Area Forecast Discussion (AFD)
Issued by Huntsville, AL (HUN)
329 FXUS64 KHUN 200823 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 323 AM CDT Tue Mar 20 2018 .NEAR TERM...(Today) Issued at 323 AM CDT Tue Mar 20 2018 After a very rough afternoon and evening yesterday, quiet weather has returned to northern Alabama and Southern Middle Tennessee. However, with clear skies and light to calm winds that settled over the area around 10 PM last night, patchy dense fog has developed and continues east of I-65. Further west, that was the case as well between 10 PM yesterday and 1 AM this morning, but a re-enforcing frontal boundary that has drier air and stronger winds behind currently is stretching from Athens southward to west of West Point has dissipated the fog in those locations as of 3 AM. Patchy dense fog will continue though in far northeastern Alabama through about 7 AM. Therefore, a special weather statement continues to highlight this threat through 7 AM east of I-65. Lows should drop a bit more towards daybreak east of I-65 into the upper 40s to around 50 degrees. Expect a bit of warming early this morning, as yet another stronger cold front pushes southeast into and then through the area this afternoon and evening. A good 30 to 35 knot 850 mb jet develops along and behind the front aloft. Soundings show the atmosphere being able to mix up to that wind energy and translate some of it to the surface. Thus, it will be brisk today with northwest winds 15 to 20 mph with gusts near 30 mph. These strong winds will efficiently advect cooler and drier air southeast into the area this afternoon/evening. Enough lift at 700 mb with this front and enough moisture around 700 mb and below should allow for scattered to more numerous light rain showers to develop along and behind it, especially in locations north of the Tennessee River. Temperatures will remain well above freezing through the day, so this should remain all rain. SHORT TERM...(Tonight through Wednesday night) Issued at 323 AM CDT Tue Mar 20 2018 As we move into the evening hours today, temperatures will fall into the mid to upper 30s primarily. This could cause lingering scattered precipitation to become a mix of light rain and snow in Southern middle Tennessee and in northern Jackson county in Alabama. However, this looks to move northeast of the area just after 10 PM. So not expecting any accumulation of snowfall at this time. Could see some flakes of snow in those areas, but not many other locations. Skies should clear around and after midnight from west to east. This along with strong cold air advection should allow low temperatures to drop just to or below freezing for a few hours before daybreak on Wednesday. The colder air really moves southeast into the area behind the departed front by Wednesday, as highs only climb into the mid 40s to lower 50s despite abundant sunshine. A return to more widespread freezing conditions look to shape up on Wednesday morning, as winds lighten as high pressure builds into the area and good radiational cooling occurs. Could see some locations dip into the upper 20s in Southern Middle Tennessee. .LONG TERM...(Thursday through Monday) Issued at 323 AM CDT Tue Mar 20 2018 A sprawling surface high pressure remains in control of the local weather on Thursday. Aloft, we will be under northwesterly flow on the back side of a trough departing the northeast. However, a mid level ridge will be centered over LA and help push up heights and therefore, a warming trend. Thursday should be sunny and highs will warm into the upper 50s to around 60 degrees. Clouds will increase slightly Thursday night as a shortwave dives southeast along the upper trough. Lows will also be able to warm above freezing and into the mid 30s to lower 40s. There will be a slight chance of rain showers with that shortwave. A weak upper low will develop over the midwest Friday evening with surface cyclogensis in the KS/MO area. Looks like a warm front will be extending southeast with guidance showing QPF along it down through most of the forecast area. There is quite a bit of uncertainty with the system this weekend especially moving into Saturday. The surface low shifts east-southeast over SE MO with the frontal boundary ahead of it. This boundary eventually dissipates before another frontal boundary moves in Sunday ahead of an upper trough digging into the desert southwest. Really tough to tell at this point where the rainfall gradient will be and when the highest rain chances will be. At this point, just left the blended chance pops in the forecast from Friday through Tuesday with the highest chances int the Monday/Tuesday range. Although thunderstorm parameters aren't impressive, with the area in the vicinity of multiple fronts, kept isolated thunder in for Sat through Monday. In terms of temps, southwest winds and rising heights push highs Friday to the upper 50s/lower 60s and upper 60s/lower 70s for Sat/Sun/Mon. Lows will also slowly warm and be back into the mid 50s by Sat night. && .AVIATION...(For the 06Z TAFS through 06Z Tuesday night) Issued at 1232 AM CDT Tue Mar 20 2018 VSBYS at KHSV are still LIFR and oscillating between 1/4 and 3/4 of a mile. Expect this to continue through 20/09Z, before winds increase with a re-enforcing front just to the west of KMSL. Already have seen VSBYS become VFR quickly as a result of this boundary at KMSL and expect them to remain VFR, as winds remain between 5 and 10 knots through daybreak. Expect this to occur at KHSV after 20/09Z. Then expect cigs to lower and become MVFR after approximately 20/15Z at both terminals with showers near both terminals through the afternoon hours. For now only put VCSH both terminals. This should linger into the evening hours, before cigs improve and become VFR towards midnight. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...KTW SHORT TERM...KTW LONG TERM...LN AVIATION...KTW For more information please visit our website at weather.gov/huntsville.