713 FXUS63 KJKL 212010 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 310 PM EST Thu Feb 21 2019 .SHORT TERM...(This evening through Friday night) Issued at 310 PM EST THU FEB 21 2019 The focus in the short term portion of the forecast will the potential for heavy rainfall and flooding across eastern Kentucky from Friday night through early Sunday morning. There is also an outside chance for a few severe thunderstorms to move across the area Saturday night, but we have low confidence in that scenario playing out at this time. A strong area of low pressure is forecast to move across the central Mississippi River valley and Ohio and Tennessee valley regions Friday through Saturday night. Initially, a warm front associated with this weather system will move from south to north across the area Friday through Saturday, bringing with it widespread rain showers. The rain should begin moving to the southern portion of our forecast area this evening, and will gradually overspread the entire area overnight. The warm front will move very slowly at first, and may even stall for a bit, before finally lifting through and out of the area on Saturday. The showers could be intense at times and could lead to flooding across the area Friday night and Saturday. With area rivers, creeks, and streams already running high from recent heavy rains, there will be an enhanced risk for flooding across the area Friday night and Saturday. A few thunderstorms will also be possible on Saturday and Saturday night. These storms could drop enough rain quickly enough to cause localized instances of flash flooding. This will be especially the case Saturday night, as a cold front moves across the region. We may even see an outside shot at some severe weather Saturday night. However, there is a good deal of uncertainty as to whether or not conditions will support severe weather Saturday, mainly limited instability and the timing of the passage of the cold front. Because of this uncertainty, we are going to focus on the flood risk at this time. A flash flood watch has been issued to deal with flooding potential. Temperatures during the period will continue to run well above normal. Low temperatures the next two nights will range from the mid 30s to the 40s. Highs on Friday will be fairly mild, with max readings ranging from the upper 40s to lower 50s across the area. .LONG TERM...(Friday night through Wednesday) Issued at 422 AM EST THU FEB 21 2019 ...Significant Flood Threat Developing Friday Night Through Saturday Night... All eyes continue to be on another round of very heavy rain early this coming weekend. Models are in fairly good agreement right now which aids in a bit better confidence with the expected flood threat this weekend. Southerly flow will increase as we head into Friday night ahead of a strong upper level PV anomaly developing across the southern plains. This southerly flow will help to pump generous amounts of moisture northward across Tennessee and Kentucky. A warm front will shift back to the north with time across the area, but ever so slowly, allowing for heavy rain to develop late Friday night into Saturday morning. PW's during this time are forecast to reach at least 1.25 inches, with the NAM suggesting 1.40 would be a possibility. This would put PW's near record territory for the date based on upper air sounding climatology at both KBNA, and KILN sites. Forcing will be aided by a 250mb jet streak across the mid Atlantic and a jet streak emerging out of the southern plains. We should be in favorable region on both jet streaks for enhanced lift aiding in the potential for heavy rainfall. With the strong dynamics, it does appear some weak elevated instability will also try to work into the area early Saturday, enhancing the heavy rain threat. With the ground already very saturated, it won't take much to cause some significant flooding concerns. The heavy rain threat will gradually edge northward through Saturday morning. However, models generally support some potential for showers through most of the day, although QPF may drop slightly during the afternoon hours. This decline in intensity will be short lived as a cold front will be shunted eastward as the PV anomaly moves northeast into the Great Lakes region. Showers and storms are expected to develop along the front well to our west Saturday evening, then track east into and across east Kentucky during the overnight hours on Saturday night. GFS/NAM soundings have PW's increase to near 1.50 inches as the front nears, supporting the continued threat for heavy rainfall. In addition, impressive speed shear will accompany the cold front, leading to a marginal severe threat. The problem for our area is whether we can generate any surface instability ahead of the front. Given the strong warm advection ahead of the front, its possible some instability could be advected into the region just ahead of the front, providing the needed instability to generate a few strong to severe storms. SPC has placed all of eastern Kentucky into a slight risk for severe storms for Saturday night. The main threat will be damaging winds with any more organized line segments. Will continue to highlight the strong storm threat in the HWO. For the flooding threat, we will go with an ESF (hydrologic outlook) this morning as the main flood threat is still a few days off. A flood watch will likely be needed soon. Significant flooding could occur if current forecast rainfall totals materialize between 2 and 3 inches. It finally looks like we can dry out by Sunday morning, but we will continue to deal with some river flooding through the weekend. A surface ridge will track across the area Sunday night into Monday, providing a continuation of the dry weather. We will start to see some return flow develop by Monday night into Tuesday as the surface ridge retreats to the east. This may allow for some isentropic ascent to build back into the region by the middle of the week, allowing for the return of some rain chances. Right now, the period has very little agreement and in fact, looks very different than just 24 hours ago. Thus, with a low confidence forecast, will just carry some very small rain chances from Tuesday night through Wednesday. && .AVIATION...(For the 18Z TAFS through 18Z Friday afternoon) ISSUED AT 107 PM EST THU FEB 21 2019 We should see VFR conditions at all the TAF sites through late this evening. Cloud cover will be on the increase through the period, and we should see BKN to OVC cloud cover over the entire area by late this afternoon or early this evening. MVFR conditions due to rain and low level clouds should begin occurring at the TAF sites between 5 and 6Z tonight. Winds should be light and out of the north or northeast as an area of low pressure approaches from the southwest. The rain showers should persist through 10 or 11Z Friday before scattering out through the end of the period. && .JKL WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch from Friday evening through Sunday morning for KYZ044-050>052-058>060-068-069-079-080-083>088-104-106>120. && $$ SHORT TERM...AR LONG TERM...KAS AVIATION...AR