Area Forecast Discussion (AFD)
Issued by Huntsville, AL (HUN)
366 FXUS64 KHUN 160915 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 415 AM CDT Thu Aug 16 2018 .NEAR TERM...(Today) Issued at 415 AM CDT Thu Aug 16 2018 Area radars are showing a large mass of light/mod showers, with some embedded tstms, spreading ewd into much of west TN this early Thu morning. This activity looks to be associated with a weak upper level impulse embedded within a weak shrtwv axis traversing ewd into the OH Valley/Mid South regions. This convection is also developing ahead of a weak frontal boundary located from the Midwest into the srn Plains. Closer to home, high pressure at the sfc remains fairly stagnant over the srn Atlantic Basin, which is translating into a return flow pattern across much of the region. Latest model suites continue the convective development trend over the Mid South area later today as it spreads more to the east. The upper shrtwv axis to the north/west looks to become even more sheared to the NE later today, thereby helping to keep much of the shower/tstm activity displaced just to the north. However, trailing bands of energy back to the SW may be enough to result in iso/sct showers/tstms forming across parts of the cntrl TN Valley later today, especially for areas along/north of the TN River. Even with the chc of rainfall and associated cloud cover, afternoon temps again look to be seasonably warm for this time of the yr, with highs mainly in the lower/mid 90s for most locations. .SHORT TERM...(Tonight through Saturday) Issued at 415 AM CDT Thu Aug 16 2018 Lingering iso/sct showers/tstms may continue into the evening hrs, as weak upper disturbances continue to move ewd across the region. Most of the rainfall though should taper off by the onset of the overnight period, with early morning lows Fri falling mainly into the lower/mid 70s. Rain chances are then xpcted to increase heading into Fri, as a stronger upper trough pattern out of the Great Lakes drops into the Midwest/OH Valley states. The weak frontal boundary to the NW may also drift sewd, but it is xpcted to stall well north of the local area. With moisture increasing into the region from the WSW, sct/num showers/tstms look to develop thru the day Fri and continue into Fri night. With SBCAPE values increasing into the 2-3K J/kg range coupled with 25-30kt of 0-6km Bulk Shear, a few strong/marginally svr tstms capable of brief damaging wind gusts and hail cannot be ruled out Fri afternoon/evening. Not much change is then xpcted for Sat, with the upper trough axis remaining fairly stagnant across the region. This should again result in num showers/tstms Sat, with a few of these storms potentially strong in nature. With the increase in cloud cover/rainfall, afternoon temps Fri/Sat may trend a little bit cooler, with highs more in the mid/upper 80s for most areas. .LONG TERM...(Saturday night through Wednesday) Issued at 415 AM CDT Thu Aug 16 2018 Unsettled weather will continue for the start of another week. At the surface, high pressure situated off of the southeast coast will maintain a moisture laden S-SW surface flow across the region. This moist flow, upgliding in the 305K region (800-900mb), and the approach of a frontal boundary from the northwest, will result in more clouds than sun, and scattered showers and thunderstorms on Sunday and Sunday night. Along with the surface features, a more southward extent of the polar jet moving in from the northwest, will bring a trough across the Ohio/Tennessee Valley region early next week, helping to raise rain chances even more during Monday. Precipitable water amounts range in the 1.7 to 2.1 inches in this timeframe, which will result in locally heavy rainfall. Forecast soundings indicate surface based CAPE values rise into the 2-3K range, but with little shear. Inverted-V signature with high instability values could result in microburst type wind from collapsing storms, and frequent lightning. The above noted upper system will help to develop a surface low over the mid Mississippi Valley on Monday. This low will move to the northeast during Tuesday. A cold front trailing from this low should move across the forecast area during Tuesday. The passage of this front should bring drier air across the region, with lowering rain chances Tuesday night, and dry conditions for Wednesday. High temperatures for most of the extended period should range in the mid/upper 80s through Tuesday, then "only" into the low/mid 80s next Wednesday, with lower thickness values and a dry northerly surfaced flow. && .AVIATION...(For the 06Z TAFS through 06Z Thursday night) Issued at 1220 AM CDT Thu Aug 16 2018 With weak high pressure remaining in place over the srn Atlantic states, VFR conds are xpcted thru the TAF period. Mid/high clouds will again spread into the area from the west heading into the morning hrs Thu, but cigs are xpcted to remain above VFR levels. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...09 SHORT TERM...09 LONG TERM...RSB AVIATION...09 For more information please visit our website at weather.gov/huntsville.