Area Forecast Discussion
Issued by NWS Huntsville, AL
Issued by NWS Huntsville, AL
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098 FXUS64 KHUN 151815 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 115 PM CDT Wed May 15 2024 ...New NEAR TERM, SHORT TERM... .NEAR TERM... (Tonight) Issued at 115 PM CDT Wed May 15 2024 The mid/upper low will continue to shift eastward into the Southern Appalachians and eventually the Carolinas this evening and overnight as light showers taper off with the setting sun. The end result will be clearing conditions from west to east as a drier air mass filters into the region in wake of this system. Subsequently, there will be a clearing sky and a decent setup for radiational cooling as temperatures fall back into the mid/upper 50s. The clear/calm conditions and moist boundary layer from earlier rainfall will create conditions favorable for patchy fog late tonight into early Thursday morning -- especially in sheltered valleys. && .SHORT TERM... (Thursday through Friday night) Issued at 115 PM CDT Wed May 15 2024 A brief bout of ridging will take place on Thursday just prior to the arrival of the next storm system. This will promote a mostly sunny and very warm day as southerly winds help to reinforce this air mass -- as highs will climb into the mid to upper 80s by the afternoon. Although we will not be in the ballpark of heat related products, those that are very sensitive/vulnerable to heat should take an extra precaution if attending an outdoor event such as graduations, sporting events, etc on Thursday afternoon/evening. Things will change quickly by Friday and Friday night as the next storm system swings into the Deep South, bringing very high (70-90%) chances for showers/storms -- and potential for a few strong to marginally severe storms depending on how the environment evolves. Guidance continues to indicate a fairly robust MCS along the northern Gulf Coast of MS/AL/FL during the morning hours -- which will likely keep us "cut-off" from the more favorable instability and air mass well to our south. However, later in the afternoon and evening, this activity along the AL/FL coast should have shifted well east into the Big Bend/Peninsula region of Florida. As a result, southerly flow may help to recover our air mass from earlier showers/elevated storms in the morning. An additional round of showers and storms may develop along the cold front sometime during the late afternoon/evening or even into portions of the overnight hours Friday night. If morning convection can wane quickly and air mass recovery can be realized, a severe threat (mainly damaging winds and small hail) may evolve during the afternoon/evening. However, there is still a decent amount of spread between the solutions and for now the threat remains at Marginal (1/5) per the latest SPC Day 3 Outlook. Additionally, locally heavy rainfall and a low chance for localized flooding concerns may also be a threat, especially if training occurs. && .LONG TERM... (Saturday through Tuesday) Issued at 348 AM CDT Wed May 15 2024 To start the long term, an upper shortwave trough is expected to traverse the Mississippi and Tennessee Valleys on Saturday. However, there remains disagreement in the model guidance with regards to timing and evolution of the trough. Once this feature moves east of the area (Sunday morning), upper ridging looks to take hold and persist through early next week. Although, a shortwave may sweep over the Midwest and over the Ohio Valley on Monday. At the surface, a low pressure system is shown to move over the lower Ohio Valley and Tennessee Valley Saturday morning, with northern Alabama and southern middle Tennessee in the warm sector. Anticipating this low to continue eastward and move over Virginia and North Carolina by Sunday morning, with high pressure building in behind it over our area for Monday. This high pressure will then begin to shift east on Tuesday, ushering moisture into the region with return flow. Looking at thunderstorm potential, guidance varies a bit with bulk shear and instability Saturday morning. But, values look to be at least 40 knots with around 500-700 J/kg. 0-3 km SRH values also range between 100-150 m2/s2 in the morning and into the afternoon. This, the trajectory of the surface low, and potentially a LLJ around 40-50 knots moving over the Tennessee Valley Saturday morning increases confidence in the potential for strong to possibly severe storms Saturday morning and into Saturday afternoon. The main question is with the timing of this system through the area. If it`s later (afternoon hours), then there will be more time for warming which would lead to more instability and high potential for severe. If it`s earlier (morning hours), there may not be as much instability for storms to tap into (especially with showers/storms possible Friday night) and perhaps less of a severe threat. Although, that`s not to say we can`t have strong to severe storms in the morning. Ultimately, we`ll be monitoring this system and trends closely over the coming days with subsequent model runs to better determine any severe potential. For sensible weather, expect medium to high chances (50-70%) of showers and storms on Saturday. These could at least bring gusty winds, frequent lightning, and heavy downpours. As was mentioned previously, we`ll continue to analyze trends for the potential for any severe weather. At this point, chances of showers and storms dwindle from west to east in the evening, but timing could change a bit in subsequent forecast updates. Sunday will then be mostly dry, but some spots over the far northeastern portion of Alabama and southern middle Tennessee could see a few showers/storms in the afternoon. With an upper level shortwave moving over the Ohio Valley on Monday (mentioned above), low chances (15-20%) of showers and possibly a storm are forecast Monday evening and overnight. Low chances (15-20%) of showers/storms are then possible on Tuesday. Temperatures will be on the rise through Tuesday. Highs Saturday afternoon are expected to top out in the upper 70s to lower 80s due to the higher coverage of clouds and precipitation. Highs Tuesday are then slated to reach the mid to upper 80s! As for low temperatures, values will generally remain in the lower to mid 60s each night. && .AVIATION... (18Z TAFS) Issued at 1148 AM CDT Wed May 15 2024 Current MVFR conditions are forecast to become VFR as broken cloud cover becomes scattered into the afternoon hours. Winds are forecast to continue gusting from the WNW around 15-17 kts this afternoon, but should subside this evening. Overnight, as winds calm and skies clear, a low chance of patchy fog is possible. This has not been officially added to the TAF package at this time due to low confidence, however, it may be added in future updates. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...None. TN...None. && $$ NEAR TERM...AMP.24 SHORT TERM....AMP.24 LONG TERM....26 AVIATION...HC