Area Forecast Discussion
Issued by NWS Greer, SC

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474 FXUS62 KGSP 300137 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 937 PM EDT Mon May 29 2017 .SYNOPSIS... A series of weak cold fronts will cross the area through mid week. Weak high pressure will make Thursday the drier day of the week. Expect a stronger cold front to reach our region over the weekend. && .NEAR TERM /THROUGH TUESDAY/... As of 930 PM: Updated PoP and overnight temps. Overall precip chances were reduced, but still reflecting the advancing blob of showers with embedded convection that is moving into the western CWFA from GA/TN. There is very little lightning seen with this activity, and it is appearing increasingly disorganized as it encounters more stable air. Though the activity NW of Atlanta looks healthier, it too is expected to diminish before it reaches us, for the same reason. Latest GLAMP guidance has trended toward more widespread fog in the early morning hours, which is plausible. Therefore this has been used to refine the fog wording in the grids. As was seen last night, any dense fog will likely be brief and/or patchy due to profiles that only marginally support it, particularly in light of overhead convective debris. Surface trough remains in place for tomorrow, and southwest flow aloft continues. This will will allow for another round of diurnal convection, possibly enhanced a tad with the proximity of the trough aloft. Best chances for Tuesday remain across the Piedmont (especially SC/GA where the trough will linger) and the SW mountains. Guidance is trending cooler for tomorrow but we`re warming up more than anticipated today so have erred on the warm side, but still right at seasonal normals. Lows tonight a handful or so degrees above. && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/... As of 200 pm Monday: At long last, the axis of the upper trough, that has been over the central Conus for what seems like ages, will finally push to the East Coast by the end of the short term. This will drag a weak cold front through our area on Wednesday. While this should provide a focus for deep convection Wed afternoon, coverage may not meet the expectations of a typical late-spring fropa. Progged mid-level lapse rates are very poor, while forecast soundings depict a well-mixed/relatively dry boundary layer. As a result, no short term guidance source depicts anything more than modest levels of CAPE Wed afternoon and pops will be advertised only in the 20-30% range across much of the area (maybe 40% in the high elevations near the Blue Ridge). Deep layer shear will remain somewhat respectable, so a severe storm or two cannot be ruled out, but the threat should be limited by the overall lack of robust buoyancy. By Thursday, guidance suggests weak but relatively dry high pressure should be building into the area, limiting diurnal destabilization. In fact, most guidance produces little or no qpf response across our area Thu afternoon. Pops will be limited to a slight chance across roughly the southern half of the area (closer to the departing frontal zone). Temps will generally remain close to normal, perhaps a degree or two above, through the period. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... As of 210 PM Monday: A deep SW flow out of the Gulf will develop Thursday night and persist into the weekend. The persistent upper level closed low and trough over eastern Canada will rotate and surge a bit further south during the weekend with axis roughly along the East Coast. A surface cold front will be pushed south with moderately strong high pressure dropping down from the western Great Lakes. This cold front will be the focus of more widespread convection as it reaches our region late Saturday night and Sunday morning. If this scenario occurs with front arriving in the cooler part of the day, this should prevent stronger convection. Of course, this is nearly a week away and timing of frontal passage could speed up or slow down. Some strong convection ahead of the cold front may reach the NC mountains Saturday evening before weakening Saturday night. Late Saturday is the best chance of severe with prefrontal forcing and effects of convective generation from diurnal max heating. Drier air should filter in from the north by late Sunday night. The front should stall out over Florida to start the upcoming week with drier weather for at least a couple of days. Max temps are forecast to be near normal and Min Temps forecast to be about 5 degrees above normal due to the cloud cover and higher moisture level preventing radiational cooling. && .AVIATION /02Z TUESDAY THROUGH SATURDAY/... At KCLT and elsewhere: The threat of impactful convection most likely has passed all the TAF sites this evening. Lingering stratiform rain may occur at the NC sites in the first 2 hrs or so, but otherwise the evening will be relatively settled. Some of the latest hi-res models do bring another round of precip into the area later tonight, the remnants of convection over AL/GA, though not likely causing troubles except perhaps MVFR vsby in rain. Weak low level convergence, and moisture trapped underneath nocturnal inversion, are expected to produce an area of IFR to LIFR stratus over the Piedmont, with some patchy IFR fog in areas with wet soils and/or in mtn valleys. This will take some time to burn off in the morning. TS chances for the afternoon are in the PROB30 range at all sites except KHKY. Outlook: A few afternoon and evening TSRA are possible again Wed, bringing periodic restrictions. Areas of morning fog and/or low stratus may potentially develop Wed and Thu mornings especially where RA fell the previous evening. Somewhat drier conditions are expected to end the work week as high pressure builds in. Confidence Table... 01-07Z 07-13Z 13-19Z 19-00Z KCLT High 95% Med 70% Med 70% Med 62% KGSP High 99% Med 72% Med 65% High 100% KAVL High 91% High 94% High 96% High 100% KHKY Med 78% Med 61% Low 59% High 100% KGMU High 92% Low 43% Low 56% High 100% KAND High 91% Med 71% High 81% 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 and ensemble forecasts 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...TDP/Wimberley SHORT TERM...JDL LONG TERM...DEO AVIATION...Wimberley

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