textproduct: Charleston

WHAT HAS CHANGED

All sections have been updated.

KEY MESSAGES

- 1) Rounds of unsettled weather will continue through Monday.

DISCUSSION

KEY MESSAGE 1: Rounds of unsettled weather will continue through Monday.

Through tonight: Aloft, the forecast area will remain within zonal flow while at the surface a stationary boundary will sit along a west to east orientation along the Gulf Coast and north FL. Overall, there really isn't a notable feature to concentrate or focus shower an thunderstorm activity through the period. Instead, the area will continue to reside in a relatively moist environment with precipitable water values ranging from 1.3-1.5" across the southeast SC and up to 1.5-1.7" along and south of the I-16 corridor. Currently, radar imagery shows remnant stratiform rain from a large MCS to the west and southwest tracking into southeast GA from the west. The environment is quite stable, thanks to widespread cloud cover and the arriving stratiform rain. This should keep any additional convective development this afternoon and evening from occurring, and if anything does develop it should be on the weaker end of the spectrum. So, the best chance for rain through the evening will be along and south of I-16, where the stratiform rain is moving through currently, with only isolated to scattered showers elsewhere. Overnight, model guidance is a bit mixed but generally favors a west to east feed of occasional showers within the corridor of higher precipitable water. Again, there isn't an identifiable feature to focus or organize development so it is hard to confidently expect anything other than passing scattered showers. As such, there isn't really any severe threat or heavy rainfall threat.

Sunday: Zonal flow will prevail aloft, while a shortwave trough ripples across the zonal flow just to the south of the local area. At the surface a stationary front will be located just south of the forecast area through midday. A plume of moisture will advect northward of the stationary front, putting the local region in an area of PWATs ~1.7", which would be above the 90th percentile according to SPC Climatology. With high temperatures reaching into the low to mid 80s, some instability will develop into the afternoon. ML CAPE values are forecast to generally be around 500-700 J/kg across the region. The combination of the moisture, instability, and the afternoon sea breeze could trigger some isolated showers. However, placement of the shortwave trough aloft to the south of the region will likely limit the amount of widespread precipitation. Areas along the Altamaha River, GA will see the highest precipitation chances. There is a very low risk across SE GA for a strong to possibly severe thunderstorm to develop, however the best severe risk looks to be further south, closer in proximity to the shortwave aloft.

Monday: A shift from zonal flow to broad troughing will develop into Monday as a mid-level trough swings eastward over the Great Lakes and towards the East Coast. Along the southern flank of the broad trough a shortwave trough will dig across the Deep South Monday into Monday night. Ahead of the approaching shortwave and an associated surface cold front, numerous to widespread showers and thunderstorms are forecast across the region. PWATs are forecast to reach as high as 1.8-2", which would approach the daily max according to SPC Climatology. Forecast soundings show ML CAPE values reaching around 1000-1500 J/kg. The moist conditions combined with the instability will lead to a risk of strong to severe thunderstorms, with the main hazard damaging wind gusts.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

The 18z TAF period begins with VFR conditions at KCHS, KJZI, and KSAV. An area of light rain will move through KSAV over the next couple of hours and while VFR conditions should prevail there could be some periods of MVFR ceilings and visibilities with the rain. Once this passes, the rest of the afternoon and evening should mostly bring isolated showers across the area with VFR conditions at the TAF sites. Overnight, overall confidence isn't particularly high in the forecast. The area will remain in a moist environment with showers capable of developing at almost any time. There are hints in model guidance that an area of showers (and possibly a thunderstorm) will develop and move through during the early Sunday morning hours. However, it is unclear how widespread this area will be or if it will be more concentrated offshore. There are also hints of MVFR or lower ceilings and visibilities across the region. The generally time period of concern is roughly from around 06z through about 14z for sub-VFR conditions and showers.

Extended Aviation Outlook: A cold front will approach the region on Monday, bringing the risk of flight restrictions from showers and thunderstorms. Conditions will improve Tuesday with no concerns through the remainder of the week.

MARINE

Through tonight: Overall, quiet conditions across the local waters. Southwest winds no more than 10-15 knots with seas averaging 2-3 feet. There is potential for occasional thunderstorm development through the period, and these storms could produce gusty winds and lightning.

Extended Marine: A stationary front will linger across the local waters on Sunday, with a cold front pushing through on Monday followed by building high pressure through the remainder of the week. Sub-SCA conditions are forecast Sunday into Monday. Winds are forecast to increase Monday ahead of the cold front, reaching Small Craft Advisory gusts of 25 knots. Gale conditions cannot be ruled out Monday night into Tuesday as high pressure builds in behind the cold front. Conditions will quickly improve late Tuesday through the remainder of the week as high pressure becomes the dominant synoptic feature.

CHS WATCHES/WARNINGS/ADVISORIES

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