2025 Spring/Summer Mountain Thread

[Met1985]

Pouring the rain again today. Storming all around.

[Met1985]

Brevard rd at the Tanger outlets are fixing to get hammered.

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[Met1985]

Downtown Asheville is getting hit hard currently. 

[Maggie Valley Steve]

Mesoscale Precipitation Discussion 0966 NWS Weather Prediction Center College Park MD 243 PM EDT Thu Aug 21 2025 Areas affected...Southern Appalachians Concerning...Heavy rainfall...Flash flooding possible Valid 211845Z - 220045Z Summary...Slow moving showers and thunderstorms will expand across portions of the Southern Appalachians through this evening. Rainfall rates at times may reach 3"/hr which could overwhelm soils, especially in sensitive terrain. Flash flooding is possible. Discussion...The GOES-E experimental day-cloud phase micro-physics RGB this afternoon shows a rapid uptick in ice-bearing clouds suggestive of strengthening updrafts into Cbs from NW NC through central GA. These updrafts are associated with deepening convection, and there has been a recent uptick in lightning detection within these storms. This suggests that the environment is becoming increasingly favorable for thunderstorms containing heavy rain, as thermodynamics continues to intensify reflected by PWs measured by GPS between 1.6 and 1.9 inches, around the 90th percentile for the date, overlapped with MUCAPE as much as 3000 J/kg. Despite the relatively recent growth across the area, radar-estimated rainfall rates have already exceeded 1.5"/hr according to KGSP. As the aftn progresses, the CAMs are in decently good agreement in both coverage and placement of activity. It appears likely that convection will become widespread as PWs surge to above 2" outside of the higher terrain. This will support rain rates within thunderstorms that will likely exceed 2"/hr (HREF neighborhood probabilities above 30%) and may reach 3"/hr at times as reflected by HRRR 15-min rainfall above 0.75" in a few locations. Storms that develop will be of the pulse variety in response to limited bulk shear, but will also move very slowly on 0-6km mean winds of just around 5 kts. This indicates that despite the relatively short lifetimes expected of any individual cell, total rainfall could reach 2-3" in some areas, and this will be most likely where any boundary collisions, storm mergers, or terrain influences can impact the relative strength and motion of these storms. Soil moisture across the Southern Appalachians is generally well above normal as reflected by NASA SPoRT 0-10cm percentiles that exceed 98% in many areas. This has reduced 1-hr FFG to as low as 1-1.5" in some areas, for which the HREF exceedance probabilities peak above 25%. This is in addition to the general sensitivity across this area due to the terrain, as well as within any urban areas, so any slow moving thunderstorm could produce impacts due to flash flooding through this evening. Weiss ATTN...WFO...FFC...GSP...MRX...RNK