textproduct: Charleston

WHAT HAS CHANGED

The Aviation Section has been updated to reflect the 00Z TAF issuance.

KEY MESSAGES

- 1) Near record warm through tonight with sea fog along parts of the coast. Showers and a few thunderstorms will impact the region later this afternoon into tonight.

- 2) Strong to severe storms possible on Saturday afternoon and evening.

- 3) Sub-freezing temperatures return on Sunday night and persist into the mid-week.

DISCUSSION

KEY MESSAGE 1: Near record warm through tonight with sea fog along parts of the coast. Showers and a few thunderstorms will impact the region later this afternoon into tonight.

Temperatures are still rising steadily early this afternoon and are track to max out near record levels at both KCHS and KSAV. The cooler waters of Charleston Harbor should keep the observed high well below record territory at KCXM. It will be a warm and humid night as the warm sector ahead of an approaching cold front becomes better defined. Lows may actually occur around midnight with temperatures expected to hold or slowly rise overnight in response to a strengthening low-level jet. Lows look to generally bottom out in the mid 60s which could challenge the record high minimums for February 21. See the climate section below for additional details.

Sea fog will linger along mainly the South Carolina beaches through this evening before lifting. Another round of sea fog could impact the beaches early Saturday.

One or possibly two bands of showers/tstms will move in from the west later this afternoon and settle across parts of the Lowcountry into interior Southeast Georgia. Some brief, heavy rainfall could accompany this band, but no flooding issues are expected. Gusty winds and a few cloud-to-ground lightning strikes could also occur given activity will be moving into an area of higher DCAPE (500-800 J/kg). Some degree of shower activity will linger overnight due to increasing isentropic ascent/warm air advection. Sub-freezing temperatures return on Sunday night and persist into the mid-week.

KEY MESSAGE 2: Strong to severe storms possible on Saturday afternoon and evening.

There are no major shifts in the ongoing synoptic reasoning for the weekend storm system. A cold front will approach the area late tonight and will stall over parts of the South Carolina Lowcountry Saturday morning. The front is forecast to shift north of the area late Saturday afternoon as deep-layered forcing associated with a shortwave that digs across the Tennessee Valley and Southern Appalachians spreads east. This forcing coupled with increasing moisture will support a large area of showers/tstms which will move from west-east across the area into Saturday night.

While most of Southeast Georgia and the southern South Carolina Lowcountry look to remain in the warm sector, there remains some uncertainty how quickly and how far the warm front lifts north to allow some degree of instability to work north into the Charleston Tri-County region as well as areas adjacent to the CSRA and Southern Midlands. This uncertainty is well reflected in the large interquartile range (IQR) noted at KMKS, KCHS and KDYB. Farther south, the confidence in instability is much higher with some spots in Southeast Georgia likely to see SBCAPE nearing 1000 J/kg at at times. Complicating matters is a southerly flow from off colder Atlantic shelf waters will likely have some stabilizing influence even if the warm front pushes north of the Santee River and into the Southern Midlands, especially along the coastal counties of the Lowcountry. Given the degree of bulk-shear of 50-70 kt, clusters and bands of organized convection are a possibility with the primary risk being damaging winds with a secondary risk for an isolated tornado near breaks in any QLCS/bowing line segments. The risk for severe tstms still looks highest across Southeast Georgia between 2 PM-9 PM, roughly along/south of I-16 and away from the immediate coast, possibly as far north as Beaufort and Hardeeville in southern South Carolina. This is the area where the best juxtaposition of instability and shear is expected.

Day 2 WFO guidance from the SPC currently outlines the entire forecast area in a marginal risk (level 1 of 5) for severe tstms which still looks appropriate for the current set up and level of uncertainty. Should the risk for higher instability be realized, then the risk level may be increased in future forecasts, especially in Southeast Georgia, possibly far southern South Carolina.

KEY MESSAGE 3: Sub-freezing temperatures return on Sunday night and persist into the mid-week.

