Area Forecast Discussion
Issued by NWS Huntsville, AL
Issued by NWS Huntsville, AL
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775 FXUS64 KHUN 062017 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 317 PM CDT Mon May 6 2024 ...New NEAR TERM, SHORT TERM, LONG TERM... .NEAR TERM... (Tonight) Issued at 318 PM CDT Mon May 6 2024 A couple of shortwaves can be seen in satellite imagery over the southeastern CONUS. One is centered over extreme NE Tennessee and SW Virginia. This one has been producing some strong thunderstorms over Georgia NE into Virginia. Another shortwave is centered over south central Kentucky and north central Tennessee. A trough axis aloft stretches southwest from this feature into northwestern Mississippi. The best forcing with this feature is concentrated over Tennessee and Kentucky. However, weak forcing with this trough axis could produce some isolated to scattered (20-30%) showers or thunderstorms over northern Alabama into southern middle Tennessee before dissipating this evening. Given SBCAPE and MUCAPE between 2000 and 3000 J/KG in SPC meso- analysis fields, low level lapse rates between 7.5 and 8.5 degrees/km, and DCAPE values between 800 and 1000, there does exist a low chance of a severe thunderstorm or two as this upper level trough axis moves east this afternoon (mainly in southern middle Tennessee). Confidence is low given the weak nature of the upper level trough axis that convection will develop south of the Tennessee River, but cannot rule it out into the early evening hours. Expect this instability to wane early this evening fairly quickly. && .SHORT TERM... (Tuesday through Thursday) Issued at 318 PM CDT Mon May 6 2024 Upper level ridging builds into the area tonight behind the departing shortwave trough axis as it slides east. This should give us a break from shower and thunderstorm activity later this evening into Tuesday morning. Winds in most guidance remain between 5 and 10 mph tonight. These winds and cloud cover should keep fog from forming, despite some clear skies tonight. As a parent low from a destructive storm system over the Midwestern states today moves northeast into the Dakota states, A pre-frontal trough axis moves east ahead of it into the Ozarks and Minnesota areas. Upper level ridging remains in place well southeast of it over much of the Tennessee Valley. It does weaken some though Tuesday afternoon into the evening hours and may allow a weak shortwave to ride over the top of the ridge into the area. With a very unstable airmass in place and dry air aloft on Tuesday afternoon (2500 to 3500 J/KG of MUCAPE/SBCAPE) and DCAPE values between 1000 and 1200 J/KG, severe storms will be able to develop if that shortwave is able to move into the area in the afternoon. Lapse rates aren`t ideal, but they are between 6.0 and 6.5 degrees/km in most guidance. 0-6 km shear is not great, but enough for some organized cell structure and maybe some supercells to develop. There is too little helicity in place though for any tornado threat. However, very large hail and damaging winds look possible if the shortwave doesn`t fall apart moving into the upper ridge, which a few models are hinting at. How long this lasts past the evening hours is a bit of a question mark. However, believe that we should see a break in the activity later in the evening hours. Strong southwesterly flow will develop ahead of an approaching storm system Wednesday into Wednesday night. This brings very warm low level temperatures into the area. Ridging and a low level cap ahead of this develop storm system should limit convection over Alabama. However, as this storm system and approaching cold front moves into Arkansas and the Ohio Valley Wednesday night, a strong MCS will likely form over Arkansas and Kentucky and moves southeast ahead of the front into the southern middle Tennessee around midnight. This should continue to move southeast through the overnight hours into the early morning hours on Thursday morning. Expect this to be on a weakening trend (due to weakening instability trends) as it moves into the area. However, some severe thunderstorms still look possible around and shortly after midnight. If this MCS accelerates southeast more than current guidance suggests, then this severe window could be pushed back a bit and start in the late evening hours. The main threats would be large hail and damaging winds, but a tornado cannot be ruled out especially if this MCS moves into the area before midnight. Trailing stratiform precipitation in the wake of a rather broad MCS early Thursday morning will likely be in progress across much of the region at 12Z Thursday, but should slowly spread southeastward over the course of the morning. Additional showers and perhaps a few storms may also redevelop during the afternoon as a cold front shifts southeastward through the TN Valley, but airmass recovery in the wake of widespread early morning precip should not be sufficient to raise concern for strong-severe convection. && .LONG TERM... (Thursday night through Monday) Issued at 318 PM CDT Mon May 6 2024 A final round of postfrontal showers may occur late Thursday night, along the northern fringe of another well organized convective complex traveling eastward along the central Gulf Coast. Beyond this point, a cooler/drier airmass in the wake of the cold front will reduce POPs to around 10% on Friday and Saturday. However, there are indications that another Gulf low may develop late in the weekend, with a slight chance POP for showers introduced on Sunday. Highs this weekend will be in the lower 70s, with lows in the l-m 50s. && .AVIATION... (18Z TAFS) Issued at 1200 PM CDT Mon May 6 2024 VFR flight weather conditions will persist through tonight. There is a very low probability of isolated TSRA this afternoon and early evening, but too low to include either TAF site. Low clouds of 015-025agl (MVFR) are expected to develop by 11Z and overspread the area through mid to late Tuesday morning. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...None. TN...None. && $$ NEAR TERM...KTW SHORT TERM....KTW LONG TERM....KTW AVIATION...17