west and up in the Blue Grass, reaching to about 30 mph. Focus shifts to tonight with a strong cold front approaching the area as it moves eastward across the region. This system is expected to produce some strong to severe thunderstorms across the area with a primary risk of damaging winds. The risk for severe weather becomes greatest as you move NW toward northern KY and portions of the Ohio Valley. A line of convection associated with the front appears to move into the SME area by around 04Z and exit to the east of SJS by around 08Z. Timing is still a bit uncertain but will likely have a more approximate timing of storms into our terminals by next issuance. CIGS and VSBYS will drop into MVFR range with and for a several hours behind the front. Winds will be quite gusty again Saturday, from the west at around 10 kts gusting to about 20 kts. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...RAY SHORT TERM...DJ LONG TERM...AR AVIATION...RAY

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