textproduct: Columbia

WHAT HAS CHANGED

Rain chances tonight into Thursday remain very low. Aviation discussion updated for the 18z TAF issuance.

KEY MESSAGES

- 1. A front will bring breezy winds Thursday and frost/freeze potential late this week into the weekend.

DISCUSSION

Key Message 1: A front will bring breezy winds Thursday and frost/freeze potential late this week into the weekend

The forecast the remainder of the week remains on track. The southern stream shortwave is noted in WV imagery across the Lower Mississippi Valley with the northern wave further off to the northwest across the Mid-Mississippi Valley. Broken clouds will all that will be noted with the southern stream as it approaches the area today. These waves are expected to remain out of phase with the southern most shortwave moving in later this evening and overnight before the deepening northern one shifts through the region Thursday and Friday. This offset in forcing brings limited moisture advection (PWATs under 1") ahead of a cold front tonight into Thursday morning despite a 35-40 kt LLJ. Ensemble guidances continues to trend downward on precip potential, although a few sprinkles remain within the realm of possibility Thursday morning. As the front moves through early Thursday, a tightening pressure gradient develops with a surface low shifting into the Mid- Atlantic. As mentioned above, a robust 30-40 kt LLJ is expected to develop overnight tonight into Thursday, but soundings indicate a strong inversion should prevent this from mixing down until late Thursday morning. Once the inversion breaks, BUFKIT soundings indicate westerly gusts to 25-35 mph should begin mixing down. This should fall short of Lake Wind Advisory criteria across area lakes, but Lake Marion possesses the greatest, albeit a low probability (20 to 30% per latest REFS guidance) of a few gusts reaching 25 kts Thursday afternoon.

A secondary front is expected to move in late Thursday into early Friday morning, bringing much drier air and a push of CAA that is expected to influence temperatures through early next week. In general, the two frontal passages are expected to yield temperatures that cool the remainder of the week with temperatures Thursday remaining in the low to mid 70s before dropping into the upper 50s to low 60s Friday and finally the mid to upper 50s this weekend into early next week. As has been advertised, this northwesterly flow regime and the associated CAA favors frost potential Saturday and Monday mornings and a possible freeze Sunday morning. NBM probabilities for low temperatures less than 32F Sunday morning remain around 25-50% across the area, highest (50 to 75%) in the northern Midlands while probabilities for low temperatures less than 35F are up to 50-70% Saturday, Sunday, and Monday mornings. The need for frost/freeze products this weekend and early next week will continue to be monitored.

AVIATION /18Z WEDNESDAY THROUGH MONDAY/

Expecting a continuation of VFR the next 24 hours.

Satellite showing a fairly good swath of broken mid and high level cloudiness about to be moving into the region ahead of an approaching shortwave this afternoon. This will overspread taf sites through the evening, then some clearing should occur as the wave exits by 06z. Do not anticipate any low level cloudiness through the period at this time, so vfr expected. The main issue over the next 24 hours is going to revolve around winds, and the development of a strong low-level jet, and potential llws that will accompany that. Winds this afternoon will generally be around 5 knots or so, somewhat variable but eventually turning more out of the west by this evening. Low-level inversion sets up overnight, and surface winds will remain at or below 5 knots, but winds 1-2kft will increase to around 35 knots between 03z-06z. This should meet the criteria for llws at times, and will continue with mention of llws later tonight and into Thursday morning. Once the inversion breaks around 14z Thursday, stronger winds will mix downward, and surface winds will increase to between 10-15 kts, and gusts between 20-25 kts will become increasingly common at all locations. With the mixing expected tonight, do not expect any visibility restrictions, so vfr there also.

EXTENDED AVIATION OUTLOOK...Dry air will likely prevent widespread restrictions through the extended. Gusty winds expected again into Friday as a cold front passes.

CAE WATCHES/WARNINGS/ADVISORIES

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