A cold front, along with any lingering shower activity, will push off the coast Sunday morning and cold high pressure will begin to build into the region. This will usher in a considerably colder airmass for the early part of next week with well below normal temperatures, widespread below freezing temperatures Monday and Tuesday mornings, as well as the potential for wind chills to dip into the upper teens to low 20s for at least portions of the area.

Temperatures will begin to fall Sunday afternoon with breezy northwest flow and strong cold advection will continue through Sunday night. Monday morning lows are forecast to fall into the upper 20s inland with low 30s along the coast. However, in the presence of persistent and gusty northwest winds, wind chill values are expected to fall into the low to mid 20s for the entire forecast area and potentially even the upper teens for some inland counties. A Cold Weather Advisory could be needed for some inland counties late Sunday night and Monday morning. Expect Monday to be a very chilly day with highs struggling to reach 50 for much of the area. Such values would be on the order of 15+ degrees below normal for late February.

The coldest night is expected to be Monday night into Tuesday morning with low to mid 20s inland and upper 20s along the coastal corridor. Though temperatures will be lower than the previous night, winds shouldn't be quite as strong. This should yield wind chill values that are quite similar, with widespread low to mid 20s and the potential for pockets of upper teens. Another Cold Weather Advisory could be needed for portions of the area. Tuesday will be yet another chilly day, though temperatures will likely rebound by several degrees from Monday. Look for most places to rise into the low to mid 50s.

AVIATION /00Z SATURDAY THROUGH WEDNESDAY/

VFR will prevail at the beginning of the 00Z TAF period at KCHS/KJZI/KSAV and dominate through most of the overnight period. Some showers could impact KSAV through around 10 PM, however restrictions are not likely with these light showers. A low pressure system is progged to impact the region tomorrow (Saturday) with the region placed within the warm sector in the morning hours. Low stratus is forecast to develop across the region, with IFR/MVFR cigs prevailing from around daybreak through most of the day. A line of showers and possibly a thunderstorm will then push through the region around sunset Saturday evening. The 00Z TAFs only mention VCSH near the very end of the TAF period as the showers/tstorms will likely impact the terminals right near the end of the 00Z TAF period.

Extended Aviation Outlook: Periods of flight restrictions will be possible through Sunday morning primarily due to potential thunderstorms Saturday afternoon and evening. Fog and stratus could also impact the terminals Saturday night until a cold front moves through Sunday morning.

MARINE

Through Saturday Night: Gusty winds will linger across mainly the Charleston Harbor and the South Santee-Edisto Beach nearshore leg through early evening, however gusts will be below Small Craft Advisory criteria and the SCA in effect earlier today has been canceled. Elsewhere, south to southwest winds should settle into the 10-15 kt range overnight with seas subsiding to 2-3 ft. There are no wind/sea concerns through Saturday night. A band of showers/tstms could push offshore of the coast during the late afternoon/early evening hours. These storms could produce localized wind gusts in excess of 34 kt, isolated waterspouts and cloud-to-water lightning.

Sunday through Wednesday: A strong cold front will move through the local waters Sunday morning and increasingly hazardous marine conditions are expected beginning Sunday afternoon. Widespread Small Craft Advisory conditions are expected to begin Sunday afternoon, with winds and seas peaking Sunday evening through early Monday morning. In fact, there is an increasing chance for a period of gales late Sunday night and early Monday morning for portions of the waters, perhaps best in the outer GA waters. Marine conditions will then gradually improve back below Small Craft Advisory thresholds Monday through Monday night.

Sea fog: Fog continues to dissipate and the Marine Dense Fog Advisory in effect for the Charleston nearshore waters has been canceled.

Guidance suggests another round of sea fog could develop around daybreak Saturday and linger into the day. Another Marine Dense Fog Advisory may be needed.

CLIMATE

Record High Temperatures:

February 20: KCHS: 82/2018 KSAV: 84/1991

February 21: KSAV: 84/2018

Record High Minimum Temperatures:

February 21: KCHS: 62/2023 KSAV: 63/2023

CHS WATCHES/WARNINGS/ADVISORIES

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