Area Forecast Discussion
Issued by NWS Greer, SC

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000 FXUS62 KGSP 250005 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 705 PM EST Wed Feb 24 2021 .SYNOPSIS... A relatively dry cold front crosses our region from the northwest late tonight and Thursday, then stall to our south setting up an active weather pattern through the weekend. Waves of low pressure will cross from west to east into the start of next week. Expect dry high pressure to build over our area later next week. && .NEAR TERM /THROUGH THURSDAY/... As of 700 PM Wednesday: Gorgeous Wednesday across the area today, with clear skies expected for the start of the nighttime period as well. Near zonal flow aloft will keep thicknesses near the same through tomorrow. A moisture starved cold front will enter the region from the northwest tonight into Thursday morning. Enough low-level moisture will be in store along the TN border to activate precipitation development, mainly during the overnight hours. However, that will stay confined to the TN border and will likely remain dry elsewhere. Some cloud development will be in store early Thursday over most locations in the cwa, but should gradually dissipate after daybreak as dry CAA filters into the region, once the front sweeps across the cwa around 12Z Thursday. This will shift winds to come out of the N to NE by tomorrow afternoon as a sfc high follows behind the frontal boundary and sets up shop over the Midwest and OH Valley by the end of the period. The frontal boundary should stall just south of the cwa as a shortwave trough approaches the area from the west. No impacts are expect during the near-term, but mid- to high-level clouds will begin to increase by the end of the day Thursday. Temperatures will be slight above normal tonight with increasing clouds and elevated dewpoints. Max T`s will remain 5-10 degrees above normal, but will be a category below what we saw today for highs. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... As of 200PM Wednesday...we begin the short term with an essentially zonal pattern across the southeastern U.S. A 500mb shortwave trough ejects out of the Four Corners region and tracks eastward through the day on Friday. Despite a distinct decrease in amplitude, the trough remains visible in model output and should provide ample QG forcing, with cloud cover ramping up Thursday night and PoPs beginning to climb by the predawn hours Friday. Meanwhile, a strong high pressure system over the north Atlantic will begin funneling cold, dry air into the Carolinas from the east, developing a CAD-like wedge. By Friday afternoon, strong, WAA-induced upglide over this wedge should induce steady rainfall through the evening. Frozen precip will be a concern Friday morning, as the dry surface layer promotes wetbulbing. Notably, this effect may continue to drop surface temperatures even after sunrise as precip continues to ramp up in the morning. For now, looks like mainly wet snow, though as WAA continues to strengthen the warm nose, some locations will see a changeover to freezing rain in the late afternoon and evening. Saturday may then see a lull in this activity, as good forcing shifts eastward. Dropped to chance PoPs into the end of the short, as the warm front clears northward. Weak surface CAA and an eastward shift in the northeast high`s position should help to erode the wedge Saturday, with the MSLP signature vanishing by mid-afternoon. Temps should consequently jump higher on Saturday, perhaps into the mid/upper 50s. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... As of 230PM EST Wednesday...a weakening 500mb trough moves offshore Saturday night, while at the surface the now stalled frontal boundary to our north continues to produce modest PoPs overnight. A deep northern stream trough tracks out over the Great Lakes from Canada, and by early Sunday will begin to push the stalled frontal boundary southeast again. Consequently, anticipating another good chance for rainfall lasting through the day Monday, before the frontal boundary passes us again as a cold front. Highest QPFs still look to be in the SW Appalachians and Tennessee. Still a good bit of uncertainty looking past this system. The GFS is trending drier, with high pressure taking hold beneath a broad upper ridge. The ECMWF and CMC both trend wetter, with a southern stream shortwave promoting development of another surface low impacting our CWA late Tuesday into Wednesday. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... At KCLT and elsewhere: Expect VFR conditions to continue through the period. Mid- to Upper-level clouds will be in store across all TAF sites tonight and Thursday morning. Expect winds to come out of the SW, but shift as a dry cold front passes through the area by 12Z Thursday. Daytime heating and drier air filtering into the region should allow for much of the clouds to dissipate during the day. This will shift winds from the SW to the NW during the morning hours and turn out of the N and NE by Thursday afternoon. Clouds will begin to increase by the very end of the TAF period and could be the start of some isolated flight restrictions. Outlook: Deeper moisture returns late Thursday into early Friday ahead of another storm system. Widespread precip and associated flight restrictions are expected to develop on Friday and persist into the weekend and possibly extending into early next week. Confidence Table... 00-06Z 06-12Z 12-18Z 18-00Z 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 100% KGMU High 100% High 100% High 100% High 100% KAND High 100% High 100% High 100% High 100% The percentage reflects the number of guidance members agreeing with the scheduled TAF issuance flight rule category. Complete hourly experimental aviation forecast consistency tables are available at the following link: www.weather.gov/gsp/aviation && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...DEO NEAR TERM...CAC SHORT TERM...MPR LONG TERM...MPR AVIATION...CAC

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