Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 231453 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 1053 AM EDT Fri Jun 23 2017 .UPDATE...
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Issued at 1052 AM EDT FRI JUN 23 2017 Forgot a zero in my 1050 AM discussion. Storm relative helicity should be 400 not 40. UPDATE Issued at 1050 AM EDT FRI JUN 23 2017 We continue to monitor the evolving weather situation regarding the interaction of the remains of Tropical Storm Cindy and the approaching cold front. The 12Z NAM has shifted the heaviest swath of rain northwest with the 2 inch and above amounts confined to the extreme northern part of the forecast area, mainly over Fleming County. However even at this short time frame would not focus on the details but on the overall trend. Regardless showers and thunderstorms this afternoon and evening will be efficient rainfall producers with precipitable water in the 2 to 2.5 inch range. Flash flood threat remains in place, with the biggest threat over the northwest one-third of the forecast area. The severe weather threat continues to be of concern. Parameters point towards the possibility of a few tornadoes this afternoon into the evening. The latest short range guidance soundings indicate surface to 1km storm relative helicity approaching or even exceeding 400 m2/s2 late this afternoon and evening as the remains of Cindy approach. Some rotating storms will definitely be possible and with lifting condensation levels low, any rotating storms may be capable of producing a brief tornado. How much instability will be realized is still in question, but satellite indicates there should be enough breaks and enough insolation to at least increase the low level lapse rates, though mid level lapse rates do not look too impressive. Main severe thunderstorm threats continue to be isolated wind damage and a few brief tornadoes. Overall forecast is on track but will continue to update NDFD for latest observational trends. UPDATE Issued at 759 AM EDT FRI JUN 23 2017 Ongoing forecast was in decent shape, and the only change was to blend early morning obs into the forecast.
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&& .SHORT TERM...(Today through Saturday) Issued at 531 AM EDT FRI JUN 23 2017 The remains of Tropical Storm Cindy were very obvious in radar and satellite imagery over AR early this morning. Meanwhile, a cold front over northern MO and northern IL was moving southeast. Models are in general agreement on the evolution of these features during the period. Interaction with the prevailing westerlies will continue to carry the tropical remnants east northeast ahead of the cold front, with a track expected to be through KY. Low to mid level wind fields will strengthen as the low approaches, and continue to transport very moist air into the area, with precipitable water expected to reach 2-2.5". A significant lull in the precip is expected through much of the day, allowing warming and destabilization. This would aid convective development as the system arrives in the afternoon and evening. Both heavy rain and severe weather are threats. In term of rainfall, the deep tropical atmosphere will support very efficient precip production. Models agree on the heaviest amounts to be in our northwest counties. This is also where the heaviest rain has already fallen. A flash flood watch was already issued area wide, but the greatest threat looks like it will be in our northwest counties. That being the case, confidence is not all that high that we will see problems in our southeast counties. However, with the watch already out, the onus is to prove that hydro problems won`t occur there. Certainly don`t want to have flips in the watch situation, so will leave it run in the southeast. In terms of severe weather, low level shear looks significant, both in terms of speed and direction. The more questionable factor seems to be the degree of surface based instability which will be present. At most, it should be rather weak for this time of year. However, with the degree of shear, any surface based instability would be a concern. Dragging down environmental winds and adding on a bit due to convection could be enough for damage. Also, the low condensation heights along with the high storm relative helicity in the soundings are supportive of brief tornadoes. Due to the warm atmosphere and lack of strong instability, hail is not a concern. The tropical remnants pull out to the east this evening, wind fields weaken, and the severe threat drops off. It will be a little while longer until the cold front passes, and some additional showers or thunderstorms could fire until it passes late tonight and early Saturday. However, mid level drying is expected when the tropical system departs, which will also allow the heavy rain threat to diminish during the night. Much drier air will arrive at the ground behind the front on Saturday. .LONG TERM...(Saturday night through Thursday) Issued at 358 AM EDT FRI JUN 23 2017 A period of drying is on the horizon and near record cool temperatures possible early next week. That said, in the wake of a cold front we will see falling heights and a building Canadian surface high pressure. The models are in fair agreement on this Canadian surface high pressure and matter of fact really strong agreement in the GFS ensemble members. Also several reinforcing waves will bring single digit 850MB temperatures into the region for the first part of next week. These temperatures will be significantly anomalous, with 500mb to 850mb temperatures expected to be 3 plus standard deviations below normal for this time of year. At the surface, the coolest day may be Wednesday morning depending on how cloud cover shakes out on Tuesday morning, but temperatures in the low to mid 50s and some valleys could drop into the upper 40s. These kinds of temperatures will be close to record temperatures for both days with JKL current record for Tuesday is 54 degrees and 53 degrees on Wednesday. However, our records at JKL may be a little weaker compared to LOZ, where LOZ records showing 48 degrees Tuesday and 50 degrees on Wednesday which may be more difficult outside of valley locations. Temperatures by Wednesday do warm, as the high pressure moves off toward the VA/NC coast line and we see increased return flow. By Thursday, the models show a little less agreement, but a wave could generate some showers by the afternoon. Past this the CPC would suggest more chances of precip becomes possible as we begin July. && .AVIATION...(For the 12Z TAFS through 12Z Saturday morning) ISSUED AT 759 AM EDT FRI JUN 23 2017 A break in the action was ongoing at the start of the period, with a mix of VFR and MVFR due to ceilings. The best conditions were generally near the WV border. An improvement to largely VFR is expected for a time today as warming occurs and condensation heights rise. The prospect of showers and thunderstorms will be rising during the day, with the most likely time for rain being late in the day and in the evening. An eventual drop to IFR and low end MVFR conditions is expected this evening, as a cold front approaches and moves through. Some of the storms and heavier showers this afternoon and early evening may bring high winds. Precip will be on the decline tonight, but low ceilings will probably still linger much of the time. && .JKL WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch through Saturday morning for KYZ044-050>052- 058>060-068-069-079-080-083>088-104-106>120. && $$ UPDATE...SBH SHORT TERM...HAL LONG TERM...DJ AVIATION...HAL

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