textproduct: Charleston

WHAT HAS CHANGED

New Key Messages 1 and 2. The Aviation Section has been updated to reflect the 18Z TAFs.

KEY MESSAGES

- 1) Notable temperature swings through Wednesday.

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

DISCUSSION

KEY MESSAGE 1: Notable temperature swings through Wednesday.

The mid-levels will consist of troughing over the East Coast this evening. It'll gradually transition to zonal flow by late Monday, followed by ridging building over the Southeast U.S. Tuesday into Wednesday. At the surface, High pressure will prevail through Sunday. A dry cold front will move south through our area Sunday night, followed by High pressure passing to our north on Monday. This will cause quite a swing in temperatures. Following lows near normal in the 40s tonight, temperatures will rise well above normal on Sunday, into the mid 70s for most locations (except cooler at the beaches), then remaining a few degrees above normal Sunday night. The wedge pattern will lead to a drastic temperatures gradient on Tuesday. Highs will range from the lower to middle 50s near the Santee River, rising to the lower to middle 70s near the Altamaha River. But given this synoptic setup, there is a high probability for high temperatures to be drastically different for any particular spot on Monday. Though, low temperatures on Monday night should be within a few degrees of normal. High temperatures rise back above normal on Tuesday, ranging from the lower to middle 70s away from the beaches. The warming trend continue on Wednesday with highs ranging from the mid to upper 70s across most of our area (except cooler at the beaches), and possibly the lower 80s across portions of inland GA south of I-16.

KEY MESSAGE 2: Warm temperatures and chances of rain for late next week into the weekend.

The region will be under the influence of high pressure, both at the surface and aloft, centered offshore late next week into the weekend. This will set the stage for warming temperatures. There is a fairly small spread in max temperature guidance, with upper 70s to even low 80s likely in most locations away from the immediate coast. Early March normals are in the upper 60s, so these values would be around 10 degrees above normal. Lows will also trend on the more mild side, in the upper 50s to around 60.

Deeper moisture will return to the area with ensemble means indicating PWats climbing to around 1.1", which falls in the 85-90th percentile of climo. While larger scale forcing is lacking, moisture and some instability could lead to isolated to scattered diurnally driven showers developing, especially in the afternoons and into the early evening. NBM indicates only a 10-20% chance for >0.25" of rain in any 24 hour period during this time frame. Severe and flooding risk looks minimal at this time.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

18Z TAFs: Satellite imagery indicates widespread stratus across our area with surface observations pointing to IFR/MVFR. Earlier model runs were too fast in clearing out the clouds and the latest runs continue to have this issue. We kept flight restrictions at all three TAF sites through this afternoon, with gradual improvements. KSAV should become VFR first, followed by KCHS/KJZI. But this will depend on satellite trends, and amendments may be needed. After conditions improve to VFR, models then hint at a round of IFR at all three TAF sites late tonight due to fog and low stratus. Given the marginal performance of the models so far, we only hinted at this with the current TAFs and will let later TAFs address this as confidence hopefully increases.

Extended Aviation Outlook: VFR.

MARINE

High pressure will prevail through the weekend. A dry cold front will move south through the waters Sunday night, followed by High pressure passing to our north on Monday. This will cause a surge in northwest winds. Small Craft Advisories will be needed for all of the ocean zones from Monday into Monday night. Models continue to hint at wind gusts approaching 35 kt across the Charleston waters, so a Gale Watch may eventually be needed. Winds trend lower late Monday night into Tuesday, though seas will be slower to subside. Advisories would expire for the waters within 20 nm first, and then the GA waters beyond 20 nm, possibly not until Wednesday.

CHS WATCHES/WARNINGS/ADVISORIES

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