textproduct: Columbia

SYNOPSIS

Warm weather continues today with scattered showers this morning ahead of a cold front. A very dry and cold air mass moves in behind the front for the remainder of Thanksgiving week. Temperatures return to near normal values late in the weekend but the chance of rain also returns by early next week.

NEAR TERM /THROUGH TONIGHT/

Key message(s):

- Scattered showers early today

Broad upper level troughing will shift eastward through the near term promoting moist, SW flow ahead of a cold front. This front is approaching the area slowly with showers moving across the forecast area early this morning. PWAT values near 1.5 inches and convergence along and ahead of the front will allow convection to develop through the morning until the front pushes through the area late in the day or evening. An isolated thunderstorm is possible with MUCAPE values from the SPC Mesoanalysis showing around 500 J/kg but weak rain rates and poor lapse rates do not support a severe weather threat. Overall, rainfall totals are not expected to be very high with most locations receiving a tenth of an inch or less but isolated locations could see up to a quarter inch.

Breezy conditions are expected with wind gusts of 25 to 30 mph at times during the afternoon and again in the evening as cold advection and a dry air mass surge into the region behind the front. A Lake Wind Advisory may be needed although gusts are expected to remain below criteria. Temperatures will continue to be warm with highs in the low to mid 70s. But temperatures plunge tonight with lows falling into the 30s under cold advection.

SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/

Key message(s):

- Cold and very dry airmass pushes in.

- Overnight lows likely fall into the 20s each night.

Not much has changed for the outlook on Thanksgiving and Friday as behind Wednesday's front, a very dry and cold airmass is expected to push in as upper troughing remains overhead before exiting and upper flow becomes more zonal Friday. Surface high pressure is expected to slowly ridge into the FA through the period before moving overhead late Friday and into Saturday. Dewpoints are expected to plummet with the help of strong CAA and downsloping each day, into the low to mid 20s on Thanksgiving and then into the teens on Friday. This should lead to near critical RH values on Thanksgiving and RH values below critical values Friday afternoon. Luckily with the departing trough and loosening pressure gradient, northwesterly winds are expected to be weaker each day, though isolated gusts near 15 mph are not out of the question on Thanksgiving.

CAA will keep temperatures well below normal each day, in the mid to upper 50s on Thanksgiving then the upper 40s to low 50s on Friday. Strong radiational cooling conditions are expected each night as well where lows into the upper 20s are possible Thursday night and into the mid to upper 20s Friday night, possibly colder. The main complication in cooling conditions Friday night with otherwise ideal radiational cooling as the high moves overhead is possible high clouds moving in as indicated in BUFKIT soundings. If little to no cloud cover is seen, the current deterministic NBM would be too warm and lows closer to the NBM25th percentile would be possible (into the lower 20s).

LONG TERM /SATURDAY THROUGH TUESDAY/

Key message(s):

- Weekend starts cooler before temperatures moderate some into the early week.

- Moisture increase toward end of the weekend with increasing rain chances early next week.

Slightly better agreement is seen in ensemble and global models in the extended. Saturday's outlooks remains in tact with surface high pressure hanging on and another day with very dry and cold air remaining in place with temperatures below normal. Moisture is expected to begin increasing Saturday night into Sunday where dewpoints originally in the upper teens Saturday afternoon could be in upper 30s to mid 40s by Sunday afternoon. This is mainly in response to returning southwesterly flow as a shortwave moves across the Midwest.

For the remainder of the period, another deep trough is progged to move into the southwest CONUS Sunday and into Monday, continuing to drive deep southwesterly flow over the region with PWAT's between 160-180% of normal, possibly a bit higher. Weak shortwaves pushing into the region along with some inverted surface troughing off the coast should drive increased rain chances Sunday and Monday, likely continuing into Tuesday as the main trough begins to eject into the region, though some timing differences exist in this still. For temperatures, this pattern generally is expected to bring near to slightly below normal temperatures each day. One caveat is temperatures may trend cooler as in-situ wedge conditions could possibly develop as early as Sunday, continuing into the early week with very moist southwest flow on top of a slightly drier near surface layer.

AVIATION /11Z WEDNESDAY THROUGH SUNDAY/

Showers and MVFR ceilings this morning with improving, but breezy, conditions through the day.

Early this morning: The KCAE VAD wind profile shows a 30 to 35 kt LLJ around 2000 ft AGL. Surface winds are generally from 4 to 8 kts so unless sfc winds go calm around sunrise, LLWS criteria is unlikely.

A cold front will move through the region today with gusty southwest winds ahead of it. Scattered showers will move across the forecast area through around 18Z then push east as the cold front and drier air begins to move into the area from the west. Although convective coverage may not be sufficient to have confidence in visibility impacts to the terminals, we do believe that all sites will see at least MVFR ceilings through the morning until the deeper moisture pushes east. Winds will gust to around 20 kts out of the SW this afternoon, turning to the west in the late afternoon or evening.

EXTENDED AVIATION OUTLOOK...Moisture increases Sunday with increasing rain chances and chances for restrictions.

CAE WATCHES/WARNINGS/ADVISORIES

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