textproduct: Columbia

WHAT HAS CHANGED

Fog favored in the CSRA early this morning and may become dense at times. Aviation discussion updated for 06Z TAFs.

KEY MESSAGES

- 1. Patchy fog developing this morning may become dense at times.

- 2. Well above normal temperatures the remainder of the week with increasing diurnal rain chances starting this weekend.

DISCUSSION

KEY MESSAGE #1: Patchy fog developing this morning may become dense at times.

Mid to high level clouds passing over the northern half of the area but clear over the southern half. Low level moisture continues to be in place once again this morning and a persistence forecast seems reasonable for fog development this morning as well with hi-res guidance favoring the southern area for the potential for dense fog. The VAD wind profile does indicate that a low level jet has strengthened to near 30 knots which would preclude widespread fog, although hi-res guidance indicates that there is a relative minimum in winds aloft in the southern portion of the forecast area. Overall, will continue to monitor the potential need for a dense fog advisory. Tonight, fog will be possible once again, mainly in the same location with lower winds aloft, although seems to favor more patchy fog versus widespread fog.

KEY MESSAGE #2: Well above normal temperatures the remainder of the week with increasing diurnal rain chances starting this weekend.

A persistent Bermuda surface high and upper ridging strengthening will lead to relatively hot and humid weather through early next week. This well advertised period continues to show high confidence in a temperature forecast with highs 10-15 degrees above seasonal average as ensemble means indicate upper ridging between 1 to 2 standard deviations above normal. Moisture will increase as well with increasing southwesterly flow, although chances for rain will be limited both today and tomorrow as upper ridging remains strong over the area. By Saturday, LREF probabilities of PWATs rising to above an inch and a quarter are between 50-60% and as the ridge likely weakens further Sunday into Monday with the axis of the upper ridge shifting a bit eastward, precip chances will increase as well as chances for thunderstorms during the afternoon.

AVIATION /06Z THURSDAY THROUGH MONDAY/

VFR mainly expected this evening before widespread fog and stratus brings IFR-LIFR restrictions by early Thursday morning.

Low level ridge has set up right over the forecast area late this afternoon and should move little overnight, providing light surface winds this evening. Patches of smoke from controlled burns have so far managed to avoid the TAF sites, and while I can;t rule out a little bit working into a couple of locations, it should not be enough to create any restrictions.

Overnight, with the temperature dropping below crossover temps, light winds, and only thin cirrus passing by, low clouds and fog will once again become dominant by the early morning hours on Thursday. Restrictions are expected at all sites starting at around 8-9Z, and ending by Noon. Biggest challenge is determining if fog or very low cigs will dominate as there is a bit of a low level jet, but I think the jet will be low enough by sunrise that fog will dominate for a few hours until the boundary layer starts to lift. It's possible that low cigs could hold on a bit longer at some spots than I am currently forecasting as stratus can be pretty stubborn to break in patterns like this, but there is not a lot of model support for keeping IFR conditions past noon.

EXTENDED AVIATION OUTLOOK...There is potential for additional morning stratus or fog into the latter half of the week along with increased shower chances for the weekend.

CAE WATCHES/WARNINGS/ADVISORIES

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