textproduct: Charleston

WHAT HAS CHANGED

All sections updated.

KEY MESSAGES

- 1) Periods of unsettled weather could continue into Tuesday. A few thunderstorms on Monday could become severe.

DISCUSSION

KEY MESSAGE 1: Periods of unsettled weather could continue into Tuesday. A few thunderstorms on Monday could become severe.

Through tonight: Aloft, nearly zonal flow will continue while a subtle stationary surface boundary continues to stretch west-east along the Gulf Coast. Morning light rain has completely dissipated and the overall outlook through the evening is for minimal diurnal convection. Though temperatures are on track to peak in the mid 80s this afternoon, model soundings are quite unimpressive with meager lapse rates. In the absence of any broad forcing or source of low- level convergence, diurnal development will be dependent on surface heating. The best chance of isolated showers and thunderstorms will be across southeast GA along and south of I-16 where some instability could pool. Hi-res model consensus is for little to no activity with no real severe weather risk. Overnight, an upstream cold front will draw closer but we should remain dry.

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. At the surface a cold front will approach the region from the west, pushing through the forecast area Monday evening. Guidance is a bit split on the coverage of showers and thunderstorms ahead of the approaching cold front. The current forecast features PoPs 50-60% roughly along and east of I-95 through the afternoon hours. This forecast leans more towards the 12Z 3km NAM, NBM, and RRFS, which depicts convection of almost a summertime pattern and pop-up in nature. The 12Z HRRR is unimpressive with precipitation, actually keeping most of the region dry and only depicting isolated showers/tstorms. While this solution is less likely, given the ongoing drought, it shouldn't be completely disregarded.

Ahead of the approaching cold front moisture will surge into the region, with PWATs reaching ~1.5" which would be above the 75th percentile according to SPC Climatology. Breaks in the cloud cover through the morning will allow the sunshine to reach most locations across the region, aiding in destabilizing the atmosphere. Forecast soundings indicate that ML CAPE could reach between 500-1000 J/kg in the afternoon. The SPC has included the entire CWA in a Marginal Risk (level 1 of 5) for the severe potential on Monday. Given the convective parameters this is reasonable. The main hazard will be damaging wind gusts, however some hail or even a weak isolated tornado can't be ruled out. The greatest tornado risk is along the coastline, where boundary interactions with the sea breeze could lead to some rotation.

MARINE

Through tonight: Quiet conditions will continue across the local waters. A modest sea breeze should result in 10-15 knots along the land/sea interface this afternoon and into the evening. Then overnight, 5-10 knot southwest flow will prevail. Seas should average around 2 feet through the period.

Extended Marine: Winds will gradually increase ahead of an approaching cold front on Monday. The front will move through the waters Monday evening, then quickly shift offshore Monday night. There will be a surge of winds and building seas behind the front, leading to Small Craft Advisories for at least the inner waters. Gale conditions cannot be ruled out for the outer waters Monday night. 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.