textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

The aviation discussion has been updated for the 12Z TAFs.

KEY MESSAGES

1. High temperatures well below normal today, with spotty showers and isolated afternoon storms. Temperatures warm closer to normal Wednesday, with diurnal convection confined to far western areas. 2. A return to hot and drier conditions is expected during the latter half of the week. A cold front will approach from the north and bring higher rain chances over the weekend.

DISCUSSION

Key message 1: High temperatures well below normal today, with spotty showers and isolated afternoon storms. Temperatures warm closer to normal Wednesday, with diurnal convection confined to far western areas.

Spotty showers will continue across the area this morning within easterly flow regime...especially across the heart of the CWA. The relatively cool ENE flow will persist through the day, as inverted surface ridge gradually weakens. Having said that, drier air is forecast to begin filtering into the CWA from the ENE later today. Thus, after widespread morning low cloud cover, portions of the NC Piedmont are expected to begin scattering out during the afternoon, while locations along the NC Blue Ridge, and much of the Upstate and northeast GA may not completely clear out before sunset. As such, the warmest temps (mid-80s) today are forecast along/east of I-77, while forecast maxes across most of the remainder of the area (excepting the mountains along the TN border) are about 10 degrees below climo. Moisture and instability will be sufficient for convection across the southwest 1/2-1/3 of the CWA, and afternoon PoPs (mainly 30-50%) are largely confined to those areas. A small risk of excessive rainfall will exist, mainly in locations across the southwest 1/3 that have received heavy rainfall over the past four days.

A weak surface ridge will remain over the area into Wed, but moisture will become increasingly shallow, with clouds more likely to scatter earlier in the day, and the air mass will quickly modify in the July sun. Temperatures are forecast to warm to near normal Wed. Moderate instability developing across the western part of the area is expected to allow for diurnal convective development across the western 1/3-1/4 of the area.

Key message 2: A return to hot and drier conditions is expected during the latter half of the week. A cold front will approach from the north and bring higher rain chances over the weekend.

Upper ridging will return with a vengeance to end the week, with above-normal temperatures forecast Thursday and Friday. Afternoon Heat Index values may reach 100+ across southern and eastern Piedmont areas both days...although confidence is low at this time. Diurnal convection is expected to be largely confined to the mountains Thu and Fri, with mostly isolated coverage expected Thu, and more like solid scattered activity forecast for Fri.

The global models generally agree in depicting falling heights across the East over the weekend, with an associated frontal boundary forecast to enhance (mainly) diurnal convective chances Saturday and Sunday, with a more typical diurnal convective cycle expected to return early next week. Lower heights should result in temperatures slightly cooling to around normal.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

At KCLT and elsewhere: Spotty showers linger across the Terminal Forecast Area this morning. If a SHRA happens to move over a TAF site, there will be a brief period of 2-4SM visby, but chances for a direct hit on a terminal are too low to include a TAF mention at this time. IFR cigs have developed across the upstate SC terminals, with mostly MVFR at the NC sites. With drier air filtering into the area on ENE winds of 5-10 kts, chances for IFR are quickly diminishing at the NC terminals, and will feature continued MVFR there until improvement to VFR occurs during the afternoon. Otherwise, IFR should improve to MVFR late this morning at the Upstate terminals, with improvement to VFR expected during mid/late afternoon. Scattered showers and perhaps some TS are expected to develop across the SW half of the area this afternoon...as locations across the NE half (i.e., KHKY and KCLT) should be too stable for convective development. Prob30s for TSRA are advertised at KAND and KGMU, with VCSH at KGSP and KAVL. Low clouds should finally scatter and any convection dissipate no later than mid-evening. Generally expect VFR to continue through tonight, but redevelopment of fog and/or low cigs can't be ruled out, especially across western areas. For now, overnight/early morning restrictions are limited to MVFR visby at KAVL.

Outlook: Drier conditions are expected to continue into Wednesday. Typical mid-July coverage of diurnal convection is expected Thursday through the end of the week. Low stratus and/or fog will be possible each morning, mainly in the mtn valleys.

GSP WATCHES/WARNINGS/ADVISORIES

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