textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

The Wind Advisory was expired earlier this afternoon. A Fire Weather Watch was issued for northeast Georgia for Monday afternoon. A Freeze Watch was issued for the northern mountains for Monday night. Forecast peak wind gusts trended higher for Monday afternoon.

KEY MESSAGES

1. Dry and breezy conditions will support elevated fire danger across much of the area through this evening and again Monday afternoon. The most critical conditions will occur in northeast Georgia, where Red Flag products are in effect based on the overlap of low humidity, dry fuels, and gusty winds.

2. Patchy frost is expected in a few mountain valleys tonight into Monday morning. Colder conditions Monday night could result in frost across larger areas of the mountains and foothills, and a freeze in some locations. A Freeze Watch has been issued for Avery, Mitchell, and Yancey counties for Monday night.

3. Dry and trending warmer through the remainder of the work week. Near-critical fire weather conditions are likely to continue. A frontal system will offer a chance for rain over the coming weekend.

DISCUSSION

Key message 1: Dry and breezy conditions will support elevated fire danger across much of the area through this evening and again Monday afternoon. The most critical conditions will occur in northeast Georgia, where Red Flag products are in effect based on the overlap of low humidity, dry fuels, and gusty winds.

Dry and breezy conditions will maintain elevated fire danger across much of the forecast area through this evening. The most critical conditions this afternoon are expected in northeast Georgia, where a Red Flag Warning remains in effect through 8 PM. Meanwhile, a Special Weather Statement for increased fire danger remains in effect across the North Carolina foothills and Piedmont, as well as adjacent parts of northeast Georgia.

Relative humidity values continue to fall quickly this afternoon as deep mixing develops and a drier air mass spreads into the region behind this morning's cold frontal passage. By mid afternoon, RH values across the foothills and Piedmont were dropping into the 25 to 30 percent range, with the lowest values near 20 percent observed in the northeast Georgia mountains and adjacent foothills. Minimum RH values are expected to bottom out in the 15 to 20 percent range across parts of the foothills and Piedmont by late afternoon, while generally remaining somewhat higher in the mountains due to cooler temperatures.

Fuel conditions also remain supportive of rapid fire spread. Several RAWS sites report fuel moisture values between 9 and 14 percent, and additional drying is expected through the rest of the afternoon given strong heating and the dry post-frontal air mass. The most critical fire weather conditions will occur in northeast Georgia, where the overlap of the driest fuels, delayed green up at higher elevations, lower humidity, and stronger winds will support the greatest fire spread potential.

Elevated fire danger is expected again Monday afternoon. A Fire Weather Watch has been issued for all of northeast Georgia, including the mountains, foothills, and Piedmont. Elsewhere, additional fire danger messaging may be needed. Although winds on Monday should be somewhat weaker than today, forecast soundings continue to support deep mixing and efficient transport of stronger winds aloft to the surface during peak heating. This should result in gusts of 30 to 35 mph in the mountains and 20 to 25 mph elsewhere, with minimum RH values falling into the 20 to 25 percent range outside of the mountains.

Despite slightly weaker winds Monday, the combination of persistent dryness and ongoing drought will keep fire danger elevated across the broader region.

Outdoor burning is not recommended. Any fire that develops will catch and spread quickly. Burn bans remain in effect until further notice across the Carolinas.

Key message 2: Patchy frost is expected in a few mountain valleys tonight into Monday morning. Colder conditions Monday night could result in frost across larger areas of the mountains and foothills, and a freeze in some locations. A Freeze Watch has been issued for Avery, Mitchell, and Yancey counties for Monday night.

Patchy frost is expected in a few mountain valleys tonight into Monday morning. A light northwest breeze should limit the frost potential early Monday morning despite temperatures forecast to bottom out in the mid 30s in the NC mountains. However, winds may relax enough for patch frost development in the most sheltered valleys.

Colder conditions Monday night could result in frost across larger areas of the mountains and foothills, and a freeze in some locations. A Freeze Watch has been issued for Avery, Mitchell, and Yancey counties for Monday night.

Continuing cold air advection should allow temperatures to fall several degrees below climo tonight and early Monday morning, reaching the mid 30s in some of the mountain valleys of NC. Dry dewpoints are expected to be a limiting factor across the board, so only patchy frost is expected where temperatures become that cold. Winds will continue to gust across the northern mountains, so frost appears somewhat less likely there, compared to the Little Tennessee and Pigeon River valleys southwest of Asheville which are more likely to go calm. The likelihood of freezing temperatures looks low tonight and Monday morning, excepting a few peaks above 5000 ft.

