textproduct: Columbia

WHAT HAS CHANGED

Changes for Key Message 1 and Aviation section updated for 00z TAF.

KEY MESSAGES

1. Light rain/drizzle possible over coming hours with patchy fog possible tonight.

2. Dry and warmer this weekend followed by cooler temperatures Monday and Tuesday.

DISCUSSION

KEY MESSAGE #1: Light rain/drizzle possible over coming hours with patchy fog possible tonight.

The front continues to sink through the FA with drier air aloft evident in WV imagery, but weak convergence along the boundary has allowed a few areas of light rain and areas of drizzle to linger across the region. This is expected to continue over the coming hours, but there is some uncertainty in how long these in-situ wedge conditions could last. It is possible as low clouds possibly build in later this evening and into tonight that periods of drizzle continue much of the night as areas north of the front become fairly "locked" in and HRRR soundings become fairly supportive of drizzle with bountiful dry air on top of a moist layer around 2500 ft deep. Either way, no meaningful rainfall is not expected and with high low-level moisture remaining in place, patches of fog will be possible tonight. A couple spots of dense fog cannot be ruled out but confidence in this is not high at the moment so any potential for a Dense Fog Advisory will continue to be monitored this evening and tonight.

KEY MESSAGE #2: Dry and warmer this weekend followed by cooler temperatures Monday and Tuesday.

Expect decreasing cloudiness and warmer temperatures on Saturday as high pressure builds into the region. The warming trend continues into Sunday with the 50th percentile for highs across the forecast area in the mid to upper 70s. A backdoor cold front shifts winds to the northeast Sunday night. Strong high pressure over New England ridges south along the spine of the Appalachians to produce cold air damming on Monday and Tuesday resulting in another pair of days featuring clouds and below normal temperatures. Upper ridging and surface high pressure anchored near Bermuda result in a pattern change during the extended period with warmer and wetter conditions favored.

AVIATION /00Z SATURDAY THROUGH WEDNESDAY/

Widespread restrictions expected through the period as in-situ wedging settles into the region.

Widespread moderate to heavy drizzle has develop along and north of a secondary, backdoor front that is shifting southward at this hour. Overall, this period of precipitation was not well anticipated by guidance or forecasts and is expected to persist for the next several hours. The setup is quite favorable for drizzle actually, with dry air aloft overspreading very moisture rich low-levels. This should favor drizzle continuing through at least 06z at many sites but perhaps longer as this wedging settles into the area. While ceiling/vis restrictions are not yet widespread, they are expected to fall into the IFR or LIFR range within the next few hours at all sites. Upstream observations near Charlotte suggest this, supporting what forecast guidance is saying. Once we go down, expect to remain IFR or LIFR for the bulk of the night and into Saturday morning. Winds will be generally light out of the east or northeast. There may be some clearing by the end of this period but with persistent southwesterly flow aloft holding the inversion in place atop this low-level moisture, skepticism exists over whether we see real clearing by the end of this period or not. Regardless, we should improve to lower MVFR ceilings by the end of the period.

EXTENDED AVIATION OUTLOOK...Some improvement back to vfr possible on by Saturday night as clouds begin to clear out. Nightly br/fg restrictions will remain possible over the weekend and into next week.

CAE WATCHES/WARNINGS/ADVISORIES

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