Area Forecast Discussion
Issued by NWS Jackson, KY

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858 FXUS63 KJKL 161902 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 302 PM EDT Fri Mar 16 2018 .SHORT TERM...(This evening through Saturday night) Issued at 302 PM EDT FRI MAR 16 2018 Low pressure at the surface and aloft was over north central Kansas early this afternoon. At the surface a frontal boundary extended east from the low across central Tennessee. The focus of this forecast will be on this system as the upper low opens up and moves east across the OH valley on Saturday and the surface low moves east southeast across Kentucky. In response to the approaching low the front over TN will lift north as a warm front tonight before stalling again Saturday. Showers will develop across our area late tonight. Instability will be limited tonight but a strong low level jet may support some elevated convection late tonight as the warm front lifts north. As such we will include a slight chance of thunder over the southwest part of the area after 09Z. As the front lifts north Saturday there will be a break in the rain chances in the southern part of the area. Breaks in the clouds will develop across the the south on Saturday, and surface heating will lead to increased instability across the south Saturday afternoon. A significant temperature gradient is forecast across the area as warm advection and a little sunshine result in temperatures climbing into the upper 60s and lower 70s in the far south while temperatures remain in the lower to middle 40s over the far northern part of the area Saturday afternoon. With the approach of the upper level short wave trough and the surface cold front Saturday afternoon, thunderstorms may develop, especially where instability is greatest in the south and southeast. With decent shear a couple of storms could be strong or even severe. SPC has placed our area in a marginal risk for severe storms Saturday, with hail and strong gusty winds both possible. As the surface low exits off to our southeast Saturday night rain chances will diminish from northwest to southeast. .LONG TERM...(Saturday night through Thursday) Issued at 515 AM EDT FRI MAR 16 2018 A bit of an active upper level pattern expected through the extended, as multiple shortwaves move across the region. The first of these will occur through the night Saturday, with ridging returns for the day Sunday. This ridging will quickly become dampened as a closed upper level low quickly gains strength and pushes into the southern Plains by Monday morning. From here it will change paths, quickly shifting eastward and across the state of Kentucky Monday night. While it is expected to exit NE of the state Tuesday afternoon, it will merge with another closed low system and result in overarching troughing in place across the region through Thursday night. Rising heights will be the story for Friday as both models agree on an area of ridging moving eastward into the state. As for sensible weather...With each passing upper level disturbance, expect impacts in our weather. Therefore, will say the extended portion of the forecast does look generally wet with varying temperatures and weather types. Saturday night will feature an exiting low pressure system and a shift to northerly winds. Ongoing rain chances at 0Z Sunday will start to exit to the east and dry out from the west during the overnight, with all rain chances exiting the CWA by 12Z. Light N to NE flow and high pressure will remain in control for the day Sunday, with abundant sunshine allowing temps to rise back into the 50s across the CWA. The high pressure system will then dissipate as it quickly shifts eastward Sunday night ahead of an approaching low pressure system over the southern Plains, correlating to the above mentioned closed upper level low in the same location. As the upper level closed low shifts eastward into the day Monday and traverses Kentucky into Monday night, so the surface system will follow. According to the latest GFS, the surface low is expected to track along the southern half of Kentucky starting between 0 and 6Z Tuesday and continuing into eastern Kentucky by 18Z Tuesday before getting hung up in the mountains by 0Z Wednesday. It should finally start shifting away from the state by Wednesday afternoon. Precip associated with this system will begin to affect the southern CWA late Sunday night, expanding across the entire CWA by Monday and Monday night. Likely precip chances will then remain in the forecast for much of the CWA through the day Tuesday and into the day Wednesday before the system shifts eastward Wednesday afternoon. Pops will be slow to taper off in the far eastern portion of the state with upslope flow aiding in moisture release. Chance pops won`t fully taper off here until Thursday afternoon. As for precip types during this period... There was some discussion of possible thunder Monday afternoon with the approaching low and increasing precip chances. However, looking at soundings, would agree with previous day shift`s decision to remove thunder from the CWA. Lapse rates and shear are good in the low levels in the southern half of the CWA where surface southerly flow is in place, but a mid level inversion and lack of instability (CAPE and LIs) are both factors that lowers confidence in its occurrence. In addition, soundings don`t look very saturated, and forecasted afternoon QPF is under 0.1 inches, so there may not be enough rainfall/precip to instigate lightning. After Monday, forecast looks more certain for only rain. However, as the bulk of precip starts to move eastward Tuesday night into Wednesday, colder NW flow could result in overnight temperatures in the low to mid 30s in some locations (mainly north). This may enable some snow to mix in with rainfall, though the ground should remain too warm during the short period of time it could mix in to produce any accumulations. As such, took out snowfall accumulations that the forecast builder had added in. Temperatures will be even colder Wednesday night into Thursday morning under continued NW flow (upper 20s to around 30), so there will be a better chance of any lingering moisture changing over to snow this night/early morning. However, QPF will be quite light by this point, so not expecting significant accumulations or impacts this far out in the forecast. && .AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon) ISSUED AT 144 PM EDT FRI MAR 16 2018 VFR conditions will prevail into the overnight period, but conditions will deteriorate late tonight and into Saturday morning as a warm front lifts north out of Tennessee and into Kentucky. The front will lift north in response to a low pressure system that will be moving east from the central plains. Clouds will thicken and lower overnight, with MVFR ceilings becoming widespread across the area by Saturday morning. Some IFR ceilings can also be expected, especially across the northern half of the forecast area. Showers will also occur late tonight and into Saturday morning. At this time the threat for thunderstorms late tonight into Saturday morning looks minimal. As a low level jet moves into the area early Saturday morning LLWS is expected to develop for a few hours. Ceilings should lift in the southern and central part of the area Saturday afternoon, but with heating from some sunshine a few thunderstorms will be possible Saturday afternoon. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...SBH LONG TERM...JMW AVIATION...SBH is the U.S. government's official web portal to all federal, state and local government web resources and services.