textproduct: Columbia

WHAT HAS CHANGED

Aviation discussion updated for 12z TAFs.

KEY MESSAGES

- 1. Dangerous heat expected to develop this weekend, continuing into next week.

DISCUSSION

Key Message 1: Dangerous heat expected to develop this weekend, continuing into next week.

Seasonably hot today, although dew points once again will be a bit lower than normal as low level moisture slowly returns. Model guidance has trended a bit cooler for tomorrow with more widespread showers and storms and increased cloud coverage expected during the afternoon associated with a weakening shortwave moving through the forecast area.

The potential for dangerous heat increases this weekend with building upper ridging over the Mississippi Valley. Ensemble mens indicate that 500mb heights will approach 2 standard deviations above normal with above average temperatures expected over the forecast area. Blended guidance does appear to be keeping dew points a bit too high compared to some raw global model output. Relatively high LREF probabilities (around 50 percent or greater) of dew points dipping below 70F each afternoon. This will limit heat indices somewhat and lowers confidence in the need for a Heat Advisory, although with the heat index still expected to approach 105F each afternoon, heat will be dangerous and persistent with strong guidance consensus in the upper ridge slowly shifting eastward into the middle of next week, leading to continued above average temperatures. Combined with little overnight relief with above average low temperatures as well, most of the area is highlighted in major HeatRisk Saturday through the Wednesday and expected to continue beyond mid-week.

Overall precipitation chances will be limited through the period with most notable chances Friday as mentioned earlier along with a shortwave along the periphery of the upper ridging Sunday which may lead to stronger storms during the afternoon and evening with highest chances in the eastern/northeastern part of the forecast area where the weak shortwave is most likely to pass nearest.

AVIATION /12Z THURSDAY THROUGH MONDAY/

VFR conditions are expected to continue through the TAF period.

Cloud bases this morning around 6-7kft with passing high clouds as well over the terminals. Scattered clouds will continue to be possible today but high confidence in remaining VFR. Winds will be generally light, around 5 knots out of the SSW. A stray shower is possible for the Augusta terminals but probability is very low. Tonight, winds become mostly light and variable. There is a small chance for near sunrise restrictions mainly for fog prone AGS/OGB but confidence is too low to include in TAF.

EXTENDED AVIATION OUTLOOK...Increasing heat and humidity into this weekend should yield daily diurnal convection and possible associated restrictions. The best chances for these showers/storms is Friday and Sunday. Brief morning vsby restrictions also possible into this weekend and early next week.

CAE WATCHES/WARNINGS/ADVISORIES

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