textproduct: Charleston

WHAT HAS CHANGED

All sections have been updated

KEY MESSAGES

- 1) Daily thunderstorms are expected across southeast Georgia and southeast South Carolina today with rain chances increasing Tuesday and Wednesday.

- 2) A mid-week cold front will bring a threat of strong thunderstorms Wednesday afternoon, followed by cooler weather and gusty winds.

DISCUSSION

KEY MESSAGE 1: Daily thunderstorms are expected across southeast Georgia and southeast South Carolina this weekend and into early next week. An increase in rain chances is expected by the middle of next week, with cooler temperatures thereafter.

Today: Very little change in the pattern from the past few days with an upper level low parked over the Florida Peninsula. Moisture continues to stream are the upper low and into the area as PWATS continue to hover around 2 inches across the area. Given rather weak forcing aloft storms will likely be more isolated in nature focused along the slowly advancing seabreeze.

Tuesday: The aforementioned upper low across the Florida Peninsula is anticipated to drift north-northeast across the Southeast United States, eventually phasing with a longwave trough shifting across the Mid-Atlantic and Northeast mid-week. Forcing associated with this feature will support increased shower and thunderstorm activity, along with the potential for a few strong or marginally severe thunderstorms Tuesday. The presence of deep moisture (PWATS 2+ inches) could also produce a threat for localized heavy rainfall and minor flooding.

KEY MESSAGE 2: A mid-week cold front will bring a threat of strong thunderstorms Wednesday afternoon, followed by cooler weather and gusty winds.

A cold front is progged to push south across the forecast area as an upper trough digs into the Southeast. Model guidance has slowed the cold front's progression across the area to late Tuesday night through Wednesday evening. While the overnight/early morning arrival will limit the severe weather threat Wednesday morning, especially across southeast South Carolina, afternoon heating south of the front will destabilize the warm and moist airmass out ahead. This creates a risk for strong to severe thunderstorms Wednesday afternoon, primarily across southeast Georgia.

Following the front, an inland wedge pattern will set up, and cool and dry conditions will persist through the remainder of the week. High temperatures will top out in the upper 70s to lower 80s in southeast South Carolina and the low to mid 80s in southeast Georgia, roughly a few degrees below normal for late September. Gusty post-frontal winds of 25 to 30 mph are also likely on Thursday.

AVIATION /12Z MONDAY THROUGH FRIDAY/

Mostly VFR conditions prevail across the area. A few scattered showers and storms are occurring across coastal GA and SC which may result in temporary reductions to MVFR vsbys and ceilings. Overall shower and thunderstorm chances look very low for Monday afternoon and evening. Winds will remain light out of the northeast becoming easterly during the afternoon.

Extended Aviation Outlook: The main potential for flight restrictions will come from afternoon and evening showers and thunderstorms each day. The best chance of showers and thunderstorms is expected to come Tuesday into Wednesday as a cold front shifts across the area. Post-frontal gusty winds will likely impact the terminals Thursday.

MARINE

Today through Tonight: A decaying surface high pressure ahead of a slowly approaching cold front will continue the benign marine weather conditions across our local waters. Periodic showers and thunderstorms during this time may be capable of gusty winds and frequent lightning.

Tuesday through Saturday: Quiet marine conditions are expected Tuesday before a cold front pushes through Wednesday. In the wake of the front, an inland wedge pattern coupled with a deepening surface low off the Mid-Atlantic coast will drive a strong surge in northeasterly winds. Conditions will deteriorate Wednesday evening with wind gusts peaking near gale force Thursday evening. Small Craft Advisories will likely be needed, and Gale Watches/Warnings could be required. In addition, seas will build alongside the surge, peaking between 5-9 ft Thursday night. Conditions will begin to improve Saturday as the pressure gradient relaxes.

Coastal Flooding: We will need to keep an eye on the potential for minor coastal flooding Thursday as strong northeasterly winds combine with astronomical high tide. Current forecast for Charleston Harbor is 6.9 Ft MLLW.

CHS WATCHES/WARNINGS/ADVISORIES

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