textproduct: Columbia

WHAT HAS CHANGED

Updated location of the front and updated mesoanalysis but overall the forecast remains on track. Update to aviation section for the 12z TAFs.

KEY MESSAGES

- 1) Cold front moves in today with periods of rain and gusty winds.

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

DISCUSSION

KEY MESSAGE #1: Cold front moves in today with periods of rain and gusty winds.

Surface analysis early this morning indicates the cold front remains to the northwest of the forecast area, moving into the southern Appalachians early this morning. Moisture transport has continued to strengthen with increasing 850mb winds, expected to continue through morning with HREF probability of 850mb winds greater than 45 knots very high (greater than 80% in southern half of the area). HREF mean PWATs increase to above 1.2 inches as a result. Light rain has developed ahead of the front over the area but coverage will continue to be limited until the front actually moves into the area later this morning into the afternoon. Total rainfall expected to be limited as has been the case for the last several days. Wind gusts have trended higher for today, however, with hires sounding profiles showing some increased mixing shortly after sunrise this morning as the inversion that sets up overnight will likely be weak with elevated winds and increased cloud coverage. This would allow some of the low level jet to mix down. While hires guidance wind gusts is likely over-mixing to some extent, there will likely be a window after sunrise where gusts around 30 mph will be possible. The jet begins to weaken into the afternoon and while gusts will continue to be breezy, not expected to be as strong.

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. Strong southerly low level jet will transport significant moisture into the southern CONUS from the Gulf. Overall thinking remains the same with blended guidance continue to show around 60-70% chance of greater than an inch of rain. Probability of thunder remains very low and there will likely be a competition between cold air damming potential to the north and warm advection across the south. Still will be something to monitor over the coming days.

AVIATION /12Z WEDNESDAY THROUGH SUNDAY/

Although mainly VFR conditions expected for majority of the period, brief mvfr conditions will be possible as showers move across the area through the day.

Surface front moving towards the region from the west will continue to bring plenty of moisture and clouds to the area into the afternoon hours today. As this system nears, ceilings will begin lowering during the morning, although they will remain within vfr outside of heavier rainfall areas. Can not rule out a brief period of mvfr conditions as the main band of showers moves through from mid-morning and into the early afternoon hours, but more confident in low end vfr at this time. As the main front pushes east and much drier air pushes into the area, ceilings will lift and begin to scatter as drier air moves into the forecast area. Winds will be southwesterly ahead of the surface front, with gusts around 20 knots possible during the day Wednesday. Behind the front, winds turning northwesterly and gusty through sunset, then winds will decouple some and wind gusts should diminish. Can not rule out some stronger winds around 2kft as low-level jet gets stronger and moves across the area, but at this time surface winds appear to be strong enough to limit mention of any llws.

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

CAE WATCHES/WARNINGS/ADVISORIES

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