textproduct: Columbia

WHAT HAS CHANGED

Update to aviation section for the 00z TAFs.

KEY MESSAGES

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

- 2) Periods of moderate to heavy rain possible late Saturday into Sunday.

DISCUSSION

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

A surface cold front will be working into the area Wednesday morning. A few light showers or sprinkles will be over the region before sunrise but dry low level air will keep amounts very light, if measurable at all, through the early morning. Moisture advection will increase through the morning ahead of the front with PWAT's reaching around 1.25" near or shortly after sunrise. This should lead to scattered showers moving into the FA through the morning and into the afternoon hours before the front clears out in the afternoon with much drier air moving in behind. 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: Periods of moderate to heavy rain possible late Saturday into Sunday.

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 /00Z WEDNESDAY THROUGH SUNDAY/

Conditions Deteriorate at the Terminals Towards Daybreak....

The gusty winds from earlier today continue to subside at the terminals this evening, increasing the risk of low-level wind shear developing as the night goes on. Have maintained the threat with this update with winds around 40-45 knots possible at 2000 feet. Surface winds rise towards daybreak as the next storm system approaches, which should reduce the threat of low- level wind shear. Clouds will continue to lower and thicken tonight, with restrictions expected to develop between 11Z and 13Z. Periods of light rain are likely for much of the daytime hours, ending from northwest to southeast late in the afternoon as drier air moves into the region. Expect a return to VFR conditions at all terminals near the end of the current TAF period.

EXTENDED AVIATION OUTLOOK...Additional restrictions are possible into the weekend with another system moving into the area.

CAE WATCHES/WARNINGS/ADVISORIES

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