Area Forecast Discussion
Issued by NWS Huntsville, AL
Issued by NWS Huntsville, AL
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876 FXUS64 KHUN 231454 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 954 AM CDT Thu May 23 2024 ...New NEAR TERM... .NEAR TERM... (Rest of Today) Issued at 954 AM CDT Thu May 23 2024 Dry conditions prevailed across the Tennessee Valley, with areal temperatures ranging from the lower 70s to around 80. Winds were from the SE-S at 5-10 mph. There is an area of clouds moving eastward over the region (with skies ranging from mostly sunny west to mostly cloudy east). This should allow more daytime heating and help boost highs later today into low/mid 80s. But...there is a complex of thunderstorms to our west, extending in a NE-SW manner from MO/AR/TN border, to near Memphis, and over southern AR. Simple extrapolation has it reaching our NW areas around 1 PM. This was also shown by the various shorter term models. Depending upon how much heating occurs beforehand, the higher instability values plus weak to moderate shear already in place could result in some storms getting strong to severe in intensity. The main threat will be damaging wind gusts and maybe large hail. This activity as of this writing was producing lots of lightning, which could impact this area as well. Big changes otherwise are not needed at this time with big picture forecasting. Will stay with higher rain chances to our west today given the current path of the approaching convection. && .SHORT TERM... (Tonight through Saturday night) Issued at 441 AM CDT Thu May 23 2024 With the loss of daytime heating, convection moving south from southern middle Tennessee should fall apart around midnight. But it might take that long given some of the remaining forcing moving south. A few of those storms could remain severe before dissipating. Main threat may shift more to large hail than damaging winds. We will have to watch for fog development overnight as winds are forecast to be very light. Persistent cloudy conditions though may keep fog from being very widespread or dense. A much stronger shortwave is progged by most guidance to develop over Arkansas and push ENE towards the area on late Thursday night into Friday. Very strong forcing at 700 mb is seen with this piece of energy aloft. As it moves east early Friday morning in to northwestern Alabama and western Tennessee, instability will be in place near and ahead of it (1000 J/kG to 2000 J/KG of MUCAPE) along with mid level lapse rates between 7.0 and 8.0 degrees/km. This instability only increases in guidance into the afternoon hours (2000 to 3000 J/KG). DCAPE is most models sounding is between 1000 and 1200 J/KG as this disturbance continues to move east into NW Alabama with ample shear to support organized severe thunderstorm development. Therefore, some storms could become severe during the late morning into the afternoon hours producing large hail or damaging winds. There is a very low chance of tornado or two given 0-3 km helicity values, but damaging wind and large hail are expected to be the main threats. Given the expected cloud cover and more widespread nature of showers and storms, high should be cooler only reaching the 79 to 85 degree range. Weaker shortwaves are shown in models lingering into the evening upstream of the area aloft. Shear weakens Friday night, but with decent elevated MUCAPE lingering (~1500 to 2000 J/KG) at least strong storms could linger into the nighttime hours. It will remain humid overnight with lows only dropping to between 65 and 70 degrees in most locations. During the morning hours on Saturday upper level ridging builds over the area behind the departed shortwave aloft well to our east over the Carolinas. This should help suppress lift and weaken upstream disturbances. Expect scattered showers and thunderstorms to continue, but coverage of showers and storms should be less as bulk shear remains weak (<25 knots). Not expecting severe storms until maybe in the afternoon, when another strong shortwave moves from Mississippi moves into the area. Shear will remain weak as this occurs, but instability will be between 2000 and 3000 J/KG and mid level lapse rates around 8 degrees/km. So damaging winds and large hail cannot be ruled out in the strongest storms. With the more scattered nature of the activity in the morning, more sunshine will likely be seen at times. So highs in the mid 80s seem reasonable. Lower chances (20 to 40%) of showers and storms are expected Saturday night, as the forcing moves east of the area into Georgia and the Carolinas. This should give us a break from the period of showers and storms overnight into Sunday. However, a potent storm system that develops in models late Saturday night into Sunday over the Upper Midwest moving into the western Great Lakes region will be the next impetus for additional showers and thunderstorm activity. This round looks to be more organized and severe. && .LONG TERM... (Sunday through Wednesday) Issued at 441 AM CDT Thu May 23 2024 We will likely get some additional cloudy conditions and maybe an isolated shower or thunderstorm with a pre-frontal trough axis ahead of this system on Sunday. However, overall should be a rain free day and hot with highs in the upper 80s to 90 degrees. This changes though as the main cold front pushes southeast Sunday night into the area. Very steep lapse rates, strong shear, high DCAPE values, and strong instability (3000 to 4000 J/KG) will provide the impetus for a MCS that develops along this front as it pushes into and through the area overnight into Monday morning. Saturated soils by then could produce a more enhanced threat for flash flooding or river flooding from this rainfall. Models differ on how quickly this system pushes through the area though, so activity cloud linger into the afternoon on Monday. However, the atmosphere will likely be worked over from earlier convection earlier in the day, so severe weather should not be much of an issue if that occurs. Finally northwest flow aloft and dry weather builds back into the area Tuesday into Wednesday. Highs will drop back into the upper 70s to lower 80s again thankfully with lows dropping back into the mid 50s to lower 60s. && .AVIATION... (12Z TAFS) Issued at 606 AM CDT Thu May 23 2024 VFR conditions will continue at both terminals despite abundant cloud cover. Expect this cloud cover to hang around through 22Z at both terminals. A tempo group for MVFR VSBYS was included for scattered or bit more widespread convection that may push into that terminal between 17Z and 21Z. Further east at KHSV, included a VCTS between 18Z and 22Z, but confidence on coverage is lower and thus the possibility of a -TSRA directly impacting that terminal. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...None. TN...None. && $$ NEAR TERM...RSB SHORT TERM....KTW LONG TERM....KTW AVIATION...KTW