8:30 AM Update: Storm Prediction Center extends slight risk throughout the Lowcountry. Damaging straight-line winds are the primary threat, with the risk of an isolated tornado or two still with us. Best chance for severe storms starts late this afternoon into the evening hours. Stay in touch with reliable, redundant sources of weather information today as the situation may change.
1:12 AM Update: Storm Prediction Center adds the Tri-County to its slight risk area. 5% tornado risk, 15% damaging wind risk within 25 miles of a point, primarily associated with prefrontal thunderstorms later Tuesday evening. There are still plenty of questions about how unstable the atmosphere is going to be Tuesday night but even meager instability could be enough with the impressive wind shear that is forecast to produce some damaging winds and perhaps an isolated tornado or two.
From the National Weather Service in Charleston’s Hazardous Weather Outlook, updated at 8:38 PM Monday evening:
A POTENT STORM SYSTEM WILL AFFECT THE AREA
TUESDAY AND TUESDAY NIGHT AND COULD BRING THE POTENTIAL FOR SEVERE
WEATHER ACROSS PARTS OF THE AREA. INITIALLY…A WARM FRONT WILL
LIFT NORTH ACROSS SOUTHEAST SOUTH CAROLINA LATE TUESDAY
MORNING…AND SEVERE THUNDERSTORMS ARE POSSIBLE DURING LATE
TUESDAY MORNING INTO EARLY TUESDAY AFTERNOON…MAINLY ACROSS
SOUTHEAST SOUTH CAROLINA AND COASTAL PORTIONS OF SOUTHEAST GEORGIA.
THEN…A LINE OF SEVERE THUNDERSTORMS COULD MOVE THROUGH FROM THE
WEST AHEAD OF AN APPROACHING COLD FRONT LATE TUESDAY
AFTERNOON/EARLY TUESDAY EVENING AND CONTINUE INTO THE EARLY
OVERNIGHT HOURS TUESDAY NIGHT. THE PRIMARY RISK WITH ANY SEVERE
THUNDERSTORMS WILL BE DAMAGING WINDS AND ISOLATED TORNADOES.
The risk for severe storms will be limited by what is expected to be meager instability; however, wind shear in the atmosphere will become increasingly favorable for storms to organize and perhaps even rotate, possibly overcoming the lack of instability to pull down some strong wind gusts and perhaps a brief tornado or two. We’ll need to watch for any breaks in the clouds that might help achieve additional instability.
The better bet, though, is the chance for heavy rain at times. The atmosphere will load up with moisture from the tropics comparable to what we see on some summer days (and would be around two standard deviations above normal for late November). Believe it or not, we’re in need of some rain around here — we’re running about a 4″ deficit since September 1.
As always, it’s good to have a few reliable and redundant sources of weather info handy, just in case.
Rain will clear the area during the day Wednesday, giving way to much cooler and drier high pressure for the holiday weekend. Thanksgiving will be clear but chilly with highs not getting too far north of 50, it looks like.