textproduct: Charleston

WHAT HAS CHANGED

All sections have been updated.

KEY MESSAGES

- 1) Showers and thunderstorms through Tuesday could produce locally heavy rainfall and isolated flooding. A few storms could also become strong to severe.

- 2) Near-normal temperatures are expected to return end of this week and warming into the weekend.

- 3) Minor coastal flooding is likely during the evening high tide cycles today through Wednesday.

DISCUSSION

KEY MESSAGE 1: Showers and thunderstorms through Tuesday could produce locally heavy rainfall and isolated flooding. A few storms could also become strong to severe.

Today and Tonight: A weak backdoor front will slowly nudge south across the region with the aid of a mid-upper lvl trough becoming positioned across the Southeast, but is likely to stall across the local area by late day as the mid-upper lvl trough begins to retrograde westward across the Mississippi River Valley overnight. The stalling front should remain the primary focus for shower and thunderstorm activity locally this afternoon into tonight, providing ample moisture convergence while a southerly sfc wind occurs along and south of this feature. Although sfc heating will not be as pronounced as previous days under some clouds and expanding shower/thunderstorm coverage during peak heating hours, deep moisture (PWATs ~2.25 inches) and activity occurring across wet grounds from previous rainfall could lead to localized flooding across Southeast South Carolina and Southeast Georgia, especially if interacting with a sea breeze and/or convective outflows from ongoing convection. Precip activity shifting toward the coast throughout the day could also pose an additional risk for flooding along coastal locations should it occur during the evening high tide cycle (see Key Message #2). The latest WPC Excessive Rainfall Outlook for today highlights the entire area in a Marginal Risk for excessive rainfall/flash flooding. The severe weather risk appears less than the previous few days, but modest instability and low-lvl lapse rates could support a few stronger thunderstorms and/or perhaps an isolated severe thunderstorm with damaging winds. The latest SPC Day 1 Convective Outlook includes the entire area in a Marginal Risk.

Tuesday: The previously mentioned stationary front/boundary should remain draped across the local area, leading to another day of shower and thunderstorm activity within an environment marked by modest instability and weak shear. Precip activity should once again become primarily focused along this feature with additional chances of isolated flooding during the afternoon/evening. WPC continues to highlight the entire area in a Marginal Risk for excessive rainfall/flash flooding. The risk for severe weather appears somewhat more limited given limited/weaker forcing locally, but a few stronger thunderstorms are possible, especially with any interacting sea breeze and/or convective outflow boundaries.

KEY MESSAGE 2: Near-normal temperatures are expected to return end of this week and warming into the weekend.

While there is some uncertainty in the strength and southern extent of a mid-level trough along the east coast later this week, the general trend is for upper level heights to build across the southeast region. This uncertainty bleeds over into the surface pattern thus affecting surface temperatures, with ensemble clustering suggesting near-normal temperatures are favored over above-normal temperatures later this week. Details remain unclear into the weekend, though the current consensus is for above-normal temperatures to return.

KEY MESSAGE 3: Minor coastal flooding is likely during the evening high tide cycles today through Wednesday.

Increasing astronomical tides associated with today's lunar perigee and Tuesday's New Moon will continue a risk of minor coastal flooding each evening through Wednesday, mainly along the coastal Charleston and coastal Colleton Counties. The greatest threat is expected this evening and Tuesday evening as astronomical tides peak just below 6.6 ft MLLW in the Charleston Harbor, and when combined with the anomaly will likely see water levels peak in the 7.3-7.5 ft MLLW range, firmly in minor flood stage. Wednesday evening is looking to peak right at/near minor flood stage. Additionally, if heavy rainfall were to occur near or during the time of the evening high tide cycles, flooding concerns would increase as total water levels would similarly increase.

AVIATION /06Z MONDAY THROUGH FRIDAY/

VFR conditions are likely at CHS/JZI/SAV terminals through 16Z today. The chances for showers/thunderstorms increases during the afternoon with PROB30 groups for thunderstorms and 4SM vsbys included at all terminals between 19Z today to 04Z Tuesday. Gusty winds along with heavy downpours could reduce vsbys further when directly impacting the terminals. VFR conditions should then return at all terminals after 04Z Tuesday.

Extended Aviation Outlook: Shower and thunderstorm coverage, along with risks of associated restrictions, will remain elevated through Tuesday.

MARINE

Today through Wednesday: A weak cold front will continue to slip through the region from north to south today and into Tuesday, yielding variable winds through Tuesday. This front is expected to increase the shower and thunderstorm activity over the waters, with isolated to scattered thunderstorms becoming strong to severe, primarily during the late afternoon and evening hours. The front is expected to remain just off to our south of Wednesday, though chances for thunderstorms will continue. Outside of thunderstorms, marine conditions are expected to remain below Small Craft Advisory criteria.

Wednesday - Friday: West-southwesterly surface flow is expected to develop Wednesday and remain into Friday, with continued sub Small Craft Advisory criteria.

CHS WATCHES/WARNINGS/ADVISORIES

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