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 12z 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 /12Z WEDNESDAY THROUGH SUNDAY/

Mainly vfr conditions expected, except through 14z this morning where mvfr ceilings may be found. An isolated shower across the CSRA or eastern Midlands can not be ruled out.

Stationary front along northern FL with a weak shortwave moving along will continue bringing moisture northward and into southern SC and the CSRA this morning. Ceilings have dropped to low end vfr and even some upper end mvfr in places as this moisture deepens. Regional radars also indicating an isolated shower or two will be possible over the CSRA and southern Midlands. Confidence in any rain remains low, and will not put in ags/dnl/aik/ogb at this time, but a few sprinkles may occur this morning. Later today ceilings will be lifting with all sites vfr by 18z as a cold front begins to approach the region from the west. This will bring winds from light and variable this morning, to more west/southwest this afternoon. Eventually winds will turn more northwesterly, but that is not expected until late in the period behind the main cold front.

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

CAE WATCHES/WARNINGS/ADVISORIES

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