textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Updated aviation discussion for the 00Z TAFs.

KEY MESSAGES

1. A Red Flag Warning is in effect for northeast Georgia and a Fire Danger Statement is in effect for most of western North Carolina (outside the northern mountains) through 8 pm. Burn bans remain in effect until further notice across the Carolinas. Any fire that develops will catch and spread quickly. Outdoor burning is not recommended. 2. A Freeze Warning remains in effect for the northern mountains of NC and a Frost Advisory remains in effect for remainder of NC mountains, the northern Foothills, and the northwest Piedmont from midnight tonight through 9 AM Tuesday. Frost and freeze conditions could kill crops, other sensitive vegetation and possibly damage unprotected outdoor plumbing. 3. Temperatures return to above normal during the latter half of the week, while very dry conditions continue. Very low or even critical afternoon RH will enhance fire danger through the end of the work week. A frontal system will bring rain chances next weekend.

DISCUSSION

Key message 1: A Red Flag Warning is in effect for northeast Georgia and a Fire Danger Statement is in effect for most of western North Carolina (outside the northern mountains) through 8 pm. Burn bans remain in effect until further notice across the Carolinas. Any fire that develops will catch and spread quickly. Outdoor burning is not recommended.

No changes to the ongoing Fire Weather products we have in place. The RH forecast for the afternoon was lowered by a few percent based on observation trends.

Rainfall remained sparse outside the northern North Carolina mountains yesterday. Thus, very dry fuels remain in place across the rest of the GSP CWA. Minimum relative humidity will fall to around 30% across the North Carolina mountains and below 25% east of the mountains. Wind gusts up to 30 mph can be expected across the North Carolina mountains, with gusts up to 25 mph east of the mountains.

A Red Flag Warning remains in effect for northeast Georgia for this afternoon and early evening as gusty winds, low relative humidity, and fuel moisture falling to 8% or less may lead to extreme fire behavior. Any fire that develops will catch and spread quickly. Outdoor burning is not recommended.

A Fire Danger Statement remains in effect for most of western North Carolina (outside the northern mountains) for this afternoon and early evening as low humidity, gusty winds, and dry fuels could increase the potential for wildfires.

With burn bans in effect until further notice across the Carolinas, open burning of any kind is illegal.

Key message 2: A Freeze Warning remains in effect for the northern mountains of NC and a Frost Advisory remains in effect for remainder of NC mountains, the northern Foothills, and the northwest Piedmont from midnight tonight through 9 AM Tuesday. Frost and freeze conditions could kill crops, other sensitive vegetation and possibly damage unprotected outdoor plumbing.

A spectacular April day will lead to another cool night across the region as high pressure settles over the central Appalachians. The 12Z model runs continue to show good radiational cooling conditions tonight, with clear sky and very light N/NE sfc flow. Given that low temps this morning were under the forecast lows by several degrees in many spots, we will mix in the cooler temps from the ensemble to undercut the NBM, especially over the NC portion. The result is a low temp fcst about ten degrees below normal. This keeps much of the nrn mountains in the Freeze Warning, so no changes to that part. Outside of the nrn mountains, we're still struggling to get much in the way of frost in the fcst using our usual techniques, possibly because the air mass remains so very dry. Bottom line is that our Frost Advisory will be left alone for now.

Take steps now to protect tender plants from the cold. In-ground sprinkler systems should be drained. Remove hoses and cover above- ground pipes.

Tonight should be the last night with the frost/freeze threat, as we have a warming trend with the sfc high center shifting off the Carolina Coast on Tuesday afternoon.

Key message 3: Temperatures return to above normal during the latter half of the week, while very dry conditions continue. Very low or even critical afternoon RH will enhance fire danger through the end of the work week. A frontal system will bring rain chances next weekend.

High pressure will persist over the southeast CONUS Wednesday through Friday, initially supported by a low to midlevel ridge aloft as upper ridge remains centered to our west. Airmass modification and generally light SW'ly winds will promote slight warming such that temps remain 7-10 degrees above normal each afternoon, but the warming outpaces moisture return and min RH near or below the critical 30% fire weather threshold still is expected each afternoon. Models still depict a weak front pushing south into the Mid-Atlantic Wednesday, east of the upper ridge, and pushing into our area late Wed afternoon or evening. While moisture looks much too paltry for this to result in a mentionable PoP, winds still look to turn northwesterly and downslope, suggesting deep mixing and a brief return of west to northwest winds, along with some gust potential over the area Wed afternoon. Thus that day arguably looks the most critical for fire weather, though unseasonably high fire danger is expected to continue at least into the weekend, when pattern change appears likely to occur.

An upper low will move from the Pacific coast to the Canadian prairie and northern Plains states by Friday, spawning cyclogenesis, reactivating the boundary to our north, and pushing a cold front into the Mississippi Valley by Friday night. Some solutions depict a triple-point low developing near the Great Lakes, and those solutions are faster in bringing the front to the Appalachians, generally Saturday versus Sunday. Confidence remains relatively low on the specifics, but there is enough of a consensus as to the pattern change for us to feature 40-60% PoPs Saturday and Sunday, with the highest values being near the TN border. Temps trend slightly cooler Sunday and Monday with the front near the area and enhanced cloud cover, along with reduced thicknesses.

AVIATION /00Z TUESDAY THROUGH SATURDAY/

At KCLT and elsewhere: VFR at all terminals through the period. Winds have been all over the place with a weak boundary moving southeast across the region. Have started with current winds then turn them light NE later in the evening. Wind becomes ENE near daybreak then SW for the afternoon. KAVL keeps low end gusts early this evening then light overnight, before picking back up from the N after daybreak, then going S for the afternoon. Altocu over the area dissipates during the evening with SKC for the rest of the period.

Outlook: VFR and dry through the work week thanks to high pressure. A frontal system may bring showers and associated restrictions for the weekend.

GSP WATCHES/WARNINGS/ADVISORIES

GA...Red Flag Warning until 8 PM EDT this evening for GAZ010-017- 018-026-028-029. NC...Freeze Warning from midnight tonight to 9 AM EDT Tuesday for NCZ033-049-050. INCREASED FIRE DANGER until 8 PM EDT this evening for NCZ035>037-048-051>053-056>059-062>065-068>072-082- 501>510. Frost Advisory from midnight tonight to 9 AM EDT Tuesday for NCZ035>037-048-051>053-056>059-062>065-501>507. SC...None.