textproduct: Charleston

WHAT HAS CHANGED

Aviation.

KEY MESSAGES

- 1) Periodic showers and thunderstorms are expected to continue through the weekend.

DISCUSSION

KEY MESSAGE 1: Periodic showers and thunderstorms are expected to continue through the weekend.

Today: Fairly quiet weather conditions should continue through the morning as the initial disturbance exits and weak ridging briefly develops aloft. Clear skies combined with strengthening southwesterly flow will yield afternoon temperatures in the low to mid 90s. This should support moderate instability by the afternoon, particularly across southeast Georgia and locations west of the I-95 corridor.

Multiple rounds of showers and thunderstorms will likely begin on late Thursday afternoon/evening as anomalously high moisture from the remnant circulation associated with Arthur moves northeastward across central Georgia toward the South Carolina Midlands and Upstate. 00Z.HREF indicates that initial development should be favored across central and southeast Georgia late Thursday afternoon/evening, with showers and thunderstorms spreading towards the South Carolina Lowcountry overnight into Friday morning. Forecast soundings indicate increasing (roughly 30-40 knots) values of deep layer shear this evening into overnight as the remnant circulation passes nearby. Low-lvl winds could also become locally backed east, or northeast, of the remnant circulation overnight. This would increase low-lvl shear and briefly enhance the tornado potential, especially across the interior southeast Georgia overnight.

However, instability will be the primary limiting factor overnight as SBCAPE values remain well below 1000 J/kg. Nevertheless, the combination of tropical moisture, relatively strong flow, and organized storm motions will support a risk for damaging wind gusts. Also, a brief tornado cannot be ruled out, particularly with isolated storms developing near the remnant circulation. Thus, SPC has highlighted the entire region in a Marginal Risk (Level 1/5) today for severe weather. Localized flooding of poor-drainage and low-lying areas will be also be possible, especially where storms repeatedly track over the same locations.

Friday: The remnant circulation should shift away from the region in the morning, and attention will turn towards the cold front settling southward towards the region. Assuming sufficient recovery behind the overnight convection, strong surface heating and surface dewpoints in the low to mid 70s could produce a moderately unstable afternoon environment. Expect showers and thunderstorms to develop along the aforementioned cold front and residual outflow boundaries. The primary hazard will again be damaging wind gusts. The front should slowly pass through the region overnight.

Saturday and Sunday: The aforementioned front should slide offshore on Saturday morning as a few showers and thunderstorms linger near the coastline. Thereafter, the typical summertime pattern will dominate the forecast as the daily chances for showers and thunderstorms initiating along the afternoon seabreeze return. However, it's important to note that coverage should be much less than Thursday and Friday. Otherwise, afternoon highs will warm into the upper 80s to low 90s.

AVIATION /12Z THURSDAY THROUGH MONDAY/

Prevailing VFR conditions through 12Z Friday. Winds will increase out of the SW this morning, becoming gusty for much of the day. Wind speeds/gusts should decrease a bit by this evening.

A cluster of showers/tstms may move into southeast GA later this afternoon, affecting KSAV. Elsewhere, probabilities are too low for TAF inclusion. Considerably better forcing will develop overnight as the remnants of TS Arthur move northeast through the SC Midlands and Pee Dee Regions. Although it still appears that the greatest coverage/intensity of showers will remain west of the terminals, there is a pretty good chance that we'll at least see scattered showers moving into the terminals late tonight.

Extended Aviation Outlook: VFR conditions should largely prevail through the weekend, with brief periods of flight restrictions possible with any showers and thunderstorms.

MARINE

High pressure will remain off the coast while the remnants of TS Arthur move through the SC Midlands into eastern NC later tonight. A tightening SW gradient will occur over our waters, with the strongest winds after midnight tonight through Friday afternoon. We have Small Craft Advisories for all waters except SC offshore.

Marine conditions will subside Saturday with no additional concerns through the weekend. Another front could approach the area on Monday, potentially leading to increasing winds and seas.

Rip Currents: Increasing swells and gusty winds will lead to a Moderate risk for rip currents at Charleston County beaches Friday.

CHS WATCHES/WARNINGS/ADVISORIES

GA...None. SC...None. MARINE...Small Craft Advisory from midnight tonight to 4 PM EDT Friday for AMZ340. Small Craft Advisory from 2 PM this afternoon to 8 PM EDT Friday for AMZ360. Small Craft Advisory from 8 PM this evening to 8 PM EDT Friday for AMZ362. Small Craft Advisory from 2 AM to 5 PM EDT Friday for AMZ364. Small Craft Advisory from 2 AM to 8 PM EDT Friday for AMZ384.