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Area Forecast Discussion
Issued by NWS Huntsville, AL
Issued by NWS Huntsville, AL
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426 FXUS64 KHUN 161742 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 1242 PM CDT Tue Jul 16 2024 ...New AVIATION... .NEAR TERM... (Rest of Today) Issued at 950 AM CDT Tue Jul 16 2024 A cluster of showers and thunderstorms continue to move east across northeastern Alabama producing heavy rainfall and some frequent lightning at times. 0.5 to 1.5 inches of rainfall has fallen over the last 3 hours in western DeKalb into Marshall county so far this morning. Luckily this whole cluster of activity is moving east a enough of a clip that flash flooding should not be a major concern. However, some backbuilding may occur and this may eventually cause some isolated flash flooding concerns. RAP13 seems to have the best handle on this activity so far. This and other models forecast this activity to fall apart around noon. However, RAP13 seems to be picking up on an outflow boundary that is moving south into north central Tennessee. This may push southeast and enhance low level convergence in southern middle Tennessee and further south in northern Alabama during the afternoon hours. This matches satellite trends in respect to the arrival of this outflow boundary. Based on current radar and expected movement of the current precipitation, have raised chances of precipitation this morning to between 40 and 60 percent in northeastern Alabama. Also, kept a 30 to 40 percent chance of additional shower and thunderstorm development in the forecast in the afternoon with the arrival of the outflow boundary. Mostly cloudy conditions were added across much of the area after 1 pm and in northeastern Alabama this morning. This will keep highs a tad cooler than previously thought (89-96 degrees). Despite the cooler temperatures, believe pooling ahead of the outflow boundary of higher dewpoints will still allow heat index values to climb to between 105 and 107 degrees this afternoon for locations west of Cullman to Lincoln counties. && .SHORT TERM... (Tonight through Friday) Issued at 405 AM CDT Tue Jul 16 2024 Tonight, low temperatures drop into the low to mid 70s. Both MSL and HSV are forecast to drop to the mid 70s which could be close to breaking their record for high minimum temperatures for July 17th. HSV`s record is 77 degrees (set in 1932) while MSL`s record is 78 degrees (set in 1980). Therefore, it is safe to say these temperatures are above-normal. Dry weather is forecast overnight before high rain chances (70-80%) return Wednesday and continue through Thursday as a cold front approaches the Tennessee Valley from the northwest. Low- medium chances of showers/storms (30-60%) continue into Friday. During this time, several rounds of showers are forecast to bring a potential for moderate to heavy rainfall, frequent lightning, and gusty winds. PWATs are forecast to be in the 1.7-1.9 range in HREF solutions, nearing the 90th percentile per BMX sounding climatology. Therefore, a low flooding threat is a concern as these continue both throughout the daytime as well as overnight. The Weather Prediction Center (WPC) has placed portions of our area in a Marginal (threat level 1/4) Excessive Rainfall Outlook Wednesday morning through Thursday morning, meaning there is at least a 5% risk of rainfall exceeding flash flood guidance. The forecast rainfall and surplus of cloud cover will allow temperatures to cool off for the remainder of the work week, capping high temperatures in the 80s Thursday and Friday. On Wednesday, high temperatures in the 90s are still forecast with heat indices in the 99-104 range, however, we will be monitoring how early rainfall develops which may mitigate the need for any Heat Products as temperatures would be cooler than currently forecast. Be sure to check back in for the latest forecast information. && .LONG TERM... (Friday night through Monday) Issued at 405 AM CDT Tue Jul 16 2024 Medium-high shower/storm chances continue through the weekend as the aforementioned front is forecast to stall to our southeast, allowing higher rain chances in our southeastern counties (Cullman, Marshall, Dekalb, Jackson) Friday before lifting back northward due to high pressure off the east coast of Florida. High temperatures in the 80s continue during this time and the need for any Heat Products is not expected. && .AVIATION... (18Z TAFS) Issued at 1242 PM CDT Tue Jul 16 2024 VFR conditions continue at both TAF sites currently. However, at least isolated to scattered -TSRA are expect to develop over the next 4-6 hours near the TAF sites. Thus, a tempo group was included between 18Z and 22Z at both terminals. This activity may not last as long at KMSL. With around 40 percent PoP, confidence is not high that MVFR CIGS or VSBYS will impact either terminal, but a possibility during that window. VFR conditions should return after 00Z. However, winds should keep any fog from forming overnight despite some clearing. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...Heat Advisory until 8 PM CDT this evening for ALZ001>007-016. TN...Heat Advisory until 8 PM CDT this evening for TNZ096. && $$ NEAR TERM...KTW SHORT TERM....HC LONG TERM....HC AVIATION...KTW