Area Forecast Discussion (AFD)
Issued by Huntsville, AL (HUN)
000 FXUS64 KHUN 150245 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 945 PM CDT Sun Oct 14 2018 .NEAR TERM...(Rest of tonight) Issued at 945 PM CDT Sun Oct 14 2018 Weak frontal boundary remains stalled N/W of the cntrl TN Valley from mid KY swwd into west TN/NW MS. Lingering shower activity has been ongoing along/just ahead of this boundary over portions of wrn/mid TN leading into north MS, but thus far most/if not all of the precip has remained out of the local area. As this boundary though begins to drift further to the south later tonight, some of this light rainfall/showers will prob work their way into the area in a corridor from srn mid TN swwd into north cntrl/NW AL. Given the abundant cloud cover in place across most of the area, current temp trends are very mild ranging from the upper 60s/lower 70s for most spots. A light influx of slightly cooler air out of the NW with the drifting front should allow these temps to lower a few more degrees into mainly the lower/mid 60s by early Mon morning. Ongoing forecast represents this overall pattern well, and no major changes are needed to the forecast package at this point. .SHORT TERM...(Monday through Tuesday) Issued at 317 PM CDT Sun Oct 14 2018 With a weak front just to the north and west of the region again on Monday, opportunities for isolated to scattered showers will be possible. The region will be caught in a transition area between a building subtropical ridge over Florida and an amplifying upper- trough over the Great Lakes. Some weak shortwaves and the aforementioned boundary to the north will serve as a focus for this activity from Monday through Tuesday, before the boundary drops through the area Tuesday night. For Monday, expect almost a mirror image of today, with high-end chance PoPs over northwest Alabama and more isolated activity further to the south and east. With a few more breaks in the clouds and southerly winds, highs in the upper 70s to lower 80s seem plausible. Big changes coming by Tuesday as an upper- wave over the Great Lakes should finally force the front south. This will result in more widespread showers, especially by the afternoon and evening as a weak shortwave rotates across the region. Think the window for highest PoPs may be 18z Tuesday through 06z Wednesday, before gradually tapering off by early Wednesday morning as the front moves south. Cooler air will filter in behind the boundary as winds shift to the north as highs in the 60s will be common on Tuesday. Much drier will filter into the region by Wednesday as discussed in the section below. .LONG TERM...(Wednesday through Saturday) Issued at 317 PM CDT Sun Oct 14 2018 On Wednesday, post-frontal showers will be ending from NW-SE during the day, as drier and slightly cooler air builds in across the area from the NW. A surface high pressure situated over the central High Plains in the midweek, will build eastward during the course of the latter half of week, reaching the Mid Atlantic coast during Friday. Northerly winds during the Wed/Thu timeframe, will become SE then southerly during Friday. This will bring slightly warmer conditions and higher amounts of moisture to the Tennessee Valley. Greater amounts of moisture pooling over the NW Gulf region will advect to the NE, returning rain chance to this area - just in time for the weekend. This next system appears to be taking on a baroclinic "overrunning" appearance from the ECMWF; with the GFS indicating a surface low forming over the lower Mississippi Valley region. This would bring higher rain chances vs the EC more leaf appearance. Timing wise, did a slight delay in timing regarding the start of the showers, not until Friday night. Scattered to numerous showers look to occur as this moisture builds and instability increases, with precip water amounts rising above 1.5 inches. Overall atmospheric instability and forcing this go around does not look sufficient for convection, so kept the forecast thunder free. Both the GFS/ECMWF indicate a front moving across the forecast area during the latter half of Saturday, with drier weather returning next Sunday. High temperatures on Friday around 70 should cool into the lower 60s by Sunday. Sunday night (a little further out than this forecast) could have lows nearing 40 to start out the next work week on Oct 22nd. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 640 PM CDT Sun Oct 14 2018 With a frontal boundary stalled north of the area, sct shra are possible in a corridor from srn mid TN into NW AL later tonight. As such, a prevailing VCSH group has been maintained at the KMSL airport from late tonight into the daytime hrs. VFR conds otherwise prevail at both main terminals, as mid/high clouds continue to spread ENE across the region. The frontal boundary to the north is xpcted to move swd thru the area later in the day Mon, with shra perhaps tapering off some in the afternoon. Cloud bases may also begin to lower more into the MVFR range around 2-3K ft following the passage of the front. Light/var sfc winds will begin to shift more to the NW near 7-8kt Mon afternoon as well in the wake of the frontal passage. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...09 SHORT TERM...AMP.24 LONG TERM...RSB AVIATION...09 For more information please visit our website at weather.gov/huntsville.