textproduct: Charleston

WHAT HAS CHANGED

Aviation section updated for the 12Z TAFs and fog section of key message 1.

KEY MESSAGES

- 1) Warming temperatures and mostly dry conditions today. Rain chances will then gradually increase this weekend and especially by early next week.

DISCUSSION

KEY MESSAGE 1: Warming temperatures and mostly dry conditions today. Rain chances will then gradually increase this weekend and especially by early next week.

Recent runs of the HRRR indicated that sfc condensation pressure deficits are forecast to lower below 3 mbs across the I-26 corridor during the pre-dawn hours. The forecast has been updated to add a mention of patchy fog for portions Dorchester, Berkeley, and Charleston Counties early this morning. Any fog that develops should dissipate during the first hour or two of sunshine.

Today, the forecast area will remain between a closed low over central FL and a H5 ridge axis running west to east across NC. Forecast soundings indicate a dry mixed layer with weak lapse rates between 800-500 mb through this afternoon. The forecast will remain dry today. High temperatures are forecast to range in the low to mid 90s this afternoon.

Convection-allowing models show a band of thunderstorms developing from the Midlands east across the Pee Dee region late this afternoon into this evening ahead of a sfc trough. These storms should push south, but should weaken as they reach an increasingly stable environment across SE GA and the Lowcountry. The forecast will feature a tier of SCHC PoPs across inland SC for showers and thunderstorms this evening. Any deep convection should dissipate before midnight. Low temperatures should range between 70-75 degrees.

The overall pattern will change this weekend as a weak cold front approaches from the north. Transport of deep moisture will drive precipitable water values up to 2.1-2.3 inches by Saturday evening. This set up will favor unsettled conditions and increased rain chances this weekend. Given the moisture-rich airmass and the presence of rounds of convection (primarily in the afternoon and evenings), there will be at least a low end threat for locally heavy rainfall. However, minimal shear and modest instability will limit the severe weather threat.

An unsettled pattern could continue into the middle of next week as a stronger cold front advances across the area.

AVIATION /12Z FRIDAY THROUGH TUESDAY/

12Z TAFs: Any ground fog this morning should dissipate during the first hour or two of daylight this morning. VFR conditions with light northwest winds this morning. A weak sea breeze should advance across the terminals between 19-20Z, turning winds from the southeast. Recent runs of the HRRR indicates that isolated showers and thunderstorms this evening, greatest chance across KCHS and KJZI. The coverage appears too limited to mention in the TAFs at this time.

Extended Aviation Outlook: Rain chances are expected to increase late this weekend and into early next week which could result in periodic flight restrictions.

MARINE

Today and tonight: Light northeast winds this morning should turn from the southeast this afternoon following the sea breeze. Winds may veer from the southwest tonight, speeds less than 10 kts. Wave heights should continue to diminish today, settling to around 2 ft tonight.

Saturday through Wednesday: Winds and seas are expected to remain well below Small Craft Advisory thresholds through the period. Winds will be 10 knots or less for much of this period, with seas generally in the 2-3 ft range. The main forecast concern will be increasing coverage of showers and thunderstorms across the local waters, especially early next week.

CHS WATCHES/WARNINGS/ADVISORIES

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