textproduct: Columbia

WHAT HAS CHANGED

Rain ending across the area this evening. Aviation updated for 00Z TAFs.

KEY MESSAGES

- 1. Rainfall ending this evening with continued below normal temperatures Sunday.

- 2. Warming trend through early week.

- 3. Unsettled weather returns for the middle of next week with a possible severe threat.

DISCUSSION

Key Message 1: Rainfall ending this evening with continued below normal temperatures.

Solid cloud deck is relegated to the eastern third of the CWA early this evening, and should continue moving to the east as the deep moisture moves out. However, strong upper vort is forcing some convective showers, and even a couple of thunderstorms, along a cold front in the upper Savannah River Valley, which should move into the CSRA in the next hour, then continue moving east into the Midlands later this evening. With the loss of daytime heating (if you could call it heating for May) and diminishing upper jet support, the convection should lose steam with time, but not before getting some locations wet during evening activities, mainly south/west of I-26. All activity should minor out by around midnight.

Key Message 2: Warming trend through early week

The cooler below normal temperatures will be short lived, at least regarding high temperatures, early this week. While a dry air mass will remain in place initially with dewpoints in the 50s Mon/Tue keeping humidity low, a developing southerly flow as the surface highs shifts offshore will support warming temperatures. Highs expected to be back near normal Monday in the upper 70s to around 80 degrees and warming further on Tuesday with highs in the lower to mid 80s. Zonal 500mb flow early in the week will become more southwesterly in response to a phasing northern and southern stream resulting in significant troughing over the middle of the country. This will provide increased southerly flow over the area as temperatures are expected to push into the mid-upper 80s on Wednesday.

Key Message 3: Unsettled weather returns for the middle of next week with a possible severe threat.

The next chance for significant rainfall should arrive mid week (Wed night into Thursday) and bring a potential severe weather threat. A phased and digging upper trough over the middle of the country Wednesday will push a frontal boundary into the forecast area sometime Thursday. The upper trough is forecast to become neutral to slightly negatively tilt as it moves into the region which is usually conducive to stronger winds and enhancing any severe threat. EC EFI showing a signal in the CAPE-Shear parameter. NAEFS ESAT showing IVT at the climatological max with PWATs in the 99th percentile, so moisture and moisture advection should be sufficient with instability to support a potential severe weather threat. Timing will be key of course with an afternoon frontal passage more favorable than something overnight, but still too far out to have any confidence in timing yet. CSU ML has a probability in line with a marginal risk at this point, along with some of the other AI severe guidance. Something to watch as we get closer to mid week.

AVIATION /00Z SUNDAY THROUGH THURSDAY/

VFR conditions returning to the terminals this evening. Some patchy fog possible Sunday morning.

A few lingering light showers are possible mainly at AGS/DNL/CAE/CUB over the next few hours, but should not cause any restrictions. Any remaining CIGS should lift to VFR by 02z, with cirrus overnight and SKC returning for Sunday. Some guidance suggests the potential for reduced VSBYs in fog early Sunday with residual moisture in place and weak winds, but this should be patchy and confined mainly to the OGB/AGS/AIK terminals and is handled by TEMPO groups. Confidence for fog is on the lower side. Sunday will feature VFR across the board with northeast winds in the morning becoming southwest to west by the afternoon, though speeds remain under 10 kts through the period.

EXTENDED AVIATION OUTLOOK...Drier conditions are expected into early next week. A midweek system brings a chance for restrictions once again.

CAE WATCHES/WARNINGS/ADVISORIES

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