textproduct: Columbia

WHAT HAS CHANGED

Potential for moderate to heavy rain on Sunday as confidence in the synoptic pattern increases. Updates to aviation section for the 18z TAFs.

KEY MESSAGES

- 1) Cold front moves in Wednesday with scattered rain chances.

- 2) Next rain chance moves in late Saturday into Sunday with periods of moderate to heavy rain possible.

DISCUSSION

KEY MESSAGE #1: Cold front moves in Wednesday with scattered rain chances and breezy winds.

The upper ridge will flatten out some on Wednesday as the remnants of the Baja low currently moving into southern Texas begins to slide eastward, but temperatures are still expected to reach toward the upper 60s to near 70. A surface cold front will also be working into the area starting Wednesday morning, clearing the FA by the late afternoon hours. Generous moisture advection ahead of the front is expected with PWAT's reaching toward 1.25" Wednesday morning and this should aid in bringing scattered rain chances to the FA through the morning and into the afternoon hours before the front clears out. Overall, not much has changed with the expected light rainfall amounts, though recent high-res guidance has bumped up a bit where spots toward 0.25" could be possible. Ahead of the front and behind it, gusty winds will be possible where gusts up to 20-25 mph will be possible. Dewpoints quickly fall from the 50s into the lower 30s by Wednesday evening and a drier air mass moves in for Thursday, though temperatures should still be around normal.

KEY MESSAGE #2: Next rain chance moves in late Saturday into Sunday with periods of moderate to heavy rain possible.

Another Baja low will begin to shift eastward Friday and into the weekend, likely bringing widespread rain chances late Saturday and into Sunday. Better agreement is seen across deterministic guidance, and less spread in solutions is evident in the latest LREF cluster analysis. The main uncertainty still revolves around how the Baja low is absorbed into the synoptic flow but in general, the upper low is expected to move into the northern Gulf through the day Sunday. It will bring strong upper support along with impressive low level moisture advection as a 25-35 kt LLJ sets up. This system is expected to bring potential moderate to heavy rainfall to the area where all 4 clusters and the mean LREF solution currently have probabilities for greater than 1" of QPF between 40-60%. The most recent NBM is fairly similar with this as well with probabilities for greater than 1" of QPF between 60-70%. There is still the potential for fairly weak MUCAPE to work into the region, but greater uncertainty in thunderstorm potential exists.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

Mainly VFR Conditions expected to continue through tonight, with MVFR ceilings possible ahead of and immediately behind the cold front on Wednesday.

Southwesterly winds have commenced over the last few hours, with winds slowly increasing in strength. Still looking at the potential for frequent gusts upwards of 20 knots this afternoon out of the southwest as the pressure gradient tightens. Skies should generally remain mostly clear with some high clouds slowly increasing this afternoon and tonight. Placed a TEMPO group for the next few hours at the Columbia and Augusta sites due to the close proximity of prescribed burns that are due southwest of each site. There is no guarantee that smoke or haze is a consistent problem but the burns are close enough that it could limit visibilities briefly at the airfields periodically through this afternoon. By tonight, surface winds are forecast to stay in the 5-10 knot range overnight as strong wind fields overspread the area ahead of our next front. SUrface flow likely won't be strong enough to avoid low-level wind shear, though, with winds around 40-45 knots at 2000 feet. Have LLWS in the TAFs from 00z through 12z at all sites to account for this. By early Wednesday morning, moisture will quickly increase and yield showers and at least mid-level clouds. There is support amongst guidance to think that some MVFR cigs will develop as well but confidence isn't super high in this at this point. Have included it in the TAFs but wouldn't be surprised if the cig forecast gets more pessimistic or more optimistic with more observations and data trends. Expecting the rain to be light enough tomorrow morning that visibility restrictions are unlikely. Most of the rain will likely clear the area just after 18z tomorrow.

EXTENDED AVIATION OUTLOOK...Restrictions should quickly clear after 18z tomorrow as winds veer out of the northwest and dry air overspreads the area. Additional restrictions possible into the weekend with another system moving into the area.

CAE WATCHES/WARNINGS/ADVISORIES

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