textproduct: Charleston

WHAT HAS CHANGED

The Aviation section has been updated for the 12z TAF. Recent trends over the past several hours suggest the severe threat may be decreasing, but will continue to monitor throughout the morning.

KEY MESSAGES

- 1) Scattered showers and thunderstorms will accompany a cold front today. A few thunderstorms could become severe.

DISCUSSION

KEY MESSAGE 1: Scattered showers and thunderstorms will accompany a cold front today. A few thunderstorms could become severe.

A somewhat slow moving cold front will approach the region from the northwest, advancing southeastward across the forecast area this evening. Some breaks in the cloud cover through the morning will allow the sunshine to aid in rather quick destabilization of the atmosphere. Forecast soundings indicate that MLCAPE could peak between 1100-1400 J/kg in the early to mid afternoon across southeast South Carolina and about 600-900 J/kg across southeast Georgia. The most favorable environment for strong to severe storms currently appears to be across the Tri-County area as this is where forcing for ascent is greatest, although a non- zero risk will still exist elsewhere.

Deep-layer bulk shear around 35-45 kt will support organized convection. DCAPE values this morning will near 900 J/kg, decreasing this afternoon as the atmosphere moistens. As a result, any storms that develop earlier in the day will have the potential to tap into a relatively favorable downdraft environment. That being said, the primary hazard will be damaging wind gusts, however isolated hail cannot be ruled out.

Guidance continues to differ regarding the coverage of showers and thunderstorms ahead of the approaching front. The HRRR is unimpressive, only depicting isolated showers/storms within a roughly 4-5 hour window this evening between 5-9 PM across the Low Country. Other CAMs have shown a similar trend, showing the greatest coverage across the Tri-County area, with the potential for the initial showers/storms to initiate as early as 1 PM. There are still solutions that show storms developing mainly along the sea breeze, ahead of the front, from the Tri- County area south to Beaufort, and into Savannah. Will have to monitor trends to see how this pans out today, however most models are quick to end convection from north to south after 8-10 PM tonight.

AVIATION /12Z MONDAY THROUGH FRIDAY/

11/12z TAF Discussion: A mix of ground fog and low stratus has been reported at the terminals early this morning, but should lift by 12z. The risk for tstm impacts will increase late afternoon and early evening with the approach of a cold front and a possible interaction with the afternoon sea breeze. There is increasing confidence that KCHS and KJZI will see direct impacts from TSRA. However, PROB30 has been introduced at KSAV due to lesser confidence, as various CAMs show convection to be greater in coverage across SE SC and only isolated across SE GA. The arrival of the front between 00-03Z Tuesday will bring elevated northeasterly winds along with gusts through the night. Ceilings could lower again late tomorrow night, with signals of MVFR or even IFR levels possible, however the timing is too far out to include specific details at this time.

Extended Aviation Outlook: A cold front could bring brief flight restrictions due to showers and thunderstorms Wednesday into early Thursday.

MARINE

Today and tonight: Winds will gradually increase ahead of an approaching cold front today. The front will advance southward across the waters late this evening. There will be a surge of winds and building seas behind the front leading to Small Craft Advisories, which have been issued for all marine zones except for the Charleston Harbor.

Extended Marine: A cold front moving off our coast Tuesday morning will be causing gusty NE winds and elevated seas. Therefore, we have Small Craft Advisories in effect. The highest winds should be during the Tuesday morning hours. Winds should stay just below 25 kt in the Charleston Harbor, so we don't have an advisory there. Winds will ease Tuesday afternoon into the overnight, with seas subsiding as well. The Small Craft Advisories should expire within 20 nm Tuesday evening, and for the GA outer waters Tuesday night. High pressure will pass well to our north later Tuesday, then shift offshore on Wednesday. Another cold front should quickly move through the waters early Thursday. Though, winds and seas shouldn't be high enough to prompt Small Craft Advisories.

Rip Currents: The combination of strong northeasterly winds and elevated seas will yield a Moderate Risk of rip currents at all of our beaches on Tuesday. Though, internal models are pointing towards a High Risk for our GA beaches. This will need to be considered, especially if winds and seas are a little bit higher there.

CHS WATCHES/WARNINGS/ADVISORIES

GA...None. SC...None. MARINE...Small Craft Advisory from 1 AM to 8 PM EDT Tuesday for AMZ360- 362-364. Small Craft Advisory from 1 AM Tuesday to 3 AM EDT Wednesday for AMZ384.