textproduct: Columbia

WHAT HAS CHANGED

Rain chances over the weekend have decreased slightly, becoming a bit more isolated to scattered. Aviation discussion updated for 12z TAFs.

KEY MESSAGES

- 1. Isolated to widely scattered diurnal storms possible again today before becoming more spotty during the midweek. Chances increase again late in the week into the weekend. A few strong storms cannot be ruled out. - 2. Increasing heat and humidity is expected starting today, peaking late in the week.

DISCUSSION

- 1. Isolated to widely scattered diurnal storms possible again today before becoming more spotty during the midweek. Chances increase again late in the week into the weekend. A few strong storms cannot be ruled out.

Another round of isolated to widely scattered diurnal storms are expected this afternoon as robust heating and dewpoints in the low to mid 70s bring SBCAPE values up around 3000 J/kg. There actually may be a bit of forcing from a weak shortwave currently rounding the large ridge out west, likely reaching the Mid- Atlantic by the late afternoon/early evening. This feature likely will not provide much forcing this far south but forecast soundings indicate a slight enhancement in wind profiles with around 20-25 kts of cloud layer shear, enough for the potential for a strong storm or two if convection can get going. A fairly similar setup is seen Wednesday as this northwest flow regime should aid in advecting another weak perturbation into the Mid- Atlantic, though PoP's are a bit lower. If this perturbation sinks a bit further south, expect PoP's to increase some and bring higher chances for scattered convection. Slight troughing over the northeastern US could allow pieces of mid level energy to reach the FA Friday and Saturday, with a weak frontal boundary expected to near during the window as well. This should bring scattered shower/storm chances each day, especially Saturday, though some uncertainty in the fronts southern extent still exists with generous spread remaining across LREF cluster analysis.

Overall, isolated to scattered diurnal convection will remain possible through the week and into this weekend where pockets of heavy rainfall and a strong storm or two cannot be ruled out.

- 2. Increasing heat and humidity is expected starting today, peaking late in the week.

Today is expected to begin a period of hot/humid conditions with temperatures 5-10 degrees above normal. Gradual mid level height rises and warming 850mb temperatures through the week are expected to keep afternoon high temperatures in the mid to upper 90s, with little relief overnight as lows stick to the mid to upper 70s each night through at least Friday night. While decent mixing is shown in BUFKIT soundings, surface dewpoints should remain in the low to mid 70s each afternoon, bringing heat indices up to around 105F today and Wednesday before peaking between 105-108F Thursday, Friday, and possibly again Saturday. LREF probabilities for heat indices greater than 105F remain around 30-50% Thursday, between 50-70% Friday, and then lower slightly to 40-60% Saturday. The EFI signal for max temperatures Friday has gotten even stronger as well with values between 0.80-0.95 now seen with a Shift-of-Tails of 1 over portions of the area, showing the potential for anomalous heat. With isolated to scattered chances for convection Friday and Saturday, confidence in reaching Heat Advisory criteria is a bit lower, but cannot rule out the potential need for heat products sometime between Thursday and Saturday. Uncertainty in the synoptic pattern beyond this weekend exists, but there is little evidence that hot/humid conditions will wane so be sure to take heat safety precautions through this week and into the weekend.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

Relatively high confidence in VFR conditions through the TAF forecast period.

FEW-SCT high level convective debris clouds will move over the terminals this morning with light surface winds either S/SW or calm. While it cannot be totally ruled out, the threat for predawn fog or stratus this morning is lower than past mornings and most guidance keeps conditions VFR through the valid TAF period. Winds should pick up from the west-southwest after 15z increasing to 8 to 10 knots after 18z. Have introduced VCSH this afternoon to cover the potential for ISOLD-SCt -SHRA/-TSRA once again. Brief reductions in VSBY/CIG are possible with the strongest showers or storms, but confidence in coverage and timing is too low to put thunder in the forecast right now. Conditions improve late this evening as any lingering precip diminishes with the loss of daytime heating and surface winds return to light and variable.

EXTENDED AVIATION OUTLOOK...A hot and drier weather pattern develops through the week. Convective coverage will be low and restrictions likely minimal as highs push into the upper 90s.

CAE WATCHES/WARNINGS/ADVISORIES

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