textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

No significant changes were made based on the 00Z guidance.

Updated for the 12Z aviation discussion.

KEY MESSAGES

1. The threat of patchy frost remains across the mountains tonight, and possibly east across the I-40 corridor Tuesday and Wednesday night. Protection of sensitive vegetation may be required in some locations. 2. Fire weather will gradually become more of a concern through mid-week as a dry air mass spreads across the region. Outdoor burning could become dangerous by Wednesday afternoon due to low relative humidity values, gusty winds, and dry fuels.

DISCUSSION

Key message 1: The threat of patchy frost remains across the mountains tonight, and possibly east across the I-40 corridor Tuesday and Wednesday night. Protection of sensitive vegetation may be required in some locations.

Cooler and drier weather will be on tap today through tonight, as high pressure builds in from the northwest. Highs today will be a few degrees below normal, and lows will be near normal tonight. Despite a weak, dry cold front crossing the mountains tonight, the mountain valleys may decouple and cool down enough for some patchy frost. Not enough confidence to warrant a Frost Advisory issuance this morning.

The situation essentially remains unchanged with regard to the cool air mass that settles over the region behind a reinforcing cold front that crosses the region early on Tuesday. The low temperature forecast remains similar to the last few model cycles, or at least it hasn't rebounded cooler at this point. That means freezing temps are no longer on the table for anywhere but above 6000 feet in the central and southern NC mountains, which means that a Freeze Warning looks unlikely. Note that the frost/freeze program remains inactive across the northern mountains of NC, so altho some parts of the nrn mountains might get below freezing Tuesday night, specifically parts of Avery County, a freeze warning would not be issued and the fcst would be allowed to speak for itself. Frost still appears to be within the realm of possibilities early Wednesday morning, but for now appears to be localized to parts of the lower TN River Valley in Swain County, possibly because the air mass looks too dry and wind stays mixed up enough. That's not exactly the case for Wednesday night/early Thursday morning, and the forecast will reflect a better chance of frost in the upper French Broad Valley and northern Foothills of NC. By that time, the center of high pressure should be located over the northern Mid-Atlantic region and Upstate NY, so wind over the mtns should be lighter in sheltered valleys. Too early to contemplate frost advisories for early Thursday, though.

Key message 2: Fire weather will gradually become more of a concern through mid-week as a dry air mass spreads across the region. Outdoor burning could become dangerous by Wednesday afternoon due to low relative humidity values, gusty winds, and dry fuels.

Beneficial rain on Sunday should help keep fuel moisture high enough today to alleviate fire concerns in spite of a drier air mass moving in from the west as a weakening sfc high noses eastward across the mountains. However, the RH is expected to drop into the 25-30 percent range this afternoon and Tuesday afternoon, and a partly cloudy sky and light NW to N wind should provide the opportunity for fuels to start to dry out through Tuesday afternoon. How quickly fuels dry out may determine the fire danger. By Wednesday afternoon, even though high temps will drop compared to the previous two days, the low RH might become more problematic if fuels dry out as expected, because of better potential for wind gusts above 20 mph. Land managers will want to keep track of this forecast problem. Once the sfc high shifts farther offshore by Thursday, some Atlantic moisture should begin to return and afternoon RH rises accordingly, with values in the middle/upper 30s expected each day through the weekend. Unfortunately, no rain is in sight for the entire seven day forecast period.

AVIATION /12Z MONDAY THROUGH FRIDAY/

At KCLT and elsewhere: VFR conditions expected thru the period, with a steady stream of mainly thin cirrus over the area. Light winds expected across the Piedmont today, although a few low-end gusts may be possible at KCLT mid-morning as mixing deepens. Winds becoming variable across the Piedmont late aftn thru tonight At KAVL, winds will remain gusty thru the day, becoming light around sunset. A weak front will push in from the north toward the end of the 12z TAF period, which will cause winds to pick up slightly out of the N or NE.

Outlook: Sfc high pressure spreads over the region behind the cold front and lingers thru the middle of week, with dry/VFR conditions expected thru at least Thursday. Easterly flow may bring some return of lower clouds late Thursday into Friday.

GSP WATCHES/WARNINGS/ADVISORIES

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