textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

The wet and cool forecast continues through the Memorial Day holiday weekend. Wet and near normal through the rest of the period.

KEY MESSAGES

1. A cold front will drop down from the northwest tonight, ushering in a change in our weather for the Memorial Day weekend. The new pattern will support a period of cooler and more unsettled weather that could ultimately put a dent in our drought as it persists into the middle of next week. At this time, the risk of severe thunderstorms and flooding rain appears low.

DISCUSSION

Key message 1: A cold front will drop down from the northwest tonight, ushering in a change in our weather for the Memorial Day weekend. The new pattern will support a period of cooler and more unsettled weather that could ultimately put a dent in our drought as it persists into the middle of next week. At this time, the risk of severe thunderstorms and flooding rain appears low.

Convection ramping up across the area and will continue into the evening. Despite the cloud cover, instability is increasing with 1500 J/kg of CAPE across most of the area. Bulk shear is weak and the best DCAPE is off to our east. Can't rule out a few strong or possibly even a severe storm, but the overall chance is low. Some brief, heavy rainfall is possible with any storm, but unless there is some training, the overall flood threat is low as well.

Once the front slips southward overnight, a sfc high over eastern Canada will nose down east of the mtns and establish a cold air damming wedge across the region by daybreak Friday. Developing low level isentropic upglide early in the day should develop enough low cloudiness to lock in the cooler air mass that will be noticeable compared to our week thus far. For now, our forecast has high temps mainly in the 70s east of the mtns, undercutting what is in the NBM by several degrees, but that could easily be ten degrees too warm if we end up with extensive light rain. The guidance continues to suggest the wedge is likely to persist through Saturday even as the transitory parent high moves off the Canadian Maritimes. Temps were once again lowered from the model blend. Support for CAD fades Sunday as the southwesterly flow aloft increases.

From that point onward, unsettled weather will continue as the Gulf remains open with a mean upper trof axis over the srn Plains/MS Valley region and a mean ridge off the East Coast. So, from Memorial Day onward, we are looking at a favorable period of above climo precip probs and rainfall coverage. If this persists as indicated by some guidance, we could eventually get to the point where flash flood risk creeps upward, but for now we will manage expectations.

AVIATION /18Z THURSDAY THROUGH TUESDAY/

At KCLT and elsewhere: Convection popping up across portions of the area with more coverage expected through the afternoon as a backdoor cold front drops into the area. Have TEMPOs and PROB30s to cover this activity. Convection lingers into the evening before becoming more showery or stratiform overnight. Initially, restrictions will be limited to the convection; however, as the front crosses the area, MVFR then IFR clouds move in from the NE. MVFR vsby restrictions develop overnight as well. Cold air damming conditions set in Fri with IFR cigs and MVFR vsby and PROB30s for LIFR cigs and IFR vsby with shra continuing. Generally SW wind, NW at KAVL, this afternoon becomes N to NE this evening and continues into Saturday.

Outlook: Cold-air damming persists thru Saturday. The CAD will likely produce widespread MVFR to IFR ceilings into Saturday. Periods of mainly diurnal convection will also continue atop the CAD wedge and into next week, even as the CAD erodes. The potential for overnight fog/low clouds will increase through the period as well.

GSP WATCHES/WARNINGS/ADVISORIES

GA...None. NC...None. SC...None.