textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Updated the aviation discussion for the 12Z TAFs.

KEY MESSAGES

1. Hot and humid conditions stick around this week, especially east of the mountains. Those with outdoor plans should stay hydrated and take frequent breaks in air-conditioned or shaded areas. Do not leave children or pets in unattended vehicles. Car interiors will reach lethal temperatures in a matter of minutes. 2. Diurnal convection can be expected area-wide again today with coverage ranging from scattered to numerous. Convection becomes more confined to western North Carolina the rest of the workweek before a cold front potentially brings convective chances back to all areas this weekend. A few severe storms are possible during peak heating each day, with the main hazard being damaging wind gusts. Make sure you have multiple ways to receive warnings, especially if you have outdoor plans.

DISCUSSION

Key message 1: Hot and humid conditions stick around this week, especially east of the mountains. Those with outdoor plans should stay hydrated and take frequent breaks in air-conditioned or shaded areas. Do not leave children or pets in unattended vehicles. Car interiors will reach lethal temperatures in a matter of minutes.

Bermuda High in the western Atlantic will allow for hot and humid days and warm and muggy nights this week, especially east of the mountains. Highs each afternoon east of the mountains will climb into the low to mid 90s. Both high and low temperatures will end up around 4-8 degrees above normal area-wide through most of the period, although slightly cooler temperatures will return behind a cold front on Sunday, allowing temperatures to range from near normal to just a few degrees above normal.

Although heat indices may flirt with Heat Advisory criteria again today across the Upper Savannah River Valley and the around the Charlotte Metro area, thinking is that afternoon convection should once again help limit heat indices. Thus, a Heat Advisory was not issued for this afternoon/evening. Luckily heat indices should remain below advisory criteria (<105 degrees) the remainder of the week.

Key message 2: Diurnal convection can be expected area-wide again today with coverage ranging from scattered to numerous. Convection becomes more confined to western North Carolina the rest of the workweek before a cold front potentially brings convective chances back to all areas this weekend. A few severe storms are possible during peak heating each day, with the main hazard being damaging wind gusts. Make sure you have multiple ways to receive warnings, especially if you have outdoor plans.

A weak upper ridge off the southeast coast in the western Atlantic will work together with an upper trough extending from the Midwest to the ArkLaTex region to funnel rich Gulf moisture into the Southeast through tonight. This will allow for another day of scattered to numerous showers and thunderstorms this afternoon and evening. With a similar environment in place compared to yesterday, the westward expansion of the SPC Day 1 Marginal Risk for Severe Weather is warranted. The aforementioned upper ridge will gradually strengthen while building north and westward Tuesday into Thursday. This should allow convection to be shunted northward, getting confined to mainly western North Carolina for the rest of the workweek. A Marginal Risk for Severe Weather was introduced for a good chunk of western North Carolina for Tuesday and again this makes sense as 1,500-2,500 J/kg of SBCAPE and a slight uptick in deep layer shear (15-20 kts) could allow for more slightly organized convection. A similar environment can be expected each day through Friday keeping a low-end threat for severe storms around. The main hazard with any severe storms that develop during the workweek will be damaging wind gusts. A cold front will impact the region this weekend, potentially allowing convection to return for all areas as well as keeping a low-end severe threat around. However, it's still a bit too early to get specific on exact details.

AVIATION /12Z MONDAY THROUGH FRIDAY/

At KCLT and elsewhere: Dry and VFR through the 12Z TAF period outside of patchy morning fog/low stratus and afternoon/evening TSRA. Any fog and low stratus that developed overnight will lift shortly after sunrise. Another round of TSRA can be expected this afternoon/evening. Maintained PROB30s for TSRA and associated restrictions across the SC terminals and at KCLT as confidence on activity tracking directly over these terminals is low. Upgraded to TEMPOs at KAVL and KHKY for TSRA and associated restrictions as confidence is higher that these terminals will see direct impacts. KAVL should see another round of fog/low stratus develop overnight so have IFR cigs and vsbys mentioned towards the end of the TAF period. KHKY could also see fog develop overnight but confidence is low. Overnight fog and low stratus development will depend heavily on how much rain occurs over KAVL and KHKY today. Cirrus will continue streaming over the terminals through the period ranging from FEW to SCT this morning and SCT to BKN this afternoon/evening. Another round of cumulus will develop today during peak heating hours. Winds will be mainly light to calm and VRB through the morning hours before picking up out of the S/SW this afternoon, ranging from 4-8 kts. Calm to light and VRB winds return this evening into tonight but locations east of the mountains could see a light SW wind at times.

Outlook: Mainly afternoon/evening shower and thunderstorm chances return for Tuesday. The pattern remains unsettled the rest of the week but confidence is low on how exactly shower and thunderstorm chances will unfold. Low stratus and/or fog will be possible each morning in the mountain valleys and in locations that see appreciable rainfall the previous afternoon/evening.

GSP WATCHES/WARNINGS/ADVISORIES

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