A dry backdoor front settling through the area Monday will reinforce CAA. Easterly winds in the southern Piedmont and even in the NC foothills appear likely to maintain at least a shallow, dry mixed layer Monday night and early Tuesday, though temperatures will trend colder compared to the previous night (tonight). Patchy frost is possible north of I-40 as the CAA should bring temps into the mid 30s, but the dry air again will be a limiting factor. The CAA and mixing are expected to be too shallow to reach much of the mountains, where weak WAA actually may occur in developing southerly winds aloft. This however suggests mountain valleys will experience radiational cooling, and are more likely to see the surface layer saturate. Thus patchy frost is more likely in the valleys and again will be mentioned. The radiational cooling should be sufficient for Avery County, and most of Mitchell and Yancey, to dip below freezing. Thus we have issued a Freeze Watch for those counties, valid midnight Monday night to 9 AM Tuesday. In subsequent forecast cycles we will reevaluate whether to expand the Watch and/or upgrade to Warning. If a Frost Advisory is issued for any areas outside the Freeze Watch/Warning, it likely would not be until Monday afternoon.

Key message 3: Dry and trending warmer through the remainder of the work week. Near-critical fire weather conditions are likely to continue. A frontal system will offer a chance for rain over the coming weekend.

Broad upper ridging will be present across the central and southeast CONUS through midweek, progressing eastward such that the ridge axis is over the Appalachians by Thursday night. Temperatures will trend warmer Tuesday night and Wednesday as the airmass modifies and heights rise, though moisture return on the briefly southwesterly winds will be very limited. RH is not expected to be quite as low Tuesday, but still near critical levels. While winds will be light fuels should continue to dry.

A weak shortwave diving down the leeward side of the ridge looks to bring a similarly weak front across the Appalachians Tuesday night and to the Carolina coast by late Wednesday. While the forcing will be weak and moisture sorely lacking for any mentionable PoP, the front will enhance the gradient aloft and lead to an uptick in winds/gusts mainly during the day Wednesday. While wind potential is not as great as on Monday afternoon, deep mixing will occur and a few gusts of 20-25 mph appear possible. RH is likely to trend lower. By Thursday the winds should turn light and southwesterly again, but at least marginally critical RH should return both then and Friday with temps continuing to trend warmer.

A deep trough will advance across the Rockies by Thursday night, with attendant low in the northern Plains pulling a cold front into the Southeast US by early Saturday. Weak instability could develop over the western fringe of the Appalachians as soon as Friday afternoon ahead of the front, though the better precip chances arrive in our CWA on Saturday. Given some spread in the models' orientation of the front and upstream convection, which limits confidence the front will provide measurable precipitation in our area, we collaborated with WPC to cap PoPs in the chance range Saturday. The likelihood of more than 0.10" precip occurring east of the Appalachian crest by Saturday evening remains less than 50%, so not terribly significant in light of the worsening drought and dry fuel moisture. A few model solutions stall the front near or over the CWA Saturday night into Sunday, so there is some potential for additional rainfall at those times.

AVIATION /19Z SUNDAY THROUGH FRIDAY/

At KCLT and elsewhere: VFR conditions will prevail through the period with no restrictions expected. The primary aviation concern remains gusty north to northwest winds in the wake of the departing cold front.

A tight pressure gradient has resulted in gusty north-northwest winds across the area today. The strongest winds have already occurred this morning, but breezy conditions will persist through the early part of the TAF period. Sustained winds of 10 to 15 kt with gusts of 20 to 25 kt will gradually diminish through roughly 00Z. KAVL will continue to see locally enhanced winds due to downsloping and channeling effects, with speeds and gusts generally 5 to 10 kt higher than surrounding terminals. At KAND, winds have remained lighter than expected, likely due to a localized weakness in the pressure gradient. Some increase in gustiness remains possible this afternoon with peak heating, with occasional gusts near 20 kt still possible.

Winds will continue to decrease this evening, with gusts subsiding around sunset. Overnight, winds become light, generally out of the west to northwest.

On Monday, northwest winds increase again with daytime mixing, though not as strong as today. Expect sustained winds of 8 to 14 kt with afternoon gusts of 20 to 25 kt.

Outlook: VFR and dry conditions persist through the first half of the week as high pressure remains in control. Winds will gradually weaken each day, becoming light to calm overnight.

GSP WATCHES/WARNINGS/ADVISORIES

GA...Red Flag Warning until 8 PM EDT this evening for GAZ010-017. Fire Weather Watch from Monday afternoon through Monday evening for GAZ010-017-018-026-028-029. INCREASED FIRE DANGER until 8 PM EDT this evening for GAZ018- 026-028-029. NC...Freeze Watch from late Monday night through Tuesday morning for NCZ033-049-050. SC...None.