Area Forecast Discussion
Issued by NWS Columbia, SC

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000 FXUS62 KCAE 211816 AFDCAE Area Forecast Discussion National Weather Service Columbia SC 216 PM EDT Mon May 21 2018 .SYNOPSIS... Moisture will remain high through the weekend with scattered showers and thunderstorms mainly in the afternoons and evenings each day. && .NEAR TERM /THROUGH TONIGHT/... Deep southerly flow around high pressure over the western Atlantic will keep a moist and unstable airmass across the region this afternoon. Models indicated weak upper energy moving northwestward across the area during the afternoon with moderate instability. Radar at 18Z indicated most of the convection over southern GA slowly moving northward...with isolated convection over the Midlands. Have continued pops in the 30 to 40 percent range. Locally heavy rainfall possible given anomalously high PWAT for this time of year and low cell movement. High temperatures still expected to reach the middle 80s. The severe weather threat appears low given weak shear. Convection should diminish early this evening with loss of heating. However, may see the chance for showers increasing again from the south toward daybreak as another weak short wave lifts northward across GA. Went with persistence for overnight lows in the 65 to 70 degree range. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... Tuesday and Tuesday night...Bermuda ridge continues offshore of the Carolinas with trough along the Gulf coast states. Deeper moisture appears to advect into the region from the Gulf coastal region Tuesday. Air mass should be moderately unstable. Although short wave energy appears weak guidance pops suggest scattered diurnally driven convection especially across the west closer to the upper trough. High Precipitable water near 2 inches continues threat for locally heavy rain. Wednesday...A northern stream short wave appears to move through the region late Tuesday night and Wednesday may be a trigger for showers and thunderstorms by early Wednesday. Convection may be more limited late in the day Wednesday across the west and north CWA with short wave moving to the southeast but still favor diurnally driven convection in weakly to moderately unstable air mass. Persistence forecast for temperatures. Max temperatures in the low to mid 80s and lows in the upper 60s and near 70. && .LONG TERM /THURSDAY THROUGH MONDAY/... With weak upper low still off to the west of the area, a southerly flow aloft will persist through the period. Longer range models still trying to indicate the potential for an area of low pressure to develop somewhere in the Gulf late this week and into the weekend. There is very little agreement in regards to any potential track or intensity. The 12z GFS has shifted west to west coast Florida. GEM model is similar to ECMWF with a low pressure system in the Gulf of Mexico late in the week. The bottom line regardless of the eventual solution is a continued somewhat wet pattern with mainly diurnally driven convection and near normal temperatures. && .AVIATION /18Z MONDAY THROUGH FRIDAY/... Mainly VFR conditions expected through this evening. Isolated to scattered convection already developing this afternoon, so have included VCSH. Restrictions will be possible late tonight/early Tuesday morning in fog/stratus due to abundant low level moisture. Have indicated cig/vsby restrictions at fog proned AGS/OGB. Winds will remain generally light from a south to southeasterly direction. The chance for convection may increase around daybreak as a weak upper level disturbance approaches the TAF sites from the south. However, showers and thunderstorms will increase in coverage toward the end of the TAF period as instability increases. EXTENDED AVIATION OUTLOOK...Unsettled weather will continue through Friday with periods of late night and morning IFR to MVFR ceilings and fog. Mainly afternoon and evening showers and thunderstorms will also continue as high moisture remains over the region. && .CAE WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. && $$

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