textproduct: Columbia

SYNOPSIS

Warm weather continues with a chance for showers today and Wednesday. A very dry and cold air mass moves in behind the front for the remainder of Thanksgiving week. Temperatures return to seasonal values late in the weekend but the chance of rain also returns.

NEAR TERM /THROUGH TONIGHT/

Key message(s):

- Showers and a few thunderstorms will move across the Southeast today and tonight

A shortwave will move over the Southeast today lifting from west of the forecast area into the southern Appalachians this morning. A broader trough will remain west of the region through the near term and promote moist, SW flow. As the pressure gradient strengthens through the day we will see winds gust to around 20 mph. Warm advection will push highs into the mid 70s to low 80s despite mostly cloudy skies.

Through the day, the chance of rain for the majority of the area remains low. With shortwave energy generally staying to our west and north, there is little support for convection in the weakly unstable environment. The exception will be for areas in or near the Upstate which will be closer to the influence of the shortwave trough. Scattered showers may develop over the western Midlands through the afternoon. The chance for widespread rain over the area as a whole is higher after sunset. As upstream convection advances eastward through the day showers and possibly a few lingering thunderstorms may enter the forecast area from the west in the late afternoon or evening. The moist air mass could continue to support additional development although CAMs generally show diminishing activity after the loss of daytime heating. Weak lapse rates will limit the threat of severe weather. Temperatures don't fall too much due to clouds and WAA with lows in the upper 50s to lower 60s.

SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/

Key message(s):

- Continued rain showers and isolated storm first half of Wednesday ahead of cold front.

- Breezy winds and warm temperatures continue Wednesday before cold/dry air is ushered in behind the front into Thursday.

Wednesday and Wednesday Night: The base of the deep upper trough begins to pivot in Wednesday, ushering in a surface cold front that is expected to clear the FA by the evening hours. Ahead of the front, deep southwesterly flow is expected with PWAT's likely reaching near 1.50" as decent moisture convergence is seen along the front during the morning hours. This should lead to scattered showers Wednesday morning and into the early afternoon where a couple embedded storms cannot be ruled out with MUCAPE on the order of 300-700 J/kg ahead of the front. This plume of moisture is expected to quickly move toward the coast through the afternoon, bringing gradual clearing and temperatures back into the mid 70s. As the front pushes through, a tightening pressure gradient is seen in model guidance with 25-30 kts of flow at 850mb, thus breezy westerly winds are expected during the afternoon, continuing into the evening as CAA pushes in as well behind the front. Gusts up to 20-25 mph are expected, possibly nearing Lake Wind Advisory criteria. Overnight, flow turns more northwesterly behind the front and weak CAA begins to push in, dropping lows into the mid to upper 30s.

Thursday and Thursday Night: Surface high pressure begins to slowly ridge into the region through the day Thursday with troughing aloft remaining in place. Much colder and drier air begins to push in behind the Wednesday's front where a combination of strong CAA and some downsloping flow drops dewpoints into the 20's Thursday afternoon, rapidly falling from dewpoints in the 50's just 24 hours prior on Wednesday. Strong CAA should also bring high temperatures below normal, in the mid to upper 50s. Overnight, solid radiational cooling and continued CAA should bring the first of multiple nights with sub-freezing overnight lows where they are expected to bottom out in the upper 20s to low 30s.

LONG TERM /FRIDAY THROUGH MONDAY/

Key message(s):

- Cold and very dry air likely remains in place into the weekend.

- Temperatures moderate some late in the weekend into early next week with possible rain chances moving in.

A continued very cold and dry airmass looks remain in place to round out the week and start the weekend, which is well supported in global guidance at this time. The surface high is expected to move overhead Friday and into Saturday as upper level heights look to level off and become more zonal. This should bring continued dry conditions with below normal temperatures where highs may barely break 50F both Friday and Saturday. Friday night looks to be the chilliest with near ideal radiational cooling conditions but Saturday night should also be on the colder side.

Ensemble and deterministic model guidance continues to be fairly spread out to end the period but the general upper level trend appears to be another deep trough digs into the southwest CONUS, leading to upper flow over the FA that becomes increasingly southwesterly with moisture returning to the area along with near average temperatures. Overall, this pattern is favorable for returning rain chances to end the weekend and into early next week, but confidence in coverage of any rain is low at this time.

AVIATION /05Z TUESDAY THROUGH SATURDAY/

Predominantly VFR conditions favored through tonight.

Southeast winds will once again pull moisture into the area through the morning. Unlike yesterday, we do not expect fog development due to a 20 to 25 kt LLJ which will help keep the low-levels mixed. There may be brief MVFR ceilings which develop prior to 15Z given the low-level moisture advection into the area. Winds will increase after sunrise and shift from SE to SW with gusts up to 20 knots possible into the afternoon.

Rain chances at the terminals are low through the 24 hour forecast period. The stronger support for convective development will lift well north of the TAF sites. The highest chance for rain at the terminals will be towards the end of the period when upstream convection could push into the forecast area. There will be little support for continued development overnight and CAMs generally show diminishing convective coverage after sunset. So there is little confidence in any impacts from convection at the terminals.

EXTENDED AVIATION OUTLOOK...The next chance of widespread restrictions will be Wednesday as a front and deep moisture move across the Southeast.

CAE WATCHES/WARNINGS/ADVISORIES

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