textproduct: Columbia

WHAT HAS CHANGED

Marginal risk for severe weather this afternoon has shifted a bit further south. Added Key Message for front moving in during the mid week. Aviation discussion updated for 06Z forecast.

KEY MESSAGES

- 1. Scattered showers and isolated thunderstorms possible late this morning and into the afternoon.

- 2. Another cold front moves through mid week with rain chances.

DISCUSSION

Key Message 1: Scattered showers and isolated thunderstorms possible late this morning and into the afternoon.

There has been minimal change in the outlook for convection later today. The surface cold front is slowing working through the southern Tennessee Valley as a shortwave extends from northern MO toward the Ark-La-Tex region. As new guidance continues to filter in, trends have continued to keep PoP's across the FA fairly isolated to scattered with mean QPF amounts in both the 00z HREF and REFS generally less than 0.10-0.25". The LPMM for QPF in each is also rather spotty, with any amounts greater than 0.50" focused mainly along and south of the I-95 corridor. The front will slowly work through the FA late this morning and into the early evening as PWAT's reach near 1.50", but the greatest moisture looks to be confined closer to the coast. In general, mean MUCAPE values are forecast to be under 500 J/kg for much of the FA with spots in the southeastern Midlands closer to 1000-1200 J/kg as deep layer shear values increase to around 40-50 kts as the shortwave impinges on the area. This environment, with decent convergence along the front, should bring isolated to scattered convection late this morning, continuing into the early evening. Ensemble paintballs continue to favor better coverage generally along/south of the I-95 corridor, but individual CAM's do suggest isolated storms could be seen closer to the I-20 corridor. Overall, with the expected lack of coverage, the risk for widespread severe weather remains low, but any robust storms/clusters could bring the risk of damaging wind gusts as DCAPE values between 600-800 J/kg are seen with a weak inverted "v" profile. A couple instances of sub-severe hail cannot be ruled out as well. In the CWA, this risk would be greatest in the southeastern Midlands, but the greatest chance for severe weather is expected closer to the coast. A Marginal (1/5) risk for severe thunderstorms remains, though has shifted a bit southward along a line roughly from Waynesboro to St. Matthews to Florence.

Key Message 2: Another cold front moves through mid week with rain chances.

There is solid ensemble and cluster consensus that by Tuesday this week a deep trough will begin digging into the Great Lakes region before deepening a bit further into Wednesday as it pushes into the Eastern CONUS. This trough is expected to drive a surface low across the northern Great Lakes with an associated cold front extending southward. This upper support and front is expected to move through the area on Wednesday into early Thursday, though moisture return ahead of this front does not look to be all to impressive as GEFS and EC Ensemble PWAT's only reach up to 110-115% of normal. Timing uncertainty remains for fropa across the area, but increased rain chances seem possible with this, mainly near the Pee Dee. A warming trend is then seen into the late week and this weekend with mostly dry conditions.

AVIATION /06Z MONDAY THROUGH FRIDAY/

Mainly VFR conditions through the period, with brief patchy ground fog possible around sunrise. Rain chances increase for midday.

Upper level cloudiness will be moving into the region through the early morning hours, which may be an inhibiting factor for fog formation. Even so, can not rule out some brief mvfr patchy ground fog developing around sunrise. Clouds will thicken through the morning ahead of and behind an approaching surface cold front. Ceilings will remain vfr with this front. Guidance still not overly impressive on showers/storms later this morning into the early afternoon hours. It appears as if coverage may be quite isolated near taf locations ahead of the front. Greater coverage and stronger activity may end up being located east of the area, closer to the coastal plains this afternoon. Even so, still kept a mention of Prob30 at all sites due to the uncertainty for now. Winds are expected to be light and variable to calm through sunrise, become mainly westerly after about 14z, increasing to 5-10 kts. May see some higher wind gusts enter the area around when the front pushes in around 20-21 z. Winds then shift to northwesterly to north once the front passes through.

EXTENDED AVIATION OUTLOOK...Conditions improve Tuesday with mainly VFR expected. Another front with more scattered showers and thunderstorms approaches the terminals Wednesday.

CAE WATCHES/WARNINGS/ADVISORIES

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