Area Forecast Discussion
Issued by NWS Huntsville, AL
Issued by NWS Huntsville, AL
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505 FXUS64 KHUN 122227 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 527 PM CDT Sun May 12 2024 ...New AVIATION... .NEAR TERM... (Tonight) Issued at 240 PM CDT Sun May 12 2024 Scattered cloud cover currently lingering over the TN Valley is forecast to increase into the evening hours and overnight as a sfc low pressure system continues eastward towards our area from the Central Plains. Temperatures are forecast to drop into the mid 50s to low 60s tonight with light, variable winds. Just before daybreak, low chances (30% or less) of showers are possible as rain moves in from the southwest in response to upper level shortwaves. More on that in the short term section below. && .SHORT TERM... (Monday through Tuesday Night) Issued at 240 PM CDT Sun May 12 2024 Rain chances will increase through the day Monday in response to an incoming area of sfc low pressure from our west (over the Central Plains moving into the MS Valley). Ahead of this, a series of upper level shortwaves will allow low-medium chances (30-60%) of showers with a low-medium chance of producing lightning through the afternoon hours Monday. As instability slightly increases Monday night (along with 6.5-7.0 C/km mid level lapse rates and ~40-50 kts of 0-6km shear), there is a low chance some storms may become strong-- bringing threats of gusty to damaging winds and hail. Confidence in strong storms remains low as the warm sector track trends to the south of our area (remaining more in South/Central AL). SPC has placed portions of our CWA (primarily areas south of the TN River) in a Marginal Convective Outlook (risk level 1/5) on Monday into Tuesday. Additionally, model PWATs between 1.3-1.5" would be nearing (just below) the 90th percentile sounding climatology for BMX. Storm total rainfall forecast Monday into Tuesday is between 0.5-1.5". WPC has placed most of our area in a Marginal Excessive Rainfall Outlook (risk level 1/4) for both Monday and Tuesday. This means at least a 5% risk of rainfall exceeding flash flood guidance. Medium-high chances (60-90%) of showers/storms are forecast to continue Tuesday morning through the afternoon hours before subsiding from southwest to northeast in the evening. Temperatures during the short term period will range from the lower to upper 70s for highs with lows in the upper 50s to mid 60s. && .LONG TERM... (Wednesday through Saturday) Issued at 330 AM CDT Sun May 12 2024 An upper level low currently over western Colorado will progress eastward, and should be moving over the eastern Ohio River Valley at the start of this period as a weakening trough. The main surface low should be moving over the VA/MD region, while a weaker low and boundary remain over eastern Tennessee. The presence of this front and remaining moisture will help bring isolated to scattered showers and thunderstorms Wed afternoon for the eastern, and much of the central areas. The area of low pressure and moisture should exit further to the east Wed night, and bringing a brief dry period on Thu. Another system nearing the area from the west will bring more shower and thunderstorm chances starting Thu evening over our far western areas, with the activity overspreading the area overnight Thu and on Fri. Have maintained likely (60-70%) rain chances on Fri. Output from some of the medium range guidance, especially the ECMWF/Canadian were hinting that some of the storms Fri afternoon/evening could become strong, with high outflow winds the main threat. Precipitable water amounts at and above 1.5" at this time could lead to locally heavy rain, with localized flooding a possibility. Despite the passage of a frontal boundary early Sat, residual moisture remaining will help continue showers as we close out the week. Clouds and showers on Wed will keep highs in the mid/upper 70s. A return of more sun early Thu and a southerly flow should help push highs into the lower 80s on Thu. Highs around 80 are expected Fri and Sat. Low temperatures in the mid/upper 50s Wed night will moderate into the 60s Thu and Fri nights. && .AVIATION... (00Z TAFS) Issued at 527 PM CDT Sun May 12 2024 VFR flight weather conditions are expected through 11-14Z before lower ceilings of 015-030agl (MVFR) arrive. A large area of -SHRA and TSRA will move through central AL Monday, with the northern extent of the -SHRA possibly affecting KMSL and KHSV at times. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...None. TN...None. && $$ NEAR TERM...HC SHORT TERM....HC LONG TERM....RSB AVIATION...KTW/AK