####018010139#### FXUS62 KRAH 161529 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1130 AM EDT Thu May 15 2025 .SYNOPSIS... Upper level disturbances moving atop an upper level ridge building across the SE US will support mainly diurnal showers and storms and unseasonably hot temperatures to end the work week. A series of cold fronts will move through the region over the weekend. && .NEAR TERM /TODAY AND TONIGHT/... As of 1130 AM Friday... The previous forecast remains in good shape, only adjusting PoPs slightly along the northern Piedmont and Coastal Plain as newer Hi- Res model data comes in. Comparing the 06z to the 12z NCAR HRR Neural Network output model show the probabilities for severe winds and hail this afternoon and overnight have shifted slightly northward. The general Hi-Res model guidance still has a large spread for both rounds this afternoon and overnight. Expecting the MCSs over the Kentucky region this morning to cross the Appalachian Mountains and and keep its energy and momentum along the NC/VA border this afternoon. With all the said, I expect the Slight Risk in VA to be expanded south into portion of Northern NC with SPCs morning update. * There remains a conditional risk for Strong/Severe Storms across the northern Piedmont and northern coastal plain this afternoon/early evening PREVIOUS DISCUSSION: Overview: Strong upper level ridge centered over the Eastern US will move offshore late in the day. A shortwave trough associated with the upper cyclone moving into the Great Lakes will approach from the west late tonight/early Saturday. Today: Model spread remains high, and forecast confidence regarding storm potential this afternoon and evening continues to be low. The upper ridge could prove quite formidable again today. The exception may be across northern portions of the forecast area where shortwave vort disturbances spilling atop the ridge could support a cluster or two of very strong and severe storms during the afternoon and evening. Strong diurnal heating(afternoon highs upper 80s to lower 90s) within the seasonably moist airmass and steep mid-level lapse rates(7.5-8 deg C/km)associated with the EML lingering over the mid south and SE US will create a strongly unstable environment with MLCAPE expected to peak between 2000-3000 J/kg. Shear is also quite impressive with 0-3km shear forecast to strengthen to 35-40 kts during the afternoon and evening. If storms do make it into the northern Piedmont and northern coastal plain, the robust instability and strong shear could allow for intense persistent updrafts and supercells to track east across the northern Piedmont and northern coastal plain counties. Large +2" hail and potentially destructive straight-line winds up to 75 mph. An isolated tornado is also possible. Alternatively, the ridge could shield central NC from the strong deep convection, diverting the severe threat north of the area, leaving it hot with considerable mid and high clouds across the area. So as you can see we are dealing with a very conditional threat for severe storms today. Stay vigilant and monitor the latest weather conditions. Tonight: Any convection should dissipate or move east of the area before midnight. The approach of the upper trough from the west could support some weakening convection moving into the western Piedmont towards sunrise. Otherwise, mostly dry overnight with record warmth expected(see climate section below). Lows 70 to 75. && .SHORT TERM /SATURDAY AND SATURDAY NIGHT/... As of 415 AM Friday... * Moderate instability and strong wly mid-level flow and shear profiles will support a conditional risk of severe storms once again Sat, especially from the ern Sandhills through the Coastal Plain during the afternoon, based on lower predictability, mesoscale influences from a decaying QLCS and outflow that will likely be moving across the NC Piedmont at the start of the period. A mid/upr-level cyclone will progress across the lwr Great Lakes and to nrn NY and VT by 12Z Sun. A significant shortwave perturbation will slightly precede the cyclone and partially phase with an energetic srn stream while moving across and offshore the Middle Atlantic through Sat. A band of convectively-enhanced vorticity, probably extending from wrn portions of the srn Middle Atlantic and Carolinas swwd into the TN Valley, and related to the aforementioned decaying QLCS there during the morning, will move ewd and across the Carolinas through early-mid afternoon. Related to the influence of each, mostly weak mid-level height falls will result over cntl NC throughout the period but maximize modestly at 20-40 meters