textproduct: Columbia

WHAT HAS CHANGED

Minimal change to forecast as a trend toward a dry frontal passage continues. Added Key Message for elevated fire weather conditions behind the cold front on Thursday. Aviation discussion updated for 06z TAFs.

KEY MESSAGES

- 1. A cold front moves through tonight where a stray shower cannot be ruled out.

- 2. Potential for increased fire weather conditions Thursday behind cold front.

- 3. Dry conditions are expected with temperatures warming above normal this weekend and early next week.

DISCUSSION

Key Message 1: A cold front moves through tonight where a stray shower cannot be ruled out.

Little has changed with the outlook for a front currently working out of the southern Great Lakes toward the Ohio and Tennessee Valley's. Through the day today, moisture advection remains fairly weak as a surface low working across the Florida Peninsula keeps low level flow more northeasterly to easterly through the first half of the day. As this feature shifts further off shore, flow becomes a bit more southwesterly and PWAT's struggle to reach near 1.0-1.10" by this evening. There remains solid consensus across the latest HREF, REFS, and their respective members, that as the front approaches, a stray shower cannot be ruled out mainly in the northern Midlands toward the Pee Dee, but mostly dry conditions should prevail. The greatest upper support keeping north of the FA and limited convergence along the front aid in precluding increased coverage of showers this evening. The front should work through the area tonight into Thursday morning, turning winds back out of the northwest to north with a very dry air mass working in.

Key Message 2: Potential for increased fire weather conditions Thursday behind cold front.

As mentioned at the end of Key Message #1, very dry air should move in behind the cold front. As low level flow becomes increasingly northwesterly to northerly, solid mixing combined with downsloping may aid in dropping dew points a bit further than currently modeled Thursday. With REFS probabilities for surface dewpoints less than 35F reaching between 50-70%, there is increasing confidence that minimum RH values Thursday afternoon will near if not fall below critical values for much of the FA. A fairly tight pressure gradient behind the front could bring wind gusts up to 15-20 mph through early Thursday afternoon before diminishing. Luckily, winds should remain weak enough to not need a fire weather product, but a lack of rainfall with this front, drought conditions, and a very dry air mass moving in should bring elevated fire weather conditions through the late afternoon hours.

Key Message 3: Dry conditions are expected with temperatures warming above normal this weekend and early next week.

Upper troughing lingerings through Friday, keeping temperatures closer to normal, but a dry air mass should remain in place. Ensemble and global guidance then indicate an upper ridge working into the Southeast this weekend with a strengthening Bermuda high, that looks to remain in place into at least early next week before potentially breaking down some during the mid week. Persistent southwesterly to southerly flow and warming 850 mb temperatures near the NAEFS 90th percentile is expected to bring warming temperatures that reach the 90s Saturday into the early week. EC EFI values remain between 0.7-0.8 through Tuesday next week, aiding in increasing confidence in this period of above normal temperatures. The airmass is expected to be fairly dry, but by Sunday there is some indication that as the FA finds itself more on the western periphery of the upper ridge and Bermuda high, increasing moisture and seasonable instability could bring spotty diurnal rain chances.

AVIATION /06Z WEDNESDAY THROUGH SUNDAY/

VFR conditions remain likely through the period.

Stationary front along northern FL with a weak shortwave moving along it early this morning will bring some moisture northward and into southern SC. Should still be enough drier air moving in from the north across the Midlands of SC and the CSRA region to keep this rainfall and deeper moisture confined to areas south and east of all taf locations. A cold front will move into the region from the west Wednesday night and into Thursday.

There will be some cloud cover associated with the system off to our south, and possibly some with the cold frontal passage, but the ceilings will remain vfr. Do not expect any visibility restrictions at this time.

Expect light and variable winds through the late morning. Winds will begin to turn more out of the west/southwest through the afternoon ahead of the cold front. The TAFs have variable winds through 18Z, then winds will increase to between 5 to 10 kts. With limited moisture available as the front moves through the region, we do not expect rainfall at any of the terminals, however there will be a wind shift to NW Wednesday night or early Thursday morning.

EXTENDED AVIATION OUTLOOK...Widespread restrictions unlikely through Sunday.

CAE WATCHES/WARNINGS/ADVISORIES

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