textproduct: Columbia

WHAT HAS CHANGED

Updates to aviation section for the 12z TAFs.

KEY MESSAGES

- 1) Light rain possible Wednesday associated with a cold front.

- 2) Stronger system moves into the area this weekend leading to chances for more heavier rain.

DISCUSSION

KEY MESSAGE #1: Light rain possible on Wednesday.

Surface high pressure shifting offshore today with low pressure moving into the Great Lakes. A strengthening front to the northwest of the area along with strengthening upper ridging will lead to well above average temperatures today and tomorrow with moisture increasing from winds out of the southwest. As the front moves into the area Wednesday, forcing is expected to weaken as a shortwave to the west from a Baja low being absorbed back into the flow continues to weaken. Models continue to favor a relatively high pop, low qpf frontal passage Wednesday with rain chances generally highest in the southern portion of the area. GEFS and EC ensemble 50th percentile amounts are around a tenth of an inch or less for the area. Behind the front, air mass not expected to be particularly cold with temperatures near average through the end of the week and into the weekend. Blended guidance shows a much more limited spread in temperature ranges through the end of the week indicating relatively high confidence.

KEY MESSAGE #2: Higher rain chances late Saturday into Sunday.

A Baja Low Friday will begin to push eastward and become the dominant synoptic feature over the CONUS leading to deepening surface low and stronger moisture transport from the Gulf with a robust southerly low level jet into the Southeast with NAEFS mean showing 850 mb winds over the 90th percentile over the Deep South. As this system moves eastward towards the forecast area, blended guidance favors much heavier rain late this weekend compared to Wednesday's system with probability of greater than an inch of rain very high, especially for a day 6 forecast (70-80%). Ensemble members are indicating the potential for some instability as well associated with this system so while thunderstorm probabilities are low at this point, will need to monitor trends in the coming days. There still remains uncertainty mainly into how and when the Baja Low is absorbed into the overall flow.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

Mainly VFR Conditions expected to continue.

Moisture will be on the increase from the southwest during the period. Majority of the forecast period will remain dry, with rain showers potentially moving in late in the taf period.

Ceilings...Morning satellite shows low-level ifr stratus deck moving slowly northeastward across central GA, and towards the CSRA. This will need to be monitored, but current blend slows the movement and keeps it just outside of ags/dnl taf locations. However, the latest hrrr does indicate the potential for this to keep moving into the CSRA, impacting those two locations towards 15z. Have kept it out for the 12z tafs, but can not rule out the need for a tempo group if it does not slow down later this morning. All other sites should remain vfr through the day with mainly some cirrus and possibly a few afternoon cumulus. Stratus and mid-level clouds will increase later tonight and into Wednesday morning ahead of the next approaching weather system, but at this time conditions will remain vfr.

Visibilities...Right now forecast to be vfr through the period. However, a few spot requests for regional burns that would be southwest of a few airports could impact visibility's at ags/dnl, and also at cae/cub. A few degrees difference in wind direction, along with low-level mixing, could be the difference between lower mvfr visibilities in haze or smoke. Have left out of current tafs due to uncertainty in regards to burns actually occurring, but if they do begin later this morning, local airports could be impacted.

Finally winds...Ahead of the approaching cold front winds turn southwest to westerly. Speeds light to start, then increase to around 10 knots late morning and remaining there through the period. Do expect to see some wind gusts reach 20 knots this afternoon. Later tonight, a strong low-level jet will be setting up, bringing 30+ knots around 2kft. As long as surface winds remain up, llws should be limited and have left out for now.

EXTENDED AVIATION OUTLOOK...Restrictions possible on Wednesday as a system pushes into the region and brings a chance of rain. Additional restrictions possible into the weekend with another system moving into the area.

CAE WATCHES/WARNINGS/ADVISORIES

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