around 18Z. An extensive and pristine EML plume will initially be in place across much of the Southeast but will migrate ewd and offshore ahead of the trough/cyclone, and also become contaminated by multiple rounds of deep convection through its wrn periphery, including into the TN Valley and wrn Carolinas, by the start of the period. At the surface, some degree of aggregate outflow will likely be in the process of moving across cntl NC, probably increasingly-ahead of decaying, parent convection. Where it slows and stalls, and how strong it remains when it does so, will likely have ramifications on subsequent convective initiation as convective temperatures are reached by early-mid afternoon. At this time, the greatest clustering from CAM guidance on its probable location would favor the Sandhills and Coastal Plain. A lee trough and progressively drier wswly flow to its west will also develop and move ewd across the Piedmont during the afternoon-evening, followed by a weak cold frontal passage Sat night While mesoscale uncertainties yield lower than average forecast confidence on sensible weather specifics, the most likely scenario related to the pattern described above will be for a band of generally weakening convection and overcast, and outflow with strong wind gusts up to 30-35 kts, to be in the process of moving across w- cntl NC early in the day. Associated stabilizing influence during the morning would then diminish as lingering precipitation and clouds dissipate by early afternoon, with those influences perhaps never reaching the ern Sandhills and Coastal Plain, where diurnal heating would be maximized beneath still relatively pristine EML. It will be there, where the aforementioned outflow boundary may have also surged and stalled, and where widely scattered storms would be most likely to develop. Shear profiles would favor a supercellular mode with attendant risks of large hail and damaging wind gusts. It should otherwise be unseasonably hot again, with highs in the upr 80s-lwr 90s. While Sat night will feature clearing initially, high-level moisture in wly flow will probably result in a return of cirrostratus ceilings Sun morning. && .LONG TERM /SUNDAY THROUGH THURSDAY/... As of 445 AM Friday... A mid/upr-level cyclone will move slowly across the Northeast and near the coast of Atlantic Canada through mid next week, while another develops across the Intermountain West and then progresses across the Rockies and Plains. The latter, preceded by shortwave ridging across the Southeast early in the week, will then progress across the OH Valley and lwr Great Lakes vicinity by Wed-Thu, during which time its influence will be most likely to impact cntl NC. At the surface, a convectively-reinforced frontal zone will likely become quasi-stationary from the mid MS Valley or upr Midwest to the srn Appalachians and wrn Carolinas, while Canadian high pressure will extend from ON to the Middle Atlantic. A lee cyclone will then track from the cntl/srn Plains to the Middle Atlantic by Wed-Thu, with typical model timing differences and forecast uncertainties at that time range. The sensible weather related to the pattern described above will feature continued unseasonably warm conditions, and mainly dry ones with the focus of convection into the srn Appalachians and wrn Carolinas, through Tue. Increasing chances of rain/convection will then result Wed-Wed night, and possibly linger into Thu, depending upon how quickly the cyclone ultimately moves through the Middle Atlantic. && .AVIATION /11Z FRIDAY THROUGH TUESDAY/... As of 630 AM Friday... 24 hour TAF period: Forecast confidence is lower than normal wrt to storm potential this afternoon and evening. Upper level disturbances spilling atop a strong upper level ridge in place across the region may support one or two strong to severe storm clusters across the northern portions of the forecast area this afternoon and evening. Alternatively, the upper ridge could largely suppress/stifle compression, keeping the area free of convection. Should storms make it far enough south, strong instability and shear would be conducive for strong wind gusts of 30- 50kt+, hail and sub-VFR conditions for the northern TAF sites(KINT, KGSO, KRDU, and KRWI). A 35-45t LLJ moving through the area tonight could bring a brief period of LLWS to all TAF sites overnight. An area of weakening convection is expected to approach the KINT and KGSO terminals between 09 to 12z Saturday. Outlook: Chances for diurnal isolated to scattered showers and storms will continue through much of the period. Morning fog and low stratus will be possible each morning, especially in areas that received significant rainfall the previous day. