textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Updated the aviation discussion for the 00Z TAFs.

KEY MESSAGES

1. Shower and thunderstorm chances return tonight, mainly west of I-26. Fog and low stratus may develop overnight, especially in the mountain valleys and in any areas that received appreciable rainfall today. 2. Heat risk will steadily increase through next week, with heat indices potentially exceeding 100 degrees across much of the Piedmont and foothills, especially by mid to late week.

DISCUSSION

Key message 1: Shower and thunderstorm chances return tonight, mainly west of I-26. Fog and low stratus may develop overnight, especially in the mountain valleys and in any areas that received appreciable rainfall today.

Dry conditions have returned across the forecast area this evening. A few showers and perhaps thunderstorms will be possible, mainly west of I-26 overnight. There will be no severe threat with any thunderstorms that manage to develop. Skies will clear overnight, but with low level moisture lingering, fog formation is possible, although the extent of this may be limited due to developing downslope flow. Fog will therefore be most likely across the Piedmont...especially in locations that see appreciable rainfall this afternoon...and in the usual fog-prone valleys beneath the mountains along the TN/NC border. Min temps will be 2-4 degrees above climo.

Key message 2: Heat risk will steadily increase through next week, with heat indices potentially exceeding 100 degrees across much of the Piedmont and foothills, especially by mid to late week.

An anticyclone and associated upper ridge will steadily intensify over the Miss and TN Valleys early this week while gradually shifting toward the central Appalachians during mid-week. This will result in building heat through the week, with temperatures expected to begin the week around 5 degrees above normal, ending the week around 10 degrees above climo...when ambient temperatures are forecast to reach the century mark across at least a portion of the Piedmont. Heat Index values of 100+ are forecast to impact the southern fringe of the CWA Monday and Tuesday...creeping N and W to encompass much of the Piedmont and foothills from Thu through next weekend. It should be said that confidence in the Heat Index forecast beyond Tue or so is very low due to the high sensitivity of dewpoint to the H.I. calculation...and the dewpoint forecast is very uncertain, as they often tend to mix out more than anticipated under the influence of strong anticyclones. While Heat Index for the next couple of days is forecast to be at least several degrees below climo Mon/Tue, values of around 105 are expected to creep into Elbert Co, GA tomorrow afternoon. In collaboration with NWS FFC, Elbert Co will be included in a Heat Advisory. Heat Advisories are likely to continue through the week...gradually expanding in coverage.

Those with outdoor plans, including holiday and recreation, should prepare for several days of elevated heat risk. Stay hydrated, take frequent breaks in air-conditioned or shaded areas, and never leave children or pets unattended in vehicles.

Otherwise, with anticyclonic flow increasing aloft, the atmosphere will become more subsident and suppressed in nature. This will tend to limit overall coverage of deep convection, with generally isolated-to-widely scattered activity expected each day across the mountains, and isolated-at-most coverage across the remainder of the area.

AVIATION /00Z MONDAY THROUGH FRIDAY/

At KCLT and elsewhere: Mostly dry and mostly VFR through the 00Z TAF period outside of the potential for mountain valley fog and low stratus as well as the potential for scattered SHRA/TSRA, mainly west of I-26. KAVL will have the best chance to see MVFR fog and IFR cigs develop overnight as this terminal saw the most rain today. Went ahead and maintained a TEMPO at KCLT for potential fog/stratus overnight but confidence is low as rain occurred around the terminal but not directly over it. Removed any mention of fog/stratus across the remainder of the terminals as very little rain, if any, occurred. Any fog/stratus that develops should lift around daybreak Monday. Although KAND and KAVL will have the best chance to see SHRA/TSRA develop in the vicinity tonight into Monday, confidence is too low on whether activity will track directly over the terminals. Thus, maintained dry conditions across all terminals through the 00Z TAF period. Winds at KAVL will be mostly N/NNW but could go light and VRB to calm overnight. Winds east of the mountains will gradually turn more NW/N overnight but could also go light and VRB to calm overnight. Winds east of the mountains will gradually turn NE throughout Monday.

Outlook: Diurnal showers and thunderstorms are expected mainly across the mountains through the workweek. Mountain valley fog/low stratus will be possible each morning.

CLIMATE

RECORDS FOR 07-02

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 93 1970 65 1943 70 2018 44 1988 1954 1931 KCLT 101 1931 64 1943 76 1991 56 2008 1970 1931 KGSP 101 1954 66 1943 77 1931 53 1899

RECORDS FOR 07-03

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 93 1970 65 1988 70 2018 50 2008 1897 1931 1937 1932 KCLT 99 1931 70 1988 76 1925 56 2010 KGSP 99 2016 70 1988 77 1925 56 1984 1970 1953

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

GSP WATCHES/WARNINGS/ADVISORIES

GA...Heat Advisory from noon to 8 PM EDT Monday for GAZ029. NC...None. SC...None.