textproduct: Columbia

WHAT HAS CHANGED

Aviation updated for 12Z TAFs.

KEY MESSAGES

- 1. Moderate rainfall and potential severe weather mid-week

DISCUSSION

Key Message 1: Moderate rainfall and potential severe weather mid-week

An upper level trough over the middle of the country will work eastward mid-week pushing a frontal boundary into the forecast area sometime Thursday. Strong moisture advection is likely ahead of the front with the NAEFS IVT now forecast at the climatological maximum. Mean PWAT values from the GEFS and ECMWF ensemble range from 1.5 to 1.75 inches on Thursday morning with deterministic models around 2 inches (about 200 percent of normal). Strong moisture transport ahead of a front supports widespread rainfall, potentially heavy at times. Warm, moist advection will work to destabilize the air mass ahead of the front on Thursday. We expect thunderstorms to develop ahead of and along the front. The exact timing of the frontal passage remains in question but there will be a threat of severe weather across much of the forecast area. At this point the greatest threat may be further east, closer to the coast, where the air mass would have more time to destabilize during the day before the front pushes through. NCAR ML/AI severe probabilities have remained somewhat consistent indicating a potential threat of severe weather but have honed in more closely on the area to our east and to the north in the Mid-Atlantic states where the dynamics will be stronger as the trough lifts. The ECMWF Extreme Forecast Index values for CAPE and Shear range from 0.6 to 0.8 with highest values to the east indicating potential for an unusual event. The front should push through the area by late Thursday with drier air ending precip from west to east.

AVIATION /12Z SUNDAY THROUGH THURSDAY/

Varying restrictions this morning followed by VFR conditions.

Fog has spread out this morning, which has been affecting all terminals except DNL. Varying restrictions due to this fog are expected to continue through about 14z or so before dissipating. VFR conditions are then expected to persist through the remainder of the TAF period. Northeast winds around 5 kts develop this morning, eventually shifting to westerly/southwesterly after about 18z. After sunset winds become light and variable once again.

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.