textproduct: Columbia

WHAT HAS CHANGED

Thunderstorm coverage today is expected to be similar to yesterday or slightly higher with some stronger storms possible once again. Temperatures early in the week ahead continue to trend downward. Aviation discussion updated for 06z TAFs.

KEY MESSAGES

- 1. Hot and breezy conditions continue tomorrow with isolated to widely scattered storms possible again this afternoon.

- 2. A frontal boundary brings higher rain chances for the weekend along with increasing confidence in below normal temps early in the week.

DISCUSSION

Key Message 1: Hot and breezy conditions continue tomorrow with isolated to widely scattered storms possible again this afternoon.

An upper trough over the Appalachians is forecast to keep sliding eastward through the day today. As it does it is expected to flatten somewhat. In addition, a weak surface lee side trough is forecast to develop, leading to breezy southwest winds gusting to around 20 mph. Despite the trough overhead, 850 mb temps are expected to reach 21-22C, leading to afternoon highs in the mid to upper 90s once again. Like yesterday, isolated to widely scattered storms are expected to develop, leading to a little bit of uncertainty of just how warm we get. Heat indices are forecast to be in the 100-105F range once again, with the same caveat as the actual air temperatures. Continue to use caution if you spend prolonged time outdoors.

Speaking of thunderstorms, a shortwave is forecast to move through the flattening trough this afternoon and into the evening, bringing another round of isolated to widely scattered storms to the area. Thinking the overall coverage of these storms will be similar to yesterday, or slightly more. There is expected to be sufficient CAPE to produce some stronger storms. Forecast soundings continue to show inverted V signatures, suggesting some storms could produce strong winds. Because of this, the Storm Prediction Center (SPC) has a Marginal Risk (level 1/5) of severe storms for the entire area for this afternoon.

Key Message 2: A frontal boundary brings higher rain chances for the weekend along with increasing confidence in below normal temps early in the week.

A frontal boundary draped over Midwest into the Great Lakes region this morning is forecast to move southward in response to a shortwave moving from the Great Lakes into the Southeast through the weekend. As the front and associated upper trough approach the area, more widespread shower and thunderstorm activity can be anticipated for the weekend. Some strong storms are possible again Saturday and Sunday. This activity could linger into early next week as latest guidance indicates that the front stalls out near the area. In addition to the increased rain chances, confidence continues to increase that we'll see below normal temperatures as we head into the new work week. The NBM interquartile range (IQR) on Monday ranges lowered a few degrees compared to last night's guidance and is now from the low 80s to upper 80s. Given the recent hot weather, the NBM takes that into account and will likely have a warm bias. So, I would not be surprised if we end up toward the cooler end of the IQR. After this system gets flushed out of the area, drier conditions and a warming trend are forecast to return.

AVIATION /06Z FRIDAY THROUGH TUESDAY/

VFR conditions expected through the TAF period except for scattered diurnal convection which may result in temporary restrictions.

Little change in the air mass and expect a similar day today with southwesterly winds picking up to around 10 to 15 mph with gusts over 20 mph late morning through the afternoon. A little better coverage of showers and thunderstorms expected today with a weak upper trough approaching from the west. Continuing the PROB30 for convection 19z-24z. Not expecting fog/stratus issues outside of convection.

EXTENDED AVIATION OUTLOOK...Increasing chances for afternoon storms this weekend and into early next week.

CAE WATCHES/WARNINGS/ADVISORIES

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