textproduct: Columbia

WHAT HAS CHANGED

Aviation discussion updated for 12z TAF.

KEY MESSAGES

- 1) Rain chances increase today and remain in place through the weekend. Thunderstorms are possible today and again on Saturday. A soaking rain looks increasingly like, with totals of 0.5"+ expected.

- 2) Cold temperatures return behind this system, with well below normal temps expected Monday and Tuesday.

DISCUSSION

KEY MESSAGE #1: Rain chances increase today and remain in place through the weekend. Thunderstorms are possible today and again on Saturday. A soaking rain looks increasingly like, with totals of 0.5"+ expected.

A cold front is currently marching towards the area from the northwest, with moisture and low level winds increasing ahead of it. Mid-level clouds are increasing as a result, with winds expected to begin increasing at the surface as the cold front gradually approaches this morning. Showers are forecast along and ahead of the front by the mid to late morning hours across the area. With dewpoints in the 60s and temps in the 70s, some instability is likely to be in place ahead of the front and isolated thunderstorms are expected. These probably won't be too widespread, though, given weak background synoptic support through the day. The surface winds are expected to be robust along and ahead of the front with gusts near 35 mph expected. A Lake Wind Advisory has been hoisted for this.

Rainfall is expected again on Saturday and into early Sunday. The aforementioned front will sag slowly southward, likely slowing down somewhere in our southern forecast area. The location of this is important for the overall forecast this weekend as it will dictate where the heaviest and most persistent rain falls during the day on Saturday. But in general, it should end up somewhere in our southern tier of counties by Friday night. As it does so, a round of increasing warm advection is expected to yield widespread showers and embedded thunderstorms after 4a on Saturday. The global models all have a good handle on this and are more realistic than the CAMs with the southward progression of the front, so leaning more into their solutions as of now. Expecting a swath of moderate rain early to midday Saturday, with another batch of showers developing on Saturday night as the deeper trough digs into the eastern CONUS. Overall, Saturday and Sunday look cooler due to clouds & the front fully clearing the area. Rainfall totals are tricky and somewhat dependent on the location of that front, with it being the impetus for the heaviest rainfall. But confidence is high that many areas should see 0.5" of rain or more, which will aid in improving our drought conditions.

KEY MESSAGE #2: Cold temperatures return behind this system, with well below normal temps expected Monday and Tuesday.

A deep trough will overspread the eastern CONUS late this weekend and into early next week. This will lead to a return to colder temperatures on Monday and Tuesday especially. Ensemble guidance shows >90% chances of temps 10F or more below normal on both days. ECE EFI suggests anomalously cool temps both days too. Expecting highs in the 40s on Monday and only the low 50s on Tuesday. Should be quite a shock to the system given how anomalously warm we have been the past few days! Moderating temps are again expected by the middle part of next week.

AVIATION /12Z FRIDAY THROUGH TUESDAY/

MVFR conditions early Friday, then mix of restrictions and precip the remainder of Friday as a front moves through.

The main story of the TAF period is an approaching front, which will bring gusty winds, showers, and a mix of vsby and cig restrictions Friday. For early Friday, strengthening winds around 2k feet will push the TAF sites close to LLWS conditions, but surface winds should remain high enough to prevent reaching criteria. Showers are expected to push across the area later this morning with winds increasing out of the southwest 20-25 knots; a few isolated thunderstorms are possible at AGS and DNL before 16z but very low confidence. Cigs will steadily drop to MVFR this morning ahead of a consolidated line of showers, and again low confidence possible thunderstorms, late morning into the afternoon, with gusts to around 30 knots; best chance for TSRA at any TAF site will be 16-20z, but again confidence is too low for a mention right now. Winds will turn out of the west behind this line of showers in the evening. Additional showers will push into the TAF sites again after 00z tonight, becoming persistent after 06z Saturday.

EXTENDED AVIATION OUTLOOK...Abundant low level moisture will bring chances for morning fog/stratus into this weekend. Chances of rain continue on Saturday with some thunderstorms possible.

CAE WATCHES/WARNINGS/ADVISORIES

SC...Lake Wind Advisory until 4 PM EST this afternoon for SCZ016- 018-020>022-025>031-035-037-038-041-115-116-135>137. GA...Lake Wind Advisory until 4 PM EST this afternoon for GAZ040- 063>065-077.