textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Updated the aviation discussion for the 12Z TAFs.

KEY MESSAGES

1. Dangerous heat continues east of the mountains through the Independence Day weekend before the heat gradually wanes next week. Those with outdoor plans for the holiday weekend should prepare for elevated heat risk. Stay hydrated, take frequent breaks in air-conditioned or shaded areas, and never leave children or pets unattended in vehicles. 2. Isolated to widely scattered diurnal showers and storms are expected mainly over the mountains for Independence Day, with chances increasing for all areas Sunday into much of next week. Per usual, a few storms could become strong to severe during peak heating hours, 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: Dangerous heat continues east of the mountains through the Independence Day weekend before the heat gradually wanes next week. Those with outdoor plans for the holiday weekend should prepare for elevated heat risk. Stay hydrated, take frequent breaks in air-conditioned or shaded areas, and never leave children or pets unattended in vehicles.

Despite the break down of the upper anticyclone, upper ridging will remain over the Southeast through this evening before shifting south of the Carolinas and northeast Georgia tonight into Sunday. This will allow oppressively hot and humid conditions to linger through the holiday weekend. Dewpoints will mix down into the lower to mid 60s for most locations east of the mountains this afternoon and early evening. Although these lower dewpoints may prevent some locations east of the mountains from reaching true Heat Advisory Criteria (which starts at 105 degrees), the "impact-based" Heat Advisory remains in effect from noon to 8 PM east of the mountains as many outdoor activities and events will take place in honor of Independence Day. Although high temperatures on Sunday are expected to be a few degrees cooler (relatively speaking), dewpoints will not mix out as much. Thus, another Heat Advisory may be needed for some, if not all, locations east of the mountains Sunday afternoon/early evening.

Although temperatures will finally abate next week, highs east of the mountains are still expected to climb into the lower to mid 90s each day. Unfortunately, the humidity will increase next week despite the return of "cooler" afternoon temperatures thanks to dewpoints ranging from the upper 60s to mid 70s each afternoon.

Key message 2: Isolated to widely scattered diurnal showers and storms are expected mainly over the mountains for Independence Day, with chances increasing for all areas Sunday into much of next week. Per usual, a few storms could become strong to severe during peak heating hours, with the main hazard being damaging wind gusts. Make sure you have multiple ways to receive warnings, especially if you have outdoor plans.

Although coverage of convection is expected to once again be best across the mountains today, the 00Z CAMs show the potential for some scattered convection to develop across the North Carolina Piedmont/Foothills late this afternoon into late this evening as the upper ridge retreats southward. If activity manages to survive long enough, convection could even make into the eastern South Carolina Upstate late this evening into the early overnight hours. Since confidence is much lower regarding convection surviving into the Upstate tonight, only added a 20% PoP across portions of the North Carolina Piedmont and Foothills for now. Confidence on convection developing over the North Carolina Piedmont/Foothills is low, especially with the 06Z NAMNest coming in dry. However, the 06Z HRRR still shows the potential for some scattered convection across the North Carolina Piedmont/Foothills. Hopefully we will get a clearer picture once the 12Z CAMs come in later this morning. Otherwise, coverage of mainly diurnal convection will increase for all areas Sunday into next week as the ridge remains south of the Carolinas and as persistent, weak upper troughing develops across the eastern CONUS. As we typically see during pulse convection season, a few strong to severe storms will be possible during peak heating hours each day through next week. Damaging winds would be the main hazard with any severe storms that develop.

AVIATION /12Z SATURDAY THROUGH WEDNESDAY/

At KCLT and elsewhere: Dry and VFR through the 12Z TAF period outside of mountain valley fog/low stratus and afternoon/evening shower and thunderstorm chances across the mountains. Once again fog and stratus are not expected to make it to KAVL overnight. SHRA/TSRA chances remain too low for a mention at KAVL. Winds will remain calm to light and VRB through the morning hours for most terminals. Winds will pick out out of the S/SW early this afternoon into late this evening, although KAVL may see VRB winds develop briefly late this afternoon. Winds will once again go calm to light and VRB late this evening into tonight across most terminals. KCLT will see S/SW'ly winds through the period. Cirrus will continue streaming over the terminals through the TAF period, with a few cumulus developing during peak heating hours today. Cannot entirely rule out some isolated SHRA/TSRA near KCLT late this afternoon into this evening but confidence remains too low to mention in the TAF.

Outlook: Mainly afternoon/evening shower and thunderstorm chances will expand to all terminals starting Sunday, lingering into much of next week. Low stratus and/or fog will be possible each morning, mainly in the mountain valleys.

CLIMATE

RECORDS FOR 07-04

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 97 1948 68 1976 70 2016 51 1986 KCLT 99 1993 70 1968 76 1993 55 1933 1955 KGSP 100 1993 70 1988 75 2018 58 2021 1996 1933

RECORDS FOR 07-05

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 96 1948 71 1976 70 2024 46 1967 2018 1933 KCLT 101 2024 66 1892 78 2024 57 1967 KGSP 101 2024 70 1976 78 2016 58 1967 1933 1892

GSP WATCHES/WARNINGS/ADVISORIES

GA...Heat Advisory from noon today to 8 PM EDT this evening for GAZ018-026-028-029. NC...Heat Advisory from noon today to 8 PM EDT this evening for NCZ035>037-056-057-068>072-082-502-504-506-508-510. SC...Heat Advisory from noon today to 8 PM EDT this evening for SCZ008>014-019-104>109.