textproduct: Columbia

WHAT HAS CHANGED

Aviation discussion updated for 12z TAFs.

KEY MESSAGES

- 1. Additional thunderstorm chances today and Monday with a couple strong to severe storms possible. Another chance for strong convection possible during the midweek.

DISCUSSION

Key Message 1: Additional thunderstorm chances today and Monday with a couple strong to severe storms possible. Another chance for strong convection possible during the midweek.

A shortwave moving into the southern Great Lakes will continue to work toward the Mid-Atlantic through the day today with a weak cold front likely settling in central NC by this evening. Weak support from the shortwave, and enhanced convergence from surface troughing will provide more synoptic-scale lift than seen the previous couple of days, but some uncertainty in coverage remains. This comes partly as the mid-level and low- level circulation of a developing tropical disturbance in the NE Gulf become better aligned. When looking at WV imagery a pocket of drier mid-level air is seen on the eastern and northeastern side of this developing system, advecting into the FA, which likely played a role in the reduced coverage seen yesterday. 00z guidance shows this drier mid-level air continuing to push through the FA, which may keep the developing cu field during the early afternoon a bit more low-topped. By the late afternoon and early evening, better mid-level moisture and the main batch of forcing from the shortwave should push in, bringing scattered storm chances, mainly along and east of the I-26 corridor. With strong surface heating and surface dewpoints in the low 70s, SBCAPE over 3000 J/kg is expected to develop. Generous mixing should also yield DCAPE values near 1000-1200 J/kg, so if a updraft can become better established and combat dry entrainment in the mid-levels, a few strong to severe storms will be possible with the risk of damaging downburst winds. This risk is expected to be maximized mainly east of the I-26 corridor where effective shear near 10-15 kts and cloud layer shear near 20-25 kts, could lead to a bit of organization into a few multicellular clusters. Portions of the northern Midlands and Pee Dee remain in SPC's Slight Risk (level 2 out of 5) for severe weather while most spots south of here are in a Marginal Risk (level 1 out of 5)

A fairly similar environment is expected Monday, where subtle shortwave energy moving through the general troughing pattern in the eastern CONUS should spark more isolated to widely scattered afternoon/evening convection. With seasonable to strong instability remaining in place with PWAT's near 2", cannot rule a strong storm or two. It is worth mentioning the developing tropical disturbance could become a bit more organized by this point, but both the 18z round of EC Ensemble and Google DeepMind guidance keep it moving toward the north/northwest into the mid week. NHC now has formation chances at 60% for this. Southerly/southwesterly flow may aid in pulling some of this deeper moisture from the Gulf toward the area.

Ensemble guidance and global models continue to indicate a fairly active pattern during the mid week, potentially carrying into the late week. A strong 594dm ridge is expected to remain anchored to the western US with troughing seen across the central/eastern CONUS. This pattern puts the FA in a favorable spot for multiple shortwaves to dive through the Midwest into the Tennessee Valley and finally into the area, bringing increased rain chances. Timing differences still exist when comparing the GFS/ECMWF and their AI counterparts, but a rather sharp shortwave and associated frontal boundary are expected to work into the CWA sometime Wednesday into Thursday. Enhanced kinematics, PWAT's 1.5-2.5 standard deviations above normal, and seasonable instability could bring another chance for severe weather and heavy rainfall as indicated in multiple forms of AI/ML guidance.

AVIATION /12Z SUNDAY THROUGH THURSDAY/

VFR conditions are expected to prevail for the forecast period outside of convection.

Restrictions remain well to the west of the terminals early this morning in central GA and high confidence that they will not impact any terminals. By this afternoon, additional cumulus will redevelop with winds increasing out of the southwest as gusts will be between 15 to 20 knots through the afternoon and into the evening. Guidance has generally been trending lower on coverage of storms, especially in the southern portion of the forecast area so have removed the prob30 for convection for all terminals expect for the Columbia terminals. Outside of any storms, VFR conditions expected to persist through the period. Wind gusts subside tonight.

EXTENDED AVIATION OUTLOOK...Potential for restrictions from showers and thunderstorms continues into next week.

CAE WATCHES/WARNINGS/ADVISORIES

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