textproduct: Columbia

SYNOPSIS

Dry weather is expected to continue through Saturday with near to slightly below normal daytime temperatures. A cold front crosses the region Saturday night and Sunday morning ushering in an arctic air mass for Sunday night into early next week. Weak ridging should then allow for air mass recovery by the middle of next week.

NEAR TERM /THROUGH TONIGHT/

Key message(s):

- Dry with near normal temperatures.

Upper trough has lifted north with zonal flow aloft across the southeast. Scattered mainly high cloudiness will move overhead from time to time as a weak shortwave moves across NC. With surface high pressure moving in, temps this morning are forecast to dip to near freezing for lows, particularly with little boundary layer mixing. The remainder of today should feature fairly benign weather. Surface winds will be southwesterly and usher in some warmer air, with highs reaching the mid 50s north to low 60s south, which is within a degree or two either side of normal for this time of year. Lows tonight should moderate a few degrees, ranging from the low 30s north to upper 30s south as heights and thicknesses increase slightly.

SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/

Key message(s): - Above average temperatures Saturday with isolated rain chances Saturday night.

By Saturday morning, zonal flow aloft expected across the area with surface high pressure offshore and an approaching strong cold front from the northwest. As a result, expect warm advection during the day with near normal 500mb heights indicated by ensemble means. Blended guidance favors above average high temperatures, generally in the low to mid 60s. Southwest flow aloft strengthening Saturday night with strong model consensus in the upper low shifting into the Great Lakes. This will lead to increasing clouds and chances for rain Saturday night into Sunday morning with LREF PWAT probabilities of greater than 0.9 inch around 40-60%. Forecast soundings do indicate much of this moisture increase will be relatively shallow with limited moisture above 10,000 feet. As a result, widespread rain not expected and amounts expected to be light. The increase in clouds will likely moderate low temperatures with blended guidance indicating mid to upper 40s for overnight lows.

LONG TERM /SUNDAY THROUGH THURSDAY/

Key message(s):

- Arctic cold front ushers in the coldest air mass of the season.

- Cold Weather Advisory likely needed Sunday night into Monday morning, possible Monday night into Tuesday morning.

Lingering showers early Sunday ahead of a cold front with strong cold and dry advection beginning for the second half of the day. High temperature likely reached relatively early with cold advection during the afternoon. Gusty winds expected associated with the frontal passage as the high pressure moving into the Central US as the NAEFS mean showing the strength of the surface high greater than 1040mb, above the 99.5th percentile in portions of the Midwest. NBM indicates the probability of max gusts greater than 30 mph around 40 to 60 percent Sunday. Cold advection will be strong into Sunday night with LREF probs remaining high for potential for Cold Weather Advisory criteria, especially in the southeastern area where the criteria is 15F. As high pressure settles over the area into Monday, temperatures likely remaining in the 30s, around 20 degrees below seasonal average. Monday night will be a favorable radiational cooling night with clear skies and a weak low level jet. EC EFI actually highlights Monday night lows below -0.9 indicating the potential for air temperatures to actually be around the same or possibly even lower than Sunday night. Winds expected to be light, however, so remains a bit more uncertain of reaching Cold Air Advisory criteria. Feel pretty comfortable with nbm 50pct lows for both Sunday and Monday night as this remains near the GEFS and ENS means with the GEPS skewing the distribution towards the colder side, although this tends to be a typical bias with the GEPS.

Temperatures expected to moderate towards the end of the week as the surface high shifts offshore and upper troughing is replaced by zonal flow once again. Dry weather generally expected to continue with a bit of a moisture increase indicated in ensembles by Thursday.

AVIATION /12Z FRIDAY THROUGH TUESDAY/

Mainly VFR conditions are expected through the TAF period.

Mainly SKC, with periods of mid and high level clouds that will move across the region from west to east in association with an upper level trough. SFC winds will be light and variable to calm through much of this morning, then increase out of the southwest at 5-10 kts after into this afternoon. Although brief patchy MVFR river fog could occur near AGS/OGB just before dawn this morning, its not in the TAFs at this time due to low confidence. Winds decouple back to light and variable or calm tonight under clear skies.

EXTENDED AVIATION OUTLOOK...Dry air likely will prevent widespread restrictions into at least Saturday, but localized fog along river valleys will be possible toward Sunday morning.

CAE WATCHES/WARNINGS/ADVISORIES

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