textproduct: Columbia

WHAT HAS CHANGED

Chances for scattered showers/storms increase over the next few hours. Aviation discussion updated for 00Z forecast.

KEY MESSAGES

- 1. Diminishing flooding threat into Sunday with continued below normal temperatures.

- 2. A return to a more summer like pattern next week with increased strong to severe storm threat mid week.

DISCUSSION

- 1. Diminishing flooding threat into Sunday with continued below normal temperatures.

Atmospheric environment continues to be favorable to support a heavy rain and flooding threat with PWATs around 2.2-2.4 inches and MUCAPE values between 1000-3000 J/kg across the forecast area. However, convective coverage does not look robust enough to yield widespread flooding probelms. We are still looking at scattered showers and storms developing overnight tonight, especially across the central Midlands. A shortwave is pushing southeastward out of the central Appalachains currently, forcing scattered showers across the upstate. Expect this activity to continue and even potentially increase in coverage over the next few hours. This should merely result in efficient rainfall as it pushes into the region from the northwest. Drier air, especially in the mid levels is expected to move into the forecast area beginning tomorrow which will help to lower the flood threat. Below normal temperatures continue with extensive clouds and light northerly winds as the stalled frontal boundary becomes more diffuse.

- 2. A return to a more summer like pattern next week with increased strong to severe storm threat mid week.

LREF clustered ensemble guidance in reasonable agreement with the overall pattern for the upcoming week featuring a strong upper ridge centered over the southern Rockies and Plains states resulting in downstream upper troughing across the eastern third of the country. This pattern should support a drier air mass over the region early in the week with downsloping northwesterly flow and deeper mixing. There also is likely to be a series of smaller difficult to time disturbances moving through the flow which may add to or enhance normally diurnal convection. The increased mid level dry air may support a slightly higher chance of strong storms and lower flooding threat than we have recently experienced. Temperatures are expected to also warm back to near or above normal early in the week with Tuesday being the warmest day most likely with highs in the mid to upper 90s.

Stronger shortwave energy is forecast to dig through the base of the upper trough into the Mid-Atlantic by late Tuesday pushing a front into the region by mid week. Increased mid level flow and 850mb winds combined with moderate instability should yield increased threat of strong to possibly severe storms Tuesday into Wednesday. SPC continues to carry a 15% risk area across the Mid-Atlantic into North Carolina while CSU ML guidance continues to show a similar signal across the Carolinas on Tuesday and Wednesday. Damaging wind gusts would be the primary threat with any severe threat that may develop.

AVIATION /00Z SUNDAY THROUGH THURSDAY/

VFR conditions with restrictions likely early Sunday morning.

Boundary remains over the area with low level moisture continuing to pool at the terminals as dew points remain in the low to mid 70s. A weak shortwave moving in overnight may generate additional showers and have included a prob30 group at all terminals except DNL/AGS for this possibility. Left out the mention of thunder as expect limited instability in the overnight hours. With continued low level moisture, guidance favors restrictions developing once again early Sunday morning, mainly as low ceilings. Highest potential for IFR is at the Columbia terminals with lower probability south and west, although at least a brief period of IFR remains possibility at all terminals. Expect improvement during the late morning and early afternoon at all terminals with VFR conditions returning. Additional showers and storms may develop towards the end of the period, favoring the eastern area but have left out the mention for now as it is towards the end of the TAF period and confidence remains somewhat limited.

EXTENDED AVIATION OUTLOOK...Drier weather and lower chances for morning restrictions expected early this coming week. By late Tuesday and into Wednesday, rain chances begin to increase again with associated restrictions possible.

CAE WATCHES/WARNINGS/ADVISORIES

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