textproduct: Greenville-Spartanburg

SYNOPSIS

Daily thunderstorm chances continue through the week and into the weekend. A few storms could produce damaging wind gusts and localized flash flooding. Hot and humid conditions stick around through most of the week.

NEAR TERM /THROUGH WEDNESDAY/

As of 110 PM EDT Tuesday: Another day of muggy weather and pop-up convection as the southeast remains under broad flow aloft. A strong Bermuda high remains parked over the Atlantic and moves a bit westward, increasing moisture advection from the south. Not much change in the amount of moisture already in the area as guidance keeps PWATs at or just above the 2.00 inch mark. For today, another round of the typical showers and thunderstorm activity starting over the mountains and eventually making its way east. CAM guidance shows more activity over the mountains with higher chances (55-80%), especially over the ridgetops. East of the mountains, PoPs max out in the 40-60% range during the typical peak heating time frame. Given the amount of moisture with the higher PWATs, any storm that can fire off has the potential to produce locally higher rain rates. This could lead to an isolated and very local flash flooding threat. Overnight, the PoPs continue to decrease, but cannot rule out a pop- up shower or thunderstorm given the moist environment. There could also be a few areas with low-level stratus developing near sunrise, but should dissipate quickly after the sun comes up. For Wednesday, the surface high continues to migrate further west, bringing more of a S/SW surface winds and even more moisture advection. The location of the high could help to direct activity into the areas of showers and thunderstorms along the mountains. However, elsewhere also has a chance (40-60%). Temperatures remain in the low 90s (mid 90s further south) with the heat index increasing into the upper 90s. A few locations in the southern zones could see HI of 100-103 today, but remains below any Heat Advisory criteria.

SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/

As of 1145 AM EDT Tuesday: The rest of the work week should be more of the same...typical hot and humid summertime with mainly diurnal storms both days...as a westward extension of the Atlantic subtropical ridge keeps us insulated from whatever happens with the system moving westward along/off the northern Gulf Coast. The forecast will feature an above-climo precip probability over the area, particularly the mountains, where differential heating will provide a focus for convection. The usual isolated pulse-severe storm threats will apply, and heavy rain could also be a problem. Fcst soundings show deep warm cloud depths and slow-moving storms, but the precipitable water will not be quite as high as the past few days, so the flash flood potential looks marginal for now. Temps will continue to run 3-5 degrees above normal, but the apparent temps over the Piedmont should stay below Advisory criteria Thursday and Friday.

LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/

As of 1225 PM EDT Tuesday: The latest model blend suggests the big story this weekend and into early next week will be the heat, as part of the Atlantic subtropical ridge breaks off and moves slowly west across the Deep South. In spite of nothing to suppress the deep convection, temps will remain on the order of five degrees above normal, while tropical moisture remains in place, keeping the dewpoints in the lower 70s. This combination is forecast to push the apparent temps up into the Advisory range each day from Saturday onward across the lower Piedmont and the Charlotte metro area/western Piedmont, even with mixing down the dewpoint from the NBM by a couple of degrees. Note that none of this is out of the ordinary for July. Confidence is marginal at this point anyway, because there is much on the mesoscale that could derail this potential, such as the weak upper wave moving past to our north on Saturday and then a more active convective regime Sunday into Tuesday as the upper high to our south oozes farther west and flattens more, possibly bringing the MCS track farther south to where it would affect the western Carolinas more directly. It's not until Monday/Tuesday when we keep precip chances going round the clock, though, because of a better signal for something going on aloft to sustain the convection overnight. Through the period, pulse severe storms and isolated flash flooding will be possible each day, which is also more or less typical for July.

AVIATION /17Z TUESDAY THROUGH SATURDAY/

At KCLT and elsewhere: A mix of VFR and MVFR conditions through the TAF period as the area remains in a typical summer pattern. Increased moisture keeps lower SCT/BKN stratus around through most of the period. With convection already popping up over the mountains, will have a TEMPO at all sites except KAND for this afternoon. Winds remain light and out of the SE and become VRB/calm overnight. There is also the chance for another round of BR at KAVL/KHKY during the morning hours. Heading into Wednesday, similar pattern as today with TSRA chances toward the end of the TAF period and a PROB30 at KCLT. Winds pick up later in the morning and turn more southerly. There is a very low chance for a brief g15 at KCLT in the afternoon, but will not prevail at this time due to low confidence.

Outlook: Thunderstorm chances each afternoon/evening. Low stratus or fog are possible each morning in mountain/river valleys.

GSP WATCHES/WARNINGS/ADVISORIES

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