textproduct: Columbia

SYNOPSIS

Increasing moisture to end the week with light rain possible tonight into Friday. The weekend looks warmer and wetter with widespread rain especially late Saturday into Sunday with a chance of storms Sunday. High pressure builds back in behind a cold front early next week with above normal temperatures expected through the middle of next week.

NEAR TERM /THROUGH TONIGHT/

Key Message(s):

- Seasonable with increasing moisture.

Flat upper ridge over the Southeastern CONUS. Upper low over the southern Plains will be moving northeast toward the Mid Mississippi Valley. There is short wave trough this morning over Alabama moving to the northeast. At the surface, a strong pressure ridge centered over New England extends southwest across the western Carolinas. Ahead of the short wave trough, high level clouds are spreading across the region. Low-level moisture is also increasing across GA and coastal SC as south-easterly warm advection/moisture flux and eventual isentropic lift increases. This moisture will spread north into central SC later this morning and through the day. Precipitable water expected to increase to around 1.00 inch through tonight. Cloudiness will likely keep temps down a bit through the day so lowered from previous forecast slightly, especially in the CSRA. Guidance pops have increased tonight, so raised pops to chance all areas, mainly after midnight, but can't rule out a few isolated light showers later this afternoon. QPF expected to be light, up to 0.05 inch. High temps low 50s and lows tonight in the upper 30s to low 40s.

SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/

Key Message(s):

- Cooler Friday, especially in the northwest with scattered light rain possible across the area. - Warming up for Saturday with increasing chances for rain showers as a front approaches from the west.

Trend in model guidance towards stronger isentropic lift across the forecast area early Friday, maximized in the northwest portion of the forecast area. The upper height pattern has also trended more progressive with the ridge axis farther to the east during the day on Friday. The result is stronger southwest flow aloft with HREF mean indicating PWATs rising to near an inch across the forecast area. Forecast soundings as a result of this deeper moisture are much more favorable for a precipitation induced cold air damming setup, especially in the northwest portion of the forecast area. Have lowered temps in the northwest below blended guidance as most of the area north of I-20 will likely remain in the 40s, although if trends continue, may not actually be low enough for the highs Friday. Increased pops as well as guidance is favoring relatively high pop, low qpf with SREF probs of QPF exceeding a tenth of an inch around 40 to 50 percent. Widespread clouds Friday night will lead to mild overnight lows with the high shifting offshore leading to southern winds which may actually allow temperatures to rise slightly in the early Saturday morning hours.

With the more progressive upper pattern, more likely that forcing associated with shortwaves pivoting through weaknesses in the ridge move into the western portion of the forecast area Saturday and as a result, pops have increased with NAEFS mean indicated that PWATs will be above the 90th percentile across the entire area. Forcing may be a bit more limited in the eastern portion of the forecast area until Saturday night but with moisture so high, have kept chance pops in place. As an upper trough strengthens over the southern Plains Saturday, heights will rise in response upstream. This along with winds increasing out of the south will lead to temperatures much warmer for Saturday with highs in the mid 60s in the northwest to low 70s in the southeast, even with widespread clouds. The upper trough and associated surface cold front will continue to approach the area into Saturday night with increasing chances for showers associated with it.

LONG TERM /SUNDAY THROUGH WEDNESDAY/

Key Message(s):

- Front moves through Sunday with widespread showers and thunderstorms possible - Temperatures remain above average through the long term.

As the upper trough and cold front move through the area Sunday, forcing across the area will be strong leading to widespread moderate showers. GEFS indicates between 40 to 60 percent probability of sbCAPE exceeding 500 J/kg so have continued the mention of thunder although there does remain some timing issues for the exact passage of the front. Any storms that do form could be organized with the potential for deep layer shear as LREF indicates around 40 to 50 percent chance of sfc-500mb wind shear greater than 30 knots. Not much of an air mass change behind the front expected with mostly zonal flow aloft into early next week. Blended guidance shows limited spread in temperatures into next week indicating relatively higher certainty, especially for highs in the long term remaining above average. Another weak system is possible towards mid-week, although moisture may be a bit more limited with around 70 to 80 percent of GEFS members indicating PWATs below an inch.

AVIATION /12Z THURSDAY THROUGH MONDAY/

VFR conditions through at least 00z Friday. MVFR ceilings develop late tonight.

High pressure centered to the northeast of the area with resulting north-easterly low-level flow. Satellite showing patchy VFR strato-cumulus across the region with some mid and high level clouds. As moisture flux increases through the day, strato-cumulus will increase in coverage and slowly lower tonight. MVFR ceiling probabilities increase after 00z especially near AGS and DNL. the lower ceilings are expected to spread north into the central Midlands by 10z.

EXTENDED AVIATION OUTLOOK...Ceiling and visibility restrictions possible Friday through the weekend as a low pressure system moves through the eastern CONUS.

CAE WATCHES/WARNINGS/ADVISORIES

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