textproduct: Charleston

WHAT HAS CHANGED

Aviation section updated for the 12Z TAFs.

KEY MESSAGES

- 1) Increased chances for showers and thunderstorms through early this week.

DISCUSSION

KEY MESSAGE 1: Increased chances for showers and thunderstorms through early this week.

The forecast area will remain on the edge of a 590 dm H5 ridge centered over the western Atlantic, and a secondary center over southern FL today. However, SW to NE oriented heights across the region will likely result in a weak disturbance or two to track across the Coastal Plain of SC/GA today. The passage of a weak disturbance seen in satellite water vapor may allow a few showers to develop over the nearshore waters this morning, possibly tracking onshore.

By mid day, temperatures are expected to warm into the mid to upper 80s with dewpoints in the low to mid 70s. SBCAPE values are forecast to increase to around 2000 J/kg, with pockets of 2500 J/kg. Steady SE winds should allow a sea breeze to develop during the morning hours, then drifting inland through this afternoon. Recent runs of the HRRR and HREF indicate that the deep convection may develop along and ahead of the sea breeze over the I-95 corridor as early as 16Z. Coverage should increase into the early to mid afternoon hours, however, Corfidi vectors indicate slow storm motions, generally 10 kts or less. Given PW values between 1.8-1.9 inches, slow storm motions, and moderate instability, localized heavy rainfall is possible with the storms inland of I-95. In fact, the 0Z HREF highlights inland GA with another round of heavy rain this afternoon, with a 30% of 3"/hr and a 70% of 1"/hr rainfall. It is possible that one or two storms may develop high echo tops, collapsing water-loaded updrafts may yield a risk of damaging wind gusts. SPC has highlighted portions of SE GA with a Marginal Risk for severe thunderstorms.

Memorial Day: Conditions are not expected to change much from today, with comparable temperatures and moisture content. The sea breeze will again be the focus for the initial thunderstorms, then coverage should expand across inland areas. Locally heavy rainfall is possible generally along and west of I-95.

Later this week, the ridge of high pressure off to our east strengthens, continuing our warm and moist conditions across the southeast United States. This is expected to bring a summer- like pattern, with showers and thunderstorms forming daily along an early afternoon sea breeze before expanding across inland areas into the early evening hours, which will continue to bring much needed rainfall to the region. Temperatures remain above average, with daily highs in the upper 80s to lower 90s and overnight lows in the mid 60s to mid 70s, possibly resulting in record high minimum (warm overnight low) temperatures.

As a surface low pressure moves off the northeast coast late this week, a cold front is expected to push through the southeast region. The trend has been for later in the week, Thursday into Friday, with cooler high temperatures in the upper 70s to lower 80s expected during the later half of the weekend.

AVIATION /12Z SUNDAY THROUGH THURSDAY/

12Z TAFs: VFR conditions expected across the terminals this morning. Showers may track onshore for develop along a early forming sea breeze around daybreak this morning, highlighted with a mention of VCSH beginning 15Z. Recent runs of the HRRR and HREF indicated that a broken band of showers and thunderstorms will develop near, perhaps just inland, of the terminals after 16Z. Storm motions should remain limited to 5 to 10 kts. Each TAF will feature a PROB30 until late this afternoon for TSRA. Showers should dissipate with the loss of heating around sunset this evening.

Extended Aviation Outlook: TEMPO flight restrictions possible with showers and thunderstorms at CHS/JZI/SAV terminals during the afternoon hours into the middle of next week.

MARINE

Today and tonight: High pressure centered over the western Atlantic will remain remain over the marine zones. As a result, winds will generally remain from the SSE through the period, favoring speeds between 10 to 15 kts. Slight increases in wave heights may occur through today, peaking overnight between 3 to 5 ft.

Monday through Thursday: Conditions are forecast to remain below Small Craft Advisory criteria into the middle of next week, with daily chances for showers and thunderstorms. High pressure to the east will drive onshore ESE flow each day, with wind speeds mostly topping out in the 10-15 knot range. Each afternoon and evening there could be some local enhancement along the land/sea interface with the diurnal sea breeze. Seas will average 2-4 feet through the period.

Rip Currents: A modest easterly swell around 3ft/8s and sea breeze influences each afternoon will keep the rip current risk in the moderate category at all area beaches through Monday.

CHS WATCHES/WARNINGS/ADVISORIES

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