textproduct: Charleston

WHAT HAS CHANGED

All sections updated.

KEY MESSAGES

- 1) Sea fog will expand across the nearshore waters and area beaches through this evening.

- 2) Notable temperature swings through Wednesday.

- 3) Warm temperatures and chances of rain for late next week into the weekend.

DISCUSSION

KEY MESSAGE 1: Sea fog will expand across the nearshore waters and area beaches through this evening.

Area web cams and satellite indicated that sea fog was pushing onshore in the wake of weak sea breeze. High resolution guidance indicates that rounds of sea fog will push onshore through this evening. Late tonight, a backdoor cold front will advance south across the SC Lowcountry and SE GA, pushing fog to the south. A Marine Dense Fog Advisory has been issued for the nearshore waters until 1 AM.

KEY MESSAGE 2: Notable temperature swings through Wednesday.

High resolution guidance indicates that a backdoor cold front will push south over the SC Lowcountry late tonight, reaching SE GA during the pre-dawn hours Monday. The rest of Monday will feature high pressure ridging SW along the east facing slopes of the Appalachians. As a result, conditions across the forecast area should remain at least mostly cloudy with steady northeast winds between 10 to 15 mph. Using a blend of the cooler MOS members, high temperatures are forecast to range from 60 to 65 across the SC Lowcountry and 65 to 72 across SE GA. Low temperatures Monday night should favor values around 50 degrees. On Tuesday, the wedge of high pressure will linger across the region, but will weaken. Light NE winds and thinning cloud cover should allow temperatures to peak in the low to mid 70s. An inverted coast trough should advance west across the forecast area Tuesday night, breaking down the sfc ridge. As a result, winds should shift from the ESE on Wednesday and temperatures are forecast to warm in the upper 70s to around 80 degrees.

KEY MESSAGE 3: Warm temperatures and chances of rain for late next week into the weekend.

Deep layered high pressure centered offshore will extend across southeast South Carolina and southeast Georgia late week into the weekend. This pattern will favor unseasonably warm temperatures. There continues to be a small spread in max temperature guidance, giving high confidence to temperatures in the upper 70s to low/mid 80s away from the locally cooler coastline. These values are around 10 degrees above early March normals. Lows will similarly lean on the mild side, ranging in the upper 50s to around 60.

Deeper moisture will also return with ensemble means indicating PWats reaching 1.1-1.2" which is around the 85th percentile of climo. Forcing for ascent is lacking but given the moisture and some weak instability, isolated to scattered showers will be possible especially in the afternoon and evenings. Thunder potential looks pretty limited, but a few rumbles cannot be ruled out. Flooding risk is minimal as probability for >0.25" of rainfall in any 24 hour period through Saturday is generally no higher than 20% per NBM.

AVIATION /20Z SUNDAY THROUGH FRIDAY/

18Z TAFs: Conditions should remain VFR with light south winds through this evening. High resolution guidance indicates that a backdoor cold front will push south over the SC Lowcountry late tonight, reaching SE GA during the pre-dawn hours Monday. A period of light fog is possible just prior to the passage of the front, highlighted with TEMPOs from 6-10Z. In the wake of the front, IFR to MVFR ceilings should spread across the terminals, beginning during the early daylight hours on Monday. Restrictive ceilings may linger over KCHS and KJZI through the rest of the TAF period, KSAV may see VFR conditions by 17z.

Extended Aviation Outlook: Restrictive ceilings possible Tuesday night into Wednesday morning.

MARINE

High resolution guidance indicates that a backdoor cold front will push south over the SC Lowcountry late tonight, reaching SE GA during the pre-dawn hours Monday. The rest of Monday will feature high pressure ridging SW along the east facing slopes of the Appalachians. As a result, conditions across the marine zones should remain at least mostly cloudy with gusty northeast winds. Small Craft Advisories have been issued for all Atlantic waters, outside the CHS Harbor to highlight gusts around 25 kts and seas up to 6 ft. Wind speeds will begin to weaken late Monday night, though seas will be slower to subside. Small Craft Advisories will expire for the nearshore waters within 20 nm Monday night, and then the GA waters beyond 20 nm on Wednesday due to lingering seas.

Thursday through Friday: Southeast to south flow will persist late week into the weekend on the backside of high pressure, with speeds and seas staying well below small craft advisory levels. We will need to monitor the potential for sea fog given the warm, moist air that is expected to move over the cooler shelf waters.

CHS WATCHES/WARNINGS/ADVISORIES

GA...None. SC...None. MARINE...Dense Fog Advisory until 1 AM EST Monday for AMZ330-350-352- 354. Small Craft Advisory from 5 AM Monday to 7 AM EST Tuesday for AMZ350. Small Craft Advisory from 5 AM Monday to 1 AM EST Tuesday for AMZ352. Small Craft Advisory from 10 AM to 7 PM EST Monday for AMZ354. Small Craft Advisory from 10 AM Monday to 4 PM EST Wednesday for AMZ374.