textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Confidence continues to increase for near-record or record high temperatures Friday.

Confidence continues to increase that very dry and windy conditions on Saturday could lead to increased fire danger or even Red Flag criteria.

KEY MESSAGES

1. Dry through Friday morning before rain chances return ahead of a cold front Friday afternoon into Friday night. Gusty winds associated with the front will linger through at least daybreak Saturday. Record high temperatures are possible Friday ahead of the front. 2. A very dry airmass moving in Saturday, along with gusty winds, will lead to the threat of Red Flag Conditions. Not as windy but still very dry Sunday. 3. An increasingly warm and somewhat more humid airmass develops through next week.

DISCUSSION

Key message 1: Dry through Friday morning before rain chances return ahead of a cold front Friday afternoon into Friday night. Gusty winds associated with the front will linger through at least daybreak Saturday. Record high temperatures are possible Friday ahead of the front.

Warm and dry surface high pressure lingers over the region through Friday morning as a cold front sinks southeastward across the Ohio Valley. The front will push across the western Carolinas and northeast Georgia Friday afternoon into Friday night bringing rain chances back to the forecast area. However, this will not be a drought busting rain by any means as the highest rainfall totals (half an inch or less) will be confined to the NC/TN border. The rest of the GSP CWA outside the NC/TN border is likely to see much lower rainfall amounts, if any. Northwest downsloping will offset already limited moisture available with the front, especially east of the mountains. Areas most likely to remain dry are northeast Georgia and the South Carolina Upstate as 12Z CAMs depict light rain mainly surviving across much of western North Carolina. So, to make a long story short, not everyone will see rain develop on Friday. Thunder chances will also be limited as the better forcing will remain north of the region and most of the high-res/global models agree that there will only be 500 J/kg or less of both SBCAPE and MUCAPE available ahead of the front. NBM probabilities agree with this assessment, showing only a 20% to 40% chance of exceeding 500 J/kg of SBCAPE Friday afternoon/evening.

The one element that will not be limited with this front is wind gusts. Breezy S/SW winds can be expected ahead of the front today into tonight before shifting NW behind the front from west to east Friday morning into Friday night while becoming gusty. Winds appear to remain below advisory criteria (<45 mph) across the majority of the GSP CWA. However, some of the higher elevations, mainly along the Blue Ridge Escarpment, could see gusts meet or exceed advisory criteria briefly Friday night. For now, this appears too isolated and short-lived to warrant a Wind Advisory.

Record breaking heat is looking more likely on Friday ahead of the front, especially at KGSP and KCLT, thanks to NW downslope flow. The NBM shows a 90% chance for KCLT to break their record high of 85 degrees with KGSP having an 80% chance to break their record high of 86 degrees on Friday. For now it appears KAVL will remain below their record high of 85 degrees on Friday, with the NBM only showing a 25% to 30% chance of exceeding 85 degrees. Lows Friday night will drop near to below freezing across the much of the North Carolina mountains, with freezing temperatures most likely across the northern mountains and elevations above 3,500 feet.

Key message 2: A very dry airmass moving in Saturday, along with gusty winds, will lead to the threat of Red Flag Conditions. Not as windy but still very dry Sunday.

Very dry high pressure builds in behind the departing cold front on Saturday. Gusty winds will continue through the morning then slowly diminish through the afternoon as the initially tight pressure gradient relaxes. Despite the fact that the airmass is also cooler, RH values will drop below 25 percent for most of the area. The combination of low RH and gusty winds will approach Red Flag criteria. In fact, fuel moisture values are so dry, with little help from what rain falls Friday afternoon and evening, that land managers are becoming increasingly concerned about high fire danger. Coordination with the land managers is taking place and a Fire Weather Watch may be issued for Saturday as early as this evening, but may be with the overnight forecast package. Either way, Fire Weather will be the main concern. High pressure moves off shore Sunday with some weak southerly flow possibly developing; however, it won't be enough for any significant moisture return. Sunday's RH values will be nearly as low as Saturday, especially with slightly warmer temps. Winds won't be as strong but some low end gusts are likely for the mountains during the afternoon. Still, high fire danger will remain a concern, and another Red Flag Warning or Increased Fire Danger statement may be needed. Highs Saturday up to 5 degrees below normal and near normal on Sunday. Lows Saturday night will be up to 10 degrees below normal with a freeze likely for the mountains and possibly the NC foothills and Piedmont. They could trend colder given the airmass. Lows Sunday night warm above normal ending the freeze threat.

Key message 3: An increasingly warm and somewhat more humid airmass develops through next week.

An upper ridge slides east over the area Tuesday and Wednesday with the parent anticyclone off the Carolina coast on Thursday. South to southwesterly flow sets up across the area between There will be a slow but steady increase in moisture as this flow develops. There's no synoptic scale forcing, but some weak instability may develop. Model blend shows a slow increase in the chance of diurnal convection beginning on Tuesday, with chance PoP limited mainly to the mountains. Temps around 10 degrees above normal Monday steadily rise to around 15 degrees above normal for Wednesday and Thursday.

AVIATION /18Z THURSDAY THROUGH TUESDAY/

At KCLT and elsewhere: VFR and dry through the 18Z TAF period, with the exception of KCLT towards the end of the period. Winds will remain S/SW ahead of an approaching cold front through late tonight across the mountains before shifting NW behind the front early Friday morning. Winds east of the mountains will remain SW through Friday morning before turning NW behind the front Friday afternoon and evening. Low-end gusts will linger through early this evening before tapering off. Low-end gusts should return Friday afternoon. KCLT is the only terminal that will see SHRA develop towards the end of the period since the TAF goes out 30 hours, so introduced a PROB30 this cycle. Although an isolated TSRA cannot be ruled out Friday evening at KCLT, confidence is too low to mention at this time.

Outlook: SHRA and flight restrictions should linger through late Friday night at KCLT. Gusty NW winds will linger through Saturday afternoon behind the front. Otherwise, dry and VFR conditions can be expected this weekend into early next week.

CLIMATE

RECORDS FOR 03-27

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 85 2020 32 1955 60 1921 11 1955 1894 KCLT 85 1950 40 1894 62 1949 19 1955 1944 KGSP 86 2020 45 2011 60 1921 15 1894 1947

GSP WATCHES/WARNINGS/ADVISORIES

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