textproduct: Columbia

WHAT HAS CHANGED

Thursday-Friday rain and storm chances updated. Aviation discussion updated for 06z TAF.

KEY MESSAGES

- 1) Breezy conditions expected on Thursday. Rain and thunderstorm chances increase throughout Thursday and into Friday.

DISCUSSION

KEY MESSAGE #1: Breezy conditions expected on Thursday. Rain and thunderstorm chances increase throughout Thursday and into Friday.

Ahead of southward sinking front, breezy conditions are expected again Thursday outside and with any showers-storms. Wind gusts to around 35 mph are expected starting late morning and into the evening, with sustained winds generally around 15 mph. 850mb jet tops out around 50 knots from ~17z through 22z, so winds may briefly gust higher in any strong showers- storms this afternoon.

This cold front will bring widespread showers and a few thunderstorms across the region by late morning into the evening. HREF guidance is in good agreement with current observations and shows a consistent picture of this sinking line of convection. ML CAPE is able to climb to a couple hundred J/kg thanks to persistent low level moisture convergence but the lack of steep lapse rates aloft and widespread cloud cover will limit instability potential. Showers will overspread the area after 15z as the strongest WAA arrives with that aforementioned 850mb jet. The strong convergence on the northwestern flank of this jet will provide some enhanced forcing for a more aggressive line of heavy showers and storms this afternoon- evening. Limited instability should mitigate the severe thunderstorm threat, but some gusty winds over 50mph are possible in the heaviest convection thanks to the pronounced jet aloft.

This front will slowly sink south into Friday and continue to produce widespread heavy showers into Friday. There remains some disagreement as to how far south the heaviest precip band will actually make it, but generally south of I-20 has a much better chance at exceeding 1.0" for event total. NBM and HREF mean has ticked up again along and south of I-20, with a mean around 0.75-1.0" but a the percentile of near 3.0". This high end potential across the southern Midlands and CSRA continues given the favorable synoptic, mesoscale, and profile setup with a slow moving front, parallel flow aloft, and saturated-conditional unstable soundings with PWAT's around 1.5".

AVIATION /06Z THURSDAY THROUGH MONDAY/

VFR conditions generally expected through 12z then restrictions possible with moisture advection and light showers ahead of an approaching front.

A frontal boundary currently extends through the southern Ohio Valley and will gradually move southeast toward the area today before moving through the area tonight. Ahead of the front breezy southwesterly winds expected around 10 to 15 knots with gusts to 25 knots before winds diminish around 10 knots or less with sunset. Increasing moisture will result in a gradual lowering of cigs through the day with mixed signals in guidance but think some stratus possible with light showers this morning so included in a PROB30 group 10-15z. Otherwise restrictions probably hold off until around 18z-20z when more steady showers arrive ahead of the front with MVFR vsby restrictions in rain and possible thunderstorms. As the front moves through and eventually stalls cigs expected to crash to IFR after 00z-03z time frame all terminals with light rain continuing.

EXTENDED AVIATION OUTLOOK...Widespread restrictions and rain expected Thursday night and into Friday as a front moves through the area.

CAE WATCHES/WARNINGS/ADVISORIES

SC...Lake Wind Advisory from 8 AM this morning to 5 PM EST this afternoon for SCZ016-018-020>022-025>031-035-037-038-041- 115-116-135>137. GA...Lake Wind Advisory from 8 AM this morning to 5 PM EST this afternoon for GAZ040-063>065-077.