Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 291440 AAA AFDJKL AREA FORECAST DISCUSSION...UPDATED National Weather Service Jackson KY 1040 AM EDT Sat Apr 29 2017 .UPDATE... Issued at 1040 AM EDT SAT APR 29 2017 14z sfc analysis shows a warm front located over the northwest portion of Kentucky just north of the JKL CWA. This is the main focus of storm development and training resulting in a high potential for flash flooding along and north of the Ohio River. Although an outflow boundary has pushed south into eastern Kentucky, this has not been able to activate any additional convection this deep into the mid level and sfc ridge. However, it will need to be watched for potential development later in the afternoon. Otherwise, plenty of clouds blown off from the convection to the northwest will continue to affect at least the northern parts of the CWA with more sunshine south. Will reflect this in the grids along with slightly cooler temps north than south, though all locations will make it to the upper 80s with some 90s expected in the south. These are record highs and when combined with dewpoints in the low to mid 60s will make for heat indices in the lower 90s - an early taste of the heat and humidity of summer. Currently winds are out of the south at 5 to 10 mph most places, but expect deep mixing to promote some gustiness from the southwest by midday. Have update the forecast mainly to fine tune the sky cover and PoP grids along with some nudging for current obs and trends in the T/Td grids. These have been sent to the NDFD and web servers. A ZFP update will follow before noon to clean up morning wording. UPDATE Issued at 714 AM EDT SAT APR 29 2017 Updated the forecast package for lingering showers in our east which were generated by an outflow boundary that is beginning to stall out across the heart of the area. Interestingly there are a few feint echoes further south which suggests the cap in place across the area may not be as strong as forecast soundings suggested. Should the cap not be strong enough to keep convection in check later today, the convective outflow boundary could play a role in the refiring of afternoon showers and thunderstorms. The HRRR did pick up on this activity to our south but suggest convection will still be at a minimum this afternoon. && .SHORT TERM...(Today through Sunday) Issued at 505 AM EDT SAT APR 29 2017 A stationary front stretches west to east roughly along the Ohio River this morning. Convection has been firing along this boundary all night and has taken a small southward drift with time. At present showers and thunderstorms are affecting locations mainly along and north of I-64. Based on Kentucky mesonet observations these storms have been producing outflows generally at or below 30 mph across our area. The Kentucky Mesonet has also shown some decent rainfall rates, upwards of about an inch per hour in the strongest thunderstorms. But storms have had some good motion and are not laying down a tremendous amount of rainfall. However there has been a considerable amount of training which has allowed totals to add up rather quickly in spots. Most recent regional IR loop has begun to show warming tops. In addition current radar is showing a decreasing trend in higher echos within these storms and a drop in rainfall rates as well. Based on JKL VAD wind profile expect the weakening trend to continue through sunrise this morning as our overnight LLJ of 30-50 kts has weakened considerably over the last few hours. Just the same felt it would be prudent to mention the possibility of locally heavy rainfall with thunderstorms this morning in the HWO along with a potential of some minor nuisance type flooding where storms tend to pass repeatedly over the same location. Showers and thunderstorms will gradually come to an end today. Am curious about the convective outflow boundary being produced across the heart of the CWA. Cap appears just strong enough to keep convection in check today. But if forecast soundings are off and some convection should fire, this residual outflow boundary would add another element to the picture. This will have to be monitored closely. The remainder of the short term is pretty much a temperature forecast. Highs today still look on track to threaten records. With moisture in the area, dew points in the lower to mid 60s and highs climbing to near 90 this afternoon, it is sure to feel a bit more like a summer out there. .LONG TERM...(Sunday night through Friday) Issued at 326 AM EDT SAT APR 29 2017 An area of low pressure will become cut off over the western great lakes at the start of the period with an occluded front pushing east across the Ohio river valley. Subsidence just ahead of this front should keep the weather dry through Sunday evening across eastern Kentucky. The front will then push across the area late Sunday night through Monday morning, bringing a round of showers and perhaps a few storms to the area. The more significant impact will be the winds associated with the frontal passage. Winds will likely pick up late Sunday night out of the south ahead of the boundary and could gust up to 30 mph at times. If we can generate some instability Monday morning, we could see some convective wind gusts much higher. 00z NAM shows some limited instability, while the 00z GFS has virtually none. Thus, right now, cannot rule out some convective gusts as the activity pushes through Monday. In the wake of the front, winds will remain gusty and likely even stronger with gusts up to 40 mph likely. Its possible we may need a wind advisory for Monday, but much too early to issue one. Winds will remain up Monday night, but should drop back a bit in strength. Cooler air will filter in behind the front Monday afternoon through Monday night. This will bring an end to our milder weather. Zonal flow takes hold into the middle of the week, with dry weather expected across the area. Temperatures will slowly rebound into the middle of the week. Our next storm system will take aim on the area by late Wednesday, with a warm front lifting north across the area on Wednesday, followed by an area of low pressure tracking across the Ohio river valley. This will bring increasing rain chances to the area from Wednesday into Thursday. Thursday and Friday are looking to be very damp days with persistent rains along with cool conditions. We may see lows in the 40s by weeks end with highs only in the 50s. Looks like the first week of May may come in on the cool and damp side. && .AVIATION...(For the 12Z TAFS through 12Z Sunday morning) ISSUED AT 714 AM EDT SAT APR 29 2017 VFR flight conditions expected through the forecast period. There is considerable amount of debris cloud cover across the area from lingering convection. However, showers and thunderstorms are coming to an end across the area this morning. May see some isolated convection refire later today, especially north closer to a frontal boundary and over the higher terrain along the Kentucky and Virginia state line. Otherwise winds will increase from the south-southwest through the day to around 10kts with some higher gusts. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GREIF SHORT TERM...RAY LONG TERM...KAS AVIATION...RAY

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