Area Forecast Discussion (AFD)
Issued by Huntsville, AL (HUN)
653 FXUS64 KHUN 200429 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 1029 PM CST Mon Feb 19 2018 .NEAR TERM...(Tonight) Issued at 1030 PM CST Mon Feb 19 2018 Enjoy the warm evening! The Southeast remains under the influence of the western flank of a strong Bermuda high pressure system with warm air advection continuing to keep temperatures well above normal for this time of year. After breaking the record high at Huntsville and tying the record high at Muscle Shoals, temperatures have only fallen into the mid to upper 60s while dewpoints hold close to 60 degrees. With sustained southerly winds of 7-10 kts not expecting temperatures to fall much tonight and kept the forecast overnight lows in the low 60s. Meanwhile, mid to high level cloud cover has scattered leaving partly cloudy conditions mainly across north central and northeast Alabama. Made some adjustments to the sky cover forecast to reflect the current trend. Additional cloud cover developing along the gulf coast will gradually move northward arriving across NW AL sometime between 10-12Z. Otherwise, the rest of the forecast is on track. .SHORT TERM...(Tuesday through Thursday) Issued at 222 PM CST Mon Feb 19 2018 Tuesday will be similar to Monday in synoptic terms with the mid level ridge continuing to strengthen and 850mb temps warming. The atmosphere will quickly mix out Tuesday morning, once again producing 10-15MPH sustained winds with gusts up to 25 mph. This will be slightly higher than Monday due to a bit higher mixing. The continued southwesterly moisture stream along the ridge and weak isentropic lift has caused guidance to show some very light QPF after 18z Tuesday. It's going to be tough to get any showers with the drying associated with the mixing but given the higher moisture and lift, and even a bit of instability (we didn't have any Monday) a 20% chance of a shower seems reasonable at this time. Even so, highs should get even warmer than Monday-in the upper 70s, possibly 80 in a few places out west. Record highs for Tuesday are: 79 in Huntsville that was set in 1986 and 79 also in Muscle Shoals, set in 1917. Even though the instability decreases Tuesday night, the continued lift in the warm sector ahead of an approaching cold front/upper trough, warrants a slight chance to chance of showers. The cold front will be near central AR Wednesday morning but it is well ahead of its parent upper trough, being propelled by a weak upper shortwave and it's movement has slowed every model run this week, due to the strength of the upper ridge. Have continued to back off the POPs, only introducing likely in the NW areas for Wed afternoon with showers possible out ahead of it. The remaining precip with the front will overspread the area Wednesday night. It weakens/washes out on Thursday with scattered showers through the day. In terms of thunder, Wednesday has good instability/shear and no cap to support thunderstorms but very little, if any, lift. Wednesday night has the lift, but not much else. But will continue the mention of isolated storms. Can't make much of an argument for storms on Thursday but given the pattern, won't remove it at this point. Temps once again will be warm Wednesday and Thursday but slightly cooler due to rain/clouds. Highs will be mid to upper 70s Wednesday and lower to mid 70s on Thursday. Lows each night will be in the mid 60s. .LONG TERM...(Thursday night through Sunday) Issued at 222 PM CST Mon Feb 19 2018 The inconsistencies over the past few days with the midweek system make it somewhat uncertain with regard to the forecast at the start of the long term. However, whether we get a true front through in on Thursday or if it stalls before it reaches our area, southerly flow will return in earnest by Friday morning. Given some warm air advection and weak lift Thursday night, we could see some isolated to scattered light showers, though these won't amount to much. Temps will remain on the mild side, with lows expected to be in the 60s. The subtropical ridge will begin to break down through the day on Friday, as a strong upper trough begins to dig into the Desert Southwest. Despite the lowering heights, continued southerly to southwesterly flow through the vertical column will keep a steady stream of warm and moist air across the area. This will help highs warm into the mid to upper 70s. Might see an isolated light shower again on Friday, but again not much in the way of precip. The upper trough will eject into the southwestern Plains on Saturday, eventually developing into a cut-off low. As it strengthens, surface cyclogensis will occur over the TX Panhandle, with a cold front trailing south of the low. This system will slowly track to the northeast through the day on Saturday, reaching the Mid Mississippi Valley by Saturday evening. As stated above, there remains some inconsistencies among models with the mid range forecast, however with this system, there is considerable agreement among the models, along with run to run consistencies as well. Therefore, a bit more confidence exists with the weekend system. Ahead of the arrival of the front/precip, an abundance of moisture will be in place and temperatures will be well above normal. Temperatures will be a few degrees lower than those observed Friday, given the lower upper heights as the trough inches closer, but we will still break the 70 degree mark. The front will enter the area Sunday night, with showers and thunderstorms moving ahead of the system. It's a bit too early to start nailing down threats with this cold front, however given the overall setup, this may bring our first shot of organized thunderstorms this year. The front will exit the area on Sunday, bringing some cooler and drier air across the region. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 528 PM CST Mon Feb 19 2018 VFR conditions should prevail across north AL/southern middle TN until 10-12Z when MVFR cigs (around 2500 feet) may develop over the gulf coast and lift north across MS/AL. These clouds will be more likely near KMSL/NW AL, but have included in KHSV as well until 18Z. Southerly wind speeds of 14 kts gusting to 25 kts have diminished to around 9-11 kts. However, these winds will strengthen to 14-15 kts gusting to 20 kts after 14-15Z. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...SL.77 SHORT TERM...LN LONG TERM...73 AVIATION...SL.77 For more information please visit our website at weather.gov/huntsville.