textproduct: Charleston

WHAT HAS CHANGED

The Aviation Section has been updated to reflect the 12Z TAF issuance.

KEY MESSAGES

- 1) Rain chances will increase this week as we return to a more typical summertime pattern of diurnally driven showers and thunderstorms.

- 2) Afternoon heat index values could climb into the 105 to 110 degree range across the I-95 corridor Friday and Saturday.

DISCUSSION

KEY MESSAGE 1: Rain chances will increase this week as we return to a more typical summertime pattern of diurnally driven showers and thunderstorms.

Mid to upper level ridging will dominate over the southeastern states through Wednesday. At the surface high pressure will prevail over the Mid-Atlantic states. Between the high pressure at the surface and the resulting drier air aloft from the upper level ridging, PoPs will be meager at best through Wednesday. The sfc high pressure over the Mid-Atlantic will shift offshore Thursday into Friday and the upper level ridging will begin to break down. This will allow moisture to increase across the SC Lowcountry and southeastern GA, resulting in isolated to scattered showers/tstorms Thursday into Friday. A cold front is then forecast to approach the region this weekend, with numerous to widespread afternoon showers/tstorms in the forecast.

KEY MESSAGE 2: Afternoon heat index values could climb into the 105 to 110 degree range across the I-95 corridor Friday and Saturday.

The pattern remains summer-like late week with mid-upper lvl ridging across the Southeast United States and sfc ridging extending across the western Atlantic. A southerly sfc flow will help advect higher dewpts across the local area while ample sunshine occurs with deep- layered high pressure in place, setting up hot and humid conditions across Southeast South Carolina and Southeast Georgia this weekend. Latest guidance supports afternoon highs in the mid-upper 90s along with low-mid 70 dewpts residing along the coastal corridor Friday and Saturday. The combination of heat and moisture could yield heat index values up to 105-110 degrees Friday afternoon and Saturday afternoon, prior to diurnally driven shower and/or thunderstorms. Should these temps/dewpts become realized, Heat Advisories could eventually be required, particularly along and east of the I-95 corridor. Precip coverage and clouds should limit warmer sfc temps and heat index values late weekend into early next week with a front possibly approaching the region.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

VFR conditions will prevail at CHS/JZI/SAV terminals through the 12Z TAF period.

Extended Aviation Outlook: VFR conditions are expected to prevail at CHS/JZI/SAV terminals. However, brief flight restrictions are possible with afternoon showers and/or thunderstorms on Thursday and Friday.

MARINE

Today and Tonight: A weak cold front will approach from the north, likely stalling and/or dissipating prior to or near coastal waters off the Charleston County Coast this afternoon. Marine conditions are expected to remain below Small Craft Advisory levels as this process unfolds, but southeasterly winds up to 10-15 kt could tip east-northeast across South Carolina waters this afternoon, prior to returning to southeast tonight. Seas will generally range between 2- 3 ft.

Wednesday through Saturday: Marine conditions should remain below Small Craft Advisory criteria across local waters throughout the week along the western edge of Atlantic high pressure. However, modest surges of southerly winds can be expected each day/evening, with highest winds anticipated near the land/sea interface where a sea breeze circulation occurs each late morning/afternoon. Wind speeds should generally top out near 15-20 kt. Seas will generally range between 2-3 ft throughout the week.

CHS WATCHES/WARNINGS/ADVISORIES

GA...None. SC...None. MARINE...None.