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...CBL NEAR TERM...CA/CBL SHORT TERM...MWS LONG TERM...MWS AVIATION...CBL ####018009672#### FXUS62 KGSP 161530 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 1130 AM EDT Fri May 16 2025 .SYNOPSIS... Warm high pressure remains over the area through today. A cold front approaches from the northwest and may bring a line of showers and thunderstorms to the North Carolina mountains late tonight into early Saturday. The front will become stationary over our region into early next week as the next storm system organizes over the plain states. && .NEAR TERM /THROUGH SATURDAY/... Key Messages: 1) Severe Thunderstorm Watch in effect for the NW corner of the CWA through 22Z/6 PM. 2) A line of strong-to-severe thunderstorms is expected to impact the mountains late tonight, with the threat decreasing eastward. 3) Very warm daytime temperatures approaching the low 90s today. As of 1025 AM EST Friday: 12Z regional observed soundings depict a rare case of the elevated mixed layer spreading much farther east than is typical, with near-dry adiabatic lapse rates from about 900 mb to near 500 mb atop a strong capping inversion. With dewpoints expected to remain in the mid/upper 60s into the afternoon, surface-based CAPE is forecast to increase to 3000-4000 J/kg across the CWA as the boundary layer warms this afternoon. However, the inversion will also create a considerable amount of inhibition. This cap is forecast to be strongest across the southern ~2/3 of the forecast area, where air parcels are very unlikely to reach their LFC...PoPs are less than 20%. The cap is forecast to be weaker north of I-40, but even there, confidence in convective development isn't great, especially in light of the ongoing cirrus shield downstream of TN/OH Valley convection, which will inhibit heating/lower the potential to overcome the cap to an extent. Having said that, cold pools associated with upstream convection may interact with the volatile environment over the northern zones by late afternoon to allow for some updrafts to get going, and PoPs in the 20-40% range appear warranted in the far north. IF any deep convection is able to initiate in our area, shear parameters are more than adequate for supercells and attendant threats of very large hail, isolated tornadoes, and damaging downbursts. The next chance for thunderstorms comes as a potential line of decaying convection leftover from the TN/KY area late tonight and into Saturday morning. At this point, modeled soundings are not too favorable with supporting the survival of this line much past the mountains. There is a strong cap in place east of the mountains that could hinder the line. There appears to be plenty of bulk shear, 40-60kts and elevated instability, but how it survives the mountains is to be seen. Though given the history of a MCS making a run for the CWA, it's likely to weaken. CAM guidance is not as impressive as previous runs either, continuing to reduce confidence in how the environment could support the line of storms. The Storm Prediction Center keeps a narrow slight risk for the TN/NC border for today, before tapering off to a marginal/general threat east of the TN/NC line. Timing appears to be well after midnight tonight and into the early hours of Saturday morning. Once this threat has dissipated, the remainder of Saturday appears to be much calmer. Expect very warm daytime highs today and Saturday and overnight temps remaining in the 60s and 70s. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/... As of 200 AM Friday... Key Messages: 1) Dry Weather Returns Briefly Saturday Evening into Saturday Night 2) Shower and Thunderstorm Chances Return Sunday Across the Western Zones with Better Coverage Expected on Monday 3) Above Normal Temperatures Stick Around Quasi-zonal flow will be in place aloft Saturday evening into Sunday before weak upper ridging builds over the region Sunday evening into late Monday. Upper shortwaves will track over the western Carolinas and northeast Georgia on Sunday and again on Monday. At the sfc, a cold front will be just south of the forecast area Saturday evening before reactivating as a warm front and lifting north across the southern half of the forecast area Sunday night into Monday morning. The front will then stall across the southern half of the forecast area Monday into Monday night. Although brief drying returns Saturday evening into Saturday night behind the cold front, daily chances for showers and thunderstorms return for the rest