Current Version Previous Versions: 1 2 3 4 5 6 7 8 9
Area Forecast Discussion
212 FXUS62 KGSP 241520 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 1120 AM EDT SUN JUL 24 2016 .SYNOPSIS... Broad high pressure will linger over the region through mid week. During the late week, a mid level disturbance is expected to slowly ripple over the forecast area. Moisture levels will gradually increase across the western Carolinas and northeast Georgia by the middle of the week as the region will remain on the warm side of a stalled mid Atlantic front. && .NEAR TERM /THROUGH TONIGHT/... As of 1100 AM EDT, southern tier dewpoints were boosted about a degree for this afternoon but this still leaves most of Elbert county with Heat Index values of 103 to 104 on average with just a sliver of 105 in the southern end. The forecast will mention up to 105 in the county but no Heat Advisory will be posted per collaboration with the surrounding offices. Regarding the storm potential, 55 dBZ core heights to 26 kft should be needed for severe storms to develop. Otherwise, as a trough in the higher-latitude westerlies continues to pull away from the East Coast today, upper heights will increase across the Southeast. In fact, short term model guidance depicts a small upper level high pressure center over western/ctrl NC this afternoon. Mid-tropospheric temps are quite warm within this bubble, as high as -4C at 500 hPa. Convective coverage should be a bit less than on Sat in light of these warming mid-level temps/poor lapse rates. Today`s highest chance pops will again be reserved for the high terrain. Mean cloud-bearing winds are expected to be out of the E/NE, thus any convection developing over the mtns will be carried away from the Piedmont, and pops drop off abruptly east of the mtns accordingly. Having said that, quite a bit of convection developed across the lower SC Piedmont and Midlands early Sat afternoon, with attendant outflows pushing north and initiating additional convection across the heart of the CWA throughout the afternoon. There are some hints in the latest mesoscale guidance that this could happen again, albeit perhaps on a smaller scale. Thus, slight chance pops will be carried outside the mtns, mainly south of I-40. Sufficient buoyancy and downdraft CAPE will yield a threat for a microburst or two. Additionally, SW flow in the low levels turning to E/NE in the mid/upper levels will yield very weak mean flow, so slow moving cells producing heavy rainfall will also be a concern. Max temps are expected to be a couple of degrees warmer than on Saturday in most areas, and heat indices are expected to range in the 100-104 range, mainly south of the I-85 corridor. Convection should diminish quickly again this evening, giving way to another unseasonably warm night. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... As of 230 AM Sunday: On Monday, H5 ridge centered over the western Atlantic as a mid level disturbance tracks west across the northern Gulf coast. Mostly clear morning sky conditions should result in steady warming, expected to reach the lower 90s east of the mtns by lunch. Temperatures are forecast to peak in the upper 80s within the mtn valleys to mid 90s along and east of I-85. Steady SE winds should keep dewpoints in the upper 60s to around 70 through the afternoon hours. The combination of the hot temperatures and RH around 50 percent should result in Heat Index values around 100 degrees east of the mtns. In addition, the hot and humid llvl conditions has resulted in interesting forecast soundings Monday afternoon. NAM soundings across the upstate of SC indicate CAPE values between 2500-2700 J/kg, LFC a little less that 5 kft, little to no late afternoon CIN, and around 2000 j/kg of DCAPE. I will forecast TSRAs to develop over the mtn ridges during the mid afternoon, then start to slide SE during the late afternoon to early evening. Areas along and east of I-77 should see the least coverage. Several of these storms will become quite tall, reaching to around 45 kft. Given the DCAPE and low shear, I would expect several damaging wet microburst with pulse thunderstorms. On Tuesday, the center of broad sfc high pressure will shift over AL as a lee trough develops across the Piedmont. The sfc pattern will result in light and steady downslope winds from the WSW. Forecast highs may peak around degree warmer than forecast for Monday. Dewpoints should range 2 to 3 degrees lower than values from Monday. Forecast soundings indicate moderate instability with weak capping east of the mtns. The forecast will continue to highlight high chc to likely across the TN border counties, fading to chc against the foothills. Foothill and Piedmont should verify well with schc pops for SHRAs and TSRAs. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... As of 245 AM Sunday...A broad H5 ridge on Wednesday will give way to a broad trough by Friday and Saturday. I will forecast diurnal chc PoPs across the CWA on Wednesday. However, the arrival of the trough would support greater coverage with less diurnal swings in coverage. I will gradually increase PoPs to high chc to low likely by Sat, keeping schc pops generally across the mtns during the overnight hours. High temperatures are forecast to range for 3 to 4 degrees above normal from Wednesday through the rest of the work week. On Saturday, high temperatures are forecast to range 2 to 3 degrees above normal. && .AVIATION /16Z SUNDAY THROUGH THURSDAY/... At KCLT/KAND/KHKY, With an upper ridge building over the area and warming temps aloft, chances for convection appear to be at their lowest in several days. Although isolated cells are expected this afternoon, the coverage should be sparse enough to preclude any convective mention attm. Winds are expected to remain light S/SW through the period. At KAVL/KGMU/KGSP, isolated to scattered convection is expected to develop once again Sunday afternoon, although coverage may tend to be a bit less than in recent days. The best coverage should be over the mtns, so a VCSH and PROB30 for TSRA is limited ti KAVL for the time being. Fog will probably redevelop in the mtn valleys tonight, although timing and the degree of restriction is still highly uncertain. MVFR conditions should be good enough at KAVL for the time being. Outlook: Isolated to scattered afternoon/evening showers and thunderstorms will continue across the mountains/piedmont through mid-week, with coverage increasing Tuesday into Wednesday. Morning fog and low stratus will be possible each day in the mountain valleys and also in locations that receive heavy rainfall the preceding afternoon/evening. Confidence Table... 15-21Z 21-03Z 03-09Z 09-12Z KCLT High 100% High 100% High 100% High 100% KGSP High 100% High 100% High 100% High 100% KAVL High 100% High 100% High 100% High 100% KHKY High 100% High 100% High 100% High 94% KGMU High 100% High 100% High 100% High 100% KAND High 100% High 100% High 100% High 94% The percentage reflects the number of guidance members agreeing with the scheduled TAF issuance flight rule category. Complete hourly experimental aviation forecast consistency tables and ensemble forecasts are available at the following link: www.weather.gov/gsp/aviation && .CLIMATE... RECORDS FOR 07-24 MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 96 1983 68 1985 71 1934 52 1966 1895 KCLT 100 1983 73 1938 78 2010 59 1947 1952 1883 KGSP 101 1952 70 1985 79 2010 59 1904 RECORDS FOR 07-25 MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 92 2010 68 2000 70 2012 51 1895 2005 2011 1987 2010 KCLT 101 2010 69 2000 79 2010 62 1947 KGSP 100 1995 72 2000 77 2010 57 1911 1890 && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...NED NEAR TERM...HG/JDL SHORT TERM...NED LONG TERM...NED AVIATION...HG/JDL CLIMATE...