textproduct: Columbia

WHAT HAS CHANGED

Rain chances for late this week and this weekend continue although coverage could be lower than blended guidance indicates. Aviation discussion updated for 18Z TAF issuance.

KEY MESSAGES

- 1. Above normal temperatures likely through mid-week.

- 2. Rain chances increase late week and into this weekend.

DISCUSSION

Key Message 1: Above normal temperatures likely through mid- week.

Above normal temperatures likely through Thursday with highs in the low to mid 90s expected and no or very little convective coverage each afternoon. PWAT values will be slightly below to around normal through Wednesday so Heat Index values will not rise to advisory thresholds. However, early season heat can contribute to an increased risk of heat-related illness.

Key Message 2: Rain chances increase late week and into this weekend.

On average, model guidance shifts high pressure eastward late this week, leading to increasing moisture over the Southeast from Thursday through Memorial Day weekend. PWAT values rise to just above normal for the season. However geopotential heights from the NAEFS are also around normal. This would point to a seasonal setup for scattered afternoon convection, possibly enhanced to our north and west with shortwave energy riding over the ridge. PoPs from blended guidance show values above what are climatologically favored and could be too high given the synoptic set up.

AVIATION /18Z MONDAY THROUGH SATURDAY/

VFR conditions expected the remainder of today with brief restrictions possible again Tuesday morning.

FEW to SCT cumulus clouds are being observed across the region with south to southeast winds around 5-10 kts. Occasional low- end gusts are possible this afternoon during peak daytime heating and mixing. Skies are expected to fully clear after sunset as winds weaken and become more variable overnight.

Lingering low-level moisture, along with recent HREF and REFS guidance, suggests the potential for fog and low stratus to develop once again tonight mainly after 08-10Z. Model guidance remains somewhat aggressive, similar to last night and this morning, indicating a 40-60% chance of ceilings below 1,000 ft near the typical fog-prone terminals. At this time, periods of MVFR visibility and/or cig restrictions appear most likely between 09-13Z. Trends will need to be watched to determine if more impactful restrictions become likely. After 13-14Z Tuesday, light winds should pick back up out of the south-southeast with clearing skies.

EXTENDED AVIATION OUTLOOK...Increased moisture may result in brief restrictions at the terminals due to low clouds and/or fog each day this week. Rain chances increase towards the end of the week.

CAE WATCHES/WARNINGS/ADVISORIES

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