of the short term. The western zones will have the best chance for showers and isolated thunderstorms on Sunday so have chance (15% to 40%) PoPs across these zones with dry conditions continuing across the eastern zones. Global models generally agree that coverage will be better area-wide on Monday so have higher PoPs and thunder chances in place. Activity may decrease in coverage as it pushes east of the mountains so went with high-end chance to low- end likely (40% to 60%) PoPs across the western zones and low-end chance (15% to 30%) PoPs across the eastern zones. Have the highest thunder chances (30% to 50%) along and north of I-85 as convection may weaken as it pushes eastward. Shower and thunderstorms may linger across the western zones Monday evening into Monday night so maintained slight chance PoPs (15% to 24%) during this timeframe. Cannot rule out some strong to severe storms each afternoon/early evening as there will be plenty of deep layer shear to work with each day, ~40-50 kts, but confidence is low as guidance is not in agreement regarding the amount of or placement of instability each day. Highs each afternoon will end up ~4-7 degrees above normal with lows each night ending up ~8-12 degrees above normal. && .LONG TERM /TUESDAY THROUGH THURSDAY/... As of 230 AM Friday... Key Messages: 1) Shower and Thunderstorm Chances Continue through the Long Term with the Best Coverage Currently Expected on Wednesday 2) Above Normal Highs Linger through Tuesday Before Cooler and Below Normal Highs Return Wednesday into Thursday Weak upper ridging remains in place over the region through Tuesday before an upper low tracks out of the west Tuesday night into Wednesday, approaching the area on Thursday. Timing/location differences remain between the global models regarding the upper low so confidence on shower and thunderstorm chances/timing will be low throughout much of the forecast period. At the sfc, the aforementioned front in the short term will remain stalled over the southern half of the forecast area on Tuesday before lifting north across the forecast area Tuesday night into Wednesday. The sfc low pressure system associated with the upper low will approach out of the west on Wednesday before tracking across the forecast area late Wednesday into early Thursday. With the front stalled over the forecast area on Tuesday, another round of showers and thunderstorms are possible. However, models are not in great agreement regrading the coverage of activity on Tuesday so capped PoPs to chance (50% or less) area-wide. Better coverage of showers and thunderstorms arrives on Wednesday and may linger into Thursday. However, guidance is not in agreement on when moisture associated with the low pressure system will push out of the forecast area. The latest GFS shows precip pushing east overnight Wednesday into daybreak Thursday while the latest Canadian and ECMWF hang on to precip through the day Thursday. The Canadian keeps precip in place area-wide on Thursday while the ECMWF only keeps precip around across the northern half of the area. Thus, have the highest PoPs (50% to 70%) on Wednesday with PoPs on Thursday capped to chance (45% or less) across the northern zones. Strong to severe storms will be possible on both Tuesday and Wednesday ahead of the low pressure system thanks to 40-60 kts of deep layer shear in place and 1,200-1,800 J/kg of SBCAPE developing each afternoon/early evening. However, models all seem to be in agreement that severe weather is looking unlikely on Thursday thanks to more stable conditions developing behind the low pressure system. && .AVIATION /16Z FRIDAY THROUGH TUESDAY/... At KCLT and elsewhere: VFR conditions prevail through the TAF period at most terminals. Any BR forming over KHKY this morning should clear quickly once the sunrises. For this, a TEMPO for BR through 13z. Winds remain light to calm through daybreak and southerly, with KAVL remaining N/NW before turning S after 18z. Low end gusts could develop at a terminals east of the mountains after 00z, but confidence is low. There is a chance for some LLWS at KAVL between 12z-14z. There is a PROB30 for TSRA at most of the terminals except KCLT and KAND for a more robust line of TSRA overnight. Confidence is too low for a PROB30 at KCLT at this time as it appears that the line could weaken before reaching the terminal. Outlook: Active pattern of thunderstorm activity continues during the weekend and into next week, bringing possible temporary restrictions. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...AR NEAR TERM...CP/JDL SHORT TERM...AR LONG TERM...AR AVIATION...CP